Starch Science Advancement: Isolation Techniques, Modification Strategies, and Multifaceted Applications

Abstract

Starch is one of the most abundant biopolymers in nature and is widely utilized across various industries, including food, pharmaceuticals, textiles, and packaging. Its attractiveness stems from its renewability, biodegradability, versatility, and abundance in nature. However, native starches have limitations, including poor solubility, thermal instability, retrogradation, and susceptibility to enzymatic degradation. Despite the broad range of applications of starch, challenges persist in optimizing its modifications, addressing cost constraints, and ensuring regulatory compliance in food and pharmaceutical applications. These shortcomings necessitate modifications to enhance their physicochemical and functional properties. Additionally, recent trends indicate a shift towards bioengineered starches with enhanced functional properties, utilizing artificial intelligence for process optimization, and expanded applications in advanced biomaterials to achieve sustainable development goals. Thus, this review delves into the diverse sources of starch, highlighting extraction techniques and comparing their characteristics. Additionally, the review examines various modification strategies and discusses their effects on starch structure, gelation, and industrial applications. Recent advancements in dual-modification approaches, nanotechnology integration, and eco-friendly modification techniques have been examined in the context of sustainable development. Moreover, this review highlights the role of modified starch in various pharmaceutical applications, including drug delivery systems and bioadhesives, as well as its importance in biodegradable plastics, food packaging, wastewater treatment, and bioethanol production.

1. Introduction

Starch, a carbohydrate polymer commonly found in plant-based materials, has become increasingly favored owing to its functional properties, affordability, and complete biodegradability without the production of harmful byproducts [1]. Throughout history, starch has played a crucial role in diets since ancient times, acting as a primary energy source for numerous cultures and bolstering agricultural economies worldwide [2]. Starch is produced annually in amounts ranging from 88.1 to 97.7 million tonnes from various plant sources, such as corn, potato, rice, and cassava, and plays a crucial role in both the food and non-food industries [3]. Starch is a vital source of nutrition, as it is enzymatically broken down into glucose during digestion by α-amylase. Glucose is metabolized through oxidative processes, producing readily available energy that is utilized for various cellular and metabolic functions [4]. Starch granules consist of both amorphous and crystalline regions, which affect their ability to absorb water. The high crystallinity of these granules restricts water penetration, resulting in a higher gelation temperature. Chemically, starch is a homopolymer composed of α-D-glucopyranose units, represented by the chemical formula (C₆H₁₀O₅)n. It comprises two types of macromolecules, amylose and amylopectin, which are polysaccharides. Amylose is formed by glucose molecules arranged in a linear structure linked by α-1,4 glycosidic bonds.

In contrast, amylopectin has a branched structure, with glucose units connected through α-(1,6)-glycosidic bonds, as illustrated in Figure 1. Generally, amylose comprises approximately 20–30% of starch granules, whereas amylopectin accounts for approximately 70–80% of the starch content [5]. Amylose and amylopectin are organized in a semicrystalline structure within starch granules. Consequently, they serve as a significant source of energy for humans. Starches with high amylose content tend to form complex, rigid gels and strong films, whereas high amylopectin starches disperse easily in water, forming soft gels and weak films [6,7]. In addition to their physicochemical functions, these structural variations substantially influence the nutritional properties of starch. Starches with a high amylose content are digested at a slower rate, leading to a reduced glycemic index and increased production of resistant starch, which is advantageous for the gut microbiota and colonic health. In contrast, amylopectin is swiftly hydrolyzed into glucose through the enzymatic activity of α-amylase during digestion, thereby supplying an immediate energy source to fulfil cellular metabolic requirements [8].

The structural arrangement of amylose and amylopectin influences the packing integrity of starch granules by forming blocklets and growth rings, as depicted in Figure 2. Amylose contributes to an amorphous matrix owing to its linear, long-chain structure, which features α (1→4) glycosidic bonds. In contrast, the branched, double-helical structure of amylopectin, with α (1→6) branching, imparts a semi-crystalline quality to the starch. The ratio, molecular configuration, and structural arrangement of amylose and amylopectin chains determine the diverse physicochemical and functional properties of starch [9].

2. Materials and Methods

This review presents information gathered from the scientific literature. To obtain pertinent data on the green synthesis of metallic nanoparticles, searches were conducted in various databases, including Google Scholar, Springer, Elsevier, PubMed, ResearchGate, MDPI, and Hindawi, using keywords such as “starch,” “biopolymers,” “biodegradable,” “green chemistry,” “cationic starch,” and “starch modification.” Only articles from reputable journals were selected for scholarly information extraction. Additionally, this review highlights starch-based functional materials developed through eco-friendly modification techniques. These materials hold promising applications in biomedical engineering, environmental remediation, innovative packaging, and controlled-release systems. This review further explores how the molecular versatility and biodegradability of starch render it an ideal candidate for sustainable innovations in materials science.

3. Importance of Starch as a Polysaccharide

Starch is an essential carbohydrate widely utilized in various industries, particularly food and pharmaceuticals. Owing to its polymeric and branched structure, starch is less soluble in water and reduces its capacity to absorb both water and oil. It demonstrates excellent pasting properties, providing consistency, smoothness, and clarity, and can form thin films upon application. While starch can endure moderate temperatures and pressures, it remains vulnerable to acid- and enzyme-catalyzed hydrolysis, and is highly valued for its functional properties, biodegradability, renewability, and widespread availability. Starch, derived from plants such as corn, wheat, rice, potatoes, and cassava, forms granules that vary in shape and size. Although insoluble in cold water, starch exhibits essential properties such as gelatinization and viscosity changes when heated. These characteristics make it a valuable ingredient in the food industry, serving as a thickener, stabilizer, and texture enhancer [10]. Beyond food, starch is essential in paper manufacturing, textile sizing, and adhesives and plays a key role in producing biodegradable plastics for sustainable packaging. Modified starches, produced through various treatments, enhance their applications by improving their solubility, heat resistance, and emulsifying properties. Native starch granules are insoluble in water and resistant to enzymatic activity. Furthermore, they tend to retrograde in response to changes in pH, temperature, and shear forces. Consequently, starches often require modifications to enhance their physical and functional properties [11]. These renewable resources are at the forefront of sustainability efforts, particularly in replacing synthetic materials in food packaging, bioplastics, and other eco-friendly products. Cereal grains and legume seeds, including beans, garden peas, and chickpeas, are the primary sources of starch [12]. Several techniques for starch isolation, such as alkaline and non-alkaline extraction, have been previously reported. The unique physical, chemical, functional, and nutritional properties of starch make it a vital ingredient in various applications, including nutritional, pharmaceutical, and industrial uses. Starch-based hydrogels can significantly enhance the water retention capacity of soil owing to their hydrophilic properties, network structure, and ability to form strong hydrogen bonds with water molecules. Consequently, soils treated with these hydrogel fertilizers retain more water [13]. They are widely used in bioethanol production, the production of biodegradable materials and green chemical applications. Ongoing research focuses on advanced applications in agriculture, medicine, and environmental solutions, such as starch-based hydrogels, nanoparticles, and hybrid biomaterials. As a natural polymer, starch is used in the food industry to replace plastics in food material coatings and to produce edible films. They are often combined with food components to protect them from mechanical damage, extend their shelf life, and enhance their appearance. It is also used as a recyclable component in the production of food industry molds. It is a bulking agent in food and pharmaceutical formulations to enhance handling and stability, preserve the component texture, and enhance viscosity [14,15]. Polysaccharides are essential for addressing environmental issues owing to their renewable and biodegradable nature. Starch and cellulose materials are utilized as sustainable alternatives to synthetic plastics in packaging and manufacturing, aiming to reduce pollution. Their role in bioplastics, biofilms, and soil conditioners highlights their contribution to eco-friendly solutions. Figure 3 illustrates the functions and applications of starch in the pharmaceutical industry.

