Pineapple-Derived Nanocellulose for Nanocomposites: Extraction, Processing, and Properties

Abstract

Pineapple waste is an underexplored source for producing nanocomposites, from which nanocellulose, namely cellulose nanocrystals (CNCs) or cellulose nanofibers (CNFs), can be produced. This review summarizes extraction methods from different pineapple residues (leaves, crown leaves, stem, peel, pulp, and pomace), covering top-down processes (hydrolysis, oxidation, carboxymethylation, and mechanical fibrillation) and bottom-up strategies (ionic liquids and deep eutectic solvents). The review examines the influence of the morphology and crystallinity of nanocellulose on the functional performance of the nanocomposites. Strategies for processing pineapple-derived nanocellulose composites are analyzed by technique (solution casting, film stacking, and melt blending/extrusion) and polymer matrices (starch, PVA, chitosan, PLA, PHBV, PBAT, proteins, and polysaccharides), including typical loading levels for most polymer-reinforced systems (0.5–5 wt.%), while higher levels (15–50 wt.%) are used in particular cases such as PVA, CMC, and cellulosic matrices. The impact on mechanical strength, barrier behavior, UV shielding, and optical properties is summarized, along with reports of self-reinforced and hybrid cellulose-derived matrices. A benchmarking section was prepared to show nanocellulose loading ranges, trends in properties, and processing-relevant information categorized by type of matrix. Finally, the review describes the potential roles of pineapple waste within a bioeconomy context and identifies some extraction by-products that could be incorporated into diverse value chains.

1. Introduction

Agriculture ranks among the leading sectors for biomass production. Among biomass resources, lignocellulosic matter predominates, primarily originating from agro-industrial and forestry sectors [1]. These residues, often underutilized, serve as a valuable source of raw materials that can be converted into energy, chemicals, and advanced materials [2]. The circular bioeconomy focuses on the conversion of biomass and waste into more valuable bioproducts by using circular economy processes to reduce waste [3,4,5]. This valorization can contribute to market diversification and foster the development of sustainable jobs through the conversion of plant biomass into high-value products [6,7].

The processing of pineapple, a highly cultivated tropical fruit, produces large volumes of residues such as leaves, peels, crowns, and cores [8,9]. These by-products contain abundant lignocellulosic compounds, and their composition changes depending on the specific part of the plant, which has an impact on its valorization [1]. Cellulose is the main component and has become a research focus for the production of nanocellulose, given its abundance and functional properties [8,10,11].

Nanocellulose, which can be obtained as cellulose nanocrystals (CNCs) or cellulose nanofibers (CNFs), is a renewable and biodegradable nanomaterial [8,12] with several applications in biocomposites [13], packaging [14], water purification [15], electronics [16], and biomedical engineering [17], among other areas.

For the extraction of nanocellulose from the lignocellulosic biomass derived from pineapple agroindustry, various top-down approaches have been applied, each influencing the resulting type of nanocellulose (CNC and CNF). Physical methods such as steam explosion [18] have been used to facilitate fiber breakdown. However, chemical methods are the most commonly applied, particularly acid hydrolysis [19] and oxidation techniques [20]. These are often combined with mechanical processes such as sonication [19], ultrafine grinding [21], and high-pressure homogenization to enhance fibrillation [10]. Bottom-up approaches have also been explored, including the use of an ionic liquid for cellulose dissolution and subsequent production of regenerated nanocellulose [22].

Because the main application of pineapple-derived nanocellulose to date has been the development of nanocomposites, this review adopts a perspective focused on nanocellulose extraction and its implementation in nanocomposite development. The paper links extraction-driven surface chemistry and particle geometry with processing routes, interfacial adhesion, and property enhancement.

According to our benchmarking analysis, the nanocellulose loadings in most reinforced polymer systems are in the range of 0.5–5% by mass, while higher contents are only observed in particular cases, for example, CMC-based formulations, self-reinforced cellulosic matrices, or certain polymers such as PVA and starch.

In recent decades, with increased interest and numerous experimental studies using pineapple residues as raw material, some reviews have addressed the specific utilization of leaves (PALF) with an emphasis on macro- or microscale composite materials (processing, treatments, and properties) rather than nanocellulose [23,24,25] or reviews of nanocomposites with nanocellulose, either general or focused on specific sectors [26,27] without focusing on a specific source such as pineapple. Other reviews of nanocellulose either do not differentiate the source or focus on manufacturing, properties, and applications in a broad sense [28,29]. There are also reviews on the comprehensive valorization of pineapple waste for the extraction of bioactive components without focusing on nanocellulose or nanocomposites [1,30], while another review has focused on the biotechnological transformation of pineapple waste [8].

Therefore, the aim of this review was to comprehensively explore the extraction methods of nanocellulose derived specifically from pineapple (CNC and CNF) with the production and yield of nanocomposites, covering all plant fractions (leaves, crown, stem, peel, pulp, and bagasse), comparing top-down and bottom-up routes. This review summarizes processing pathways to produce nanocomposites and matrix-specific outcomes, including cases where nanocellulose serves as the matrix to produce nanocomposite hybrid materials.

2. Scope and Review Method

This review synthesizes and integrates the extraction and application of pineapple-derived nanocellulose in nanocomposites, both nanocrystals and nanofibers extracted from the different fractions of the plant (leaves, crown, stem, peel, core, and pomace). The initial comprehensive search was conducted to identify studies reporting the extraction of pineapple nanocellulose. Subsequently, based on this stage, information regarding the fabrication and performance of nanocomposites using pineapple nanocellulose was identified and summarized. For the review, Scopus, Web of Science, and Google Scholar were consulted without date filters. The first published report on nanocellulose extraction from pineapple was made by Cherian, Leão, De Souza, Thomas, Pothan, and Kottaisamy [18]; hence, the review was conducted between 2010 and 2025. To identify the contributions to date on the topic, searches were performed using the terms: “nanocellulose” AND “pineapple”, “nanocellulose pineapple” OR “pineapple cellulose nanocrystals” OR “pineapple cellulose nanofibers” OR “pineapple cellulose nanowhiskers”, without restricting other nomenclature variants and pineapple varieties. This was complemented with backward/forward citation tracing from the included works. Only peer-reviewed journal articles in English were included; preprints and conference papers were excluded. This work is a narrative literature review, not a systematic review, and no PRISMA protocol was applied.

Studies that isolate CNC and/or CNF from any section of the pineapple plant were incorporated, including leaves, crown, stem, peel, core, pulp, and pomace. Microfiber studies without nanocellulose isolation or nanocellulose from sources other than pineapple, as well as review articles, were excluded, as the focus is on reporting extraction and practical application. After screening the titles and abstracts and evaluating the full texts, a corpus of 80 studies was consolidated. Information was extracted from each study, identifying the source, country where the study was conducted, nanocellulose extraction method, properties, and the reported application in each case. From this initial stage, 38 studies were identified that described the use of pineapple nanocellulose to obtain nanocomposites, either as a reinforcement material or as a matrix. The identified works were classified according to the type of matrix used in each investigation. Technical information was extracted from each study to identify the matrix, reinforcing filler, processing technique, applied surface modifications, and reported properties.

All quantitative data (e.g., cellulose content, extraction yields, nanocellulose dimensions, and mechanical and barrier property values) were extracted manually from the original articles and cross-checked by at least two authors to ensure accuracy. When inconsistencies were detected (e.g., duplicated values, missing baselines, or unclear sample identifiers), the information was verified by referring back to the original publication or by omitting data that could not be unequivocally confirmed. Only values explicitly reported by the primary sources were included, and no secondary estimates were used. When necessary, unit conversions were performed to standardize data reporting across all sources (e.g., TS in MPa, WVP in g·m⁻¹·s⁻¹·Pa⁻¹, and WVTR in g·h⁻¹·m⁻²), ensuring consistency for comparative analysis. This process of verification improves the reliability of the numerical data used in the benchmarking and comparative sections.

Given the methodological heterogeneity, a narrative synthesis was conducted, summarizing the main nanocellulose extraction approaches and nanocellulose types. A benchmarking table was then compiled, which was organized by polymer matrix and processing route; property changes were extracted and reported, and qualitative arrows (↑/↓/≈) or absolute values with units and test conditions were reported. Non-reported items were marked (NR), and “opt.” indicates the loading at which the best properties were observed.

During the preparation of this literature review, generative artificial intelligence (GenAI) tools were used for tasks related to language editing and clarity improvement. All scientific content, data extraction, interpretation, and critical analysis were performed by the authors. The authors thoroughly reviewed and verified all AI-assisted text to check accuracy and originality and take full responsibility for the final content.

3. Pineapple Cultivation and Biomass Residues

Pineapple is the second most important tropical fruit globally, consumed both fresh and in processed forms [31]. In 2022, global pineapple exports reached 3.1 million tons, mainly supplied by Costa Rica and the Philippines, followed by Ecuador and Mexico [9]. Pineapple belongs to the family Bromeliaceae, and is scientifically known as Ananas comosus [32].

The most widely used pineapple variety worldwide is the Smooth Cayenne, but Costa Rica, the world’s leading exporter, primarily grows MD-2 (Golden) hybrid, which has a greater amount of sugar and weighs around 2 kg. Pineapple is a perennial plant that thrives in tropical or subtropical regions with humid conditions [33]. The plant has a height of 0.75–1.5 m, and the leaves reach 0.9–1.2 m in length [34]. According to d’Eeckenbrugge and Leal [35], the main morphological components of the plant include the stem, the leaves, the peduncle, the syncarp (multiple fruit), the crown, the shoots, and the roots, as shown in Figure 1.

Table 1 summarizes the composition of the main pineapple biomass fractions and the analytical methods used to obtain these values, presenting the ranges reported for cellulose, hemicellulose, lignin, and ash across the reviewed studies. Beyond listing these data, the table allows a direct comparison of compositional patterns among fractions, revealing consistent anatomical trends alongside clear methodological influences. Leaves display the highest cellulose contents (37–81%), followed by crown leaves (51%), reflecting their structural and load-bearing roles, whereas peels show markedly lower cellulose levels (17–46%) and greater variability in hemicellulose and lignin due to their heterogeneous epidermal and parenchymatic tissues. Core and pulp present intermediate cellulose values (45–68%) and lower lignin, consistent with their softer, less lignified nature, while pomace shows unusually high hemicellulose content (60%) due to the partial solubilization of extractives during juice extraction. Stems contain cellulose levels comparable to leaves but slightly higher lignin, as expected for supportive tissue. Importantly, part of the observed variability arises not only from anatomical and varietal differences but also from the analytical techniques employed. Studies following ASTM protocols (e.g., D1103, D1104, and D1106) tend to report higher cellulose and lower lignin values due to their specific solvent selectivity, whereas TAPPI methods (T222, T203, and T204) often yield broader ranges because of differences in hydrolysis strength, residue recovery, and extractive removal. Therefore, the combination of intrinsic biological diversity and divergent ASTM/TAPPI methodologies helps explain the wide compositional ranges reported in the literature.

Pineapple leaves (plant and crown leaves) are the most studied residues, and the third most studied pineapple residue is the fruit peels, suggesting a moderate potential to recover both structural polysaccharides and lignin. The least studied pineapple residues are the core, pulp, stem, and pomace. The core can be a good substrate for microbial fermentation or enzymatic hydrolysis. The pineapple stem is mainly used for the extraction of bromelain, an enzyme currently marketed, but after bromelain extraction, the remaining fibrous material can be used for cellulose extraction [39,40].

Table 1. Chemical composition and analytical methodologies for pineapple biomass fractions.

Pineapple Part	Cellulose * (%)	Hemi Cellulose (%) *	Lignin (%) *	Ash (%) *	Methods Used
Leaves	37.25 [41]–81.27 [18]	12.31 [18]–33.93 [41]	3.46 [18]–15.9 [42]	5.32 [41]	ASTM D1103-55T, ASTM D1104-56, ASTM D1106-56, ASTM D4442-92 [18,41,43]; TAPPI T9M-54, TAPPI T13M-54, ASTM D1104-56 [42]
Crown leaves	51.2 [44]–51.4 [45]	13.3 [44]–13.4 [45]	12.2 [45]–13.40 [44]	2.30 [44]–6.73 [45]	TAPPI T 550 om-03, TAPPI T 204 cm-97, TAPPI T 222 om-02, TAPPI T 203 cm-99 [45], Chesson–Datta) [44]
Peels	16.9 [46]–45.52 [41]	15.8 [46]–39.55 [41]	15.43 [41]–28.9 [46]	3.82 [41]–3.92 [46]	ASTM D1103-55T, ASTM D1104-56, ASTM D1106-56, ASTM D4442-92 [41], TAPPI T222 om-88, Browning method [46]
Core	67.86	31.64	9.31	1.70	ASTM D1103-55T, ASTM D1104-56, ASTM D1106-56, ASTM D4442-92 [41]
Pulp	44.89	27.31	15.09	2.56	ASTM D1103-55T, ASTM D1104-56, ASTM D1106-56, ASTM D4442-92 [41]
Pomace	31.78	60.19	3.44	-	ASTM D1103-55T, ASTM D1104-56, ASTM D1106-56 [47]
Stem	31.86 [48]–37 [49]	37 [49]–46.15 [48]	18.60 [48]–20 [49]	0.40 [48]	Modified Iwamoto et al. [50] method [48], standard methods (numbers not specified) [49]

* Ranges show minimum [ref] to maximum [ref] from published studies; additional references in the methods column report intermediate values within the range.

