Recent Advances in Sustainable Anthocyanin Applications in Food Preservation and Monitoring: A Review

Abstract

Anthocyanins, a group of naturally occurring flavonoid compounds, have garnered increasing attention due to their wide-ranging biological activities that suggest their considerable potential to be utilized not only as natural food colorants but also as functional additives that can enhance food preservation and contribute to the development of health-promoting functional foods. Additionally, their sensitivity to environmental factors such as pH and temperature makes anthocyanins promising candidates for use in intelligent packaging systems, particularly as natural indicators for monitoring food freshness and quality throughout storage and distribution. Despite challenges related to their stability and regulatory acceptance, continued research into anthocyanins remains crucial for advancing sustainable, clean-label food technologies and reducing reliance on synthetic additives. To fully leverage their economic and health potential, it is essential to gain a comprehensive understanding of the various plant sources of anthocyanins, their chemical composition, extraction methods, and roles in different applications. Moreover, integrating anthocyanins into food and intelligent packaging systems presents various technical and regulatory challenges that are also summarized in this review.

1. Introduction

During the last decades, the importance of natural compounds was highlighted by the numerous applications of such compounds, not only as food additives [1], but also as key agents in pharmaceutical development [2,3], cosmetics [4,5,6,7], agriculture [8,9,10], and environmental sustainability [11]. Their diverse biological activities, including antioxidant [12,13,14,15], antimicrobial [13,16,17,18], anti-inflammatory [13,18,19], antidiabetic [13,20,21] and anticancer [13,22,23] properties, have made them valuable tools in both traditional and modern scientific fields. As a result, natural compounds continue to play a central role in the search for safer, more effective, and eco-friendly alternatives to synthetic chemicals [24].

An important domain where plant-based compounds have gained interest recently is represented by food packaging systems [25], where natural pigments tend to replace synthetic ones in response to increasing concerns over synthetic food additives and the growing consumer preference for natural alternatives [24,26].

In addition to its fundamental functions, such as containment, preservation, and protection against environmental, physical, and microbiological factors, food packaging has recently taken on a more specialized role as a quality indicator for packaged food products, driven by evolving consumer preferences and expectations [25,27,28]. Thus, two types of interactive packaging systems were developed and named active and intelligent packaging [29,30]. The active packaging interacts actively with the food or the surrounding environment to enhance food safety, shelf life, or quality [25,31], based on the use of active substances like antimicrobials, antioxidants, ethylene absorbers, oxygen scavengers, moisture absorbers, CO₂ emitters [32].

Figure 1 highlights the interconnected aspects of anthocyanin research and development, from raw material selection to final application in the food industry.

Intelligent packaging, also known as smart or clever packaging, monitors the condition of the packaged food or the environment surrounding it and provides real-time information about its freshness, quality, safety, and shelf life [25,27]. They contain mainly pH-sensitive indicators, gas indicators, or volatile compound indicators [33] which interact with the inner environment of the package, signaling the state of the food product [25].

Compared with other classes of natural pigments and sensing compounds, anthocyanins offer several distinct advantages for food quality control applications. Unlike carotenoids, chlorophylls, or betalains, anthocyanins exhibit high sensitivity to environmental changes such as pH, temperature, and oxidation. Further attributes, such as antimicrobial and antioxidant properties, wide availability, and non-toxicity, make them suitable for incorporation into food packaging [28,33] to preserve the food, and/or to provide information about its quality and freshness. Anthocyanins uniquely combine the properties of natural antioxidants and color indicators, making them ideal for next-generation food packaging systems that are clean-label, smart, and sustainable.

Thus, this review aims to provide a comprehensive and up-to-date overview of recent studies employing anthocyanins from different sources as functional additives that can enhance food preservation, and as natural indicators for monitoring food freshness and quality throughout storage and distribution. It will explore the various plant sources of anthocyanins, their chemical composition, extraction methods, and roles in food preservation and monitoring. Also, various technical and regulatory challenges regarding the integration of anthocyanins into food and intelligent packaging are also highlighted in this review.

Although most recent reviews have addressed anthocyanin applications in foods and packaging, most have remained descriptive and have not clarified how anthocyanin molecular structure influences stability and functional performance within different polymer matrices. The present review emphasizes a comparative, mechanism-based perspective, examining how biopolymer-based systems differ in their dominant intermolecular interactions and their resulting effects on pigment retention, antioxidant activity, and color responsiveness. On this basis, practical design guidelines are outlined to support the rational selection and formulation of anthocyanin-containing films for active and intelligent packaging.

2. Chemical Structure, Color Behavior, and Stability

Anthocyanins are naturally occurring water-soluble pigments belonging to the flavonoid family, which are responsible for the vivid color of various plant tissues such as petals, fruits, leaves, stems, roots, tubers, or seeds [34,35,36]. In plants, these pigments accumulate in the cell vacuoles, playing a significant role in reproduction by attracting pollinators and seed dispersers with their vibrant colors, and also in protection and adaptation to various biotic and abiotic stresses [37,38,39,40,41].

Historically, the term anthocyanin was derived from the Greek words anthos (flower), and kyanos (blue) and is attributed to German pharmacist Ludwig Clamor Marquart, who named and described these pigments in 1835 in his publication “Die Farben der Blüthen” (The Colors of Flowers) [42,43,44].

Structurally, anthocyanins are glycosylated forms of anthocyanidins (aglycones), characterized by a basic C6-C3-C6 skeleton configuration, known as 2-phenyl-benzopyrylium (flavylium) cation (Figure 2). The cation consists of two benzoyl rings (A and B) connected by a positively charged aromatic pyrylium ring (C) [45,46].

There is a broad structural diversity of anthocyanins widespread in nature, with over 700 structurally distinct anthocyanins [47] and around 31 monomeric anthocyanidins (aglycons) identified [48]. Their diversity arises mainly from the number of hydroxyl and methoxy groups, the type and number of sugar attachments in their structure, the organic acids linked to the sugar, and the position of these bonds [49,50].

Cyanidin, delphinidin, pelargonidin, peonidin, malvidin, and petunidin are the most common anthocyanidins identified in nature, differing in the number and position of the hydroxyl and methoxy groups in the flavylium ion structure [51]. Anthocyanins are rarely found in nature as free aglycons (anthocyanidins), with the exception of 3-deoxyanthocyanidins, a rare class of anthocyanins, which are mainly found in plant tissues in the aglycone form (3-deoxyanthocyanidin) [52,53,54].

Anthocyanidins can be glycosylated at different hydroxyl groups of the molecule to form anthocyanins [55]. In addition, sugar moieties can be further linked to other sugars via glycosidic bonds or acylated with aromatic or aliphatic organic acids via ester bonds [56]. The majority of anthocyanins are 3-O-glycosides and around 50% of known anthocyanins are based on the cyanidin structure. Anthocyanins from flowers show a higher degree of glycosylation and acylation than those found in fruits and vegetables [57].

The UV-Vis spectrum of anthocyanins exhibits a typical absorption profile due to their unique structural conformation, which includes a long chromophore with eight conjugated double bonds and a positive charge at acidic pH [56,58]. In general, their UV–Vis spectrum shows two main wavelength regions, with absorption maxima between 490 and 550 nm in the visible region and between 260 and 280 nm in the UV region [58,59].

The chromatic characteristics of anthocyanins are strongly affected by the substitution mode at the B ring [47,60,61,62]. For example, a larger number of hydroxyl groups lead to a more pronounced blueness, while the redness is increased with the degree of methylation [62,63]. Structural modifications of anthocyanins related to glycosylation and/or acylation, as well as other factors such as pH, copigments, and metal ions, also contribute to the diversification of the colors of these pigments and influence their stability [61,64].

Although anthocyanins have great potential for practical applications in various industries, their use is limited due to their low stability. They are highly susceptible to degradation under the influence of various factors such as pH, temperature, light, oxygen, enzymes, solvents, metal ions, copigments, proteins, etc. [35,49,65,66].

Anthocyanins are unique among flavonoids due to their reversible structural transformations in aqueous solutions depending on pH [56]. Depending on the pH of their environment, they undergo acid–base, addition–elimination of water, and isomerization reactions, resulting in a mixture of colored and colorless forms in equilibrium [67]. In aqueous medium, four essential anthocyanin species exist in chemical equilibrium: the flavylium cation (red), the quinoid base (blue), the carbinol pseudobase (colorless), and the chalcone (colorless or light yellow), their relative proportion being strongly dependent on pH [56,68] (Figure 3).

Numerous review articles [35,48,49,65,69] have extensively discussed the stability of anthocyanins and the various factors that influence them. However, improving anthocyanin stability remains a key challenge for their effective use in different applications like food, pharmaceutical, and cosmetic products.

Several strategies have been proposed to enhance the stability of anthocyanins and reduce their susceptibility to degradation. One common approach is copigmentation (intermolecular copigmentation, intramolecular copigmentation, self-association, and metal complexation) [70,71], where anthocyanins form molecular or complex associations with other organic compounds or metallic ions [49], through noncovalent and covalent interactions [57,71], leading to color stabilization and reduced degradation.

Structural modifications involving acylation, glycosylation, pyranization, or other methods can also improve their structural stability [65]. For example, acylated anthocyanins exhibit greater stability than their nonacylated analogs during processing and storage, the addition of acyl groups decreasing their vulnerability to degradation induced by heat, light, pH changes, and oxidation [72]. The attachment of acyl groups, particularly aromatic ones, induces intramolecular copigmentation through π–π stacking, which shields the flavylium chromophore against nucleophilic attack from water and other reactive molecules [67,72].

Also, a wide range of natural and synthetic materials such as polysaccharides, proteins, liposomes, emulsions, and composite materials [65] have been explored as encapsulation agents to protect anthocyanins from degradation and to improve their bioavailability. More recently, nanomaterial-based carriers such as nanoemulsions, nanoparticles (metal-based nanoparticles, porous organic frameworks, quantum dots, biopolymeric nanoparticles), nanofibers, nanoclays, and nanomicelles, have emerged as promising encapsulation platforms offering controlled release and ensuring the functional integrity of anthocyanins [73].

Additionally, controlling extraction, processing, and storage conditions, such as by maintaining low temperatures, minimizing light exposure, and adjusting pH toward more acidic values, is essential to preserve the structural integrity, color stability, and functional properties of anthocyanins [74].

Overall, a synergistic approach that combines molecular-level interactions, protective matrices, and optimized environmental conditions can provide the most promising pathway to improve the stability and functional performance of anthocyanins, thus expanding their industrial applicability.

3. Anthocyanin Applications as Colorants and Preservatives

Anthocyanins are naturally occurring, water-soluble pigments belonging to the flavonoid group of polyphenolic compounds. They are responsible for the vivid red, purple, and blue coloration observed in many fruits, vegetables, flowers, and grains [75]. As plant-derived colorants, anthocyanins are considered eco-friendly dyes due to their biodegradability, low toxicity, and renewable sources. Beyond their coloring properties, anthocyanins are widely recognized for their bioactive potential, including antioxidant and antimicrobial activity. Their properties further highlight their value as functional food components and nutraceutical agents and make anthocyanins highly attractive for use in the food and packaging industries [76].