4. Sources of Starch

Starch can be classified based on its botanical sources into cereal, root tuber, legume, fruit, and other or novel starches. They are also broadly categorized into conventional and non-conventional sources, reflecting a diverse array of plant materials. Primary conventional sources of starch include cereals (e.g., corn, wheat, and rice), root and tubers (e.g., potato and cassava), and legumes (e.g., peas and beans). Non-conventional sources, including fruits, pulses, and certain types of agro-industrial waste, are being explored. This distinction in sources significantly influences the physicochemical properties of starch, which, in turn, determines its functionality and applicability across the nutrition and food sectors. Table 1 lists the conventional sources, with cereals such as maize and wheat being the most prominent sources. Their high starch yields and good digestibility make them especially valuable [16].

In comparison, tubers such as cassava and potato also serve as key starch sources, often exhibiting variations in amylose and amylopectin content that influence starch digestibility and applications in food products [17]. For instance, cassava is known for its high starch yield, which is influenced by factors such as variety, extraction method, and seasonal conditions [18]. Moreover, starch granule characteristics from different sources can be visually differentiated using techniques such as confocal scanning laser microscopy, which highlights the morphological variations that contribute to their functional differences [19]. The emergence of non-conventional starch sources, particularly from agro-industrial waste and fruit pomace, has garnered attention in recent years owing to sustainability concerns and the need for alternative raw materials that do not compete with the food supply. Such sources often contain unique starches with beneficial properties for specific applications, potentially adding value to what would otherwise be discarded. For example, fruit waste has been shown to contain significant starch content and can serve as a viable alternative in the food and pharmaceutical industries [20]. A comparative evaluation of these unconventional starches reveals intriguing possibilities; however, substantial empirical evidence is still required to assess their comprehensive functionality and economic viability [21].

Table 1. Different sources of starch.

Examples	Characteristics	Amylose Content	Amylopectin Content	Moisture Content	Shape\ Size (µm)	Reference
Corn, wheat, rice, barley	High gelatinization temperature, moderate water absorption	20–30%	70–80%	10–14%	Polygonal/spherical (2–35)	[22,23]
Potatoes, cassava, sweet potatoes	High water-binding capacity, low gelatinization temperature	18–22%	78–82%	12–20%	Oval/rounded (5–100)	[24,25]
Banana, green plantain	High-resistant starch, suitable for dietary and functional foods	17–21%	79–83%	11–15%	Elongated/oval (10–50)	[26,27]
Beans, garden peas, chickpeas	Resistant starch, good nutritional properties	25–30%	70–75%	8–13%	Oval/irregular (10–60)	[28]
Sago Palm, Arrowroot	Fine texture, easily digestible	20–25%	75–80%	10–15%	Smooth/rounded (10–45)	[29]
Yam, taro, pumpkin	High water-binding capacity, excellent viscosity, and gelling	20–25%	75–80%	60–80%	Oval/rounded (5–80)	[30,31,32]
Amaranth, quinoa (pseudo cereals)	Gluten-free, high gelling and stability properties for bioplastics and food use	15–25%	75–85%	30%	Small/polygonal (1–3)	[33,34]
Ginger (rhizomes)	High starch content, used for medicinal and food purposes	15–20%	75–80%	8–12%	Irregular/fibrous (3–20)	[35]
Avocado pits	Starch found in avocado seeds has potential in food processing and biodegradable films	18–22%	75–80%	41%	Round/irregular (3–15)	[36]
Duckweed, water chestnuts (aquatic),	High starch yield, promising for biofuel production	15–25%	75–85%	8–12%	Rounded/smooth (3–12)	[37]
Chestnuts, lotus seeds (nuts and seeds)	High amylose, potential for functional food applications	22–28%	72–78%	6–10%	Irregular/spherical (8–25)	[38]
Red algae, brown algae (seaweed-derived)	Polysaccharides with unique gelatinizing and stabilizing properties	10%	80–85%	5–8%	Fibrous/irregular (2–10)	[39]
Date palm seeds, oil palm trunk	Rich in non-conventional starch, useful in biodegradable plastics	20–25%	75–80%	7–9%	Rounded/granular (5–20)	[40]
Water hyacinth, kudzu	High starch content, eco-friendly solution for invasive species	20–25%	75–80%	85–95%	Irregular/granular (5–15)	[41]
Bamboo shoots, sorghum	Abundant cellulose and starch, potential for biofuel application	18–22%	78–82%	30–50%	Fibrous/polygonal (5–50)	[42]

Table 1. Different sources of starch.

Examples	Characteristics	Amylose Content	Amylopectin Content	Moisture Content	Shape\ Size (µm)	Reference
Corn, wheat, rice, barley	High gelatinization temperature, moderate water absorption	20–30%	70–80%	10–14%	Polygonal/spherical (2–35)	[22,23]
Potatoes, cassava, sweet potatoes	High water-binding capacity, low gelatinization temperature	18–22%	78–82%	12–20%	Oval/rounded (5–100)	[24,25]
Banana, green plantain	High-resistant starch, suitable for dietary and functional foods	17–21%	79–83%	11–15%	Elongated/oval (10–50)	[26,27]
Beans, garden peas, chickpeas	Resistant starch, good nutritional properties	25–30%	70–75%	8–13%	Oval/irregular (10–60)	[28]
Sago Palm, Arrowroot	Fine texture, easily digestible	20–25%	75–80%	10–15%	Smooth/rounded (10–45)	[29]
Yam, taro, pumpkin	High water-binding capacity, excellent viscosity, and gelling	20–25%	75–80%	60–80%	Oval/rounded (5–80)	[30,31,32]
Amaranth, quinoa (pseudo cereals)	Gluten-free, high gelling and stability properties for bioplastics and food use	15–25%	75–85%	30%	Small/polygonal (1–3)	[33,34]
Ginger (rhizomes)	High starch content, used for medicinal and food purposes	15–20%	75–80%	8–12%	Irregular/fibrous (3–20)	[35]
Avocado pits	Starch found in avocado seeds has potential in food processing and biodegradable films	18–22%	75–80%	41%	Round/irregular (3–15)	[36]
Duckweed, water chestnuts (aquatic),	High starch yield, promising for biofuel production	15–25%	75–85%	8–12%	Rounded/smooth (3–12)	[37]
Chestnuts, lotus seeds (nuts and seeds)	High amylose, potential for functional food applications	22–28%	72–78%	6–10%	Irregular/spherical (8–25)	[38]
Red algae, brown algae (seaweed-derived)	Polysaccharides with unique gelatinizing and stabilizing properties	10%	80–85%	5–8%	Fibrous/irregular (2–10)	[39]
Date palm seeds, oil palm trunk	Rich in non-conventional starch, useful in biodegradable plastics	20–25%	75–80%	7–9%	Rounded/granular (5–20)	[40]
Water hyacinth, kudzu	High starch content, eco-friendly solution for invasive species	20–25%	75–80%	85–95%	Irregular/granular (5–15)	[41]
Bamboo shoots, sorghum	Abundant cellulose and starch, potential for biofuel application	18–22%	78–82%	30–50%	Fibrous/polygonal (5–50)	[42]

5. Classification of Starch-Based Polymorphic Forms

Starch crystallinity results from the orderly arrangement of amylopectin double helices within the unit cell. These helices consist of two intertwined polysaccharide chains. Starch can be classified into polymorphic forms, primarily A, B, and C types, based on their distinct crystalline arrangements, X-ray diffraction (XRD) patterns, and botanical origins. A-type starch is predominantly found in cereal grains like rice, wheat, and corn [43]. Type A granules are irregular polygons with concave surfaces and possess a highly compact and dense crystalline structure with orthorhombic symmetry and low water content, which facilitates enzyme accessibility through naturally occurring surface pores and internal channels. The lattice parameters for A-type starch are a = 10.69 Å, b = 11.72 Å, c = 17.71 Å, with α = β = γ = 90°, forming an orthorhombic unit cell.