Table 1. Chemical composition and analytical methodologies for pineapple biomass fractions.

Pineapple Part	Cellulose * (%)	Hemi Cellulose (%) *	Lignin (%) *	Ash (%) *	Methods Used
Leaves	37.25 [41]–81.27 [18]	12.31 [18]–33.93 [41]	3.46 [18]–15.9 [42]	5.32 [41]	ASTM D1103-55T, ASTM D1104-56, ASTM D1106-56, ASTM D4442-92 [18,41,43]; TAPPI T9M-54, TAPPI T13M-54, ASTM D1104-56 [42]
Crown leaves	51.2 [44]–51.4 [45]	13.3 [44]–13.4 [45]	12.2 [45]–13.40 [44]	2.30 [44]–6.73 [45]	TAPPI T 550 om-03, TAPPI T 204 cm-97, TAPPI T 222 om-02, TAPPI T 203 cm-99 [45], Chesson–Datta) [44]
Peels	16.9 [46]–45.52 [41]	15.8 [46]–39.55 [41]	15.43 [41]–28.9 [46]	3.82 [41]–3.92 [46]	ASTM D1103-55T, ASTM D1104-56, ASTM D1106-56, ASTM D4442-92 [41], TAPPI T222 om-88, Browning method [46]
Core	67.86	31.64	9.31	1.70	ASTM D1103-55T, ASTM D1104-56, ASTM D1106-56, ASTM D4442-92 [41]
Pulp	44.89	27.31	15.09	2.56	ASTM D1103-55T, ASTM D1104-56, ASTM D1106-56, ASTM D4442-92 [41]
Pomace	31.78	60.19	3.44	-	ASTM D1103-55T, ASTM D1104-56, ASTM D1106-56 [47]
Stem	31.86 [48]–37 [49]	37 [49]–46.15 [48]	18.60 [48]–20 [49]	0.40 [48]	Modified Iwamoto et al. [50] method [48], standard methods (numbers not specified) [49]

* Ranges show minimum [ref] to maximum [ref] from published studies; additional references in the methods column report intermediate values within the range.

Although the studies included to determine the compositional ranges for each type of pineapple residue apply standardized (ASTM and TAPPI) or well-described protocols (e.g., Wise, Chesson-Datta, Browning), the variation between studies could be influenced by the selectivity of the protocols and the inherent uncertainty of determinations that underlie these procedures [51].

Furthermore, reviews on pineapple leaf fibers suggest compositional diversity among cultivars and regions [52], so the reported data could reflect both the actual variability of the material and the methodology applied. Despite the relevance of reporting the composition of the starting materials for interpreting nanocellulose extraction, most studies do not include it [53]; in this review, only 19% of the reviewed papers reported it.

Therefore, a pending task for pineapple waste is to standardize the reporting of methods used to measure the composition of the biomass, or at least report, in detail, the procedure applied, so that results can be comparable across studies. This is especially important for poorly studied fractions, such as the stem, for which the available information is limited.

The elevated cellulose content of pineapple residues evidences their potential as a feedstock for nanocellulose production, and it may influence the extraction method applied for nanocellulose. In the following section, the processing conditions and nanocellulose main properties are summarized.

4. Pineapple Nanocellulose

Cellulose is the main component of pineapple waste and is found in plants in a hierarchical structure. Figure 2 shows the hierarchical structure of cellulose in the pineapple plant.

Individual plant cells contain primary and secondary cell walls, the latter being rich in a lignocellulosic matrix composed of cellulose, hemicellulose, and lignin. Cellulose is the main component and the most abundant biopolymer in nature; this biopolymer plays a structural role in plant cell walls and consists of β-1,4-linked glucose units forming semicrystalline chains [12]. The chains aggregate into microfibrils through hydrogen bonding and van der Waals interactions and are composed of both crystalline and amorphous regions, which determine the properties of the resulting nanocellulose.

In top-down methods, the first step to process the biomass is cellulose extraction; based on the studies reporting detailed extraction protocols, the most common treatment is alkaline pulping using NaOH, typically at concentrations from 2 to 5 wt.%, with 2 wt.% being the most common, at 80 to 100 °C for 1 to 4 h. For example, Dos Santos, Neto, Silvério, Martins, Dantas, and Pasquini [19] used NaOH 2 wt.% for 4 h and 100 °C [19]. A second approach is steam explosion, which involves soaking the fiber in a 2 wt.% NaOH solution followed by steam explosion under pressure [18,43,54]. Recently, the use of organosolv pulping to extract cellulose was reported [55], and Tian et al. [56] reported the use of enzymes before nanofiber extraction, showing a tendency to follow more sustainable processes.

After cellulose extraction, usually a bleaching process is applied to eliminate lignin residues. The most common process applied is by using sodium chlorite (NaClO₂) [19,43], another process is hydrogen peroxide bleaching, [55,57] which is considered a more sustainable option. Another approach is hypochlorite bleaching, combining sodium hypochlorite (NaClO); the treatment is repeated for as many cycles as needed until a desired bleaching level is reached [18,54]. The microfibrils extracted can be disassembled into two major types of nanocellulose: cellulose nanocrystals (CNCs)—composed primarily of crystalline domains—and nanofibrillated cellulose (CNF)—which retains both crystalline and amorphous regions.

4.1. Extraction Pathways

Nanocellulose (NC) includes both nanocrystals and nanofibers. Figure 3 shows the main routes to obtain each type of nanocellulose.

Cellulose nanocrystals (CNCs) can be extracted mainly by sulfuric acid hydrolysis, where the amorphous zones are hydrolyzed, and the crystalline regions are maintained. Its dimensions (length and width) vary with the cellulose source and the hydrolysis conditions [12]. For this type of hydrolysis, extraction yields of 16.5% (relative to initial biomass) have been reported for leaves [58], and from 3.65 to 15% for peels (relative to initial biomass), using high concentrations of H₂SO₄ (60–65%) [59,60]. At lower concentrations of the same acid (3 M ≈ 25 wt.%), higher yields have been reported, from 76.2 to 79.37% (relative to initial biomass) for crown leaves, with higher values obtained at shorter hydrolysis times [44]. Other methods used to obtain CNC utilize HCl (30 wt.%), with yields of 39% (relative to initial biomass) for pineapple peels [61]. Extraction using ammonium persulfate oxidation (APS) on pineapple leaves has also been reported, obtaining a yield of 30% (relative to initial biomass) [62].

On the other hand, cellulose nanofibers (CNFs) form long networks with a similar or larger width than CNCs. CNF extraction methods are more mechanical, which include high-pressure homogenization, ultrasonic treatment, and high-shear grinding, which are less severe than acid hydrolysis [63]. In general, CNF yields are higher than those obtained for CNC. CNF has been isolated using mechanical methods, such as high-pressure homogenization of pineapple crown leaves, yielding 45% (relative to initial biomass) [64]. Similarly, ball milling of pineapple peels in a basic medium has yielded values of 47.9% to 71.6% (relative to initial biomass), with greater purification of the initial biomass increasing the yield [65]. CNF has also been obtained from pineapple pomace, yielding 70% (relative to initial biomass) with oxalic acid treatment and autoclaving, and 62% (relative to initial biomass) with hydrolysis using 50% H₂SO₄ [47]. Spherical particles of nanocellulose have been reported by H₂SO₄ (60 wt.%) acid hydrolysis of peel and leaves, reaching yields of 7% and 12%, respectively (relative to initial biomass) [66], and more recently by leaves TEMPO oxidation [67].

Only 13% of the reviewed studies report the extraction yield with respect to the initial biomass; some (9%) report the yield with respect to the previous extraction step, which is usually obtaining the cellulose. Because yields vary depending on the raw material and the conditions used, it is important to consistently report extraction yields to allow for comparisons between studies, ensure the reproducibility of the methodology, and assess the scalability of the process. Furthermore, the majority of studies (87%) do not report extraction yields relative to the initial biomass, which limits the ability to compare extraction routes and evaluate material efficiency across different sources and methods.

Although extraction yield is essential for assessing material efficiency, scalability, environmental impact, and techno-economic feasibility, most studies report only partial or step-based yields (typically relative to purified cellulose rather than initial biomass), and 87% do not provide any biomass-referenced yield at all. This omission makes it difficult to compare extraction routes, evaluate the true efficiency of top-down versus bottom-up approaches, or determine the suitability of specific pineapple fractions for industrial-scale processes. Authors should systematically report extraction yields relative to the starting biomass to ensure reproducibility, enable cross-study comparison, and support the transition from laboratory-scale experiments to scalable biorefinery operations.

In contrast, only a few studies regarding the bottom-up approach for obtaining nanocellulose from pineapple waste have been reported. In this type of process, cellulose is dissolved and then regenerated. Zhu et al. [68] reported the use of BmimCl to dissolve cellulose from pineapple leaves assisted by microwave radiation, then the solution was passed through a high-pressure homogenizer, and the particle size reached 800 nm. Similar work was reported by Dai, Zhang, Ma, Zhou, Yu, Guo, Zhang, and Huang [22] using the same ionic liquid (BmimCl) to dissolve peel cellulose; the process was followed by hydrolysis with sulfuric acid under sonication, and the nanofibers obtained had 25 nm in width and 330 nm in length. The dissolution was added to a mixture of polyvinyl alcohol and pineapple carboxymethyl cellulose to generate pH/magnetic sensitive hydrogels containing Fe₃O₄ nanoparticles.

Deep eutectic solvents based on choline chloride/glycerol and choline chloride/oxalic acid, assisted by sonication, were reported to obtain nanocellulose from crown leaves. Rod-like shape nanocellulose with lengths from 80 to 120 nm and a negative zeta potential (−25 mV) was obtained, although the extraction yield from initial biomass was not reported [69].

The trend in publications on pineapple nanocellulose extraction reveals three main stages: a period from 2010 to 2015, where reported and known methods to extract CNC were applied and adapted to pineapple biomass [18,19], followed by a period from 2016 to 2019, where there was greater reporting of CNF extraction and diversification of extraction methods [21,42,70] and a period from 2020 to the present where the interest in looking for the application of new approaches or greener methods have increased [69,71,72,73].

Based on our analysis of the 80 reviewed publications, research is mainly led by Asia, with China [22,65,68,74,75,76,77] and India [14,70,78,79,80] contributing to the largest number of publications. Southeast Asia also contributes to the literature (Indonesia [21,42,81,82], Thailand [83,84,85,86], Malaysia [62,87,88,89], and Vietnam [67,90,91]); there is also active contribution from the Americas (Brazil [18,19,54,92,93] and Costa Rica [10,39,58,59]). This distribution coincides with the main pineapple-producing regions and large consumer markets [9], which suggests that researchers use biomass sources locally available. It should be noted that a large part of the research is conducted through collaborations between countries and institutions. Analysis of the reviewed literature revealed that leaves are the most studied part of the plant and are the main pineapple production waste, followed by fruit peels and crown leaves. Nanocellulose extractions have been reported in smaller numbers for pomace [47], stem [39], pulp, and core [41]. However, the last four sources still offer considerable potential for exploration.

Although a systematic comparison of extraction cost, scalability, environmental impact, and surface chemistry would be ideal, such categorization is currently limited by the lack of quantitative information reported in the literature. Most studies do not provide cost estimates, energy demand, reagent recovery, or life-cycle data, and extraction conditions vary widely across reports. However, general trends can be established: sulfuric acid hydrolysis produces CNCs with sulfate ester groups but requires high acid consumption and generates effluents; hydrochloric acid hydrolysis yields sulfate-free CNCs with higher crystallinity but lower colloidal stability; APS introduces surface carboxyl groups and is described in the literature as a milder route that avoids the use of strong mineral acids, although it involves longer reaction times; TEMPO-mediated oxidation enables efficient fibrillation relative to purely mechanical disintegration methods, as commonly reported in the nanocellulose literature.

4.2. General Applications of Pineapple Nanocellulose

The main applications reported for pineapple nanocellulose are in the field of nanocomposites. The following section will develop this area in detail. In general terms, pineapple-derived nanocellulose has been combined with natural polymers, such as starch [70,79,82,94], chitosan–starch blends [95], alginate [81], gellan gum [77,86], whey protein isolate (WPI) [96,97], gelatin [14], carrageenan with starch [98], carboxymethyl cellulose (CMC) [99], and dissolved pineapple cellulose [75].