Therefore, due to their excellent physiological effects, wide availability, lack of side effects, and the support of advanced production technologies, the development and application of anthocyanin-based products are both practical and promising for the food industry and economy [76].

Food colorants are crucial in the food industry for enhancing visual appeal, masking undesirable colors, and attracting consumers [77]. Moreover, color serves as an indicator of a product’s freshness, safety, and sensory quality [78].

Throughout history, natural colorants have been used in foods to enhance their visual appeal, but due to their weak stability to environmental factors and production processes, over time, new technologies have emerged to create artificial pigments with higher stability, cost-effective production, and superior coloring capacity [79].

For decades, the food industry has utilized synthetic additives to improve the aesthetic appeal, technological functionality, and storage stability of food products [26]. However, the ongoing use of synthetic additives in food processing and preservation has caused significant concerns among consumers regarding their undesirable side effects on health. Novel plants with strong functional compounds have been researched by scientists and food experts as an alternative source of natural compounds, such as anthocyanins, that are suitable for the production of safe food additives [80]. Consequently, over the past decade, there has been growing interest in exploring plant-derived compounds, particularly natural pigments, as sustainable alternatives to synthetic additives in food applications [81].

Depending on their sources, pigments can be classified into artificial and natural pigments. Natural pigment refers to an edible pigment that is derived from plants, fruits, animals, and micro-organisms, such as anthocyanins. Natural pigments from animal and plant tissues are generally safe and harmless and have no side effects [76].

On the other side, preservation of food is a necessary step to extend the limited shelf life of food, which is linked to several factors. Food preservation aims to extend the shelf life and maintain the quality of food, crucial for global food security and public health, by preventing, or reducing microbial spoilage or degradation that makes the food unacceptable [82].

The use of chemicals in foods is a well-known method of food preservation. Wide varieties of chemicals and additives are used in food preservation to control pH, as antimicrobials and antioxidants, and to provide food functionality as well as preservation action [82].

In our modern society, there is an increasing demand from consumers for safe, nutritional, and top-quality food products that offer specific functional properties and health benefits [83].

Thus, the inclusion of natural additives in processed food formulations is a key strategy for enhancing consumer acceptance and aligning with clean-label trends. Anthocyanins have garnered significant attention in both research and the food industry due to their diverse nutritional and pharmacological properties, distinguishing them from other plant-derived pigments [84]. Anthocyanins, a class of plant-derived flavonoid pigments, are particularly valued for their vivid coloration and potential functional properties [85].

Due to anthocyanins functional attributes, such as antioxidant and anti-inflammatory activity, they can be harnessed in the food industry for the development of food additives and fortified foods and beverages with beneficial health effects. The potential of anthocyanins as additives in foods such as jams, beverages, ice cream, meat, and fruit purees have been explored in various studies [80].

Hence, the contribution of anthocyanins in food coloring has become progressively more important [86], especially due to their additional functions including antioxidant and antimicrobial properties.

In terms of applicability as natural food colorants, anthocyanins are widely used in various food products, such as ice pops, wafers, macarons, and dairy products [80], and in home cooking to enhance natural colors, to compensate for color loss during processing, or to add color to colorless foods [87].

The coloring process in bakery products is used to enhance visual appeal and mask natural color variations, with both natural and artificial options available. Since the presence of artificial colorants in these bakery goods is harmful to human health, the application of anthocyanins as natural colorants, derived from sources like fruits, vegetables, and plants, are gaining popularity due to consumer preference for clean labels and potential health benefits. They can be used in various baked goods to enhance their visual appeal and potentially increase their antioxidant properties. However, their stability and color during baking and storage requires careful consideration for successful utilization [88].

For instance, Albuquerque et al. (2020) [89] investigated the incorporation of an anthocyanin-rich extract (AE) of jabuticaba epicarp obtained by heat-assisted extraction (HAE) and ultrasound-assisted extraction (UAE) methods into macarons to assess its coloring capacity. The HAE method proved to be more efficient and selective than UAE, yielding 81 ± 2 mg/g extract under optimal conditions (t = 21.8 min, T = 47.1 °C and S = 9.1% ethanol, v/v). Afterwards, the color and nutritional value of the macarons containing AE were compared and evaluated over a 6-day shelf-life at ~5 °C to those of control macarons containing the commercial colorant E163 (produced and stored under the same conditions). The study concluded that this natural extract gave the macarons a more stable color than the commercial colorant E163 during a 6-day evaluation, suggesting that AE could be a viable natural alternative for food coloring. Papillo et al. (2018) [90] developed anthocyanin-rich powders from Oryza sativa L., var. Artemide via spray-drying, using maltodextrins (MD) and gum arabic (GA) (50:50, w/w) as coating agents. Microencapsulation enhanced the stability of polyphenols, maintaining their integrity during storage at −20 °C for at least 30 days. Biscuits enriched with the encapsulated extract exhibited significantly higher levels of polyphenols, anthocyanins, and antioxidant activity compared to controls, despite partial thermal degradation during baking. The results support microencapsulation of Oryza sativa L., var. Artemide extract as a viable approach for functional food and nutraceutical applications. In another study, Ab Rashid et al. (2021) [86] focused on developing an antibacterial food colorant through microencapsulation technology by using anthocyanin extracted from Clitoria ternatea (butterfly pea) flowers. Maltodextrin was used as a carrier agent in the spray drying process. The resulting microcapsules demonstrated stability to light exposure for up to 21 days, and the best color stability was observed within the temperature range of −20 °C to 4 °C. Furthermore, the study explored the potential of these microcapsules as a bio-preservative in baked goods like muffins, and they exhibited broad-spectrum antibacterial activity against foodborne Gram-bacteria, showing promise in inhibiting foodborne bacteria in baked goods, offering alternatives to synthetic preservatives.

López et al. (2019) [91] prepared an extract from Arbutus unedo L. fruits as a natural colorant with bioactive properties, suitable for pastry/bakery products. The cyanidin-3-O-glucoside extract was incorporated into wafers, which were monitored for a 6-day storage period. The results showed that the extract’s incorporation did not cause changes in the nutritional components of wafers but added colorant and antioxidant properties.

Lavelli et al. (2016) [92] used maltodextrin-encapsulated grape skin phenolics as a functional colored ingredient for apple puree and characterized its stability under heat treatment and storage conditions. The research indicated that the encapsulated phenolics, particularly anthocyanins and flavonoids, showed good stability in the apple puree, even under heat processing and storage, when compared to other fortified juices or beverages. The outcomes suggest that this approach could be a valuable strategy for the food industry, offering a natural, cost-effective, and stable alternative for coloring and adding health benefits to food products. The research presented by Shamshad et al. (2023) [93] demonstrated the potential of arabic gum and maltodextrin for the production of microencapsulated black carrot anthocyanin powder for utilization in ice cream processing and storage. The results concluded that the addition of microencapsulated anthocyanin powder in ice cream (143.21 ± 1.14 mg/100 g) demonstrated significant potential to enhance the ice cream’s quality attributes and sensory characteristics.

Montibeller et al. (2018) [94] investigated the effect of applying anthocyanins obtained from grape skins as a food colorant in kefir and carbonated water. The study showed that in carbonated water, malvidin-3-glucoside exhibited higher stability when stored in the dark, with its half-life time value being nearly four times longer compared to storage in light. Light exposure negatively impacted the color of carbonated water, while the colored kefir did not significantly alter its physical properties compared to kefir without additives. Therefore, anthocyanins extracted from grape skins and incorporated into food matrices present better thermal stability and higher half-life time when stored in the dark and can be used as a natural food additive in beverages or dairy products, while also offering potential health benefits due to their antioxidant activity.

Due to their antioxidant and antimicrobial activity, the uptake of these pigments in the confectionery industry is notable. Moreover, these characteristics present an important advantage in extending the shelf life of food products and preserving their nutraceutical value by preventing oxidation and degradation [95]. In this sense, Trentin et al. (2024) [96] succeeded in obtaining a ready-to-use extract rich in anthocyanins from grape pomace (GP) used in wine production, using natural eutectic mixtures, to be incorporated into functional foods such as gummies, acting as natural colorants, which resulted in a total anthocyanin content (TAC) of up to 60 µg, equivalent to the cyanidin-3-glucoside/g of dry GP. This research highlighted promising colorimetric and sensory qualities of these anthocyanin-rich extracts incorporated into gummy candies, showcasing the potential of GP as a sustainable source and natural source of colorants and health-promoting ingredients in the confectionery industry.

Further studies supporting the application of anthocyanins in food preservation and fortification are summarized in

Table 1. Anthocyanins as food colorants and preservatives.

References	Source of Anthocyanins	Extraction Method/Other Formulation Components	Applications	Advantages, Perspectives
[89]	Jabuticaba epicarp	Heat-assisted and Ultrasound-assisted extraction in acidified ethanol	Natural colorant in macarons	Potential use as natural food colorants; more stable color than the commercial colorant E163 during a 6-day shelf-life
[91]	Arbutus unedo L.	Heat-assisted extraction	Natural colorant in wafers	Good antioxidant and antifungal activity; potential industrial application as alternative source for natural colorant
[90]	Oryza sativa L., var. Artemide	Heat-assisted extraction in acidified ethanol/Microencapsulation of Artemide rice extract in maltodextrin and arabic gum	Functional ingredient for bakery foods	Stable and useful ingredients for functional foods and nutraceuticals; could minimize the production costs, turning a secondary product into a high added-value one
[86]	Clitoria ternatea flowers	Distilled water–acetic acid extraction/Microencapsulation of anthocyanins in maltodextrin	Blue colorant for baked food products (Muffins)	Improved the color stability index of anthocyanins by micro-encapsulation; broad spectrum antibacterial activity against foodborne Gram-bacteria
[94]	Grape skin	Acetate buffer extraction	Natural food colorant in kefir (and carbonated water)	Natural additive in beverages or dairy products; can substitute the synthetic colorants in processed food
[93]	Black carrot	Ethanolic extraction/Microencapsulation of anthocyanins in gum arabic and maltodextrin	Functional additive for ice cream products	Significant potential to stabilize the anthocyanins during processing and storage of ice cream and other products
[96]	Grape pomace	Eutectic mixture extraction (choline chloride, acetic and citric acids)	Gummy candies natural food dye	Sustainable source of natural colorants in the food industry; suitable for incorporation into functional food products
[97]	Rubus ulmifolius Schott fruits	Heat-assisted extraction	Natural colorant (rose/purple) in donuts	Good coloring capacity, maintains nutritional value; antimicrobial properties; high coloring potential that could be used to replace artificial additives
[98]	Eggplant peels	Ultrasound-assisted extraction	Functional ingredient to improve the antioxidant potential of ice-cream	Extract-enriched ice-cream showed higher antioxidant potential and consumer acceptability than the blank ice-cream formulation
[99]	Black carrot pomace	Ultrasound-assisted extraction in acidified ethanol	Colorant and functional ingredient in yogurt formulations	Improves the nutritional and color of the yogurts, providing a visually appealing product; improves yogurt’s bioactive content and antioxidant capacity
[100]	Elderberry pomace	Extraction in water	Natural food additive in blueberry sorbet	Higher antioxidant activity compared to the control; better consumer acceptability; prebiotic potential: stimulate the growth of probiotic bacteria

.