In contrast, B-type starch is typical of tubers, fruits, and stem sources such as potatoes, sago, bananas, and high-amylose maize [43]. Type B granules display a variety of shapes, including spherical, elliptical, and irregular forms, with generally smooth surfaces or slight roughness. It has a more open and hydrated crystalline structure with hexagonal symmetry. It typically lacks surface pores and channels, with lattice parameters of a = b = 18.50 Å, c = 10.40 Å, α = β = 90°, and γ = 120°, contributing to its lower digestibility and resistance to enzymatic hydrolysis. C-type starch, commonly found in legumes such as lentils, peas, and beans, is a heterogeneous mixture of A- and B-type crystalline structures. C-type starch granules typically exhibit a composite crystalline structure, in which regions of A-type crystallinity encase a B-type core. Its microstructure displays intermediate properties, including moderate digestibility and variable surface pores and internal channels. C-type starches are primarily spherical, with sizes similar to type As, generally below 20 µm in diameter. These granules often exhibit irregular shapes and multiple facets, which are attributed to natural mechanical imperfections. The lattice parameters for this starch type are as follows: a = b = 18.50 Å, c = 10.47 Å, α = β = 90°, and γ = 120°. The differences in crystallinity and microstructure among these starch types significantly influence their behavior in physical, chemical, and enzymatic modification processes, ultimately affecting their applicability in drug delivery, biodegradable packaging, and wastewater treatment [44,45,46].

6. Starch Importance, Isolation, and Modification

6.1. Industrial and Scientific Importance of Starch

Starch serves as a drug activator and encapsulation agent, aiding in the delivery of drugs to target organs [47]. It also offers an alternative to plastics in food packaging materials and coatings [48]. Although native starch is extensively used, its performance under certain conditions, such as extreme temperatures or mechanical stress, often falls short of industrial standards. Modifying starch through physical, chemical, enzymatic, and biotechnological methods has become crucial for overcoming these challenges in the food industry. These modifications enhance its functionality and expand its applicability, allowing for the creation of specialized materials, such as biodegradable plastics, drilling fluids, and bio-based coatings. Recent progress in genetic engineering and nanotechnology has broadened the scope of starch-based innovations by providing tailored solutions to meet contemporary industrial demands. In the food industry, starch is commonly employed as a thickening, stabilizing, and gelling agent to improve various food product textures, structures, and consistencies [49]. In the paper industry, starch plays a vital role in enhancing paper’s strength, surface quality, and durability. Its adhesive properties are advantageous for manufacturing corrugated boxes, gummed tape, and other paper-based products [50]. In the textile sector, starch is used to impart stiffness, improve the finish, and increase the durability of fabrics during processing [51]. It also plays a significant role in the fermentation industry, where it is hydrolyzed into sugars and fermented to produce ethanol, a key component of biofuels and alcoholic beverages [52]. The development of modified starches has further expanded their applications, enabling their use in biodegradable plastics, drilling fluids, and emulsion stabilization applications. This versatility underscores the significance of starch in driving innovation across various industries, particularly in sustainability and materials science. Its multifaceted properties make it a critical resource for industrial and scientific advancement.

6.2. Isolation of Starch from Different Sources

6.2.1. General Isolation Process

Starch processing encompasses several essential steps, starting with the selection of a suitable starch source, such as corn, potato, or rice, based on the desired properties for specific applications. Initially, the starch may need to be washed to eliminate impurities, which can be done by soaking and draining. Subsequently, sodium chloride (NaCl) is used at a concentration typically ranging from 1% to 5% by weight in starch slurry. This NaCl solution is mixed with the starch, allowing the processing to proceed. Following this, an alkali treatment employs sodium hydroxide (NaOH) at concentrations typically ranging from 0.10 to 0.30 M [53]. The NaOH solution is mixed with the starch and left to stand for a specified time to facilitate the swelling of the starch granules. This treatment is crucial as it aids in degrading glycosidic bonds, enhancing gelatinization properties [54]. The next step involves washing the mixture with water after mixing the starch with the saline solution. This can be achieved through air or oven drying at low temperatures (approximately 40–60 °C), which removes excess moisture while preserving the starch’s integrity. The aim is to achieve a moisture content suitable for storage and further processing, typically below 14%. Once adequately dried, the starch is pulverized to achieve the desired particle size. This can be done using mechanical grinders or mills, followed by sifting to ensure uniformity in the final product. Pulverized starch has various applications, including in food products, pharmaceuticals, and bioplastics.

6.2.2. Isolation from Various Sources

Starch is commonly isolated from various botanical sources, such as cereals, tubers, pulses, and pseudocereals, through wet milling, which involves steeping, grinding, and separating starch from other cellular components. In cereals like wheat and rice, wet milling typically starts with soaking the grains in water or a chemical solution (neutral, acidic, or alkaline) to soften the material and inhibit microbial growth, followed by mechanical grinding and sieving to release the starch granules. Enzymatic or alkaline treatments can remove proteins and lipids, thereby improving starch purity. For tubers such as taro or potatoes, the process involves washing, peeling, slicing, and blending, followed by subsequent filtration and sedimentation steps to separate starch from fibrous material and impurities. Chemical agents, such as sodium metabisulfite or sodium azide, are often added to prevent oxidation and microbial activity. The isolated starch is then repeatedly washed, neutralized, and dried. The specific isolation method and choice of chemicals or enzymes can significantly impact the yield, purity, and functional properties of the resulting starch, making method selection crucial for targeted applications in food, pharmaceuticals, and industry. A brief overview of the isolation of starch from various sources is presented in Figure 4, and the extraction of starch using multiple methods is presented in

Table 2. Extraction of starch from various methods.

Source	Extraction Methods	Advantages	Limitations	Reference
Legumes (chickpeas, lentils)	Dry milling: grinding seeds into flour and sieving. Alkaline extraction: soaking in NaOH to dissolve proteins. Enzymatic extraction: enzymes break down non-starch components.	Dry milling is cost-effective for small-scale operations. Alkaline methods handle high protein content well. Enzymatic extraction yields high purity.	Lower purity with dry milling. Alkaline methods produce wastewater requiring treatment. Enzymes are costly.	[55]
Cereals (maize, rice, wheat)	Wet milling: soaking grains, grinding, and centrifugation to isolate starch. Fermentation: microbial action dissolves non-starch components. Alkaline extraction: dissolves proteins.	Wet milling is widely used industrially for high yields. Fermentation improves purity and enhances starch properties.	Wet milling requires significant water and energy. Fermentation is time-intensive and less scalable for the industry.	[56]
Fruits (Banana, breadfruit)	Pulping and sieving: mashing pulp, sieving starch granules. Microwave-assisted extraction: heating disrupts cell structures for starch release.	Simple and cost-effective pulping method. Microwave methods are fast, eco-friendly, and reduce water use.	High moisture and inefficient large-scale extraction. Microwave methods are fast, eco-friendly, and reduce water use.	[57]
Roots (arrowroot, taro)	Sedimentation: grating roots, washing, and natural settling. Ultrasonic extraction: ultrasound breaks cell walls to release starch.	Sedimentation is low-cost and traditional. Ultrasonic techniques are efficient, eco-friendly, and reduce time.	Sedimentation is labor-intensive. Ultrasonic extraction requires expensive equipment.	[58]
Tubers (potato, cassava)	Wet milling: crushing, creating slurry, filtering, and sedimentation. Enzymatic extraction: amylase breaks down cell walls.	High yield and purity. Wet milling is suitable for industrial-scale production	Large amounts of water are required in wet milling. Sedimentation is labor-intensive and time-consuming.	[59]

.

6.2.3. Modification of Starch

Starch modification is crucial for improving the functional properties of native starch to meet the requirements of various industrial and commercial applications. Such enhancements are vital for expanding the versatility of starch in food processing, pharmaceuticals, and textiles. Figure 5 illustrates the different methods used for starch modification.