Nanocellulose has also been used with biodegradable polymers such as polyvinyl alcohol (PVA) [21,76,100], PVA loaded with curcumin for antimicrobial films [101], PVA blended with whey protein isolate [102], PVA–chitosan [90], and poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) [13]. Another biodegradable polymer used is polylactic acid (PLA) [20]; additionally, a cinnamate-functionalized CNC with PLA for UV absorption [85] and, recently, a gamma-irradiated PLA/PBAT (poly(butylene adipate-co-terephthalate)) blend [103] have also been reported. Synthetic matrices have also been studied, such as polypropylene (PP) [61], polymethyl methacrylate (PMMA) [104], polystyrene (PS) [105], and polyurethane (PU) [54]. Nanocellulose has additionally been combined into natural rubber (NR) [84] and epoxy resins to develop nanocomposite coatings [106].

Several authors have recently explored the development of pineapple nanocellulose-based materials for environmental applications. For example, Nguyen, Phan-Huynh, Le Anh, Van Hong Thien, Hara, and Van-Pham [67] developed graphene oxide composites for ciprofloxacin adsorption; materials for arsenate remediation have also been developed [83], as well as a silylated nanocellulose composite material with polyurethane for rhodamine B dye removal [107]. More recently, cellulose nanocrystals embedded with Ag/Ag₂O/ZnO/CNCs nanocomposites were used to remove waterborne pathogens in wastewater [108].

A related green initiative is the development of nanopapers with promising optical and mechanical properties suitable for food packaging [10,47]. Ionic liquids have also been used to produce nanopapers [68]. Recently, CNC-reinforced gelatin-based nanocomposites were spray-coated onto tissue paper, demonstrating good mechanical characteristics and air permeability [109].

Other functional uses include the incorporation of pineapple micro-/nanocellulose in wood polyvinyl acetate and urea-formaldehyde adhesives [39], which are epoxy nanocomposite coatings for corrosion protection of metal [106]. Moreover, graphitized nanocellulose has been applied in electronic and functional materials for UV photodetectors [110] and in electromagnetic shielding materials [72] are also mentioned.

A growing area is the use of nanocellulose as a stabilizer for Pickering emulsions [41,111]. In this area, Dai et al. [112] reported the complexation of cellulose nanocrystals with tannic acid; also, the stability and bioaccessibility of biomolecules have been improved by encapsulation using pineapple nanocellulose Pickering emulsions. Tang and Huang [113] incorporated curcumin in a (−)-epigallocatechin-3-gallate using this approach to increase the bioactivity. Similarly, ginger essential oil [60] and sunflower oil [56] have been emulsified using pineapple nanocellulose Pickering emulsions; also, biofoam manufacturing has been prepared using Pickering emulsions [114].

Biomedical applications have emerged as a growing field for pineapple nanocellulose. Polyurethane nanocomposites have been developed for heart valves and vascular grafts [54], drug-delivery systems [81], and a creatinine-adsorbent material for potential hemoperfusion applications [73]. Furthermore, pH/magnetic sensitive hydrogels for controlled release have been reported [22] and gels loaded with ampicillin for the treatment of skin infections [64]. Beyond these applications, cytotoxicity and molecular docking studies of CNC have been reported [87], offering relevant information to evaluate its potential for advanced biomaterials development.

4.3. Nanocomposites with Pineapple Nanocellulose

In this section, nanocomposites based on pineapple nanocellulose are discussed in more detail, classified by type of matrix. Nanocellulose (CNCs and CNFs) as reinforcements for polymer composites has drawn attention due to their biocompatibility, biodegradability, low density, low cost, renewability, low toxicity, stiffness, optical transparency, and high mechanical strength. CNCs are more crystalline and rigid, which improves the strength and barrier properties of composite materials [76]. CNFs, on the other hand, are more flexible and form networks, allowing the formation of percolation networks with polymer matrices, which improves the mechanical, thermal, and barrier properties [29]. A percolation network describes a continuous, interconnected structure formed by nanofibers once a critical filler concentration is reached, enabling efficient stress transfer within the polymer matrix [63,70].

Most studies on pineapple nanocellulose composites focus on biodegradable, bio-based systems, including biopolymers of both plant and microbial origin, such as starch (and blends) [78], followed by PVA (and blends) [76] and chitosan (and blends) [95]. Also PLA [85], PHBV [13], PBAT [103], gelatin [14], WPI [102], alginate [81], gellan gum [86], CMC [99], and synthetic polymers (PU [54], PMMA [104], PP [61], PS [105], and epoxy [106]) are less frequently reported. Recently, several studies have developed materials using cellulose as the matrix, incorporating fillers ranging from pineapple nanocellulose [75] to MXenes [72], and nanoparticles [83,108] into the cellulosic matrix to create active materials with targeted applications. Each of them is explained in detail below.

4.3.1. Starch

A widely explored matrix in nanocomposite materials with pineapple-based nanocellulose is starch, a plant storage polysaccharide composed of amylose and amylopectin. Because of its biodegradability, it is an interesting material for film production. However, due to its poor mechanical properties, limited barrier performance, and high hygroscopicity [115], there have been motivated efforts to improve these properties by incorporating cellulose nanocrystals and nanofibers.

Balakrishnan, Gopi, MS, and Thomas [79] reported the use of CNFs and CNCs (from leaves, acid hydrolysis with oxalic acid in an autoclave, and H₂SO₄ hydrolysis) to reinforce potato starch films, using 1% and 3 wt.% loadings (relative to starch) with 30 wt.% glycerol. In all cases, nanocellulose acts as a reinforcing material, achieving a higher storage modulus (E′) than neat starch film. When comparing the two types of nanocellulose, the highest reinforcing efficiency was 47.01% for CNF 3 wt.% load, attributed to the formation of a stronger network, greater entanglement (physical interlocking of nanofibers or polymer chains, which reduces molecular mobility and contributes to mechanical reinforcement [70,78]), and more effective stress transfer. Reinforcing efficiency refers to the relative improvement in mechanical properties (typically tensile or storage modules) per unit of nanocellulose added and is commonly used to compare CNC and CNF performance in polymer matrices [63]. CNCs are stiffer than CNFs, which does not allow the formation of percolation networks at low reinforcement loads. This is one of the few studies comparing both CNFs and CNCs from the same source and for the same application, providing relevant information on the differences between the two nanomaterials for nanocomposite materials production [78].

In a related work, starch–CNF films showed that loads greater than 3 wt.% cause strong aggregation. They also demonstrated improved barrier properties, lower swelling, and evidenced polymer confinement within the CNF network. This is one of the few studies quantifying entanglement, reinforcement efficiency, diffusion kinetics, and constrained polymer regions in TPS–CNF nanocomposites from pineapple. Constrained polymer regions are portions of the polymer matrix whose mobility is restricted due to strong interactions with nanocellulose surfaces, influencing mechanical and barrier behavior [70]. Using the same formulation, it was reported that composite films from pineapple leaves are UV resistant. This is a beneficial property to protect food from UV-induced degradation. A load of 3% CNF gave the highest contact angle, which contributed to increasing hydrophobicity. The addition of CNF also improves thermal stability when compared to starch alone [79].

Mahardika, Abral, Kasim, Arief, Hafizulhaq, and Asrofi [82] developed starch composite films using Bengkoang starch with CNF (from leaves, HCl hydrolysis) with 0.5 to 2 wt.% CNF. Crystallinity increased, reaching a maximum value for the films with 2 wt.% CNF load; moisture absorption and water vapor permeability (WVP) decreased significantly. In addition, tensile strength (TS) and tensile modulus (E) were improved. In contrast, elongation at break (EB) was reduced at the maximum nanofiber loading, making the film more brittle by CNF addition. This behavior is attributed to the reduction in biopolymer chain mobility and the good interfacial bonding between the nanofibers and the matrix.

The incorporation of an antimicrobial agent (rosemary essential oil (RO)) on bitter cassava starch films reinforced with 15 wt.% CNC (from leaves, with H₂SO₄ hydrolysis) has also been reported by our group [94]. CNC addition increased mechanical strength (TS and E); however, these values decreased drastically with the addition of RO. In contrast, EB decreased with CNC addition and then increased with RO addition, due to the plasticizing effect of RO. Moreover, water vapor transmission rate (WVTR) and WVP were reduced by the CNC addition, reaching values of 2.07 g/hm² and 0.121 gmm/hm² kPa. For films loaded with RO, the antibacterial activity was effective against E. coli bacteria (0.4 and 0.5% RO), S. Aureus (0.5% RO), and caused a decrease in A. niger sporulation (0.5% RO) [94].

These studies reveal the potential of using starch matrices reinforced with pineapple nanocellulose (nanocrystals and nanofibers) to develop biodegradable packaging films with improved mechanical properties, improved barrier properties, UV resistance, and antimicrobial properties (when blended with bioactive additives). It is important to consider the effect of reinforcing agent loading and the plasticizing effect of adding glycerol or essential oils [70,78,79,82,94].

4.3.2. Chitosan

Chitosan is a polymer derived from chemical deacetylation of chitin extracted from the exoskeleton of crustaceans. This polysaccharide is a biodegradable, biocompatible, and non-toxic material. Chitosan has a regenerative effect, it is hemostatic, antibacterial, and anti-inflammatory, which makes it attractive for both biomedical and food packaging applications [116,117]. But as with starch, chitosan has limited mechanical properties, which can be improved by adding nanoparticles such as nanocellulose [95].

Chitosan has been studied in combination with starch (50:50) to produce films with CNC loads from 0.3 to 1.0 wt.% (Crown leaves, H₂SO₄ acid hydrolysis). The highest storage modulus (E′) of 4709 MPa was achieved for the material with 0.7 wt.% CNC load. For the sample with 1.0 wt.% CNC, the increase in the storage module was only 26%. This demonstrates that the addition of reinforcement increases the material’s stiffness by 90% compared to the unreinforced chitosan: starch matrix, in this case with a low reinforcement load. This enhancement was attributed to strong adhesion between CNCs and the polysaccharide matrix, also evidenced by TEM microscopy analysis. An increase in glass transition temperature (Tg) was observed due to the physical interaction between the reinforcement and the matrix, which restricts polymer chain mobilization [95].

The combination of biopolymers such as starch and chitosan reinforced with pineapple nanocellulose demonstrates how the combination of these polysaccharides can generate materials with improved properties for the production of fully bio-based nanocomposites.

4.3.3. Polyvinyl Alcohol (PVA)

Polyvinyl alcohol (PVA) is a water-soluble polymer that has been used in many areas due to its physical and biological properties. This polymer is biocompatible, biodegradable, non-toxic, and has the ability to form films. Due to its hydrophilic properties, it can be easily mixed with natural polymers [118]. Despite these positive properties, PVA has water affinity, and the mechanical properties can be compromised to be used in packaging applications [76].

Films have been obtained by using CNC-reinforced PVA (peels and H₂SO₄ hydrolysis), with tannic acid (TA) [76]. Tannic acid is a natural polyphenol that can be used as a natural crosslinker because it has a glucose nucleus esterified with gallic acid units, which allows the formation of hydrogen bonds [119]. The incorporation of CNC and TA improved the thermal stability and tensile strength increased suggesting a synergistic effect between CNC reinforcement and TA crosslinking; however, elongation at break varied inversely due to the stiffness of the material. At higher CNC and TA contents, water adsorption and water solubility decrease, attributed to the formation of hydrogen bonds between the filler, the matrix, and the crosslinker. While the mechanical properties and water affinity were improved, the transparency of the films was moderately reduced, yet they remained visually transparent. These materials also demonstrate resistance to ultraviolet radiation and antibacterial activity against Staphylococcus aureus [76].

On the other hand, films have also been generated for PVA as a matrix with the incorporation of CNF (leaves and H₂SO₄ hydrolysis). The addition of the nanofiller increased the density and thickness of the films and decreased water binding due to the formation of hydrogen bonds between CNF and PVA; however, its water affinity can be modulated by adding glycerol. The crystallinity index (CI) increased to a maximum of 44.5% when adding 50 wt.% CNF, without the presence of glycerol, but decreased when adding glycerol. This behavior can be explained in terms of the plasticizing effect of glycerol (1 wt.%). Additionally, there was a significant decrease in transparency when adding CNF, which generates more opaque materials [21].

Mahardika, Masruchin, Amelia, Ilyas, Septevani, Syafri, Hastuti, Karina, Khan, and Jeon [100] reported the production of PVA films with CNF (leaves, HCl hydrolysis + mechanical processing). The optimal formulation was obtained with a 4 wt.% CNF load, resulting in increased TS, CI, and maximum degradation temperature. FE-SEM analysis was performed to demonstrate the compatibility and dispersion of the nanofibers in the matrix in the absence of the plasticizing agent. Nevertheless, it is well known that these agents are relevant for the melting temperature, fluidity, and thermal stability, especially if extrusion and injection processes are applied, but their use must be controlled, since they can generate phase separation.

The controlled release of curcumin based on PVA films using CNC (leaves and H₂SO₄ hydrolysis) has been reported. In this study, curcumin was incorporated into the PVA matrix in quantities of 50, 75, and 100 µg, and the characterization of the obtained material focused on the evaluation of controlled release and antimicrobial activity. The release profile was evaluated over a 48 h period, and curcumin release was monitored. A plateau of curcumin release was obtained after 48 h, with release rates between 90.81 and 94.96%. The cellulose nanocrystals function as a diffusion barrier, slowing the burst release action of curcumin. The films demonstrated to have antibacterial activity against B. subtilis, Streptococcus sp., and E. coli, confirming the potential of this system for bioactive agents administration [101].