These findings confirm the dual function of anthocyanins in food systems as natural colorants that enhance visual appeal and as bioactive compounds with antioxidant and antimicrobial properties that contribute to shelf-life stability. This multifunctionality makes anthocyanins particularly valuable in functional food formulations and underscores their potential as natural alternatives to synthetic colorants, promoting healthier food choices and consumer well-being [80].

4. Anthocyanin Applications in Packaging

Food packaging, which can protect food from environmental exposures and delay food deterioration, plays an important role in the whole supply chain [101].

Although conventional petroleum-based packaging materials, such as plastics, remain dominant in the food packaging industry, they primarily serve as sanitary barriers and lack the capability to monitor food freshness in real time. This limitation hinders accurate assessment of product quality and may increase the risk of food safety issues and manufacturing inefficiencies [102]. In addition, the significant amounts of waste generated as a result of the improper disposal of traditional petroleum-based packaging materials have caused significant health and environmental damage [103].

As a result, instead of the existing traditional packaging materials, there is a growing need to enhance the properties of biopolymer films by adding biodegradable materials and environmentally friendly indicators to smart packaging [104].

4.1. Polymer Matrices for Anthocyanin Incorporation

Biopolymers are emerging as sustainable and environmentally friendly alternatives to conventional petroleum-based packaging materials. Biopolymers for food packaging are classified into three main categories: natural biopolymers, synthetic biopolymers, and microbially derived polymers, each with unique features that make them appropriate for specific packaging applications [105].

Recent studies have highlighted the emergence of natural biopolymers, such as proteins [106], polysaccharides [107], and lipids [108], as viable and sustainable alternatives to conventional synthetic polymers. These biopolymers possess distinctive physicochemical properties, including biodegradability, biocompatibility, and responsiveness to environmental stimuli, making them particularly suitable for use in active and smart packaging systems aimed to enhance food safety, prolonging shelf life, and minimizing environmental impact [109,110].

Naturally active compounds, such as anthocyanins, have been shown to be safe, non-toxic, and compatible with these biopolymeric materials. When incorporated into biopolymer-based films, these compounds can serve as preservatives and effective food freshness indicators within active and smart packaging, allowing prolonged shelf life and real-time monitoring of food quality inside the package [111].

Anthocyanins are among the most extensively studied naturally active compounds, primarily due to their broad pH-responsive discoloration capabilities and their potential application as colorimetric indicators for detecting pH changes associated with food metabolites or microbial spoilage [112]. The color-changing effect and stability of anthocyanins can be enhanced due to hydrogen bonds and electrostatic interactions between these biopolymers and anthocyanins [111].

To address their stability issues [113] and preserve their functionality during processing and storage, advanced protective techniques such as co-pigmentation and encapsulation have been developed [80,114].

Over the past several years, a substantial body of research has been devoted to the development and application of functional packaging films incorporating anthocyanins, with the goal of preserving or monitoring the freshness of food [111].

Anthocyanins, which exist in a broad variety of structures, chemical compositions, and forms, are known for their ability to reversibly change their molecular structure and color in response to pH fluctuations [115]. This unique property makes them especially suitable as natural pH indicators for real-time monitoring of food spoilage and freshness [116]. As a result, anthocyanins extracted from various plant sources have been widely utilized in the formulation of both active and intelligent food packaging films [113].

The most common types of biopolymer matrix used in recent years to embed anthocyanins are presented below.

4.1.1. Polysaccharide-Based Matrices

Polysaccharides like starch and chitosan are highly compatible with anthocyanins due to their hydrophilicity and film-forming ability [110].

• Starch-Based Films

Starch matrices obtained from corn, wheat, potato, rice, cassava, etc., are good at film-forming, being biodegradable, but moisture sensitive [117,118]. The ability of film-forming relies on starch molecules (amylose and amylopectin) that can form cohesive, continuous films when gelatinized and cast [117,119]. Being a natural polysaccharide, starch can be readily degraded by microbes in soil or compost environments [120]. Also, starch contains many hydroxyl groups that readily form hydrogen bonds with water, making it sensitive to ambient humidity and water. This limitation can be countered by blending starch with hydrophobic polymers, like polyvinyl alcohol (PLA), or incorporating additives/nanofillers [121].

For instance, Prietto et al. (2017) [122] investigated corn starch films containing red cabbage anthocyanins (RCA) and found that embedding RCA significantly increased the water solubility due to the hydrophilic nature of anthocyanins, illustrating strong compatibility with polysaccharide matrices. Erna et al. (2022) [123] developed and characterized a biopolymer film also based on cornstarch and anthocyanins extracted from dried roselle calyx for prospective meat freshness monitoring applications. The indicator film showed high sensitivity to pH changes and inclusion of anthocyanin in the starch matrix led to an improvement in the mechanical stability and hydrophobicity of the film.

Cheng et al. (2022) [118] developed a smart film based on modified cassava starch (acetylated distarch phosphate) combined with red cabbage anthocyanin extract. This film demonstrated strong pH-responsive color changes compared with anthocyanin extracts from purple potatoes, red pitayas, red cabbage, Lycium ruthenicum, blueberries, and grapes, improved barrier and water-resistance properties, and provided good color stability, making it suitable for intelligent packaging.

Composite edible films based on cassava starch were developed by incorporating red cabbage and beetroot microparticles as fillers, which contain natural pigments. These fillers improved the films’ suitability for use as smart packaging. The films were applied as smart labels to monitor the spoilage of Argentine hake [124].

• Chitosan-Based Films

Chitosan is a natural polysaccharide obtained from the deacetylation of chitin from the exoskeletons of shellfish. It is water-soluble under acidic conditions and suitable for film formation [125].

Chitosan has natural antimicrobial properties, because its positively charged amino groups disrupt microbial cell membranes. It is biodegradable and biocompatible, ensuring environmental safety and suitability for food contact. Additionally, chitosan films are flexible, strong, and transparent, making them ideal for packaging applications [126].

Despite their multiple recognized properties, chitosan as a packaging material presents certain disadvantages such as high moisture sensitivity, low mechanical and thermal stability, and poor ultraviolet light barrier properties [127,128,129], often requiring improvement by blending with other biopolymers or incorporating natural antioxidants, including anthocyanins [130]. The hydrogen bond and/or electrostatic interactions between anthocyanins and chitosan can lead to changes in the barrier, optical, mechanical, and thermal properties of chitosan-based films [131].

Chitosan films serve as active packaging by offering antimicrobial protection to prolong food shelf life. When combined with pH-sensitive natural pigments like anthocyanins, they function as intelligent packaging that changes color to indicate freshness or spoilage, creating a hybrid film with both antimicrobial and real-time monitoring capabilities [132].

pH-sensitive films based on chitosan and anthocyanins extracted from black soybean seed coat (BSSCE) were successfully developed by Wang et al. (2019) [133]. Although the obtained chitosan–BSSCE films had lower moisture content and transparency compared to chitosan film, the incorporation of anthocyanin-rich extract led to an improvement in water vapor and UV–Vis light barrier properties, mechanical strength, thermal stability, and antioxidant activity.

Tavassoli et al. (2023) [134] used anthocyanins extracted from red poppy (Papaver rhoeas L.) petals and chitosan to prepare a pH-sensitive indicator film for the real-time detection of shrimp freshness. They found that the addition of anthocyanins resulted in an increase in the tensile strength and antioxidant properties of chitosan films.

Biodegradable films using chitosan derived from shrimp shell waste and anthocyanin-rich extract from grape skins were developed by Barreto Alves Zacheski et al. (2025) [135]. The incorporation of anthocyanins improved several properties of the biopolymeric films, the anthocyanin–chitosan films showing increased thickness, tensile strength, elongation at break, and water vapor permeability and significantly higher antioxidant activity.

Athanasiou et al. (2025) [136] developed biodegradable pH-responsive chitosan films enriched with anthocyanins extracted from wine lees. Compared to pure chitosan film, the developed films exhibited an excellent colorimetric response to pH changes, improved mechanical properties, nearly zero UV permeability, and increased antioxidant activity. Also, the film was applied in detecting pork freshness, showing a clear color change in the early stages of spoilage.

A chitosan-based film enriched with oregano essential oil and black rice bran anthocyanins was developed as an active–intelligent packaging with strong mechanical, antimicrobial, antioxidant, and UV-barrier properties and rapid sensitivity to pH and ammonia changes. Applied to pork stored at 4 °C, the film preserved quality, reduced microbial growth, and delayed spoilage. A visible color shift from red to green by day 12 indicated spoilage, demonstrating its effectiveness for both preservation and real-time freshness monitoring [132].

There have been many other attempts to improve the functionality of chitosan films by incorporating anthocyanin extracts from various natural matrices such as purple-fleshed sweet potato [137], purple and black eggplant [116], purple and black rice [138], Roselle plant [139], or purple tomato [140].

• Cellulose and Cellulose Derivatives

Cellulose and its derivatives are biodegradable, transparent, and film-forming materials commonly used in packaging alone or in combination with other biopolymers to enhance film functionality [141,142,143]. When incorporated with natural pigments like anthocyanins, cellulose-derivative films can serve as intelligent packaging, displaying visible color changes in response to spoilage, making them effective freshness indicators.

For example, carboxymethyl cellulose (CMC) films were loaded with natural pH indicators from Karanda anthocyanins (CA), butterfly pea flower (BA), or curcumin (CC). The film variant with CA and BA in a 75:25 ratio exhibited high sensitivity to ammonia and pH shifts, showing distinct color transitions [144]. Applied in a real food system, this indicator film proved to be the most sensitive for monitoring the freshness of shrimp, as it showed a distinct color change and a positive correlation between its response and the deterioration process of shrimp [145].

Boonsiriwitet al. (2022) [146] developed a composite film made from hydroxypropyl methylcellulose (HPMC) reinforced with microcrystalline cellulose (MCC) and roselle anthocyanin extract as a pH-sensitive indicator film. The film exhibited clear color transitions when exposed to ammonia vapor or during chicken tenderloin spoilage, showcasing its potential for real-time freshness monitoring.

Intelligent cellulose acetate-based films containing red cabbage extract rich in anthocyanins were developed by Freitas et al. (2020) [147]. The incorporation of red cabbage extract resulted in color-changing capability, increased light barrier effects, and a plasticizer effect observed in the mechanical properties of the films. The films exhibited very good colorimetric transition properties upon exposure to volatile ammonia, despite offering a lower oxygen barrier and thermal stability.

Shayan et al. (2022) [148] developed pH-sensitive packaging films using a combination of cellulose nanocrystals and nano-fibrillated cellulose as a matrix for anthocyanins extracted from red cabbage. The indicator films exhibited rapid and visually detectable color changes upon pH variation and exposure to ammonia vapor. They found that the addition of red cabbage extract improved the elongation at break and flexibility of the films, but the tensile strength and tensile modulus were reduced. The indicator film with a content of 30% red cabbage extract showed optimal physical, mechanical, and optical properties, the shortest response time at alkaline pH, and proved its effectiveness for monitoring shrimp freshness.