Physical Modifications

Physical modification refers to changes in the structural characteristics of starch without altering its chemical composition. These processes enhance the solubility, adhesion, texture, and heat resistance. Typically, standard methods include heat treatments, which break down the crystalline structure to improve solubility and digestibility, and moisture treatments, which alter texture and adhesion properties. These modifications are particularly beneficial for applications requiring high thermal resistance and improved functional consistency [60,61]. High-pressure processing (HPP), also known as cold gelatinization, modifies starch differently from traditional thermal methods. Unlike heat-based treatments that rely on high temperatures to disrupt starch granules, HPP uses intense hydrostatic pressure at ambient or mild temperatures to induce structural changes. This method effectively disrupts the crystalline regions of starch granules, leading to gelatinization without heat. Compared to thermal treatment, HPP ensures more uniform and controlled modification, preserves heat-sensitive nutrients, and avoids surface overcooking. Therefore, under controlled moisture and pressure conditions, HPP can achieve more efficient and uniform gelatinization of starch than conventional heat-based methods. Pre-gelatinized starch thickens quickly and smoothly without cooking. It is ideal for instant dishes, such as soups, sauces, desserts, and pharmaceutical tablet binding. Standard starch offers better stability in high heat but requires cooking for activation, which is commonly found in recipes that require heat, such as baked goods or puddings. Annealing is a process in which starch is treated with water below its gelatinization point, enhancing its thermal stability, raising the gelatinization temperature, and strengthening the gel. It is commonly used to improve texture in food and pharmaceutical applications. Heat–moisture treatment involves heating starch at high temperatures under limited moisture conditions (10–30%). This increases the resistant starch content, enhances thermal stability, and reduces solubility, making it useful for functional foods and fibre-enriched products. Microwave treatment exposes starch to microwave radiation, altering its structure to enhance solubility, modify crystallinity, and adjust pasting and gelling properties, thereby tailoring food textures.

HPP applies hydrostatic pressure to starch, leading to changes in granule structure, enhanced gel strength, and reduced viscosity, making it ideal for stabilizing sauces and desserts. Ultrasound treatment uses high-frequency sound waves to break starch granules, reduce particle size, alter viscosity, and improve water absorption and texture modification in food systems [62]. Finally, extrusion involves high temperature, pressure, and shear forces, which modify the gelatinization and solubility of the material. Extrusion is widely used in the production of snacks, cereals, and other biodegradable materials. These physical modifications adapt starch properties to meet the needs of various industries, such as food, pharmaceuticals, and packaging [63,64]. Modifications, such as chemical, physical, or enzymatic treatments, refine the texture, adhesion, and thermal stability of starch, making it suitable for more robust applications. Advanced techniques, such as micronization, produce ultrafine starch particles that improve the smoothness of pharmaceutical and cosmetic products. Additionally, HPP treatments enhance gel texture and thermal stability. Innovative methods, such as pulsed electric field treatment and vacuum impregnation, alter the interaction between starch and water, improving its functional consistency. Together, these physical modifications enable starch to meet the varying requirements of various industries, including food, pharmaceuticals, textiles, and bioplastics [64]. Milling physically modifies starch by applying mechanical forces that disrupt granule structure, reducing crystallinity and particle size. This results in increased solubility, digestibility, and a lower gelatinization temperature. Different milling methods (ball, jet, hammer) vary in their effects but generally increase damaged starch content and enzyme accessibility. Modified starches from milling are functional as thickeners, emulsifiers, and in controlled-release applications. Wet and dry milling are physical, non-thermal methods used to modify starch by altering its granule structure, particle size, and surface properties without the use of heat. These techniques enhance functional characteristics such as solubility, swelling power, and digestibility for various industrial applications [65].

Other techniques include shear modification, in which high shear forces alter granule size and viscosity, and pre-gelatinization, which involves gelatinizing and drying starch to produce instant starch with improved solubility [66]. Freeze–thaw cycles help reduce syneresis in starch gels, which benefits frozen food products. Spray-drying and drum-drying produce powdered or flaked starch with improved dispersibility and hydration.

Table 3. Parameters applied for the physical modification of starch.

Sources	Type	Parameters	Concentration	Properties	References
Corn, potato, mung bean, rice	Heat–moisture treatment	Temperature: 80–120 °C	Moisture content: 10% at 100 °C for 16 h	Improves resistant starch, enhances digestibility	[64,67,68]
Wheat, corn	Dry heating	Temperature: 120–150 °C	Dry heat for 20 h at 140 °C	Resistant starch alters gelatinization	[64]
Lotus, maize, wheat, potato	Freeze–thawing	Freezing cycles: 3–5	4 cycles at −20 °C for 24 h	Increases crystallinity, Improves textural properties	[69,70]
Corn, yam, banana	Annealing	Temperature: 40–60 °C	Water content: 40% for 24 h	Enhances thermal stability and gelatinization temperature	[71]
Rice, sago, wheat, banana	Ultrasonic treatment	Frequency: 20–40 kHz	Sonication for 15 min at 25 °C	Reduces particle size, modifies viscosity	[72]
Sago potato	Microwave treatment	Power: 500–1000 W, Time: 1–10 min	Microwave exposure for 5 min at 600 W	Alters crystallinity, improves solubility	[73]

presents the parameters for physical modification, and Figure 6 illustrates various physically modified starches.

Chemical Modifications

Chemical modification is the process of introducing new functional groups or changing existing ones in a polymer or compound through chemical reactions. This involves modifying the chemical composition of starch to enhance its stability and performance under various conditions, including heat, acidity, shear, and freezing. For example, acid hydrolysis breaks down starch molecules into smaller units, making them more soluble and easier to digest.

Oxidation: Oxidized starch is produced through the reaction of starch with oxidizing agents under controlled conditions. This process introduces carbonyl(–C=O) and carboxyl(–COOH) functional groups, which improve the reactivity and reduce the viscosity of the starch solution. Additionally, the incorporation of these groups prevents recrystallization and improves paste clarity, making oxidized starch suitable for applications in the paper, food, and textile industries. The oxidation process also enhances the film-forming properties and lowers the molecular weight of starch, which contributes to better biodegradability and microbial resistance. Common oxidizing agents include sodium hypochlorite, hydrogen peroxide, and periodic acid, each influencing the degree of depolymerization and the final properties of the modified starch. Oxidation introduces functional groups that improve stability and reactivity. These chemical transformations make starch more versatile, allowing it to withstand demanding processing conditions and meet diverse end-user requirements [85,86]. Sodium hypochlorite acts as a potent and more forceful oxidizing agent. It leads to considerable depolymerization by breaking the glycosidic bonds within starch polymer chains. Because of its high reactivity, NaClO adds more carbonyl and carboxyl groups to the starch molecules. This reduces the dispersion viscosity, which prevents recrystallization [85,87]. There is a significant decrease in the molecular weight and viscosity of starch dispersions. The paste becomes clearer, and the starch is less prone to recrystallization, which boosts its stability. The film-forming abilities are improved, although there may be more degradation if the reaction conditions are not meticulously managed. This makes it ideal for uses that demand low viscosity and high reactivity, such as in textile sizing and paper coating [88]. Hydrogen peroxide is a milder oxidizing agent than sodium hypochlorite (NaClO), leading to selective oxidation with less depolymerization and a moderate reduction in molecular weight. It introduces carbonyl and carboxyl groups while retaining higher viscosity compared to starch oxidized with NaClO. The modified starch shows good stability, though with slightly reduced paste clarity and reactivity. This method is ideal for situations requiring controlled modification, such as in food applications to avoid excessive degradation [89].