CNC in low concentrations (<1 wt.%) (leaves and H₂SO₄ hydrolysis) stabilized with PEG (increase in zeta potential) has been added to PVA/chitosan film composites. The obtained films present greater thermal stability (60%) and TS, attributed to the formation of interactions between CNC and PVA, as well as electrostatic interactions between CNC and chitosan, which strengthen the material network. Likewise, it shows greater thermal stability (60%) and increased waterproofing properties [90].

4.3.4. Whey Protein Isolate (WPI)

The production of composite films from whey protein isolate (WPI) blended with PVA and reinforced with cellulose nanocrystals (CNCs) extracted from pineapple crown leaves by H₂SO₄ hydrolysis has been recently reported [102]. Whey, a by-product of the dairy industry mainly composed of β-lactoglobulin, α-lactoglobulin, immunoglobulins, serum albumin, and lactoferrin [120], exhibits good film-forming ability, biocompatibility, and high affinity with hydrophilic polymers; for these reasons, whey is an interesting candidate to develop biodegradable composites [97].

Composite films based on whey protein isolate (WPI) and polyvinyl alcohol (PVA), reinforced with cellulose nanocrystals (CNCs) extracted from pineapple crown leaves via H₂SO₄ hydrolysis, have been developed to enhance mechanical and barrier properties [102]. WPI, a dairy by-product with good film-forming and biocompatible characteristics, was combined with PVA due to its hydrophilicity and flexibility. Films prepared with 3.5 wt.% CNC and varying WPI/PVA ratios showed that the 80/20 formulation achieved the highest tensile strength, with tensile strength (TS) and elongation at break (EB) of 8.489 MPa and 25.584%, respectively—values comparable to LDPE and superior to pure WPI films. The improvement arises from hydrogen bonding among WPI, PVA, and CNC, which diminishes the rigidity caused by protein denaturation. Increasing WPI content lowered transparency but improved crystallinity, whereas adding CNC and PVA reduced solubility and water vapor permeability. The 70/30 formulation exhibited the lowest solubility (24.507%) and highest thermal stability (329.78 °C), due to stronger intermolecular interactions, which limit water mobility and increase the compactness of the polymer network [102].

Previous work using CNC-reinforced WPI films (1–10 wt.% CNC) exhibited decreased transparency, attributed to light scattering caused by CNCs, as well as lower water solubility and absorption. The optimal TS (5.060 MPa) occurred at 7 wt.% CNC, indicating good compatibility between the matrix and reinforcement. Beyond this concentration (10 wt.%), TS declined because of CNC agglomeration. Although EB decreased slightly with higher CNC content, this was expected from the increase in stiffness [96].

Subsequently, Fitriani, Aprilia, Bilad, Arahman, Usman, Huda, and Kobun [97] optimized the formulation using response surface methodology (RSM), identifying that CNC and glycerol concentrations were the primary factors affecting thickness, TS, and EB. The optimal formulation contained 3.5 wt.% CNC and 4 wt.% glycerol, producing a 0.13 mm film with a TS of 7.16 MPa, EB of 39.10%, solubility of 27.15%, and WVP of 2.17 × 10⁻¹¹ g/msPa. The addition of CNC raised crystallinity to 81.14%, in contrast to the 76.49% of the glycerol-only film, due to improved intermolecular interactions that create a more compact and water-resistant structure [97].

These studies illustrate that CNCs obtained from pineapple crown leaves effectively reinforce WPI-based matrices—both alone and in WPI/PVA matrices—improving their mechanical, barrier, and thermal properties [96,97,102].

4.3.5. Bio-Based Thermoplastic Matrices

Recent works have explored the incorporation of pineapple-derived nanocellulose into bio-based thermoplastic matrices such as polyhydroxybutyrate-co-valerate (PHBV) and polylactic acid (PLA), both of which are promising candidates for sustainable packaging materials [121,122]. PHBV, a microbial copolyester valued for its flexibility and ease of processing, has been reinforced with CNC obtained from crown leaves by acid hydrolysis. Films containing 1–5 wt.% CNC showed increased crystallinity (up to 44% at 1 wt.%) and improved thermal behavior, although higher contents led to agglomeration and greater water vapor transmission, likely due to limited dispersion of the filler [13].

PLA is one of the most used bioplastics, but its brittleness and poor UV resistance restrict its applications. Pornbencha, Sringam, Piyanirund, Seubsai, Prapainainar, Niumnuy, Roddecha, and Dittanet [85] developed PLA composites reinforced with cinnamate-functionalized CNC (CNC–Cin) to improve both mechanical and UV-shielding properties. The modified nanocellulose dispersed more uniformly in the matrix, giving clearer films and higher tensile strength, with optimal values at 3 wt.% CNC–Cin. These nanocomposites also showed lower water vapor and oxygen permeability—reductions of around 50%—and a dual melting behavior related to more complex crystalline structures [85]. In a different approach, Shih, Chou, Chang, Lian, and Chen [20] used TEMPO-oxidized cellulose nanofibers (CNFs) modified by sol–gel (SGS–CNF) and methyl methacrylate polymerization (MMA–CNF). The surface treatment improved hydrophobicity and fiber–matrix compatibility, resulting in higher tensile (up to 61.1 MPa) and impact strength (26.7 J/m) compared to unmodified CNF composites. These effects were attributed to better dispersion and more efficient stress transfer. Da Costa, Dufresne, and Parra [103] combined PLA and PBAT in equal proportions, reinforced with CNF (1–3 wt.%) from pineapple leaves processed by ball milling. To improve compatibility, the PLA phase was irradiated with gamma doses ranging from 80 and 150 kGy. At 1 wt.% CNF, the films exhibited good dispersion and enhanced mechanical performance (25.84 MPa; 3.49 GPa), while higher radiation or filler contents reduced stability due to polymer degradation and aggregation. The CNFs served as nucleating agents, promoting crystallization and preserving the balance between flexibility and stiffness [103].

In summary, these investigations emphasize that moderate nanocellulose contents and suitable surface modifications are necessary to achieve good dispersion and interfacial adhesion. CNC and CNF sourced from pineapple works as reinforcements, increasing crystallinity, strength, and barrier performance in materials based on PHBV, PLA, and PLA/PBAT blends [13,20,85,103].

4.3.6. Other Proteins (Gelatin)

Other matrices that are part of the group of natural biopolymers include protein materials, such as gelatin and whey protein isolate (WPI, as previously described), and polysaccharides, such as alginate, gellan gum, and carboxymethyl cellulose (CMC), besides the already analyzed starch and chitosan. These materials have their high hydrophilicity, biodegradability, and biocompatibility in common, properties that make them attractive for applications such as biodegradable packaging, coatings, and biomaterials [123,124,125]. All of these have been used to develop composite materials with pineapple nanocellulose.

Gelatin is an animal protein obtained by partial hydrolysis of collagen, a fibrous structural protein found in connective tissue. It has good film-forming capacity, but also a high affinity for moisture [123]; however, gelatin-based films have poor mechanical properties and thermal stability [14]. The development of gelatin films reinforced with CNC (from leaves and H₂SO₄ hydrolysis) and banana leaf extract (BL) to enhance antibacterial activity has been reported. Morphological analysis evidenced good miscibility of the components. Thermal stability increased with increasing reinforcement loading; the highest value was reached for a 5 wt.% loading and BL. Also, the thickness of the films increased with increasing load, on the contrary, the swelling degree decreased with increasing nanofiber loading. The mechanical properties increased with the addition of CNCs, reaching the highest TS and EB values of 82.23 MPa and 16%, respectively, for the formulation with 5 wt.% CNC load and BL. These improvements are attributed to the formation of hydrogen bonds between the nanofibers and the gelatin matrix. This also impacted reducing WVP, reaching a minimum value of 0.74 × 10⁻⁷ g mm/m²dkPa, and also reduced oil permeability. Finally, antibacterial activity was tested against Escherichia coli and Staphylococcus aureus [14].

Later, the same research group used a similar gelatin system reinforced with CNC (from leaves and H₂SO₄ hydrolysis) as a tissue paper coating. Extracts from different sources were also evaluated, including banana leaf (BL), mantharai leaf (ML), and lotus leaf (LL). For this study, loadings of 1 to 5 wt.% of CNC were used, generating coatings with homogeneous morphology and higher viscosity than gelatin alone, as well as better interaction with the surface of the paper fibers. The addition of reinforcement significantly improved the mechanical properties, reaching the maximum TS of 68.37 MPa, as well as a higher grammage of 32.36 g/m² for the gelatin coating with 5 wt.% loading and LL, demonstrating that it is the material with the highest rigidity. In contrast, increasing the CNC load decreased EB, reaching the lowest value for the formulation with 5 wt.% and ML. On the other hand, the system with the highest EB was presented by the coating with 3 wt.% CNC load and BL. The barrier properties also improved significantly, particularly for the LL sample, reaching a WVP value of 2.09 × 10⁻¹⁰ g m/m² Pa s at 5 wt.% loading and a contact angle of 70.2°. The same formulation showed the best antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida glabrata, attributed to the presence of phenolic compounds and flavonoids from the lotus extract. This system presents the best balance of properties, showing its potential to generate a bio-based coating for tissue paper [109].

Gelatin is a promising matrix for producing biodegradable composite materials, whether used as film-forming or as coatings for paper. The addition of pineapple nanocellulose improves mechanical and thermal stability and barrier properties, and the addition of natural extracts provides antimicrobial properties, expanding its potential use in food packaging [14,109].

4.3.7. Polysaccharides

Different studies have evaluated the incorporation of pineapple-derived nanocellulose into polysaccharide matrices such as gellan gum, carrageenan, alginate, and carboxymethyl cellulose (CMC), underlining its potential to enhance the mechanical, thermal, and barrier properties of biodegradable materials [123,126]. Dai, Ou, Huang, and Huang [77] prepared gellan gum films reinforced with CNC from pineapple peel, where the nanocellulose acted as a nucleating agent, increasing crystallinity and thermal stability up to 244 °C. The best mechanical response was obtained with 4 wt.% CNC (TS = 3.32 MPa), while higher contents reduced strength due to aggregation. Sripahco, Khruengsai, and Pripdeevech [86] also worked with gellan gum reinforced with 5 wt.% CNC and A. graveolens essential oil (2–4 wt.%). Their films showed higher tensile strength (10.36 MPa), lower water vapor permeability, and antifungal activity against Aspergillus niger, showing potential for active packaging. Dmitrenko, Kuzminova, Cherian, Joshy, Pasquini, John, Hato, Thomas, and Penkova [98] produced carrageenan–starch composites reinforced with CNF (from leaves and oxalic acid hydrolysis) and functional additives such as sesame oil and aloe vera. The optimal formulation (1.5:1 carrageenan/starch ratio, 2.5 wt.% CNF) achieved a tensile strength of 5.64 MPa, low permeability to water and oil, and thermal stability up to 200 °C, suitable for packaging fatty foods [98]. In another study, a hybrid alginate–CNC system crosslinked with Ca²⁺ and coated with chitosan showed the formation of micro-/nanoparticles capable of encapsulating and gradually releasing rutin over 240 min. Particle size and surface charge were influenced by CNC and alginate concentration, while chitosan coating improved stability [81].

CMC-based composites have also demonstrated favorable performance. CNC from pineapple leaves used at high loadings (15–45 wt.%) significantly increased the tensile strength and flexibility of CMC films, with the best balance at 30 wt.% CNC (TS = 5.06 MPa; EB ≈ 220%), and reduced water vapor transmission due to greater crystallinity [99]. Similarly, Dai, Zhang, Ma, Zhou, Yu, Guo, Zhang, and Huang [22] developed PVA/CMC hydrogels containing ionic-liquid-derived nanocellulose and Fe₃O₄ nanoparticles for drug delivery. The addition of nanocellulose improved thermal stability (303 °C) and porosity, while the magnetic component enabled controlled release of naringin with 33% entrapment efficiency and sustained delivery over 11 h [22]. These works show that pineapple-derived CNCs and CNFs provide effective reinforcement and added functionality in diverse polysaccharide matrices. The improvements depend on the polymer–nanocellulose interaction, filler dispersion, and loading level, which together define the balance between mechanical strength, flexibility, barrier properties, and additional bioactive or controlled-release functions [22,77,81,86,98,99].