Tohamy (2025) [149] reported a new type of intelligent food packaging material based on hydroxyethyl cellulose (HEC) as a matrix. The pH-sensitive and fluorescent film was prepared by incorporating carbon dots modified with sulfur and nitrogen and anthocyanins derived from onion peel waste into hydroxyethyl cellulose. The film was tested on chicken meat, demonstrating its ability to visually detect changes in food quality, such as spoilage, and inhibit the growth of foodborne pathogens, such as Salmonella.

Bacterial cellulose (BC) has also been tested as a substrate for anthocyanin immobilization in the development of colorimetric films. Bacterial cellulose is an extracellular product secreted by some bacterial species during fermentation processes [150]. For example, Abdelkader et al. (2024) [151] developed a pH-sensitive film based on the immobilization of red cabbage extract in bacterial cellulose to monitor both the microbial contamination and gamma radiation of stored cucumbers. Also, anthocyanins extracted from Echium amoenum flowers [152] and black carrots [153] were incorporated into bacterial cellulose to develop intelligent pH-sensitive indicators for monitoring the freshness of shrimp [152] and fish [153].

• Alginate-Based Films

Alginates are naturally occurring polysaccharides, commonly extracted from brown algae and further processed and purified into alginate salts, such as calcium and sodium alginates [154].

Biopolymers like sodium alginate have been extensively utilized as substrates for developing anthocyanin-based films, enhancing their mechanical strength and barrier performance. Moreover, these biopolymers offer benefits such as excellent film-forming ability, non-toxicity, biodegradability, and biocompatibility [111].

Alginate-based films are edible, form-stable gels, and are highly compatible with hydrophilic dyes like anthocyanins. These properties make them ideal for use as visual indicators in intelligent food packaging, where blends such as sodium alginate with anthocyanins can detect spoilage through pH-sensitive color changes [155,156].

For example, Santos et al. (2022) [155] developed active–intelligent and biodegradable sodium alginate films loaded with Clitoria ternatea anthocyanin-rich extract for monitoring the quality of milk, pork, and shrimp. The films proved to have high light barrier capacity, improved tensile strength and thermal stability, antibacterial action against E. coli, good compatibility with aqueous and acidic foods and great colorimetric potential for indicating different pH, ammonia gas, and sterilization levels [155]. The incorporation of purple onion peel extract into the sodium alginate matrix resulted in opaque red films with enhanced antioxidant activity, film thickness, and lower water solubility, but the films did not exhibit antimicrobial activity against the microorganisms studied [157]. In a recent study, Santos & Martins (2024) [158] developed multifunctional films based on sodium alginate blended with different mixtures of butterfly pea flower and purple onion peel extracts. Combining the two extracts, better active and intelligent performances were obtained compared to the films containing a single extract. The multifunctional films protected the color of food products against the effects of UV-light and were capable of colorimetrically checking the deterioration of protein-rich products.

4.1.2. Protein-Based Matrices

Protein-based films are increasingly studied as sustainable packaging alternatives, derived from both plant (gluten, soy, zein) and animal (casein, whey, gelatin) sources. These materials offer excellent gas barrier properties, while their water repellency remains limited due to protein hydrophilicity [159].

Proteins interact well with anthocyanins and provide improved stability, nutritional, and functional properties to the complex [160].

• Gelatin-Based Films

Gelatin-based films, derived from collagen found in animal skin and bones, offer excellent flexibility and transparency, making them ideal for use in pH-responsive color-changing applications. Incorporating natural colorants into gelatin-based films can enhance their morphology and address key limitations. These additives improve film strength, gas barrier performance, and water vapor resistance, while also imparting antioxidant and antimicrobial properties [161].

Thus, Musso et al. (2019) [162] developed edible gelatin films incorporated with red cabbage anthocyanin extract which improved the films’ mechanical behavior and important antioxidant properties that function as pH-sensitive color indicators, making them ideal for smart packaging applications such as real-time spoilage detection in food. Hematian et al. (2023) [163] successfully developed a pH-sensitive film based on fish gelatin and Coleus scutellarioides anthocyanin extract. The obtained films showed good color changes at different pHs and a good ability to display fish spoilage.

• Soy Protein Isolate (SPI)

Soy protein isolate (SPI), derived from soybeans, is a sustainable, abundant, and cost-effective material with excellent film-forming ability, making it ideal for developing biodegradable and biocompatible packaging. SPI-based films are soft, transparent, uniform, and provide good gas barrier properties. Due to its safety and edibility, SPI can also be directly applied to food surfaces as an edible coating. It is often used to develop films containing anthocyanins for intelligent packaging applications [164].

For example, Wang et al. (2012) [165] studied the modification of the properties of edible soy protein isolate (SPI) in the presence of anthocyanin-rich red raspberry (Rubus strigosus) extract (ARRE). The resultant films showed significantly enhanced tensile strength which could prolong their usage life, decreased water solubility and water vapor permeability. Thus, SPI-ARRE film could be used as a drying agent in form of a water-absorbing sheet for preserving dried foods or as a food wrap with unique color.

• Whey Protein Films

Whey protein derived from dairy by-products can form transparent, flexible films with excellent oxygen barrier properties, making them suitable for edible coatings and biodegradable packaging. Developing stable films using only whey protein and anthocyanin extract is technically challenging, as the absence of plasticizers or supporting agents can lead to poor cohesion, brittleness, and compromised mechanical and barrier properties, which are typically improved by polysaccharides or synthetic additives [166].

4.1.3. Biopolyester and Composite Matrices

• Biopolyester Matrices: Polylactic Acid (PLA)

Polylactic acid (PLA), a biodegradable polyester derived from renewable sources, is widely used as a sustainable packaging material. Although PLA films offer good mechanical strength and transparency, they are usually used in combination with polysaccharides and modified with plasticizers, fillers, or active compounds such as anthocyanins to overcome brittleness and enable intelligent packaging functionalities [167,168].

For instance, León Vázquez et al. (2025) [168] designed some films of polylactic acid/cellulose acetate, incorporated with anthocyanin enriched black carrot extract for seafood preservation. To improve the physical characteristics of the film, PLA was used in combination with cellulose acetate, and PEG-DE500 was used as a plasticizer.

Moreover, a pH-sensitive indicator film made from PLA, polyethylene glycol (PEG), and elderberry anthocyanins was developed to monitor chicken freshness. The film showed good uniformity, with PLA improving barrier properties and PEG enhancing flexibility. It responded visibly to pH and ammonia vapors, changing from pink/purple to brown/gray over 6 days of cold storage, demonstrating its effectiveness for real-time spoilage detection [169].

• Blended or Composite Biopolymer Matrices

Blending different biopolymers is a widely adopted strategy in the development of intelligent packaging films, particularly those incorporating natural pH indicators like anthocyanins. Single polymers often exhibit limitations such as brittleness, poor moisture resistance, or low flexibility. By combining polymers, such as proteins, polysaccharides, and biodegradable polyesters, these limitations can be minimized, resulting in films with improved mechanical strength, barrier properties, and stability [131,167]. The most commonly used polymers used in combination with anthocyanins are polyvinyl alcohol, starch, and chitosan [33].

For example, the integration of roselle anthocyanin into a gelatin–tapioca starch matrix resulted in the obtaining of a smart film with both pH and ammonia gas sensing capabilities which was tested for its physical, mechanical, and barrier properties. The results showed that higher anthocyanin concentrations enhanced elongation properties and pH sensitivity, while also imparting clear responsiveness to ammonia gas [170].

A composite film using carboxymethyl cellulose (C) and sodium alginate (S) and 12% red cabbage anthocyanin (R) was developed by Huang et al. (2023) [171] to both preserve pork and indicate freshness. The film showed good mechanical properties, good antibacterial activity, and pH-responsive color change in response to ammonia. The resulting dual-functional CSR film showed strong potential for active and intelligent food packaging.

Smart packaging films were designed based on a carboxymethyl cellulose (CMC)-agar gel matrix containing curcumin, red cabbage, or butterfly pea flower anthocyanins, with good results regarding their thermal stability, surface and mechanical properties, Water Vapor Transmission Rate, halochromic response, and durability to environmental exposure [143].

Nadi et al. (2023) [172] demonstrated that incorporating red cabbage extract as a colorimetric indicator into a chitosan–basil seed gum film enhanced key material properties, including solubility, water vapor permeability, and flexibility. Similarly, Li et al. (2024) [173] developed a composite film combining chitosan and gelatin with butterfly pea flower anthocyanin extract for monitoring beef freshness, which exhibited exceptional pH sensitivity, capable of detecting changes not visible to the naked eye. Also, butterfly pea flower anthocyanin extract was incorporated in a cellulose–chitosan matrix by Hailu et al. (2025) [174] and used as an intelligent packaging film, proving good colorimetric response, film thickness, tensile strength, and uniform anthocyanin distribution over the biopolymer matrix.

Moreover, chitosan (CS) and carboxymethyl cellulose (CMC) composite films loaded with blackberry anthocyanins (BA) and tea polyphenols (TP) were prepared by the solution casting method and tested for their potential to preserve the chilled beef. The films showed higher tensile strength and elongation at break, and lower UV–vis light transmittance, moisture content, and water vapor permeability. The formation of chemical cross-linking (ester bonds) in the CS and CMC was also proved, along with the presence of intermolecular hydrogen bonds among TP, BA, CS, and CMC [175].

Chen et al. (2024) [156] incorporated Aronia melanocarpa anthocyanins stabilized with tea polyphenols in a sodium alginate–pectin matrix and obtained an intelligent active packaging film for shrimp preservation and monitoring. The film revealed reduced surface roughness, enhanced tensile strength, compatibility, anthocyanin stability, and pH-sensitivity and also antioxidant activity and antibacterial properties that extended the shelf life of the food.

Karadag et al. (2024) [176] developed microencapsulated grape juice powders using spray-drying with a maltodextrin (MD) and black ‘Isabel’ grape peel pectin (GP) blend. Replacing 25% of MD with GP (75:25, w/w) improved powder yield (from 46.0 ± 1.5% to 60.35 ± 1.84%) and significantly increased anthocyanin encapsulation efficiency (from 55.70% to 88.66%). The optimized powder was incorporated into jellies, resulting in stronger, less brittle textures due to increased pectin and soluble solids. The high water solubility and color properties of pigmented GP also suggest its suitability for functional beverages and pH-sensitive edible films.

The synergistic blending of matrix components also enhances the compatibility of anthocyanins within the film matrix. Anthocyanins, being water-soluble and pH-sensitive, are prone to degradation when exposed to light, oxygen, or high temperatures [33,80]. Mixed polymer systems can create a more balanced environment that stabilizes anthocyanins through hydrogen bonding, reduced mobility, and encapsulation effects [33,177]. Moreover, these systems support uniform morphology, with a continuous polymeric matrix, and preserve the color-changing response critical for freshness indication [33], enabling the development of multifunctional films with better performance, extended shelf-life potential, and reliable visual indicators for food quality monitoring [178].

4.2. Active Food Packaging

The potential of active food packaging for preserving food has been expansively studied [80], active packaging playing a dynamic role in extending the shelf life of foods and improving their safety and sensory properties, as well as maintaining their quality, through their interaction with the packaged food and the surrounding environment [29].