Esterification and etherification: Esterification typically alters the retrogradation properties of starch, resulting in limited intra-amylase chain interactions and interactions with outer amylopectin chains. Starch can be modified by replacing its hydroxyl groups with hydrophobic functional groups, resulting in derivatives such as hydroxypropylated, acetylated, and succinylated starches. This type of starch is used as a binder, disintegrant, and filler in tablet and capsule formulations. It also improves drug stability and controlled release. Hydrophilic derivatives, such as carboxymethyl starch, dissolve in cold water and are widely used as a disintegrant in pharmaceuticals and as a sizing and printing agent in the textile industry. Etherification involves introducing ether groups into starch and enhancing cold-water solubility and viscosity stability. The modification process was performed in an organic medium to prevent gelatinization and facilitate the formation of highly substituted derivatives. Native starch is activated with an alkali to form an alkoxide, a more reactive starch derivative that reacts with hydroxide (OH−) to create an acetylated derivative [86]. The hydroxyl groups of starch are replaced with acetyl groups, making starch more hydrophobic and reducing hydrogen bonding with water. This helps prevent an increase in viscosity and gel formation. Hydroxypropylation introduces propylene oxide, which disrupts the starch structure and improves its chain flexibility. The hydroxypropylation of starch involves a process of modifying its natural structure by applying propylene oxide, which enhances the flexibility of the starch chains. This modification significantly improves the starch’s water solubility, swelling capacity, and paste clarity, rendering hydroxypropylated starches highly versatile for various food applications. Notably, hydroxypropylated starch effectively reduces syneresis during freeze–thaw cycles, thereby preserving the texture of frozen foods. This method is deemed more efficacious than alternatives such as carboxymethylation, as the hydroxypropyl groups effectively inhibit the formation of intermolecular hydrogen bonds, preventing the reassociation of starch chains and ensuring superior product quality. Conversely, hydroxyethyl starch is synthesized by reacting starch with ethylene oxide. It is extensively utilized in medical applications, particularly as a plasma volume expander and a cryoprotectant for red blood cells. Furthermore, the modification of starch with phosphate groups results in mono-starch phosphate or cross-linked di-starch phosphate derivatives [90,91].

Cross-linking: Cross-linking introduces chemical bridges between starch molecules, thereby enhancing their thermal and shear resistance. Reagents such as phosphorus oxychloride (POCl₃) or sodium trimetaphosphate are typically used, along with cross-linked starches. Cross-linking strengthens starch by forming chemical bonds between its molecules and is influenced by factors such as the type of reagent, concentration, pH, and temperature. Phosphorus oxychloride is commonly used as a reagent in this process. Cross-linking improves thermal properties, increases gelatinization temperature, and reduces retrogradation, but can also cause more pronounced syneresis due to a more ordered starch structure [92]. Starch is modified with phosphate groups using chemical cross-linking agents, such as sodium trimetaphosphate (STMP) or sodium tripolyphosphate (STPP). This process creates covalent phosphate diester bonds between hydroxyl groups on neighboring starch chains, forming a stable three-dimensional network. The resulting structure improves paste clarity by preventing the aggregation of amylose and amylopectin, reducing turbidity during gelatinization [93]. The modification of starch with phosphate groups results in mono-starch phosphate or cross-linked di-starch phosphate derivatives. These phosphorylated starches exhibit enhanced stability, solubility, and functional performance, making them valuable for a range of biomedical applications. Phosphate groups also inhibit retrogradation, enhance dispersion in solution, and increase viscosity by reinforcing the starch matrix against swelling and leaching. Di-starch phosphates, in particular, produce stronger gels and improve paste thickness and stability under processing stresses [94].

Acid hydrolysis: In acid modification, hydroxonium ions hydrolyze the glycosidic linkages of starch by attacking the glycosidic oxygen. Acid first acts on the surface of the starch granule before penetrating its inner regions, altering its physicochemical properties without damaging the granule’s structure. Acid hydrolysis increases the gelatinization temperature and retrogradation rate, with the specific effects varying by the type of acid used (HCl, HNO₃, H₂SO₄, H₃PO₄), impacting properties such as molecular weight, iodine binding capacity, and viscosity [95].

Cationization: Cationic starches are modified to introduce positively charged groups such as quaternary ammonium, sulfonium, or phosphonium groups. Reagents like 2,3-epoxypropyltrimethylammonium chloride (EPTAC) or 3-chloro-2-hydroxypropyltrimethyl ammonium chloride (CHPTAC) are used [96]. Monomers such as 2,3-epoxypropyltrimethylammonium chloride or 3-chloro-2-hydroxypropyltrimethylammonium chloride are commonly used in the preparation process through extrusion, semi-drying, or wet processes. The dry process involves adding monomers to starch to create a cationic form. The process can be carried out through dry, semi-dry, or wet methods, and the selection of the reaction medium affects the degree of substitution and functionality [97]. Cationic starch derivatives synthesized via dry and wet methods exhibit distinct differences in their reaction environments and structural effects. The wet method involves suspending starch in water, leading to more uniform modification and products characterized by increased viscosity and decreased solubility in cold water. In contrast, the dry method employs minimal water, resulting in more pronounced granular disruption, higher substitution levels (up to approximately 0.5 compared to 0.07 for the wet method), enhanced cold-water solubility, and reduced viscosity. The dry cationization process offers advantages such as higher yields, reduced wastewater, and lower production costs, whereas products from the wet method retain more of the native starch characteristics and yield cleaner results post-washing. These distinctions influence their functional performance in applications such as papermaking and flocculation [98].

Anionic and amphoteric modification: Anionic starches are modified with groups like carboxymethyl and sulfonic, which enhance properties like cold-water solubility and flocculation efficiency. Amphoteric starch contains both cationic and anionic groups, which improve biodegradability. Hydroxyethyl starch, used for blood replacement, has limitations due to its effects. On coagulation and kidney function, prompting the development of lower-molecular-weight formulations to reduce these issues [99].

Arylation: Arylation involves attaching aromatic groups to starch chains, thereby enhancing hydrophobicity and improving compatibility with nonpolar polymers. This is often used in lipase-catalyzed esterification systems and can significantly enhance emulsion stability, film formation, and mechanical properties in composite systems [100]. Figure 7 depicts several chemical alterations of starch, including oxidation, crosslinking, acid hydrolysis, etherification, and esterification, applied to starches sourced from plants such as rice, corn, wheat, potato, and cassava. Oxidation adds carbonyl and carboxyl groups, which increase solubility and decrease viscosity. Crosslinking creates covalent bonds between starch chains, enhancing stability under heat and acidic conditions. Acid hydrolysis partially breaks down starch molecules, resulting in a lower molecular weight and improved solubility. Etherification involves the addition of ether groups to improve clarity, paste stability, and resistance to freeze–thaw cycles. Esterification introduces ester groups, which enhance hydrophobicity, emulsifying capacity, and film-forming properties. These modifications enhance the performance of starch for various applications in the food, pharmaceutical, and industrial sectors.

Table 4. Methods of chemical modifications of starch and their effects on its properties.

Sources	Type	Reagent	Parameters	Properties	References
Maize cassava	Esterification	Acetic anhydride	5–8% (w/w) starch with 0.1% sodium hydroxide as a catalyst at 27 °C pH 8.5–9.0	Enhances solubility, viscosity	[118,119]
Corn starch		Succinic anhydride	6% solution, reacted for 1–2 h at 60 °C pH 8.5–9.0	Improves hydrophilicity	[110,120]
Jackfruit, sago, cassava	Etherification	Propylene oxide	8–10% (v/v) solution, reaction at 45 °C for 5 h	Increases freeze–thaw stability	[121,122,123]
Cassava, wheat Maize, corn		Epichlorohydrin	0.05–0.1% (w/w) solution of starch reacts at pH 10	Improves gel strength, cross-linking	[124,125,126,127]
Potato, cassava, mug bean	Oxidation	Sodium hypochlorite	0.5–2% (v/v) for 30–60 min at pH 8	Reduces viscosity, enhances whiteness	[87,128,129]
Potato, cassava, wheat		Hydrogen peroxide	2% (v/v) solution pH 6 at 25 °C	Produces low-viscosity starch	[104,130,131,132]
Corn, tapioca Sago	Cross-linking	Phosphorus oxychloride	0.03–0.1% (w/w), reaction at pH 10, for 5 h at 40 °C	Improves shear and thermal stability	[133,134,135,136]
Corn, wheat, tapioca		Sodium Tri-metaphosphate	5% (w/w) starch solution, reaction at pH 11 for 2 h at 40 °C	Stabilizes against mechanical forces	[137,138,139,140]
Corn, potato, maize	Acid hydrolysis	Hydrochloric acid	1% HCl, stirred for 6 h at 40 °C	Reduces molecular weight, improves digestibility	[141,142,143]
Corn starch, cassava		Sulfuric acid	1.5% solution, reaction for 4 h at 50 °C	Enhances the breakdown of amylose	[108,144]