4.3.8. Synthetic Polymers

Several synthetic polymers have been combined with pineapple-derived nanocellulose, such as polyurethanes (PUs), polypropylene (PP), polystyrene (PS), and polymethylmethacrylate (PMMA) to develop high-performance composite materials. Polyurethanes are notable for their versatility and tunable mechanical properties, derived from the balance between hard and soft segments [127]. Cherian, Leão, de Souza, Costa, de Olyveira, Kottaisamy, Nagarajan, and Thomas [54] prepared PU/CNF composites using CNF from leaves (oxalic acid hydrolysis) and a polyurethane synthesized from MDI, PCL-diol, and 1,4-butanediol. Films containing 5 wt.% CNF exhibited excellent strength (52.5 MPa) and modulus (992 MPa), suitable for medical implants such as heart valves and vascular grafts. These composites showed high fatigue resistance and elasticity, maintaining mechanical integrity under long-term use [54]. Chandrashekar, Vargheese, Vijayan, Gopi, and Prabhu [107] developed silylated CNC-based PU materials for the adsorption of Rhodamine B dye. The silylation improved dispersion and thermal stability (312 °C), while 2 wt.% loading achieved the highest adsorption capacity (51.55 mg/g), evidencing potential for wastewater treatment. Both studies demonstrated the adaptability of bio-based PUs reinforced with pineapple nanocellulose for biomedical and environmental applications [54,107].

Other thermoplastic polymers, such as polypropylene (PP) [61], polystyrene (PS) [105], rubber [84], epoxy resins [106], and urea-formaldehyde resins [39], have also been reinforced with CNCs or CNFs to overcome their inherent hydrophobicity. Agarwal, Mohanty, and Nayak [61] produced PP/CNC composites (from peels and HCl hydrolysis) via melt blending and injection molding, using maleic anhydride-modified PP (MAPP) as a compatibilizer. With 3 wt.% CNC, the material reached 38.75 MPa tensile strength and improved modulus, while impact strength also increased due to uniform CNC dispersion [61]. PS-based systems used CNF modified by styrene and phenyltriethoxysilane polymerization to enhance compatibility. The sol–gel-modified nanofibers improved heat distortion temperature (93.8 °C) and tensile strength (31 MPa), while maintaining higher transparency than unmodified CNF composites [105].

Similarly, PMMA composites developed by Shih, Chou, Lian, Hsu, and Chen-Wei [104] with TEMPO-oxidized and MMA-modified CNFs showed better interfacial adhesion, increasing modulus (3.58 GPa) and tensile strength (44.2 MPa) at low loadings (1–3 wt.%). The modified nanofibers increased hydrophobicity and dispersion, maintaining optical transparency and improving impact resistance by about 23% [104]. These studies reveal that surface modification of pineapple nanocellulose is essential to achieve compatibility with hydrophobic matrices such as PU, PP, PS, and PMMA. Proper dispersion of the nanofillers enhances strength, stiffness, and thermal stability, while preserving transparency in PS and PMMA-based systems. The versatility of these composites supports their potential use in biomedical devices, structural applications, and functional materials for packaging and environmental remediation [39,54,61,84,104,105,106,107].

4.3.9. Natural Rubber (NR)

Another matrix that has been used to obtain pineapple nanocellulose nanocomposites is natural rubber (NR), a natural elastomer obtained from the latex of the Hevea brasiliensis tree. The repeating unit is cis-1,4-isoprene, with small amounts of lipids and proteins. Elastomers are characterized by their high elasticity and ability to deform significantly and recover their shape. NR is characterized by its mechanical strength and excellent fatigue resistance [128]. Chawalitsakunchai, Dittanet, Loykulnant, Sae-oui, Tanpichai, Seubsai, and Prapainainar [84] studied the preparation of NR composites using CNC (from leaves and H₂SO₄ hydrolysis), applying sulfur vulcanization (SV) and electron beam irradiation (EB) processes. Vulcanization is a process where crosslinking of the rubber chains is formed, which transforms soft and sticky natural rubber into a strong, elastic and resistant material [128]. For the preparation of nanocomposites by SV, the NR is mixed with the vulcanizing agents and then with the reinforcement (2.5, 5, 7.5, and 10 parts per hundred parts of rubber: phr), followed by stirring and thermal drying. In the EB method, the NR is subjected to irradiation (200 kGy), mixed with the reinforcement, and then heat is applied to dry, without the use of chemical additives [84].

The materials showed a homogeneous distribution at 2.5 phr, but at higher loads, agglomerates were observed. The maximum TS was obtained for the SV material at a load of 2.5 phr (19.4 MPa), which means an increase of 11.5% compared to the unreinforced NR; for the vulcanized by EB, the maximum value was 15.8 MPa, which implies a 17% improvement. The modulus increased with the reinforcement content, which shows the increase in the stiffness of the materials when reinforced, and the EB decreased for the same reason. Vulcanization with sulfur generated denser networks with greater mechanical resistance than vulcanization by EB. For sulfur-vulcanized materials, these properties are attributed to the interaction of cellulose with the double bond in the NR structure. On the other hand, radiation can cause chain scission of the polymer chain, which affects the mechanical properties. Finally, toluene absorption tests demonstrated this difference, as the SV nanocomposite materials showed a lower swelling ratio (4.86) than for the irradiated material (6.18) [84].

4.3.10. Epoxy and Urea-Formaldehyde Resins

Thermosetting polymers such as epoxy and urea–formaldehyde (UF) resins have also been combined with pineapple-derived nanocellulose to improve mechanical and functional performance [129]. Epoxy resins, known for their rigidity and thermal resistance, were used by Grumo, Lubguban, Capangpangan, Yabuki, and Alguno [106] to develop nanocellulose-based coatings (from pineapple leaves and H₂SO₄ hydrolysis) for mild steel corrosion protection. Coatings containing 0.5–2 wt.% nanocellulose significantly reduced corrosion current density and shifted corrosion potential to less negative values, achieving protection efficiencies between 88.8% and 96.2% at 2 wt.% loading, with a corrosion rate of only 1.87 × 10⁻⁴ mm year⁻¹. The improved performance was attributed to a “maze effect” created by the nanocellulose, which sealed microdefects and limited diffusion of corrosive agents (H₂O, O₂, Cl⁻) [106]. Rigg-Aguilar, Moya, Oporto-Velásquez, Vega-Baudrit, Starbird, Puente-Urbina, Méndez, Potosme, and Esquivel [39] incorporated micro-/nanocellulose (from pineapple stem and H₂SO₄ hydrolysis) into UF and polyvinyl acetate (PVAc) adhesives—materials commonly used in wood applications. Small additions (0.5–1 wt.%) increased the thermal stability of both adhesives and enhanced their shear strength. In PVAc, strength improved by 35% for Vochysia ferruginea, while in UF adhesives, the greatest adhesion increase (31%) occurred for Cordia alliodora. These improvements were linked to hydrogen bonding between the MNC and polymer chains, which strengthened the adhesive network [39]. These studies show that pineapple-derived nanocellulose can effectively enhance thermosetting resins and adhesives, improving corrosion resistance, thermal stability, and interfacial bonding. The results demonstrate its potential use in coatings, structural composites, and wood-based applications [39,106].

4.4. Self-Reinforced and Cellulose-Based Nanocomposites

In addition to polymer-based systems, recent studies have explored self-reinforced [75] and hybrid cellulose nanocomposites in which pineapple-derived nanocellulose serves as the main structural component, often combined with inorganic phases such as MXene [72] or metallic nanoparticles [83,108]. These materials extend the application of pineapple nanocellulose beyond packaging to multifunctional composites with potential uses in electromagnetic shielding, water purification, and high-performance structural systems. Qian, Kuang, Zhang, Wei, Liu, Wang, and Chen [72] developed composite films using CNF (from leaves, carboxymethylation, and high-pressure homogenization) combined with delaminated titanium carbide (Ti₃C₂T_x) MXene to produce electromagnetic interference (EMI) shielding materials. The CNF/MXene suspensions were mixed and vacuum-filtered to form flexible films with varying CNF contents (20–80 wt.%). Electron microscopy revealed an ordered lamellar “brick-and-mortar” structure similar to nacre, in which CNFs acted as flexible linkers between MXene sheets. Increasing CNF content enhanced both strength and toughness, reaching 192.8 MPa and 21.1 MJ m⁻³ at 80 wt.% CNF. The 50 wt.% CNF film exhibited the best balance of conductivity (specific shielding effectiveness = 6541 dB cm² g⁻¹ at 12.4 GHz) and mechanical strength (159.6 MPa), remaining flexible enough to support a 500 g load without damage. These improvements were attributed to synergistic interactions between MXene and CNF via hydrogen bonding and van der Waals forces. The films effectively blocked wireless signal transmission, showing their potential to produce lightweight, bio-based EMI shielding materials [72].

Zhu, Cheng, and Han [75] reported the fabrication of an all-cellulose nanocomposite using pineapple peel cellulose as both matrix and reinforcement. The cellulose was dissolved in BmimCl/DMSO, combined with carnauba wax for hydrophobicity and CNF (5–20 wt.%), and regenerated by water coagulation. The resulting films exhibited hydrophobic surfaces (contact angle > 100°) and strong mechanical performance (TS = 53.8–61.4 MPa; modulus = 2.8–4.0 GPa), though transparency decreased with wax addition. Barrier properties improved markedly, with oxygen transmission dropping to zero at 20 wt.% CNF. The films blocked UV light (200–400 nm), showed slight gains in thermal stability, and degraded completely in soil after 30 days. When used to package cherry tomatoes, the film with 15 wt.% CNF limited weight loss to 4.1%, outperforming polyethylene controls, confirming its promise as biodegradable food packaging [75].

Recent works have also been explored for environmental applications. Deewan, Tanboonchuy, Khamdahsag, and Yan [83] prepared CNC/iron nanocomposites (from crown leaves, HCl hydrolysis) for arsenate (As⁵⁺) removal from water. Using mango-peel extract as a green reducing agent, nano-zero-valent iron (G-NZVI) particles were uniformly deposited on the CNC surface, increasing specific surface area from 1.7 to 28 m² g⁻¹. The composite exhibited high adsorption capacity (5488 mg g⁻¹) and followed Langmuir and pseudo-second-order kinetics, with CNC contributing to the formation of active adsorption sites [83]. Similarly, Aththanayaka, Thiripuranathar, and Ekanayake [108] produced CNC-based nanocomposites incorporating Ag/Ag₂O/ZnO nanoparticles for microbial adsorption and water disinfection. The nanoparticles were synthesized in situ using aqueous pineapple crown extract as a reducing agent, generating stable nanometric particles well-dispersed on the CNC matrix. The hybrid nanocomposite achieved 98.9% bacterial reduction (including E. coli, S. aureus, and S. typhi) and maintained efficiency over multiple filtration cycles (up to 1200 mL). The CNC provided structural stability and enhanced nanoparticle dispersion, yielding an effective antimicrobial and adsorptive material for wastewater treatment [108].

The self-reinforced and cellulose-based nanocomposites demonstrate that pineapple-derived nanocellulose can serve not only as reinforcement but also as the main matrix component, supporting multifunctional applications ranging from electromagnetic shielding and packaging to water purification and antimicrobial systems [72,75,83,108].

5. Quantitative Benchmarking Across Systems

According to the literature review, a benchmarking analysis was performed to find extraction–processing–compatibilization combinations associated with improved performance of nanocomposites made with pineapple-derived nanocellulose. In the analysis, materials where nanocellulose functions as reinforcement and all sources of pineapple waste (leaves, crown, stem, peel, and bagasse) were reported. The analysis is presented in Table 2, where the main results are classified according to the type of matrix used, indicating the predominant processing methods applied, loading range of nanocellulose, compatibilization or treatment strategies, and property trends.

These include elastic modulus (E), storage modulus (E′), tensile strength (TS), elongation at break (EB), maximum elongation (ME), impact strength (IS), shear strength (SS), toughness (TU), reinforcing efficiency (RE), water vapor permeability (WVP), water vapor transmission rate (WVTR), oxygen transmission rate (OTR), oil permeability (OP), water absorption (WA), moisture absorption (MA), moisture content (MC), swelling (SW), solubility (SOL), contact angle (CA), water contact angle (WCA), diffusion coefficient (DC), glass transition temperature (Tg), melting temperature (Tm), crystallization temperature (Tc), onset temperature (Tonset), maximum degradation temperature (Tmax), heat distortion temperature (HDT), transparency (TP), UV-blocking (UVB), crystallinity index (CI), density (d), thickness (Th), and antimicrobial activity against the listed microorganisms (Antimic).

Table 2 summarizes property changes reported across different studies and polymer matrices. Because the included systems involve diverse polymers, processing routes, and testing standards, the reported values are not intended for direct cross-material comparison. Baseline (unfilled) values are shown whenever the original study reported them under comparable experimental conditions; when no baseline was provided, only the composite value is shown. Property changes are reported in a standardized “baseline → composite” format, and percent improvements are included when available. All nanocellulose loadings are expressed in wt.%. Wide property ranges reflect underlying differences among polymer families, fabrication methods, and measurement protocols rather than variability within a single system.

Table 2. Benchmark of pineapple-derived nanocellulose nanocomposites.