Active packaging contains active substances within the packaging materials, which are released into the food or absorb components from the surrounding environment [179], creating a barrier and blocking features that either suppress or inhibit microbial growth within the packaged product [180] and can enhance the shelf stability of foods by decreasing the microbial growth and prolonging the lag phase [181]. Also, the active substances can act to reduce the oxidative stress caused by free radicals through scavenging of reactive oxygen species [182], counteracting the oxidation of food during storage and its undesirable changes like color, taste, texture, and nutritional value [111].

In this context, anthocyanins have garnered significant attention in active food packaging [80,183] due to their powerful antimicrobial properties and antioxidant capacity, making them ideal functional materials for active packaging [133,184].

Considering the antimicrobial and antioxidant properties of anthocyanins, Wang et al. (2025) [185] developed a sustainable photothermal antibacterial film using chitosan (CS), ferric ions, and anthocyanin-rich purple corn cob extract (PCCE) for cherry tomato preservation. Among the formulations, the CS-PCCE/Fe2 film (8 mg/mL PCCE, 2 mg/mL FeCl₃, 4% w/v CS) was selected for its lower photothermal temperature and optimal performance. When applied to cherry tomatoes and exposed to NIR light (5 min on days 1, 6, 12, and 18 at 25 °C), the CS-PCCE/Fe2 film effectively preserved fruit quality, showing reduced pH changes, lower weight loss, and minimal hardness degradation. It also exhibited strong antibacterial activity under NIR irradiation, particularly against S. aureus, highlighting its potential as an eco-friendly, active packaging material for shelf-life extension. In a recent study, Wu et al. (2025) [186] successfully incorporated purple sweet potato anthocyanin into a chitosan/polyvinyl alcohol film matrix loaded with silver nanoparticles and demonstrated its application in strawberry preservation. The findings suggest that, by utilizing the PVA/CS-AgNPs-PSPA10 composite film, with superior physical and functional attributes compared to other variants, the shelf life of strawberries reached 13 days at 4 °C, preserving their nutrients and appearance. Also, it showed antibacterial activity through its remarkable antibacterial properties which thus demonstrated its significance in developing antibacterial indicator composite packaging materials for fruit and vegetable preservation.

Yu et al. (2025) [187] prepared chitosan/corn starch (CTS/Corn)-based films by adding nanocomplexes of Vaccinium vitis-idaea anthocyanins encapsulated with carboxymethyl chitosan (CMC), chitosan hydrochloride (CHC), and whey protein isolate (WPI) as active packaging materials in shrimp preservation using the solvent casting method. According to the results, the CTS/Corn-AN film had a longer-lasting antioxidant capacity compared to CTS/Corn-FA film, the anthocyanins in the nanocomplexes of the CTS/Corn-AN film were progressively released compared to the free anthocyanins in the CTS/Corn-FA film, and CHC/CMC-WPI acted as a physical barrier to prevent anthocyanins from being affected by the surrounding environment. Furthermore, the results demonstrated that the CTS/Corn-AN film effectively preserved the freshness of shrimp given its long-lasting antibacterial and antioxidant properties. Hence, the CTS/Corn-AN film proved to be a promising active packaging material for shrimp preservation.

Chen et al. (2025) [175] developed chitosan (CS) and carboxymethyl cellulose (CMC) edible films loaded with blackberry anthocyanins (BA) and tea polyphenols (TP) as an environmentally friendly food packaging material through the solution casting method for applications in beef preservation. Afterwards, meat samples were stored at 4 °C in a refrigerator for 12 days and put in sterilized fresh-keeping bowls sealed with the CS/CMC, CS/CMC/BA, CS/CMC/TP, and CS/CMC/BA/TP films. Unsealed meat samples were treated as the control (CON). In comparison with CS/CMC film, the CS/CMC/BA/TP film displayed better freshness-keeping properties by decreasing protein degradation, enhancing oxidative stability, and preventing aerobic bacterial growth on beef, leading to a longer shelf life. These findings indicate that the film has the potential to be used as a promising alternative for active food packaging.

In another study, Wang et al. (2019) [188] fabricated cranberry anthocyanin (ACN) nanocomplexes using chitosan hydrochloride (CHC) and carboxymethyl chitosan (CMC), incorporated into a gelatin-based film formulation (Gel CHC/CMC-ACNs film), as a functional food packaging for olive oil protection. In addition, the effects of Gel-CHC/CMC-ACN films on inhibiting lipid oxidation in olive oil were evaluated by measuring the peroxide value (POV) in stored olive oil compared with pure gelatin film (Gel film) and unencapsulated ACN-gelatin mixed film (Gel-ACN film). The results demonstrated that the Gel-CHC/CMC-ACN film considerably slowed olive oil oxidative deterioration (21.2 meq O₂/kg of peroxide value at the 56th day) when compared with the films composed of gelatin only (Gel film, 28.4 meq O₂/kg of peroxide value at the 56th day) or ACN (unencapsulated form) and gelatin (Gel-ACNs film, 24.3 meq O₂/kg of peroxide value at the 56th day). Thus, the Gel-CHC/CMC-ACN film can be beneficial as a functional, edible film used in food packaging to extend the shelf life of fatty foods [188].

More studies supporting the application of anthocyanins as films for active food packaging are detailed in

Table 2. Anthocyanins as components in Active Food Packaging.

References	Source of Anthocyanins	Extraction Method	Applications	Film Matrix/Other Active Components	Advantages/Disadvantages
[185]	Purple corncob	Ultrasonic assisted extraction with ethanol	Cherry tomato preservation	Chitosan matrix	Photothermal properties, hydrophobicity, thermal stability, high bactericidal activity and tensile strength/Generated heat could affect the texture, taste, and nutritional content of delicate products; limited applicability
[189]	Grape peels	Ultrasonic assisted extraction with ethanol	Cherry tomato preservation	γ-cyclodextrin metal- organic framework loaded with titanium dioxide	Improved resistance of anthocyanins to high temperature, UV light and oxidation; phage stability extended to 30 days at room temperature; effective and efficient antioxidant and bacteriostatic effects
[190]	Blueberry	-	Blueberry preservation	Polylactic acid/quaternized chitosan electrospun nanofiber	Enhanced water resistance; antioxidant and antimicrobial properties; great potential in extending the shelf life of blueberries/Reduced stiffness and gas barrier properties of the film
[186]	Purple sweet potato	-	Strawberry preservation	Chitosan/polyvinyl alcohol film matrix loaded with silver-nanoparticles	Excellent antibacterial properties; antibacterial indicator composite packaging materials for fruits and vegetables preservation/Excessive anthocyanin content led to a decrease in brightness
[191]	Lingonberry	Ultrasonic assisted extraction with ethanol	Fish (crucian carp) preservation	Gelidium amausli polysaccharide matrix	Strong antioxidant activity; free radical scavenging ability, antibacterial properties, and oxygen barrier performance; enhances the shelf life of the fish/Small sample size, restricting the generalizability of the findings
[187]	Vaccinium vitis-idaea	Sonication extraction in ethanol	Shrimp preservation	Chitosan/corn starch matrix	Effective preservation of shrimp; durable antibacterial and antioxidant properties; superior mechanical, moisture-resistance, and thermal stability qualities; suitable for long-term food packaging
[156]	Aronia melanocarpa	Ultrasonic extraction in acidic ethanol	Shrimp preservation	Sodium alginate/pectin matrix	Good antioxidant and antibacterial properties; capability to extend the shelf life of shrimp by approximately 12 h compared with the control group; substantial potential for food preservation
[192]	Blue honeysuckle	Sonication extraction in ethanol	Pork preservation	Chitosan/polyvinyl alcohol blend matrix	Antibacterial properties and durable antioxidant properties; suitable for long-term food packaging, effectively prolonging the storage period of pork
[193]	Wild cranberries	Ultrasonic crusher with ethanol	Pork preservation	κ-carrageenan/potato starch matrix	Antioxidant and antimicrobial properties (especially against Staphylococcus aureus); extended the shelf life of pork by up to 40 h compared to control group
[175]	Blackberry anthocyanins	Ultrasonic assisted extraction with ethanol	Beef preservation	Chitosan-carboxymethyl cellulose matrix	Protein breakdown capacity, improved oxidative stability, preventing the growth of aerobic bacteria on beef, extending its shelf life; good tensile strength, elongation at break, lower UV–vis light transmittance, and water vapor permeability
[194]	Purple sweet potato	Ethanol extraction	Beef preservation	Double-layer film: inner layer, agar; outer layer, κ-carrageenan-oregano essential oil Pickering emulsion/silver nanoparticles	Outstanding antioxidant and antimicrobial properties, with deceleration of beef spoilage rates; enhanced hydrophobicity and UV–vis barrier properties; good capabilities in food preservation
[195]	Lycium ruthenicum Murr.	Ethanol extraction	Mutton preservation	Soybean isolate protein/xanthan gum/agar	Mechanical and waterproof properties; strong antioxidant activity, significantly extending the shelf life of lamb meat during storage
[196]	Lycium ruthenicum Murr.	Ethanol extraction	Pork preservation	Cassava starch	Water vapor and ultraviolet-visible light barrier ability, tensile strength and antioxidant potential; can be used as active packaging films to extend the shelf life of food
[197]	Red cabbage	Ethanol–water extraction	Pasteurized milk preservation	Polyvinyl alcohol/starch	Good antibacterial activity against foodborne bacteria, like, E. coli and MRSA; can be utilized effectively for enhancing shelf life of food
[198]	Red cabbage	-	Gouda cheese preservation	Carboxymethyl cellulose/polyvinyl pyrrolidone/guar gum	Good antimicrobial, physical, mechanical, and thermal properties; the shelf life of cheese was extended for more than 10–12 day compared to the conventional packaging system/Reduced biodegradability of films with essential oil addition
[199]	Lycium ruthenicum	-	Milk preservation	Sodium alginate/konjac glucomannan	Significantly improved mechanical, barrier and antioxidant/antibacterial properties; excellent preservation effect in milk
[200]	Prunus maackii pomace	Ethanol extraction	Oil preservation	κ-carrageenan/hydroxypropyl methylcellulose	Increased flexibility, barrier properties, and antioxidant properties in the film, extending the oil’s shelf life; potential use for oil packaging
[188]	Cranberry	-	Olive oil preservation	Chitosan hydrochloride/carboxymethyl	Improved mechanical properties, thermal stability, and antioxidant capacity; edible packaging film suitable for extending the shelf life of fatty foods

. These findings prove the great potential of anthocyanins in the development of active packaging.

4.3. Intelligent Food Packaging

The great interest in the development and application of functional packaging films incorporating anthocyanins has consistently demonstrated the effectiveness of anthocyanin-based films, particularly when combined with intelligent packaging technologies, in providing real-time, visual indicators of food quality. Such systems enable both consumers and producers to assess freshness and detect early signs of spoilage in a wide range of perishable food products, including meat, seafood, dairy, fruits, and vegetables, through easily observable, pH-sensitive color changes [111].