summarizes the methods used for chemical modification and their effects on the properties of starch. Esterification, involving agents such as acetic or succinic anhydride, is conducted at a slightly alkaline pH level (8.5–9.0) and moderate temperatures ranging from 27 to 60 °C. This process enhances the solubility, viscosity, and hydrophilicity of starch, rendering it suitable for applications in food and pharmaceutical products. Etherification with propylene oxide is performed at 45 °C, significantly improving freeze–thaw stability, which is advantageous for refrigerated and frozen food products. Crosslinking, utilizing agents like epichlorohydrin or phosphorus oxychloride, is executed at a high pH (10–11) and moderate heat (40 °C), thereby enhancing shear, thermal stability, and gel strength, resulting in starches appropriate for industrial processes involving high temperatures or shear. Oxidation techniques, employing sodium hypochlorite or hydrogen peroxide, are carried out at lower concentrations and room temperature, yielding different outcomes—sodium hypochlorite reduces viscosity and increases whiteness, whereas hydrogen peroxide produces starch with low viscosity. Acid hydrolysis, using HCl or H₂SO₄, necessitates extended reaction times (4–6 h) and results in starch with a lower molecular weight and improved digestibility, making it suitable for prebiotic or dietary applications.

Dual Modifications

Dual modification of starch involves two modification techniques, including chemical, physical, or enzymatic methods, to enhance its properties. This enhances the stability, solubility, and functional properties of starch for various food industry applications. Common approaches include combining oxidation with acetylation or crosslinking with hydrothermal treatment, making starch more useful in food, pharmaceuticals, and biodegradable materials [145]. For instance, combining heat treatment with chemical modification can result in starches with better thickening ability and improved texture in food products. Additionally, dual modification can enhance the resistance of starch to retrogradation, which is beneficial for products that require a longer shelf life. This method can also improve the emulsifying properties of starch, making it suitable for use in sauces and dressings. By carefully selecting the types of modifications, manufacturers can create starches that meet the demands of specific formulations, such as gluten-free products or those requiring low-calorie options. Furthermore, dual modification can facilitate the development of starches with unique gelling properties, which are advantageous for creating novel food textures. Overall, the versatility of dual modification opens up new possibilities for innovation in food technology and other industries. The dual modification process can also involve the use of additives or cross-linking agents to further enhance the stability and performance of starch. This can lead to the creation of starches that are more resistant to shear and heat, making them ideal for high-temperature cooking applications. Additionally, the combination of different modification techniques allows for more precise control over the final properties of starch, enabling manufacturers to tailor their products to specific applications, such as instant foods or ready-to-eat meals.

Table 5. Parameters for dual modification of various sources of starch.

Starch Source	Dual Modification	Properties	References
Tapioca starch	Crosslinking with esterification	Composite film preparation, improving hydrophobicity	[146]
Taro starch	Hydroxypropylation with crosslinking	Improving physicochemical properties, enhancing stability	[147]
Foxtail millet starch	Single and dual modifications	Stability, structural characteristics improvement	[148]
Cassava starch	Acetic acid with ultrasound	Pasting, rheological, and digestibility properties	[149]
Cassava starch	Crosslinking with octenyl succinylation	Physicochemical properties, in-vitro digestibility, and emulsifying properties	[150]
Sweet potato starch	Acetylation with dual modification	Physicochemical, rheological, and morphological characteristics	[151]
Indian rice starch	Acetylation with crosslinking	Improving physicochemical characteristics	[152]

presents a comparative analysis of dual modification techniques for various starches. The ability to modify starch enhances its functional attributes and expands its potential use in multiple formulations, including those that require specific dietary considerations, such as low-glycemic index products. As research in this area continues, new methods and combinations of modifications are likely to emerge, further enhancing the capabilities of modified starches for diverse applications.

Enzymatic Modifications

The enzymatic modification involves using enzymes to catalyze biochemical reactions that alter the molecular structure of substrates, such as starch, resulting in modified properties. Enzymatic methods utilize specific enzymes to modify starch molecules and improve their properties, such as texture, solubility, and digestibility. Using enzymes like amylase helps break down starch into simpler sugars, making digestion easier and broadening its uses. Similarly, glucoamylase converts starch into glucose, the basis of various sweetener applications. The advantages of enzymatic approaches include their specificity and ability to make targeted modifications without relying on harsh chemicals [153,154]. Enzymes act as biological catalysts that accelerate specific reactions under mild conditions, allowing for precise control over starch modification without the use of hazardous substances. The following are the key enzymes used for starch modification: Glucoamylase, which hydrolyzes both α-1,4 and α-1,6 glycosidic bonds to produce glucose. Pullulanase targets α-1,6 bonds and is used in conjunction with other enzymes to enhance the saccharification process. Isoamylase hydrolyzes α-1,6 bonds in = amylopectin to yield linear chains. It is often used for debranching starch [153,155].

Table 6. Parameters for the modification of starch using various enzymes.

Enzyme	Sources	Mechanism	Conditions	Function	References
Amylase (α-Amylase)	Maize	Hydrolyzes α-1,4 glycosidic bonds	Enzyme concentration: 0.1–0.5% (w/v) Temp: 60–70 °C Time: 30–60 min. pH: 4.5–6.5	Breakdown of starch into dextrins or maltodextrins	[156]
Pullulanase	Potato sorghum rice	Hydrolyzes α-1,6 glycosidic bonds	Enzyme concentration: 0.2–1.0% (w/v) Temp: 50–60 °C Time: 10–30 min pH: 4.5–5.5	Debranching amylopectin	[154,157]
Isoamylase	Maize rice	Cleaves α-1,6 glycosidic bonds in amylopectin	Enzyme concentration: 0.2–0.8% (w/v) Temp: 50–60 °C Time: 30–60 min pH:4.5–6	Debranching of starch molecules	[158,159,160]

summarizes the key parameters that influence the enzymatic hydrolysis of starch, including enzyme concentration, temperature, pH, and reaction time.

Biotechnological Modifications

Biotechnological modifications incorporate advanced techniques, such as genetic engineering and fermentation, to create starch with novel properties in food products. Similarly, glucoamylase converts starch into glucose, providing a foundation for various applications of sweeteners. Enzymatic approaches are advantageous because of their specificity and ability to produce targeted modifications without hazardous chemicals. Biotechnological modifications employ advanced techniques, including genetic engineering and fermentation, to produce starch with novel properties. Genetic engineering enables the development of microorganisms that synthesize starch molecules with tailored characteristics, and fermentation processes can create starches with enhanced solubility, texture, and stability. These methods are promising for producing starch with unique functionalities that meet specific industrial requirements. The various processes and parameters used for biotechnological modification of starch and its application are presented in

Table 7. Parameters for biotechnological modification of starch.

Modification	Parameters	Mechanism	Application	References
Genetic modification	Gene editing using CRISPR or RNAi	Alters starch biosynthesis genes to modify amylose/amylopectin ratio	Development of genetically modified starch with desirable traits	[161]
Fungal enzyme treatment	Enzyme conc.: 0.5–1.0% (w/v) Temp: 50 °C pH: 5–9	Use of fungal α-amylase and glucoamylase to break down starch	Enhanced hydrolysis for unique starch structures	[162]
Bacterial enzyme treatment	Enzyme conc.: 0.2–0.8% (w/v) Temp: 40–50 °C pH: 6.5–7.5	Bacterial pullulanase or isoamylase for debranching; bacterial cyclodextrin glycosyltransferase (CGTase) for cyclodextrins	Introduction of novel enzymes for branching/debranching starch	[163]

.