Matrix	NC Type, Pineapple Fraction, and Method	Loading (wt.%) and Additives or Treatment and Process	Properties and Trends *
Starch (potato)	CNF (leaves, acid hydrolysis, oxalic acid in autoclave)	1–4% (optimum 3, relative to starch). Glycerol (30 wt.%, relative to starch). Solution casting.	@ 3%. WVTR: 4.39 → 3.41 g·h−1·m−2 (−22%); SOL: 76.14 → 36.09% (−53%); MA: 16.1 → 11.56% (−28%); DC: 1.59 → 0.087 × 10−4 mm2·s−1 (−95%) RE: 47%; Tonset: ↑; E′ ↑; Tmax ↑; UVB ↑; TP ↔; WCA ↑ [70,78,79]
Starch (bengkoang)	CNF (leaves, HCl hydrolysis, high shear homogenization, ultrasonication)	0.5–2% (optimum 2, relative to starch). Glycerol (20 w/v%, relative to starch), ultrasonication. Solution casting + ultrasonication.	@ 2%. TS: 3.8 → 9.8 MPa (+158%); MA: 20 → 9% (−55%); WVP: 5.6 × 10−11 → 4.5 × 10−11 g·m−1·s−1·Pa−1 (−20%); Tmax: 245 → 310 °C (+27%); CI: 21.71 → 35.17% (+62%); OP: 91.2 → 253.7 AU (+178%, TP: ↓); E: ↑; EB: ↓; [82]
Starch (bitter cassava)	CNC (leaves, H2SO4 hydrolysis)	15% (fixed, relative to starch). Glycerol (20 wt.%). Solution casting.	@ 15%. TS: 1.26 → 1.80 MPa (+43%); E: 4.47 → 11.95 MPa (+167%); EB: 76.77 → 41.75% (−46%); SOL: 6.34 → 4.76% (−25%); WVTR: 2.47 → 2.07 g·h−1·m−2 (−16%); WVP: 4.0 × 10−11 → 3.36 × 10−11 g·m−1·s−1·Pa−1 (−16%); Tmax: 345 → 346 °C (+0.3%); OP: 16.59 → 17.75% (+7%, TP: ↓) [94]
PVA	CNC (peel, H2SO4 hydrolysis)	2–8% (optimum 2%, relative to PVA). Tannic acid (2–8 wt.%, optimum 8%, relative to PVA). Solution casting.	@ 2% + 8% TA. TS: 58.5 → 108.7 MPa (+86%); TP @ 500 nm: 79 → 72% (−9%); EB: ↓; WA: ↓; SOL: ↑ with TA; ↓ with CNC; UVB: ↑; Antimic: S. aureus [77]
	CNF (leaves, ultra-fine grinder)	10–50% (optimum 20–40). Glycerol (1 wt.%). Solution casting.	@ 40%. d: 0.68; MC: 6.03 → 5.62% (−7%); Th: 0.11 → 0.02 mm; Tm: 329.54 → 315.27 °C (−4%); CI: 38.3 → 37.8% (−1.3%); WVTR: ↑; TP: ↓ [21]
	CNF (leaves, high-shear homogenization + ultrasonication)	1–5% (optimum 4, relative to PVA). Solution casting.	@ 4%. TS: 22.5 → 28.9 MPa (+28%); EB: 178.4 → 211.4% (+18.5%); CI: 74.8 → 78.8% (+5%); Tmax: 336.3 → 341.8 °C (+1.6%); TP: >75% all films [100]
PVA/chitosan blend (2:1)	CNC (leaves, H2SO4 hydrolysis)	~0.44% (fixed, relative to total polymer matrix). PEG (2 wt.%). Solution casting.	@ 0.44%. TS: 11.40 → 18.25 MPa (+60%); Tonset: 248 → 274 °C (+11%); SW: 442 → 282% (−36%) [90]
Chitosan/Starch (50:50)	CNC (crown leaves, H2SO4 hydrolysis)	0.3–1.0% (0.7 optimum). Sorbitol (0.5 mL/g starch). Solution casting.	@ 0.7%. E′ (40 °C): 2484 → 4709 MPa (+90%); Tg: 66 → 73 °C (+11%); thermal stability ↔ [95]
WPI	CNC (crown leaves, H2SO4 hydrolysis)	3–7% (optimum 3.5% via RSM). Glycerol (4–8%, 4 wt.% optimum). Solution casting.	@ 3.5% (RSM-optimized). TS: 7.16 MPa; EB: 39.10%; WVP: 2.21× 10−11 → 2.17 × 10−11 g·m−1·s−1·Pa−1 (−2%); SOL: 30.21 → 27.15% (−10%); CI: 74.82 → 81.14% (+8%); TP: ↓ [97]
WPI/PVA (70/30)	CNC (crown leaves, H2SO4 hydrolysis)	3.5% (Fixed). Glycerol (4 wt.%). Solution casting.	@ 3.5%; no baseline reported for 70/30 blend. TS: 7.061 MPa; EB: 68.831%; WVP: 1.765 × 10−11 g·m−1·s−1·Pa−1; SOL: 24.507%; Tonset: 258 °C; Tmax: 330 °C; TP: ↑ vs. WPI; Degradation: 35% weight loss @ 24d. [102]
Gelatin	CNC (leaves, H2SO4 hydrolysis)	1–5% (optimum 5). Glycerol (10% w/v) + banana leaf extract (BL). Solution casting.	@ 5% + BL. TS: 4.71 → 82.23 MPa (+1646%); EB: 2 → 16% (+700%); Thermal stability: ↑; OP: ↓; SW ↓; WVP ↓; Antimic: E. coli, S. aureus, C. perfringens [14]
		1–5% (optimum 5). Glycerol + lotus extract (LE). Tissue paper spray coating.	@ 5% + LE, baseline: uncoated tissue paper. Th: 0.125 → 0.591 mm (+373%); Grammage: 23.48 → 32.36 g/m2 (+38%); d: 0.765 → 0.498 g/cm3 (−35%); WVP: 24.56 × 10−10 → 2.09 × 10−10 g·m−1·s−1·Pa−1 (−91%); WCA: 74.6 → 70.2°; TS: ↑; EB: ↓; Antimic: S. aureus, E. coli, C. glabrata [109]
Carrageenan (+ starch granules)	CNF (leaves, acid hydrolysis, oxalic acid in autoclave)	0.2–0.3% (optimum 0.2). Glycerol (0.6 wt.% + sesame oil + aloe vera gel 3%). Solution casting.	@ 0.2% (Carr:Starch 1.5:1); no baseline reported. TS: 5.64 MPa; ME: 4.62 mm; WVP: 6.4 × 10−10 g·m−1·s−1·Pa−1; OP: 2.0%; SOL: 42%; MA: 29%; Th: 150 μm; d: 1.34 g/cm3; WCA: 71°; Thermal stability: stable to 200 °C [98]
Gellan gum	CNC (peel, H2SO4 hydrolysis)	2–10% (optimum 4, relative to gellan gum). Glycerol 15 wt.% (relative to gellan gum). Solution casting.	@4%. TS: 2.24 → 3.32 MPa (+48.2%); Tonset: 161 → 165 °C (+2.5%); Tmax: 241 → 243 °C (+0.8%); EB: ↓; CI: ↑; TP @ 800 nm ↓; [77]
		5% (1.2 mL) (+ essential oil 4%). Glycerol 0.01% + Tween20 5 vol.% + Anethum graveolens oil.	@5 (1.2 mL) + 4% oil, no baseline reported. TS: 10.36 MPa; EB: 78.87%; SOL: 60.11%; WVP: 5.16 × 10−12 g·m−1·s−1·Pa−1; Antimic: A. niger. [86]
PLA	CNC (leaves, H2SO4 hydrolysis, cinnamate functionalized)	0.5–5% (optimum 3). CNC cinnamate grafting via esterification. Solution casting.	@ 3%. TS: ↑ (+70%); E: ↑ (+37%); EB: ↓; WVP: ↓ (−54%); OP: ↓ (−55%); Tg: 58.3 → 55.2 °C (−5.3%); Tc: 116.7 → 108.1 °C (−7.4%); Tm: 149.4 → 140.8/150.5 °C; UVB: Effective absorption (280–320 nm); TP @visible: ↔ [85]
	CNF (leaves, TEMPO oxidation)	1–3% (optimum 3). MMA grafting. Melt blending + compression molding.	@ 3%. TS: 49.8 → 61.1 MPa (+22.7%); IS: 17.1 → 26.7 J/m (+56.1%); Tmax: 380.7 → 377.4 °C (−0.9%); Tc: 108.5 → 114.1 °C (+5.2%); Tm: 147.2/157.5 → 147.4/153.1 °C [20]
PHBV	CNC (crown leaves, H2SO4 hydrolysis)	1–5% (optimum 3, relative to PHBV). Solution casting.	@ 3%: CI: 37.0 → 41.0% (+10.8%); Tonset: 262 → 264 °C (+0.8%); Tmax: 286 → 287 °C (+0.3%); Tm: 156.0 → 153.5 °C (−1.6%); WVP: 1.39 × 10−11 → 4.14 × 10−11 g·m−1·s−1·Pa−1 (+198%); Tc: ↓; Crystallization rate: ↑; Lifetime @180 °C: no degradation 1000 min [13]
CMC	CNC (leaves, H2SO4 hydrolysis)	15–45% (optimum 30, relative to CMC). Glycerol 30 wt.% (relative to CMC). Solution casting.	@ 30%. TS: 1.60 → 5.07 MPa (+217%); WVTR: 2.77 → 2.10 g·h−1·m−2 (−24%); Tonset: 179 → 184 °C (+3%); Tmax: 260 → 261 °C (+0.4%); EB: 200 → 220% (+10%); TP: ↓ [99]
Rubber (NR)	CNC (leaves, H2SO4 hydrolysis)	2.5–10 phr (~2.4–9.1%, optimum (~2.4%). SV or EB (200 kGy). Casting + vulcanization (SV)/irradiation + casting (EB).	@ 2.5 phr (~2.4%) (S-vul). TS: 17.4 → 19.4 MPa (+11%); EB: 604 → 634% (+5%); E@100%: 1.08 → 1.83 MPa (+69%); SW: 4.42 → 4.86 (+10%) (toluene, 7 d). @ 2.5 phr (~2.4%) (EB). TS: 13.5 → 15.8 MPa (+17%); EB: 783 → 806% (+3%); E@100%: 0.63 → 0.87 MPa (+38%); SW: 6.26 → 6.18 (−1%) (toluene, 1 d) [84]
PP	CNC (peel, HCl hydrolysis)	3% (fixed). MAPP 5 wt.%. Melt blending + injection molding.	@ 3% + MAPP. TS: 33.60 → 38.75 MPa (+15.3%); E: 1238 → 1665 MPa (+34.5%); EB: 420 → 61% (−85%); IS: 21.96 → 25.7 J/m (+17%); E′−25 °C: 3975 → 4998 MPa (+26%); WCA: 92 → 80° (−13%); Tg ↑ [61]
PS	CNF (leaves, TEMPO oxidation)	0.5–3% (optimum 1.0 SF; 3.0 GF). Styrene suspension polymerization (SF) or Sol–gel + phenyltriethoxysilane (GF). Melt blending + compression molding.	@ 1.0% (SF). TS: 23.1 → 31.1 MPa (+34.6%); HDT: 90.3 → 92.8 °C (+2.66%). @ 3.0% (GF). TS: 23.1 → 28.9 MPa (+25.1%); HDT: 90.3 → 93.8 °C (+3.9%) [105]
PMMA	CNF (leaves, TEMPO oxidation)	0.5–3% (optimum 1%). Suspension polymerization with MMA. Melt blending + compression molding.	@ 1%. IS: 14.8 → 18.2 J/m (+22.9%); TS: 43.5 → 44.2 MPa (+1.6%); E: 2350 → 3020 MPa (+28.5%); EB: 12.95 → 9.52% (−26.5%); Tmax: 371.4 → 373.9 °C (+0.7%); TP @ visible: ↔ [104]
PU	CNF (leaves, oxalic acid hydrolysis, and steam explosion)	2–10% (optimum 5%). Film-stacking + compression molding.	@ 5%. TS: 17.5 → 52.6 MPa (+201%); E: 37.5 → 992.4 MPa (+2546%); Fatigue: 608 million cycles (~15 years); EB: ↑ [54]
Cellulose matrix (pineapple peel)	CNF (peels, Pretreatment with Fe2+ assisted cold plasma + nanofibrillation)	5–20% (application 15%, relative to cellulose). Carnauba wax 20 wt.% (relative to cellulose). Coating + aqueous coagulation bath + annealing.	@ 15%. Tmax: 332.7 → 337.1 °C (+1.3%); WCA: >100° (↔); OTR: ↓; TS:↑; E:↑; EB:↑ [75]

* Values reported at optimal nanocellulose loading (i.e., formulation with best general properties or as recommended by authors). Format: baseline → composite (% change) or composite only if no baseline reported. Arrows: ↑ increase, ↓ decrease, and ↔ no clear change. Example: “TS: 1.26 → 1.80 MPa (+43%)” means tensile strength increased from 1.26 MPa (neat matrix) to 1.80 MPa (nanocomposite), a 43% improvement. “TP: ↓” indicates qualitative trend when values are not reported. Abbreviations in text.

Table 2. Benchmark of pineapple-derived nanocellulose nanocomposites.