Fresh meat and seafood are rich in proteins and lipids, which, during storage, undergo degradation processes that lead to the formation of various biogenic amines, primarily ammonia, triethylamine, and dimethylamine. These compounds, collectively referred to as total volatile basic nitrogen (TVB-N), are widely recognized as key physicochemical indicators for evaluating the freshness and quality of meat products [201,202,203].

These compounds contribute to enzymatic and microbial degradation in protein-rich foods, leading to noticeable pH fluctuations within the packaged products [204]. Such pH variations can be effectively monitored using smart pH-sensitive indicator films, which allow for real-time assessment of product spoilage [205]. Consequently, the development of reliable freshness indicators for meat products has become increasingly important, given their high vulnerability to microbial contamination and rapid deterioration [206].

Thus, the growing interest in anthocyanins for the development of pH-based colorimetric sensors for usage in intelligent packaging has received considerable attention from the meat industry. Anthocyanin-rich extracts can be encapsulated in films to monitor the spoilage/freshness of any meat product by visibly changing the color of the films [113].

For example, Liu et al. (2021) [207] developed novel colorimetric films by immobilizing different concentrations of anthocyanin extracted from red cabbage (RCAs) into a polyvinyl alcohol/sodium carboxymethyl cellulose (PVOH/CMC-Na, CPVH) matrix. The colorimetric films showed noticeable color changes, from red to blue-green, when applied to monitor the freshness of pork at 25 °C for 24 h. The application test concluded that CPVH/RCAs-20 colorimetric film exhibited a more noticeable color variation compared to the other types during the shelf life of the pork sample, indicating that lower concentrations of incorporated RCAs can show pork spoilage more clearly in response to the ammonia produced during storage. Therefore, the study highlights that the prepared colorimetric films containing RCAs have potential as freshness indicators and intelligent packaging for meat products. Alizadeh-Sani et al. (2021) [208] fabricated novel multifunctional halochromic smart films by incorporating saffron petal anthocyanins into a methyl cellulose/chitosan nanofiber matrix to protect and detect the freshness of a model meat product (lamb). The total anthocyanin content of the solution was determined to be 1.994 ± 0.005 mg/mL. The research indicated that during storage, the films color variation changed from reddish/pink to violet to green to yellow as the pH was increased from 1 to 14 and went from violet to green/yellow when the ammonia vapor concentration was increased. Therefore, the color-changing ability of halochromic smart films in response to pH and ammonia level alterations can be used in smart packaging materials for monitoring changes in the freshness of meat products during storage. In another study, Lan et al. (2021) [209] successfully developed multifunctional food packaging films by incorporating red apple pomace extract (APE) into a chitosan-based (CS) film reinforced by TiO₂ nanoparticles, which were then applied as an indicator to monitor the freshness of salmon filets. The study shows that during storage, CS-TiO₂-APE films showed fast and intensive color variations in the pH range from 6 to 8; the pH of salmon samples increased from 6.08 to 6.62 in 24 h, then reached 7.14 at 48 h because of the formation of volatile amine compounds, indicating the spoilage of the fish. Hence, the developed films were successfully applied as indicators to monitor the freshness of salmon filets.

It is well known that dairy products are naturally very sensitive to chemical and microbial spoilage during distribution and storage. Therefore, it is extremely important to develop cost-effective and time-efficient methods for real-time detection of spoilage in these products [210]. In recent years, considerable research has been directed toward the development of innovative pH-sensitive indicator films utilizing anthocyanins from various natural sources to detect spoilage in such dairy products. During storage, the metabolic activity of lactic acid bacteria and the accumulation of organic acids result in changes in pH and acidity, ultimately affecting the stability and quality of these products [137].

Milk quality can be effectively assessed through its pH and titratable acidity, both of which serve as critical indicators of microbial activity and spoilage. Fresh milk generally exhibits a near-neutral pH, typically ranging between 6.6 and 6.8, reflecting minimal microbial fermentation and high microbiological quality [211]. As spoilage progresses, primarily due to the growth of lactic acid bacteria and the accumulation of organic acids, the pH decreases significantly, often falling within the range of 4.5 to 5.5 in spoiled milk. In parallel, titratable acidity rises, and when it exceeds 30 °Thorner (°T), the sensory characteristics of milk, such as sour taste and altered odor, become perceptible even to untrained individuals, clearly indicating the onset of spoilage [212]. Thereby, the pH value and acidity are the two main indicators for the evaluation of milk freshness [209].

Given these aspects, Yong et al. (2019) [116] prepared active and intelligent food packaging films by mixing chitosan (CS) with anthocyanin-rich purple eggplant extract (PEE) or black eggplant extract (BEE). The anthocyanin content in PEE and BEE was 93.10 and 173.17 mg/g, respectively. The pH-sensitivity of CS-PEE and CS-BEE films with different amounts (1, 2, and 3 wt%) of PEE or BEE were further used to monitor milk spoilage. CS-PEE III, CS-BEE II, and CS-BEE III films showed obvious color changes when immersed in the spoiled milk stored at 40 °C for over 10h. The color of CS-PEE and CS-BEE films changed from purple to green/blue due to the growth of organic acids and lactic acid bacteria which leads to changes in pH activity. Therefore, the results of the study suggest that CS-PEE and CS-BEE films could be used in the future as active and intelligent packaging films.

Goodarzi et al. (2020) [210] developed an intelligent freshness indicator by immobilizing anthocyanins from black carrots within a starch matrix with a total anthocyanin content of 10 mg/100 mL to monitor milk freshness and spoilage. After one month of storage at different conditions, the prepared label exhibited noticeable color variation as a function of pH and excellent color stability. The total color difference (TCD) value of the indicator corresponded to the pH, acidity, and microbial growth of the pasteurized milk. The developed label can differentiate fresh milk from the milk entered into the initial (TCD: 7.8 after 24 h) and final (TCD: 34.8 after 48 h) steps of spoilage. The research findings highlight a new perspective, to use anthocyanins incorporated into biopolymer-based materials in the development of intelligent milk packaging.

In a study conducted by Weston et al. (2020) [213], an Active Use-By Date (AUBD) indicator was developed using red-cabbage-derived anthocyanins immobilized within an agarose matrix via the solution casting method. The sensor was tested by immersing it in real milk samples subjected to spoilage conditions at 30 °C over a 24 h period. A distinct and progressive color change was observed in response to increasing lactic acid concentration, which correlated with microbial spoilage: the film displayed a blue hue at pH 6.8 (indicative of fresh milk), shifted to purple at pH 5.5 (signaling the onset of spoilage), and turned pink at pH 4.3 (indicating spoiled milk). These results demonstrated the sensor’s ability to accurately and visually differentiate milk samples with varying pH levels, effectively simulating different stages of spoilage. The study thus highlights the potential of anthocyanin-agarose films as practical, visual indicators for real-time freshness monitoring in dairy products.

A different study was published by Zhang et al. (2024) [214] referring to a smart packaging film based on polyvinyl alcohol (PVA) and blueberry anthocyanin (ACN)-loaded sodium alginate–chitosan quaternary ammonium salt (HACC-SA) nanocomplexes for monitoring milk freshness. Based on the study results, the initial pH and acidity of fresh milk were 6.69 and 16.20 °T, respectively. After 48 h, the pH of the milk decreased to 5.49 and the milk started to deteriorate, while the color of the film changed from purple to red-purple. When the milk was tested after 72 h, the pH was 4.60 and the acidity was 33.03 °T, suggesting that the milk was totally spoiled and showing that the P/HACC-SA-ACN films were suitable and promising as smart packaging materials.

To date, anthocyanin-based films remain relatively underutilized in food packaging, particularly for fruits and vegetables. However, they are attracting increasing interest due to their pH-sensitive color-changing properties, which make them promising candidates for use as freshness indicators [111].

In a sealed package, as fruits and vegetables start to deteriorate, the released CO₂ accumulates, potentially leading to a more acidic atmosphere within the package, causing the intelligent indicator films to change color, which can be easily observed, providing a quick and non-destructive way to determine the food’s freshness. This can be a valuable tool for consumers and producers to assess food quality without opening the package [215,216]. These films are considered “smart” or “intelligent” packaging because they can provide real-time information about the food’s condition. This can be particularly useful for fresh-cut produce, where spoilage can occur rapidly. This is particularly useful for fruits and vegetables, where spoilage can be difficult to detect visually in the early stages [217]. However, in order to use them in intelligent food packaging, some anthocyanin-based films can be sensitive to light and heat and may have limitations in terms of mechanical strength and flexibility, which can affect their color and functionality [218]. Despite these challenges, their potential for enhancing food packaging and freshness monitoring is substantial, and ongoing research is focused on overcoming these limitations.

For example, Xu et al. (2025) [190] developed a novel polylactic acid (PLA) electrospun nanofiber film incorporating blueberry anthocyanins (ACN) and hydroxypropyltrimethyl ammonium chloride chitosan (HACC), designed for dual functionality as both intelligent and active packaging in blueberry preservation. Among films with varying ACN content (2–10 wt%), the 6% ACN/PLA/HACC film demonstrated the most notable color response and performance during storage. The film exhibited distinct pH-sensitive color changes across a pH range of 3 to 11 and responded visibly to blueberry spoilage: changing from white on day 0 to pink-purple by day 4, deep purple on day 6, and light pink by day 8. These changes were attributed to CO₂ release and organic acid volatilization, which lowered the surface pH. The findings suggest that the 6% ACN/PLA/HACC film holds strong potential for extending shelf life and monitoring quality in blueberry packaging.

Maftoonazad and Ramaswamy (2019) [219] prepared an electrospun nanofiber mat based on polyvinyl alcohol and a natural pigment from Brassica oleracea L. extract (RCE) to function as a pH biosensor and monitor pH-linked changes in fresh date fruit (Rutab). In order to examine the pH sensors’ color shift during storage, three biosensor mats were placed directly on the fruits’ surface in different areas. To correlate the color shift in the indicator with the spoilage of Rutab fruit during storage, samples were taken at different time points, and the pH was monitored to detect fruit spoilage. The results showed that the designed mat can be used as a pH sensor by indicating pH value shifts between 2 and 12. The studies conducted on fresh Rutab fruit have confirmed that the pH mat responses correlate well with pH variations in packaged dates, therefore allowing real-time monitoring of pH-linked variations inside the package.

Recently Yi et al. (2025) [220] prepared a film from Fe²⁺-loaded red radish anthocyanin (RRA) and zein composite nanoparticles (FZNPs) loaded onto chitosan/zein (C/Z), resulting in a highly sensitive smart film for mushroom freshness monitoring. The developed films were placed in a sealed package containing fresh mushrooms and stored at 4 °C for 15 days. Subsequently, the color changes in smart films were monitored on days 0, 3, 6, 9, 12, and 15. The smart film displayed noticeable color variations in response to pH changes and acetic acid gas. As the mushroom deteriorated, the smart film’s color variation indicated a clear sign of quality loss. Afterwards, a WeChat Mini Program was developed for mobile devices to monitor the freshness of mushrooms in real time based on the color parameters of the smart film. The RGB values of the film were manually added by users and then compared with a predefined database. In summary, this system demonstrated a quick and dependable method for assessing food quality, with potential applications in food monitoring and supply chain management.