7. Application of Modified Starch

7.1. Starch-Based Nanomaterials for Wastewater Treatment

The rising demand for clean water and increasing discharge of industrial effluents have intensified the need for advanced sustainable wastewater treatment solutions. Conventional treatment methods often fail to effectively remove complex pollutants, such as dyes, heavy metals, and persistent organic compounds. In this context, nanotechnology has emerged as a transformative approach that offers enhanced surface reactivity, selectivity, and functional versatility. Cationic starch (Cs) significantly contributes to the performance of the 3D nanocomposite cryogel owing to its modified chemical structure, which contains positively charged groups, typically quaternary ammonium functionalities. These positive charges enable Cs to interact strongly with negatively charged contaminants, such as anionic dyes like Reactive Blue 49, through electrostatic attraction. This interaction enhances the cryogel’s ability to capture and remove pollutants from wastewater. In addition to its charge-based interactions, Cs possess a high-water affinity and the ability to swell. This helps create a gel-like network that allows better diffusion and interaction of dye molecules with the active sites. This property also contributes to forming a highly porous 3D structure, which increases the available surface area for adsorption.

When used as the main component of cryogels, Cs form a structural framework that supports the incorporation of other functional materials. As a reinforcing agent, nano-fibrillated cellulose (NFC) improves the mechanical properties, whereas silver nanoparticles (Ag NPs) provide antimicrobial action. Together, these components create a multifunctional cryogel capable of removing chemical and biological contaminants [164]. Almonaitytė et al. also optimized cationic starch synthesis using it as a flocculant to separate wastewater sludge and microalgae. The positive charge of cationic starch binds to negatively charged particles in wastewater, aiding the aggregation and settling of solids. This method provides an environmentally friendly solution for improving water treatment efficiency, reducing chemical usage, and managing sludge [165]. Cationic starch is an efficient and eco-friendly flocculant for separating algal biomass from wastewater using reverse osmosis (RO) concentrate. Its positive charge interacts with negatively charged algal cells, causing them to aggregate into larger flocs that settle easily. This aids in efficient biomass recovery and improves the overall treatment process of RO concentrate using microalgae [166]. Zhang et al. examined crosslinking-grafting cationic starch flocculants to enhance the removal of textile dyes from wastewater. The ability of starch to adsorb and aggregate dye molecules can be improved by combining crosslinking and grafting techniques. This process enables effective dye separation, providing an environmentally friendly and efficient solution for wastewater treatment in the textile industry. This helps minimize pollution and promote sustainability [167]. The cationic starch-grafted cationic polyacrylamide/graphene oxide (Cs-g-CPAM/GO) ternary composite is an advanced flocculant developed to enhance the treatment of oil sludge suspensions. Cationic starch is a biodegradable and positively charged base material in this composite, promoting initial interactions with negatively charged particles in the sludge. Grafting with cationic polyacrylamide (CPAM) enhances flocculation efficiency through charge neutralisztion and bridging mechanisms, which help form larger and more stable flocs. The incorporation of graphene oxide (GO) further strengthened the performance of the composite due to its high surface area and the presence of oxygen-containing functional groups, which supported stronger adsorption and particle aggregation. Consequently, the combined action of these components significantly improves the separation of oil and solid particles from wastewater, rendering this ternary composite highly effective for environmental remediation [168]. According to Chittapun et al., cationic cassava starch facilitates the separation of microalgal biomass by carrying a positive charge that attracts and binds to the negatively charged algal cells. This causes the cells to clump into larger flocs, making them easier to separate from the water.

Cassava starch is an eco-friendly flocculant due to its natural, biodegradable, and safe properties. When used alone or combined with other materials, it improves floc size and settling, making the separation process more efficient [169]. Recent advances in starch-derived materials for wastewater purification have focused on enhancing their adsorption potential through various chemical and structural modifications. Processes such as quaternization impart a positive charge to the starch backbone, enhancing its affinity for negatively charged pollutants. Polymer integration and nanomaterial incorporation enhance mechanical integrity and introduce multifunctional properties. Techniques such as crosslinking form robust 3D frameworks, while nanoengineering increases surface roughness and porosity, accelerating contaminant capture. These innovations render starch-based adsorbents sustainable, economical, and highly effective for extracting dyes, heavy metals, and other impurities from polluted water [170]. The role of starch-based nanomaterials in wastewater treatment is depicted in Figure 8.

7.2. Biomedical Potential of Cationic Starch-Based Advanced Drug Delivery Systems

Santander et al. investigated nanoparticles synthesized from novel starch derivatives for their potential use in transdermal drug delivery systems. This study demonstrated that starch derivative nanoparticles enhanced drug encapsulation and release properties, thereby improving skin penetration, ensuring controlled release, and increasing drug bioavailability. These nanoparticles exhibit excellent biocompatibility and fewer side effects compared to traditional methods [171]. Xu K et al. researched Green Starch-Based Hydrogels with Excellent Injectability, Self-Healing, Adhesion, Photothermal Effect, and Antibacterial Activity for Promoting Wound Healing, focusing on creating an environmentally friendly starch-based hydrogel ideal for wound healing. This hydrogel is designed to be injectable, allowing it to adapt to the contours of a wound easily. It features self-healing capabilities that enable it to repair itself when damaged. It also has strong adhesive properties, ensuring it remains at the wound site. The photothermal effect enhances the hydrogel, generating heat when exposed to light, which stimulates blood flow and tissue regeneration. Furthermore, it exhibits antibacterial activity and reduces the risk of infection. The findings demonstrated that this hydrogel significantly promoted the healing process by facilitating tissue regeneration, preventing disease, and enhancing overall recovery, thereby positioning it as a potential solution for chronic wounds and skin injuries [172]. Savekar et al. focused on developing a pH-responsive hydrogel film for diabetic wound healing by incorporating a citric acid cross-linked matrix. This film was loaded with pomegranate peel extract, which contains bioactive compounds, including antioxidants, that help reduce inflammation and support tissue repair crucial for wound healing. The hydrogel is made from β-cyclodextrin, a cyclic sugar, and carboxymethyl tapioca starch, which have been modified to respond to pH changes. This pH sensitivity allows the hydrogel to release the pomegranate peel extract in response to the acidic environment typically found in wounds. The controlled release of therapeutic agents, combined with the hydrogel’s adaptability to the wound’s pH, makes this a promising approach for enhancing the healing process of diabetic wounds [173]. Xiuli Wu et al. Dual-modified cassava starch films reinforced with strengthening agents offer eco-friendly solutions for cosmetics. They are invaluable for biodegradable packaging, facial masks, and under-eye patches due to their flexibility and durability. These films also aid in the controlled release of skincare ingredients, such as antioxidants and moisturizers, thereby enhancing the effectiveness of the products. Additionally, they improve the texture and stability of cosmetic formulations, making them sustainable alternatives in the industry [174]. Stimuli-responsive injectable hydrogels composed of chitosan and starch are effective for repairing articular cartilage, as they gel under physiological conditions, enabling minimally invasive applications. Starch improves the strength and compatibility of the material with bodily tissues, while chitosan facilitates cell adhesion. The incorporation of adipose-derived stromal cells accelerates the healing process by promoting the formation of new cartilage at the site of injury [175]. Nano-inspired biopolymer hydrogel scaffolds are highly effective for bone and periodontal tissue regeneration because they mimic the natural extracellular matrix. These hydrogels provide a supportive and biocompatible environment that promotes cell attachment, growth, and differentiation. Their nanoscale features enhance their mechanical strength and biological activity, making them ideal for guiding tissue repair and regeneration in dental and orthopaedic applications [176]. Figure 9 illustrates the biomedical applications of starch-based materials, particularly in transdermal drug delivery and bone tissue engineering. In the upper part of the figure, starch is processed into a film-forming solution and cast into thin sheets, which are layered to develop multifunctional transdermal patches. When applied to the skin, these patches enable controlled drug release, thereby improving therapeutic efficacy. The lower part of the figure depicts the application of the modified starch in bone regeneration. Starch was chemically modified and used as a matrix for incorporating nanoparticles, thereby forming a porous scaffold. This scaffold supports the adhesion and proliferation of stem cells, facilitating tissue repair and bone regeneration at the injury site. This figure highlights the versatility of starch in designing functional materials for advanced biomedical therapies.