Matrix	NC Type, Pineapple Fraction, and Method	Loading (wt.%) and Additives or Treatment and Process	Properties and Trends *
Starch (potato)	CNF (leaves, acid hydrolysis, oxalic acid in autoclave)	1–4% (optimum 3, relative to starch). Glycerol (30 wt.%, relative to starch). Solution casting.	@ 3%. WVTR: 4.39 → 3.41 g·h−1·m−2 (−22%); SOL: 76.14 → 36.09% (−53%); MA: 16.1 → 11.56% (−28%); DC: 1.59 → 0.087 × 10−4 mm2·s−1 (−95%) RE: 47%; Tonset: ↑; E′ ↑; Tmax ↑; UVB ↑; TP ↔; WCA ↑ [70,78,79]
Starch (bengkoang)	CNF (leaves, HCl hydrolysis, high shear homogenization, ultrasonication)	0.5–2% (optimum 2, relative to starch). Glycerol (20 w/v%, relative to starch), ultrasonication. Solution casting + ultrasonication.	@ 2%. TS: 3.8 → 9.8 MPa (+158%); MA: 20 → 9% (−55%); WVP: 5.6 × 10−11 → 4.5 × 10−11 g·m−1·s−1·Pa−1 (−20%); Tmax: 245 → 310 °C (+27%); CI: 21.71 → 35.17% (+62%); OP: 91.2 → 253.7 AU (+178%, TP: ↓); E: ↑; EB: ↓; [82]
Starch (bitter cassava)	CNC (leaves, H2SO4 hydrolysis)	15% (fixed, relative to starch). Glycerol (20 wt.%). Solution casting.	@ 15%. TS: 1.26 → 1.80 MPa (+43%); E: 4.47 → 11.95 MPa (+167%); EB: 76.77 → 41.75% (−46%); SOL: 6.34 → 4.76% (−25%); WVTR: 2.47 → 2.07 g·h−1·m−2 (−16%); WVP: 4.0 × 10−11 → 3.36 × 10−11 g·m−1·s−1·Pa−1 (−16%); Tmax: 345 → 346 °C (+0.3%); OP: 16.59 → 17.75% (+7%, TP: ↓) [94]
PVA	CNC (peel, H2SO4 hydrolysis)	2–8% (optimum 2%, relative to PVA). Tannic acid (2–8 wt.%, optimum 8%, relative to PVA). Solution casting.	@ 2% + 8% TA. TS: 58.5 → 108.7 MPa (+86%); TP @ 500 nm: 79 → 72% (−9%); EB: ↓; WA: ↓; SOL: ↑ with TA; ↓ with CNC; UVB: ↑; Antimic: S. aureus [77]
	CNF (leaves, ultra-fine grinder)	10–50% (optimum 20–40). Glycerol (1 wt.%). Solution casting.	@ 40%. d: 0.68; MC: 6.03 → 5.62% (−7%); Th: 0.11 → 0.02 mm; Tm: 329.54 → 315.27 °C (−4%); CI: 38.3 → 37.8% (−1.3%); WVTR: ↑; TP: ↓ [21]
	CNF (leaves, high-shear homogenization + ultrasonication)	1–5% (optimum 4, relative to PVA). Solution casting.	@ 4%. TS: 22.5 → 28.9 MPa (+28%); EB: 178.4 → 211.4% (+18.5%); CI: 74.8 → 78.8% (+5%); Tmax: 336.3 → 341.8 °C (+1.6%); TP: >75% all films [100]
PVA/chitosan blend (2:1)	CNC (leaves, H2SO4 hydrolysis)	~0.44% (fixed, relative to total polymer matrix). PEG (2 wt.%). Solution casting.	@ 0.44%. TS: 11.40 → 18.25 MPa (+60%); Tonset: 248 → 274 °C (+11%); SW: 442 → 282% (−36%) [90]
Chitosan/Starch (50:50)	CNC (crown leaves, H2SO4 hydrolysis)	0.3–1.0% (0.7 optimum). Sorbitol (0.5 mL/g starch). Solution casting.	@ 0.7%. E′ (40 °C): 2484 → 4709 MPa (+90%); Tg: 66 → 73 °C (+11%); thermal stability ↔ [95]
WPI	CNC (crown leaves, H2SO4 hydrolysis)	3–7% (optimum 3.5% via RSM). Glycerol (4–8%, 4 wt.% optimum). Solution casting.	@ 3.5% (RSM-optimized). TS: 7.16 MPa; EB: 39.10%; WVP: 2.21× 10−11 → 2.17 × 10−11 g·m−1·s−1·Pa−1 (−2%); SOL: 30.21 → 27.15% (−10%); CI: 74.82 → 81.14% (+8%); TP: ↓ [97]
WPI/PVA (70/30)	CNC (crown leaves, H2SO4 hydrolysis)	3.5% (Fixed). Glycerol (4 wt.%). Solution casting.	@ 3.5%; no baseline reported for 70/30 blend. TS: 7.061 MPa; EB: 68.831%; WVP: 1.765 × 10−11 g·m−1·s−1·Pa−1; SOL: 24.507%; Tonset: 258 °C; Tmax: 330 °C; TP: ↑ vs. WPI; Degradation: 35% weight loss @ 24d. [102]
Gelatin	CNC (leaves, H2SO4 hydrolysis)	1–5% (optimum 5). Glycerol (10% w/v) + banana leaf extract (BL). Solution casting.	@ 5% + BL. TS: 4.71 → 82.23 MPa (+1646%); EB: 2 → 16% (+700%); Thermal stability: ↑; OP: ↓; SW ↓; WVP ↓; Antimic: E. coli, S. aureus, C. perfringens [14]
		1–5% (optimum 5). Glycerol + lotus extract (LE). Tissue paper spray coating.	@ 5% + LE, baseline: uncoated tissue paper. Th: 0.125 → 0.591 mm (+373%); Grammage: 23.48 → 32.36 g/m2 (+38%); d: 0.765 → 0.498 g/cm3 (−35%); WVP: 24.56 × 10−10 → 2.09 × 10−10 g·m−1·s−1·Pa−1 (−91%); WCA: 74.6 → 70.2°; TS: ↑; EB: ↓; Antimic: S. aureus, E. coli, C. glabrata [109]
Carrageenan (+ starch granules)	CNF (leaves, acid hydrolysis, oxalic acid in autoclave)	0.2–0.3% (optimum 0.2). Glycerol (0.6 wt.% + sesame oil + aloe vera gel 3%). Solution casting.	@ 0.2% (Carr:Starch 1.5:1); no baseline reported. TS: 5.64 MPa; ME: 4.62 mm; WVP: 6.4 × 10−10 g·m−1·s−1·Pa−1; OP: 2.0%; SOL: 42%; MA: 29%; Th: 150 μm; d: 1.34 g/cm3; WCA: 71°; Thermal stability: stable to 200 °C [98]
Gellan gum	CNC (peel, H2SO4 hydrolysis)	2–10% (optimum 4, relative to gellan gum). Glycerol 15 wt.% (relative to gellan gum). Solution casting.	@4%. TS: 2.24 → 3.32 MPa (+48.2%); Tonset: 161 → 165 °C (+2.5%); Tmax: 241 → 243 °C (+0.8%); EB: ↓; CI: ↑; TP @ 800 nm ↓; [77]
		5% (1.2 mL) (+ essential oil 4%). Glycerol 0.01% + Tween20 5 vol.% + Anethum graveolens oil.	@5 (1.2 mL) + 4% oil, no baseline reported. TS: 10.36 MPa; EB: 78.87%; SOL: 60.11%; WVP: 5.16 × 10−12 g·m−1·s−1·Pa−1; Antimic: A. niger. [86]
PLA	CNC (leaves, H2SO4 hydrolysis, cinnamate functionalized)	0.5–5% (optimum 3). CNC cinnamate grafting via esterification. Solution casting.	@ 3%. TS: ↑ (+70%); E: ↑ (+37%); EB: ↓; WVP: ↓ (−54%); OP: ↓ (−55%); Tg: 58.3 → 55.2 °C (−5.3%); Tc: 116.7 → 108.1 °C (−7.4%); Tm: 149.4 → 140.8/150.5 °C; UVB: Effective absorption (280–320 nm); TP @visible: ↔ [85]
	CNF (leaves, TEMPO oxidation)	1–3% (optimum 3). MMA grafting. Melt blending + compression molding.	@ 3%. TS: 49.8 → 61.1 MPa (+22.7%); IS: 17.1 → 26.7 J/m (+56.1%); Tmax: 380.7 → 377.4 °C (−0.9%); Tc: 108.5 → 114.1 °C (+5.2%); Tm: 147.2/157.5 → 147.4/153.1 °C [20]
PHBV	CNC (crown leaves, H2SO4 hydrolysis)	1–5% (optimum 3, relative to PHBV). Solution casting.	@ 3%: CI: 37.0 → 41.0% (+10.8%); Tonset: 262 → 264 °C (+0.8%); Tmax: 286 → 287 °C (+0.3%); Tm: 156.0 → 153.5 °C (−1.6%); WVP: 1.39 × 10−11 → 4.14 × 10−11 g·m−1·s−1·Pa−1 (+198%); Tc: ↓; Crystallization rate: ↑; Lifetime @180 °C: no degradation 1000 min [13]
CMC	CNC (leaves, H2SO4 hydrolysis)	15–45% (optimum 30, relative to CMC). Glycerol 30 wt.% (relative to CMC). Solution casting.	@ 30%. TS: 1.60 → 5.07 MPa (+217%); WVTR: 2.77 → 2.10 g·h−1·m−2 (−24%); Tonset: 179 → 184 °C (+3%); Tmax: 260 → 261 °C (+0.4%); EB: 200 → 220% (+10%); TP: ↓ [99]
Rubber (NR)	CNC (leaves, H2SO4 hydrolysis)	2.5–10 phr (~2.4–9.1%, optimum (~2.4%). SV or EB (200 kGy). Casting + vulcanization (SV)/irradiation + casting (EB).	@ 2.5 phr (~2.4%) (S-vul). TS: 17.4 → 19.4 MPa (+11%); EB: 604 → 634% (+5%); E@100%: 1.08 → 1.83 MPa (+69%); SW: 4.42 → 4.86 (+10%) (toluene, 7 d). @ 2.5 phr (~2.4%) (EB). TS: 13.5 → 15.8 MPa (+17%); EB: 783 → 806% (+3%); E@100%: 0.63 → 0.87 MPa (+38%); SW: 6.26 → 6.18 (−1%) (toluene, 1 d) [84]
PP	CNC (peel, HCl hydrolysis)	3% (fixed). MAPP 5 wt.%. Melt blending + injection molding.	@ 3% + MAPP. TS: 33.60 → 38.75 MPa (+15.3%); E: 1238 → 1665 MPa (+34.5%); EB: 420 → 61% (−85%); IS: 21.96 → 25.7 J/m (+17%); E′−25 °C: 3975 → 4998 MPa (+26%); WCA: 92 → 80° (−13%); Tg ↑ [61]
PS	CNF (leaves, TEMPO oxidation)	0.5–3% (optimum 1.0 SF; 3.0 GF). Styrene suspension polymerization (SF) or Sol–gel + phenyltriethoxysilane (GF). Melt blending + compression molding.	@ 1.0% (SF). TS: 23.1 → 31.1 MPa (+34.6%); HDT: 90.3 → 92.8 °C (+2.66%). @ 3.0% (GF). TS: 23.1 → 28.9 MPa (+25.1%); HDT: 90.3 → 93.8 °C (+3.9%) [105]
PMMA	CNF (leaves, TEMPO oxidation)	0.5–3% (optimum 1%). Suspension polymerization with MMA. Melt blending + compression molding.	@ 1%. IS: 14.8 → 18.2 J/m (+22.9%); TS: 43.5 → 44.2 MPa (+1.6%); E: 2350 → 3020 MPa (+28.5%); EB: 12.95 → 9.52% (−26.5%); Tmax: 371.4 → 373.9 °C (+0.7%); TP @ visible: ↔ [104]
PU	CNF (leaves, oxalic acid hydrolysis, and steam explosion)	2–10% (optimum 5%). Film-stacking + compression molding.	@ 5%. TS: 17.5 → 52.6 MPa (+201%); E: 37.5 → 992.4 MPa (+2546%); Fatigue: 608 million cycles (~15 years); EB: ↑ [54]
Cellulose matrix (pineapple peel)	CNF (peels, Pretreatment with Fe2+ assisted cold plasma + nanofibrillation)	5–20% (application 15%, relative to cellulose). Carnauba wax 20 wt.% (relative to cellulose). Coating + aqueous coagulation bath + annealing.	@ 15%. Tmax: 332.7 → 337.1 °C (+1.3%); WCA: >100° (↔); OTR: ↓; TS:↑; E:↑; EB:↑ [75]

* Values reported at optimal nanocellulose loading (i.e., formulation with best general properties or as recommended by authors). Format: baseline → composite (% change) or composite only if no baseline reported. Arrows: ↑ increase, ↓ decrease, and ↔ no clear change. Example: “TS: 1.26 → 1.80 MPa (+43%)” means tensile strength increased from 1.26 MPa (neat matrix) to 1.80 MPa (nanocomposite), a 43% improvement. “TP: ↓” indicates qualitative trend when values are not reported. Abbreviations in text.