Singh et al. (2021) [221] developed intelligent pH indicator films using a combination of anthocyanins extracted from the flower of Clitoria ternatea and the fruit of Carissa Carandas, which were incorporated into biodegradable chitosan/poly (vinyl alcohol) films for monitoring beverage freshness. The extracts and anthocyanin-incorporated films demonstrated excellent colorimetric changes from pH 2 to 8. In addition, the C. ternatea test films showed visible color shifts in the stored juice after 72 h at 25 °C, indicating their potential for detecting spoilage, and thus these could be further incorporated into packaging as a quality and freshness indicator for beverages.

Further studies regarding intelligent packaging are depicted in

Table 3. Anthocyanins as components in Intelligent Food Packaging.

References	Source of Anthocyanins	Extraction Method	Applications	Film Matrix/Other Active Components	Advantages/Disadvantages
[190]	Blueberry	-	Blueberry freshness monitoring	Polylactic acid/quaternized chitosan electrospun nanofiber	Dual functions including quality control and color monitoring; pH color responsive properties; good potential as a pH indicator in intelligent packaging/Reduced stiffness and gas barrier properties of the film
[186]	Purple sweet potato	-	Strawberry freshness monitoring	Chitosan/polyvinyl alcohol matrix	pH sensitivity and UV–visible light barrier properties; promising applications in fruit and vegetable freshness monitoring/Excessive anthocyanin content led to the decrease in brightness
[219]	Brassica oleracea L.	Macerated in ethanol–water mixture	Rutab fruit monitoring	Polyvinyl alcohol nanofiber	Real time monitoring of pH-linked changes within the package; reversible and stable pH sensor; rapid and sensitive detection of pH and associated changes in Rutab fruit during storage
[220]	Red radish	-	Mushroom freshness monitoring	Chitosan/zein composite nanoparticles	pH-sensitive smart film; rapid analysis, high sensitivity, low-cost and high accuracy; development of a mini WeChat program that could directly read the freshness of mushrooms/Limited by environmental factors (lighting or ambient temperature,) affecting the RGB readings
[191]	Lingonberry	Ultrasonic extraction with ethanol	Fish (crucian carp) freshness monitoring	Gelidium amausli polysaccharide matrix	Smart film sensitive to pH variations; excellent gas-sensing sensitivity; real-time freshness monitoring
[156]	Aronia melanocarpa	Ultrasonic extraction with acidic ethanol	Shrimp freshness monitoring	Sodium alginate/pectin matrix	UV-blocking properties; potential as a pH indicator for the development of intelligent packaging films; substantial potential for monitoring food freshness
[193]	Wild cranberries	Ultrasonic crusher with ethanol	Pork freshness monitoring	κ-carrageenan/potato starch matrix	pH-sensitive smart packaging film; good color sensitivity; significantly improved optical, mechanical and barrier properties
[194]	Purple sweet potato	Ethanol extraction	Beef freshness monitoring	Double-layer film: inner layer, agar; outer layer, κ-carrageenan-oregano essential oil Pickering emulsion/silver nanoparticles	Noteworthy pH sensitivity and ammonia responsiveness, monitoring beef freshness through color changes; effectively alleviated beef spoilage (extending the shelf life of beef for 1 day)/Improvements are needed to enhance the color stability and sensitivity of the film
[195]	Lycium ruthenicum Murr.	Ethanol extraction	Mutton freshness monitoring	Soybean isolate protein/xanthan gum/agar	Good water vapor, oxygen, and light transmission rate and mechanical properties; effectively monitored the freshness of the meat
[203]	Red radish	Extraction with acidified methanol	White prawn and chicken freshness monitoring	Starch/gelatin matrix	Low-cost, eco-friendly, fast responding, and easy to use pH-sensitive films; good mechanical properties and reliable performance in the food industry as pH indicator for food spoilage
[222]	Roselle	Ethanol extraction	Whiteleg shrimp freshness monitoring	Polyvinyl alcohol/hydroxypropyl methylcellulose matrix	Great ammonia-sensitive ability; mechanical properties, light barrier ability and color stability; real-time shrimp freshness monitoring
[223]	Rosa rugosa	Extraction with absolute ethanol	Shrimp meat freshness monitoring	Polyvinyl alcohol/okra mucilage polysaccharide composite matrix	Good mechanical and barrier properties; distinguishable color changes at pH 2–12 and high sensitivity to volatile ammonia; potential in intelligent packaging for freshness monitoring of aquatic products and meat food
[209]	Red apple pomace	Extraction with acidified ethanol	Salmon filet freshness monitoring	Chitosan-based films reinforced by TiO2 nanoparticles	pH-responsive color-changing properties; intensive color variations at the pH range from 6 to 8
[207]	Red cabbage	Ultrasonic extraction with alcoholic solution	Pork freshness monitoring	Polyvinyl alcohol/sodium carboxymethyl cellulose matrix	Good water solubility and elongation at break, decreased swelling index and tensile strength
[224]	Red barberry	Extraction with water/ethanol	Lamb meat freshness monitoring	Methylcellulose/chitosan nanofiber matrix	Suitable for indicating the change in food pH, the formation of volatile nitrogen compounds, and food decay; smart indicator for real-time freshness monitoring of meat and seafood products
[208]	Saffron petal	Percolation with water/ethanol	Lamb meat freshness monitoring	Methyl cellulose/chitosan nanofiber matrix (MC/CNFs/SPAs)	Good mechanical, moisture- resistance, thermal, light-screening, and gas barrier properties; real-time information about the quality and safety of meat and seafood products, decreasing waste and improving the sustainability of the food supply
[201]	Red barberry	Extraction with water/ethanol	Fish filet freshness monitoring	Methylcellulose/chitin nanofiber matrix	Good mechanical properties, moisture resistance, and UV–vis screening properties; monitoring freshness and spoilage of food products in real-time; pH-sensitive colorimetric film
[225]	Ruellia tuberosa L. flower	Methanol extraction	Tilapia fish freshness monitoring	Pectin membrane matrix	Monitoring the rigor mortis phase of fish meat, useful in food industry/Improvements are needed to obtain smooth surface morphology to improve the optical sensor performance
[196]	Lycium ruthenicum Murr	Ethanol extraction	Pork freshness monitoring	Cassava starch matrix	pH-sensitive properties; monitored the freshness of food (e.g., pork, shrimp and fish) in real-time
[202]	Clitoria ternatea L.	Water extraction	Broiler chicken meat freshness monitoring	Polyvinyl alcohol/chitosan matrix	Sensitive to pH changes during broiler chicken meat storage
[226]	Blueberry skin	Ethanol extraction	Mutton freshness monitoring	Poly-L-Lactic Acid matrix	Accurate, simple, low-cost nanofiber film for detection of meat freshness; highly sensitivity to ammonia
[227]	Butterfly pudding	Sonication extraction with alcoholic solution	Fish freshness monitoring	Chitosan matrix	Biodegradable composite films, providing evident color response of fish spoilage; highly pH-sensitive film for monitoring fish freshness
[228]	Hibiseus sabdariffa L.	Ethanol extraction	Silver carp freshness monitoring	Starch/polyvinyl alcohol matrix	Real-time fish freshness indicator by visible color changes; nontoxic, biodegradable, safe, and eco-friendly colorimetric films; fish freshness indicators
[212]	Black carrot	-	Milk freshness monitoring	Cellulose/chitosan matrix	Usage of food grade biomaterials; entirely distinguished fresh pasteurized milk from spoiled milk
[140]	Solanum lycopersicum BS003	Extraction with water– ethanol	Milk and fish freshness monitoring	Chitosan matrix	Progressive color changing during spoilage of milk or fish; improved elongation at breaking and Swelling Index by adding purple tomato anthocyanin/Increase in anthocyanins concentration led to a sharp decrease in tensile strength, Young’s modulus and SI%
[229]	Lycium ruthenicum Murr.	Extraction with ethanol–water	Milk and shrimp freshness monitoring	κ-carrageenan matrix	Good antioxidant activity; pH = 2–10 change indicator, reversible color change; great potential for monitoring the freshness of milk and aquatic products
[210]	Black carrot	-	Milk freshness monitoring	Starch matrix	Simple and easy-to-use for milk freshness indicator; capability to distinguish the fresh, medium fresh and spoiled milk
[197]	Red cabbage	Extraction with water–ethanol	Milk freshness monitoring	polyvinyl alcohol/starch composite matrix	Bio-degradable intelligent films; great color response against different pH = 2–14
[116]	Purple and black eggplant	Extraction with ethanol	Pasteurized milk freshness monitoring	Chitosan matrix	Remarkable antioxidant ability; UV–vis light barrier, good mechanical, antioxidant and pH-sensitive properties
[230]	Purple sweet potato	-	Pasteurized milk freshness monitoring	Starch/polyvinyl alcohol doubly cross-linked by sodium trimetaphosphate and boric acid	Good mechanical strength, distinguishable change in colors when immersed in solutions (pH = 1.0–14.0); good color indication and antimicrobial activity on pasteurized milk
[231]	Mulberry	Ethanol extraction	Milk freshness monitoring	κ-carrageenan matrix	Thermal stability, elongation at break and UV–vis light barrier ability; novel active and intelligent food packaging materials
[198]	Red cabbage	-	Gouda cheese freshness monitoring	Carboxymethyl cellulose/polyvinyl pyrrolidone/guar gum matrix	Almost completely (95 ± 5%) biodegraded within 60 days under moist soil conditions; successfully confirmed freshness of cheese/excessive essential oil content led to the decrease in film biodegradability
[213]	Red cabbage	Water based extraction	Milk freshness monitoring	Agarose matrix	Real-time indicator between fresh and spoiled milk; visible color changes from blue to purple to pink in response to lactic acid
[214]	Blueberries	-	Milk freshness monitoring	Polyvinyl alcohol/sodium alginate/chitosan quaternary ammonium salt nanocomplexes	Good mechanical properties, water resistance and stability; higher sensitivity to different pH buffer solutions; suitable and promising applications as smart packaging materials
[199]	Lycium ruthenicum	-	Milk freshness monitoring	Sodium alginate/konjac glucomannan composite matrix	Improved mechanical, barrier, and antioxidant/antibacterial properties of the films; excellent pH response ability
[200]	Prunus maackii pomace	Ethanol extraction	Oil freshness monitoring	κ-carrageenan/hydroxypropyl methylcellulose matrix	pH-responsive film; great potential for applications in oil packaging and real-time detection of the freshness of protein-rich food
[221]	Clitoria ternatea and Carissa carandas	Ethanol extraction	Beverage freshness monitoring	Chitosan-polyvinyl alcohol matrix	Intelligent colorimetric pH indicators; good qualities for sensing beverage spoilage; enhanced radical scavenging efficacy

.

Regarding the outcomes of these studies, intelligent packaging materials proved their potential to significantly improve food safety and quality by preventing food waste and promoting the healthiness and sustainability of the food supply [201].