This type of analysis allows the comparison of key nanocomposite properties, mapping improvements due to the incorporation of nano reinforcements, and identifying parameters implemented in the preparation of these pineapple nanocellulose-based nanocomposites, such as improved compatibility between nanofibers and the matrix. It also allows the identification of gaps in research related to composite materials made with pineapple nanocellulose and opportunities for standardization.

Various matrices have been used to develop these nanocomposite materials, ranging from hydrophilic materials such as starch, PVA, chitosan, proteins, and gums. The addition of nanocellulose has been shown to improve mechanical properties, stiffness, and barrier properties, typically using loadings between 0.5 and 5 wt.% and in some cases using high loadings (15–30 wt.%) for some matrices such as PVA, starch, CMC, cellulose, which in all cases consist of hydrophilic matrices with a high affinity for nanocellulose, this allows for higher reinforcement loads to be achieved [130]. In the case of self-reinforced material, high loads are used, where the nanocellulose can form a double or co-continuous network and ceases to be a reinforcement and acts as part of the load-bearing phase [75].

On the other hand, the addition of reinforcement in most cases sacrifices the elongation due to the nanocellulose stiffness and transparency of the materials, especially at higher loadings. For bio-based thermoplastic matrices such as PLA or PHBV, surface modification using techniques such as esterification and functionalization also improves properties such as stiffness and barrier properties by improving the adhesion between the nanocellulose and the matrix.

For thermoplastic matrices such as PP, PS, and PMMA, compatibilization processes are needed due to the low affinity between hydrophilic nanocellulose and hydrophobic matrices. These processes include silylation of nanocellulose and the addition of compatibilizing agents such as methacrylated resins, which play a fundamental role in improving dispersion and therefore impact on the fiber/matrix interface, thus improving mechanical and thermal properties. For materials such as PMMA, where the transparency is a key factor, this property is maintained at low nanocellulose loadings. In these matrices, the most commonly used techniques are melting, blending, and extrusion/injection, which are commonly employed in industry.

In materials such as natural rubber and polyurethane, the addition of nanocellulose has been used to improve mechanical strength and, in specific formulations, barrier properties and fatigue behavior or durability under cyclic loading—aspects relevant to biomedical applications and other demanding environments. Processing routes such as film-stacking and vulcanization are used in these systems, which differ from those used in hydrophilic matrices, where solution film-forming methods predominate.

Beyond the nanocomposite systems included in the benchmarking in Table 1, several studies use pineapple-derived nanocellulose as a matrix or functional support, instead of using it solely as conventional reinforcement, or combine it with thermoset matrices such as epoxy and urea–formaldehyde resins for coatings and specialized functional materials. These include fully cellulose-based, self-reinforced hydrophobic materials with virtually zero oxygen transmission [75], as well as MXene-loaded nanocellulose matrices for the development of electromagnetic interference (EMI) shielding materials [72], and systems incorporating metallic nanoparticles or zero-valent iron onto the nanocellulose matrix for antimicrobial and remediation applications (e.g., Ag/ZnO/CNC [108], Fe⁰/CNC [83]).

These systems were considered in the literature review but were not included in the benchmarking table because their target properties (EMI shielding efficiency, pathogen elimination, anticorrosive performance, contaminant removal, etc.) are not directly comparable to the structural and barrier properties evaluated in the nanocomposites summarized in Table 1.

6. Conceptual Framework and Potential for Bioeconomy Integration

The valorization of pineapple waste supports the principles of the circular bioeconomy, particularly when approached through an integrated biorefinery model [131]. Pineapple processing generates several streams of residues—leaves, peels, crowns, cores, and pulp—each with distinct chemical compositions and therefore with different potential roles in a potential multi-product valorization system [132]. Under a theoretical biorefinery framework, these residues could be fractionated into complementary product streams, reducing waste while enabling the production of materials, chemicals, and bioactive compounds [133]. These sustainability outcomes have not yet been demonstrated experimentally or validated through scale-up, LCA, or techno-economic analysis; they remain as conceptual expectations rather than confirmed results.

In this context, cellulose, hemicellulose, and lignin are the three main structural polymers targeted for recovery and as summarized in previous sections, cellulose is the primary component and can be used for nanocellulose production (both CNF and CNC), with applications in packaging [14,75,79,86], composites [13,20,61] biomedical materials [54,64,81], and environmental applications [83,107]. Pineapple leaves, due to their higher cellulose content and fiber morphology, remain the preferred source for nanocellulose extraction.

In addition to cellulose, peels are rich in hemicellulose, with contents up to 30%. These hemicelluloses can be valorized as xylitol, xylooligosaccharides, or hydrogels [134]. Simultaneously, hemicelluloses can be extracted from peels and cores using alkaline treatments or green solvents, and further converted into xylooligosaccharides, bio-based hydrogels, or fermentation substrates [2,30]. Lignin, although often underutilized, can be recovered from both leaves and peels and used in antioxidant formulations, UV-protective coatings, adhesives, and as a platform for aromatic chemical production. Selective removal of lignin and hemicellulose can improve the efficiency of downstream cellulose hydrolysis [135,136]. The recovery of lignin from black liquor obtained from the soda pulping of pineapple peels by precipitation with H₂SO₄ has been reported. The recovered material was subsequently characterized and its energy potential evaluated [137].

Beyond the cell wall polymers, other extractable compounds such as enzymes, pectin, chlorophyll, sugars, acids (citric acid, lactic acid, ferulic acid), vitamins (vitamin C), and essential oils (limonene can be recovered in early stages of processing and used in nutraceutical, cosmetic, or pharmaceutical formulations) [4,138].

Pineapple has a well-known enzyme called bromelain, which is currently marketed, and the main source is the stem of the plant, but its extraction has also been studied from other parts, such as pineapple peels; although it is another type of bromelain variety, it also has potential applications in the food industry. After the extraction of this enzyme in aqueous media, the fibrous part could be used for the extraction of nanocellulose [39,40]. Also, the presence of starch from the stem specifically has been reported, which could be extracted and used for food and non-food applications [139]. Another interesting component is chlorophyll, which has been reported to be extracted from pineapple plant waste, with potential application as an alternative natural dye in dye-sensitized solar cells [140].

In a biorefinery process, lignocellulosic residues can be fractionated into multiple product streams using environmentally friendly extraction and conversion technologies [2,134,141]. It begins with biomass classification and mild pretreatments, followed by sequential extraction of soluble compounds, hemicellulose, and lignin, and culminates with the isolation of cellulose and its conversion into nanostructured forms. Integrated processing minimizes energy and reagent use by tailoring methods to the specific anatomical part and composition of the biomass.

The potential co-products listed in this section cannot necessarily be obtained simultaneously from a single process configuration. Many of these valorization routes are chemically or operationally incompatible: for example, severe acidic or alkaline pretreatments required for cellulose isolation can degrade bromelain, pectin, and phenolic compounds; pigment extraction may alter the structural integrity of fibers; and lignin recovery often depends on conditions that preclude subsequent use of hemicellulose-rich fractions. Additionally, sequential extraction increases processing complexity and may reduce yield or purity due to competing reactions and mass-loss steps. Consequently, real biorefinery designs must prioritize specific product streams and acknowledge trade-offs between material quality, process efficiency, and economic feasibility.

Such integrated valorization routes from a conceptual view could support “zero-waste” approaches by sequentially using each fraction for the highest-value possible application, and only diverting residual streams to energy recovery or composting [2,131,133]. However, these statements refer to theoretical possibilities rather than proven performance, as there have been no life cycle assessments (LCAs), evaluations of carbon footprints, or techno-economic analyses (TEA) conducted for pineapple-based nanocellulose systems or for more extensive pineapple biorefineries.

Consequently, pineapple waste valorization may contribute to more sustainable supply chains in producing regions—particularly in countries with strong pineapple industries such as Costa Rica, the Philippines, and Mexico. However, achieving these sustainability outcomes will require advances in scalable extraction technologies, optimization of resource and energy use, and evaluation of environmental and economic impacts would be essential before such systems could be considered viable beyond the laboratory scale [1,3,4,142,143].

The integration of pineapple residues into circular bioeconomy models remains promising, but such perspectives must be understood as conceptual and conditional, pending rigorous LCA, TEA, and pilot-scale demonstrations.

7. Limitations and Challenges

The reviewed literature shows several gaps that limit cross-study comparability and the advancement toward scalable processes. (1) Biomass-referenced extraction yields are absent in 87% of studies, while only 13% report yields relative to the initial biomass. (2) Compositional characterization of pineapple residues is inconsistently documented, with only 19% of studies reporting full cellulose–hemicellulose–lignin data. (3) No studies include life-cycle assessment (LCA) or techno-economic analysis (TEA), which is a barrier to evaluating environmental or economic feasibility. (4) Mechanical, thermal, and barrier testing conditions lack standardization across studies, varying in test temperature, strain rate, sample thickness, and conditioning. (5) All reported extraction and composite fabrication work remains strictly at laboratory scale, with no pilot- or industrial-scale demonstrations. (6) Extraction methods generally lack documentation of operational cost, reagent consumption, and energy demand, further limiting scalability assessments. These gaps evidence the need for more rigorous, standardized reporting practices and the integration of sustainability and scale-up metrics in future research.

Applying a bioeconomy model for the comprehensive use of pineapple biomass has a series of technical, economic, social, and regulatory challenges that must be addressed to move toward practical bioeconomy models and more sustainable use of pineapple biomass. These challenges include the search for greener technologies that reduce chemical consumption in extraction processes, as well as reducing costs and decreasing energy and water consumption, for example, by optimizing processing conditions [1,4].

All the reported processes in this review are at laboratory scale, which requires scaling up processes to be developed, which implies having solid business models for the products to be obtained. Furthermore, it requires high investment in infrastructure and logistics costs, in addition to the implementation of public–private partnerships [3,142,143]. Another important point is the costs related to the collection, transportation, and storage of pineapple waste, because these residues are produced in the field and by the fruit processing companies. This implies a need for strategic locations of the biorefinery initiatives, as well as the application of the multi-feedstock biorefineries, which can be versatile for utilizing various waste products in the same facilities [1,3,4].

Also, there are regulatory gaps, a lack of standards, and a lack of incentives to promote the generation of bioproducts. The generation of new bioproducts also involves a process of social adaptation and local participation, which requires a multi-sector dialog, awareness-raising processes, and technical training [5,142,143]. The development of new bioproducts also entails the development of markets and strategies to prioritize the generation of higher-value products, rather than those of lower market value [1,3].

8. Conclusions

Pineapple waste is an underused biomass source for nanocellulose (CNC and CNF) production, where morphological properties, size, and chemical characteristics can be obtained according to the extraction route. The most common techniques for CNC production are H₂SO₄ hydrolysis, in addition to TEMPO-mediated oxidation or mechanical fibrillation for CNF production. All these are top-down techniques, but recently, there have been some reports of bottom-up approaches using ionic liquids and eutectic solvents, which are often described as more sustainable alternatives due to reduced mineral acid use, although quantitative LCA data are not yet available. Leaves are the most explored source for pineapple nanocellulose extraction, followed by the fruit peels and crown leaves; stem, core, pulp, and pomace have been less explored but are very promising due to their high cellulose content.

The main application of pineapple nanocellulose is the production of nanocomposites where nanocellulose acts as a reinforcement. However, recent research has also shown the potential of pineapple-derived nanocellulose to serve as a matrix material, particularly in self-reinforced and nanocellulose-based hybrid systems. These types of materials integrate nanocellulose as the primary structural phase and incorporate inorganic or metallic components, enabling multifunctional performance. Examples include applications in electromagnetic interference (EMI) shielding, water purification, adsorption, antimicrobial activity, and other advanced functional uses. These developments indicate that pineapple nanocellulose exhibits a dual application, can be used as reinforcement in conventional polymer composites, and as a matrix in high-value engineered materials.

The detailed review of extraction and nanocomposites evidence that pineapple nanocellulose (CNC and CNF) is a versatile material for designing new materials across a wide variety of applications, where structure–interface–property relationships can be tailored for different types of polymers, or where nanocellulose acts as the matrix. Furthermore, pineapple processing can generate by-products that can be valued within a bioeconomy framework, where co-products can be recovered and upgraded, expanding their value and improving the process sustainability.

This review identified research gaps that require attention for future research, like the need to use systematic and standardized compositional characterization of pineapple residues (cellulose, hemicellulose, lignin, extractives, and ash), using consistent analytical protocols to enable comparison across cultivars, growing regions, and processing residues.

Extraction studies should report biomass-referenced yields along with detailed information on energy demand, reagent consumption, and solvent or oxidant recovery. Additionally, studies should clearly specify process conditions to enable meaningful comparison across methodologies. Such standardized reporting is essential for assessing process efficiency and providing reliable inputs for scale-up, life-cycle assessment (LCA), and techno-economic analysis (TEA).

Understanding of structure–property relationships remains incomplete; further study is needed to quantify how nanocellulose morphology, surface chemistry, and crystallinity affect mechanical, barrier, optical, and functional performance in different polymer matrices and nanocellulose-as-matrix systems.