4.4. Comparative Assessment, Mechanistic Basis, and Design Guidelines

The stabilization efficiency of anthocyanins strongly depends on the type and compatibility of the biopolymer matrix. Polysaccharide matrices primarily enhance anthocyanin stability through hydrogen bonding and electrostatic interactions, forming dense hydrophilic networks that reduce oxygen and moisture penetration [130,232,233]. Chitosan generally provides superior protection due to electrostatic interactions between its cationic amino groups and the negatively charged anthocyanin molecules, combined with its good film-forming ability and moderate hydrophobicity that limit oxygen and moisture penetration [130,131]. Starch-based systems mainly stabilize anthocyanins through hydrogen bonding and physical entrapment within semicrystalline helices, but their high hydrophilicity may promote pigment leaching and reduce stability [234]. Cellulose derivatives, particularly nanocellulose, contribute to strong hydrogen-bonding networks and mechanical reinforcement [141], though with fewer specific binding sites for anthocyanins compared to chitosan [131]. At the molecular level, stabilization and functional enhancement in anthocyanin–polysaccharide films primarily arise from hydrogen bonds formed between hydroxyl and carbonyl groups from anthocyanins and the hydroxyl groups from polysaccharides. These bonds strengthen polymer networks and restrict pigment mobility, improving mechanical strength and barrier properties [123,130,235]. Also, additional electrostatic interactions can appear and protect anthocyanins from pH-induced degradation [123,130]. In some particular cases, π–π stacking between anthocyanin aromatic rings and conjugated or phenolic residues in the matrix helps preserve chromophore integrity [235]. Together, these interactions explain the commonly observed improvements in mechanical strength and color stability in anthocyanin-loaded polysaccharide films.

Protein matrices provide multiple binding mechanisms—hydrogen bonding, hydrophobic, and π–π stacking interactions—between anthocyanins and amino acid residues [236], contributing to superior pigment stability, antioxidant activity, and structural reinforcement [161,165]. Gelatin typically offers superior film-forming properties and effective pigment entrapment due to its thermally reversible gel network and abundance of hydroxyl, carboxyl, and amide groups, which promote hydrogen bonding with anthocyanins and limit molecular mobility [170,237]. Soy protein provides diverse binding sites through its phenolic and hydrophobic residues, enabling hydrophobic interactions and hydrogen bonds with anthocyanins [238], which enhance pigment [236,238] but may increase brittleness if the matrix is not sufficiently plasticized [239,240]. Whey protein forms compact and crosslinked networks upon heating, stabilized by disulfide bonds. These dense matrices act as oxygen and moisture barriers [238] while also supporting hydrogen bonding and hydrophobic interactions between anthocyanins and aromatic residues [238,241]. Thus, anthocyanin stability in protein matrices depends on (i) the hydrogen bonding and hydrophobic/π–π interactions, (ii) the degree of protein denaturation and crosslinking, and (iii) the local pH and charge environment that modulate pigment–protein affinity.

Biopolyester matrices such as poly (lactic acid) (PLA) exhibit excellent barrier and mechanical properties but a weak affinity for hydrophilic anthocyanins unless modified or blended with more polar biopolymers [242].

Blending of different biopolymers, forming composite matrices, can synergistically combine the functional advantages of individual components—such as the film-forming ability of proteins, the moisture barrier of polyesters, and the binding capacity of polysaccharides [243]. Mechanistically, enhanced stabilization in composite systems arises from (i) synergistic molecular interactions—hydrogen bonding, electrostatic complexation, and hydrophobic/π–π interactions—that increase pigment–matrix affinity; (ii) modified microstructure and phase distribution that restrict pigment diffusion and exposure to oxygen and moisture; and (iii) enhanced crosslinking or filler–matrix interactions that improve barrier and mechanical resilience. These synergistic effects explain why certain composite formulations show markedly improved anthocyanin retention, color stability, and antioxidant activity compared with single-polymer matrices [243].

In light of the above considerations, a rational design of anthocyanin-based films should follow a matrix–function matching approach: (i) Polarity alignment. The matrix polarity should match the hydrophilic nature of anthocyanins. Hydrophilic matrices are optimal for responsive color-indicator films, while combining with hydrophobic components improves moisture resistance for longer shelf life. (ii) Synergistic blending. Combining complementary polymers can merge functional advantages like strong film-forming ability, enhanced barrier capacity, and improved pigment retention through interfacial hydrogen bonding and physical entanglement. (iii) Crosslinking and plasticization. The crosslinkers should stabilize the polymer network and anthocyanin binding without excessive rigidity/brittleness while maintaining transparency. (iv) Processing parameters. pH should be maintained between 3 and 5 to preserve the flavylium cationic form of anthocyanins, maximizing color intensity and antioxidant capacity. Thermal treatment should remain below degradation thresholds (60 °C) to avoid pigment degradation. (v) Functional targeting. For intelligent packaging, hydrophilic matrices with free hydroxyl groups are preferable for a rapid pH-sensitive response. For active packaging, biopolymer matrices capable of controlled release of anthocyanins are preferable, ensuring prolonged antioxidant protection. High-barrier packaging need polyester or multilayer films combining structural reinforcement and protective outer layers.

Overall, there is no universal approach to fulfill all structural and functional requirements for anthocyanin-based packaging. However, the most promising strategy lies in composite or multilayer architectures that integrate the favorable properties of each component and ensure compatibility with the incorporated anthocyanin. To accelerate formulation optimization, future trends should focus on predictive design by linking molecular interaction models and thermodynamic compatibility data with targeted film performance. Moreover, establishing quantitative structure–property relationships for anthocyanin–matrix systems will enable more efficient tailoring of color stability, antioxidant activity, and mechanical durability across diverse food-packaging applications. In this context, artificial intelligence and machine learning techniques can also play a pivotal role by analyzing large datasets of material compositions, environmental conditions, and performance metrics to predict optimal formulations, guide the selection of compatible polymers or additives, and simulate long-term stability under various storage conditions. Such AI-driven approaches could significantly reduce experimental workload, enhance reproducibility, and accelerate the development of smart, sustainable anthocyanin-based packaging solutions.

5. Limitations and Constraints of Anthocyanin Applications in the Food Industry

Although the benefits of anthocyanins are well-documented, their application in the food industry is limited due to stability issues, low bioavailability, possible interactions with food matrix, cost and source limitations and regulatory and labeling constraints.

Additionally, anthocyanins possess an inherent instability, which makes them susceptible to internal and external factors, including anthocyanin structure, pH, light, temperature, oxygen, enzymes, and metal ions, which can lead to color loss and reduced bioactivity during processing and storage [244,245], even when incorporated into films [25]. For this specific reason, in the production and use of anthocyanins, effective extraction methodologies are required [76,246], posing scalability and economic feasibility issues for industrial applications [247]. Thus, besides conventional solvent extraction using mainly acidified aqueous ethanol or methanol [49,85], newer non-conventional techniques, such as ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), and enzyme-assisted extraction (EAE), have gained attention for improving yield, reducing solvent use, and preserving pigment stability [248,249]. Furthermore, green extraction technologies employing deep eutectic solvents (DES) or supercritical fluids (SCF) offer environmentally friendly alternatives with enhanced selectivity and recyclability [249,250]. The choice of extraction method strongly influences anthocyanin purity, stability, and color intensity; therefore, optimizing solvent composition, temperature, and extraction time is essential to balance efficiency with pigment preservation.

However, despite their promising attributes, including wide-range pH-sensitive color change properties, the practical application of anthocyanins in intelligent packaging is still limited by their sensitivity to environmental factors, for instance, the poor stability of anthocyanins in meat packaging with high moisture content, that leads to a substantial reduction in their indicative performance and stability [27]. Therefore, ensuring their stability and functionality throughout the shelf life of the product remains a critical challenge that must be addressed through the stabilization techniques [251] mentioned above. Moreover, when used as colorants, the fact that anthocyanins exhibit different colors at different pH levels complicates their use as consistent natural pigments [77]. Due to the structural transformations depending on the pH, the same anthocyanin may display markedly different hues in products with distinct pH environments, such as acidic beverages (pH 2–4), near-neutral dairy systems (pH 6–7), or slightly acidic jams (pH 4–5) [49,252,253,254]. Consequently, achieving color uniformity and standardization across food matrices is challenging, as the pigment’s visible tone depends not only on its concentration but also on the product’s formulation and buffering capacity [49,255]. Such variability complicates product development and color matching, limiting the direct interchangeability of synthetic pigments with anthocyanins unless stabilization or encapsulation strategies are employed to control their color response [255]. Therefore, each type of application requires a specific approach.

The bioavailability of anthocyanins depends on food matrices, including other antioxidants and macronutrients present in food, affecting the absorption and antioxidant activity of anthocyanins [256]. Moreover, anthocyanins may interact with proteins, polysaccharides, and other food components. These interactions are significant for food processing, as they can stabilize anthocyanins [232] or, conversely, lead to their degradation [80,257], potentially affecting texture, taste, and overall product quality [80].

Additionally, regulations on the use and labeling of natural colorants, including anthocyanins, vary by region (FDA (USA) and EFSA (EU)) and can delay product development or international marketing. Both systems require adherence to specific limitations on amounts and types of food in which the colorant can be used [258,259]. Specific anthocyanin-derived compounds though gained FDA approval as natural color additives, under the status “exempt from certification”, such as grape color extract, grape skin extract and butterfly pea flower extract for blue/purple hues in foods [260,261,262]. EFSA approved anthocyanins under the food color additive E163, and JECFA has established an ADI of 2.5 mg/kg bw/day for anthocyanins from grape skin extracts [259].

Regarding the active and intelligent packaging, for now, there are no commercialized food packaging products that utilize anthocyanins or other plant-derived pigments for preservation or freshness monitoring [247]. Most of the existing technologies remain in the research, or patent stage [263,264]. However, strong research interest is clearly driving the development of anthocyanin-based active and intelligent packaging. While no products have reached the market yet, patents and prototypes suggest commercialization as a possibility in the near future.

6. Conclusions

Anthocyanins are the most abundant flavonoid constituents naturally found in many plant tissues. In addition, anthocyanin pigments are biodegradable, renewable, low-toxic, and safe to be effectively used as food components.

Anthocyanins serve a dual role in food systems as natural colorants and bioactive compounds, offering both visual appeal and functional benefits like antioxidant and antimicrobial activity, making them valuable in functional foods and as natural alternatives to synthetic additives.

The packaging industry is increasingly focusing on developing eco-friendly, non-toxic solutions that maintain food quality while reducing pollution from petroleum plastics. In this context, modified anthocyanin-based films, with improved stability, are emerging as advanced options for freshness monitoring and food preservation. Intelligent and active packaging incorporating anthocyanin extracts offers significant advantages over traditional packaging methods. These solutions can provide a double benefit in reducing unnecessary food waste and environmental challenges while promoting sustainable practices.

However, anthocyanins’ broad applicability and bioavailability have been limited by their relative instability to several environmental conditions, leading to difficulties for large-scale practical applications in the packaging industries. Thus, alternative techniques and methods aimed at enhancing anthocyanin stability for potential applications in the food industry is the target of future studies.

Hopefully, the challenges in anthocyanin research will encourage scientists in the fields of food and packaging industry to pursue innovative studies focused on developing cost-effective and efficient methods for anthocyanin production, as well as to explore the practical use of anthocyanin-rich films across the broad range of perishable foods.