7.3. Sustainable Applications of Modified Starch: From Bio-Ethanol Production to Biodegradable Composites

Modified starch has a wide range of uses in sustainable practices, from producing bioethanol to creating biodegradable composites. The versatility of starch, a readily available and renewable resource, stems from its structural properties and the ability to be chemically modified for various industrial purposes. In bioconversion processes, starch plays a crucial role as a substrate for producing bioethanol. It can be broken down into fermentable sugars through enzymatic hydrolysis, which can then be converted into ethanol. Rashwan et al. emphasized the significance of modified starch for sustainable applications. Its ability to decompose naturally and its potential to replace petroleum-based materials make it an important alternative. Modified starch also boasts enhanced properties, such as increased durability and water resistance. They are widely used for producing bioplastics, eco-friendly adhesives, and protective coatings. Furthermore, it promotes greener agricultural practices as a slow-release fertilizer and seed-coating component. Sustainably extracted and modified plant starch offers high-purity applications in food, bioplastics, and pharmaceuticals, while reducing energy, wastewater, and carbon footprints by up to 40%. Its growing use in plant-based meat and biodegradable packaging supports a circular economy [177]. Krajang et al. Single-step ethanol production from raw cassava starch is a highly effective process seamlessly integrating hydrolysis and fermentation. Enzymes such as alpha-amylase convert insoluble cassava starch into glucose, making it readily available for yeast. Subsequently, yeast (Saccharomyces cerevisiae) efficiently ferments glucose to produce ethanol and carbon dioxide. Ethanol is a valuable resource for biofuel and industrial applications, and some residual biomass is generated during its production. This method is both efficient and cost-effective, seamlessly combining starch breakdown and fermentation into a streamlined process [178]. Monroy et al. developed a sustainable panel design using modified cassava starch bioadhesives and wood-processing by-products. Techniques such as cross-linking have improved adhesive strength and water resistance, allowing the production of durable particleboard and plywood. This eco-friendly approach reduces waste and offers a biodegradable alternative to synthetic adhesives for wood panel manufacturing [179]. Pimpisai et al. produced bioethanol from cassava starch by breaking down starch into simple sugars using saccharolytic moulds. These sugars are fermented by Saccharomyces cerevisiae TISTR 5088 to produce ethanol. The co-culture method enhances efficiency by combining enzymatic hydrolysis and fermentation in a single process [180]. Chamorro et al. examined hydrogels made from cassava starch and citric acid, which are used as eco-friendly, biodegradable carriers for fertilizers. They act like sponges, absorbing nutrient solutions, such as ammonium and potassium, and gradually releasing them into the soil over time. This slow-release behavior helps improve nutrient-use efficiency, reduces the need for frequent fertilization, and minimizes nutrient loss through leaching or runoff. Such hydrogels are especially beneficial for sustainable agriculture because they enhance soil moisture retention and provide a steady supply of nutrients to plants, ultimately supporting better growth and yield [181]. Zhao et al. investigated the fact that magnesium-modified starch cryogels are innovative, porous materials developed to recover Nitrogen (N) and Phosphorus (P) from wastewater. These cryogels are created by crosslinking starch and incorporating magnesium ions, which play a key role in capturing phosphate and ammonium through precipitation and ion exchange, respectively. Their high surface area and porous structure allow for the efficient adsorption of nutrients from polluted water. Once saturated with nutrients, cryogels can be applied directly to the soil as a slow-release fertilizer substitute, offering a sustainable approach to wastewater treatment and nutrient recycling in agriculture. This dual-function material supports circular economy principles by converting waste into valuable resources [182]. Rice starch was used as a biomass precursor to produce disordered carbon materials suitable for use as anode materials in lithium-ion batteries. The process involves enzymatic hydrolysis of rice starch to control its molecular structure and enhance uniformity before carbonization. After enzymatic treatment, the starch is carbonized at high temperatures, producing disordered carbon with a porous structure and a high surface area. Further surface modifications are applied to enhance the electrochemical performance, including improvements in conductivity and lithium-ion storage capacity. The resulting material offers high capacity, good rate capability, and cycling stability, making it a promising and sustainable alternative to traditional graphite anodes [183]. Lodi et al. study focuses on spray-drying microencapsulating the beneficial bacterium Bacillus megaterium using a matrix composed of polyvinyl alcohol, cationic starch, and zinc oxide nanoparticles. Cs plays a key role as a natural and biodegradable carrier that helps form a stable matrix for encapsulation. This process protects the bacteria from environmental stress and ensures their controlled release in the soil. The inclusion of zinc oxide not only enhanced bacterial survival but also supplied bioavailable zinc to soybean plants. When applied to soil, this bioformulation promotes plant growth and root development, while also improving zinc uptake efficiency, and offers a sustainable alternative to chemical fertilizers [184]. Cs is a versatile and sustainable biopolymer that delivers exceptional performance in wastewater treatment, drug delivery, and biodegradable packaging. Its enhanced surface reactivity, strong electrostatic interactions, and excellent biocompatibility make it a powerful candidate for next-generation eco-friendly and biomedical applications.

8. Patent Information

Starch science has seen remarkable advancements in recent years, particularly in isolation methods, modification strategies, and diverse applications. Isolation techniques have been refined to obtain starches with tailored physicochemical properties, as reported in several studies on rice and banana starches, where the choice of isolation method significantly impacts the functional attributes of the final product. Modification strategies, encompassing chemical, physical, enzymatic, and genetic approaches, have been developed to overcome the limitations of native starch, such as poor thermal stability and high water absorption, thereby expanding its industrial applications. Chemical modifications, such as cross-linking, grafting, esterification, and etherification, have enabled starch to serve in a range of applications, including food and packaging, pharmaceuticals, tissue engineering, and wastewater treatment. These advancements underscore starch’s versatility as a biodegradable, renewable polymer with growing significance in both food and non-food sectors, ultimately resulting in several patents. Recent information on modified starch and its applications is presented in

Table 8. Recent patent protection information on modified starch and its applications.

Title	Use	Year	Patent ID	Ref.
Cross-linked emulsified modified starch, as well as preparation method and application thereof	Emulsifier	2024	CN118530378A	[185]
Potato starch vacuum sterilization device and use method thereof	conveyors and a spiral roller for automated, uniform sterilization, improving efficiency and safety while reducing costs.	2024	CN117441845A	[186]
Formaldehyde-Free Impregnated Paper Adhesive and Preparation Method Thereof	Paper adhesives, eco-friendly adhesives, wood, and the paper industry	2024	CN117757384A	[187]
Makeup removal cleaning cream with moisturizing and skin care effects	Moisturizing, makeup removal	2024	CN118078729A	[188]
Wet modified starch and hydroxypropyl-modified starch mixed sewage treatment process	ability to improve the sedimentation and removal of suspended solids and other impurities	2023	CN116282640A	[189]
Curcumin-Loaded Composite Gel Microsphere Based on Cross-Linked Corn Porous Starch, And Preparation Method Therefore	Paper adhesives, eco-friendly adhesives, wood, and the paper industry	2023	WO2023151350A1	[190]
Low Acetylated Pea Starch as Egg White Replacer	Replacement of egg proteins	2022	EP 3 987 941 A1	[191]
Starch-based release-modifying excipients and pharmaceutical	Used as a release excipient in controlled release, to improve release profiles and overcome issues with conventional systems like Contramid®	2022	(US20210299259A1)	[192]
Method for preparing nanoscale cross-linked starch microspheres	Microsphere	2021	CN113121852A	[193]
Starch cross-linked tea polyphenol antibacterial degradable food packaging material and preparation method thereof	Antibacterial properties as a barrier for food packaging	2021	CN111171385A	[194]
Waste heat clean utilization system in corn starch production	Heat exchangers remove harmful gases like SO2 using a washing tower, which helps reduce corrosion, steam consumption, and production costs.	2020	CN210229574U	[195]
Efficient pulping device for modified starch	Quick and stable pulping of modified starch with water	2020	CN210206558U	[196]
Medicament Exhibiting Wound-Healing Action	Effective for wound healing	2020	RU2712088C1	[197]
A kind of liquid foundation containing a compound modified starch and a preparation method thereof	Used in liquid foundation enhances the skin	2019	CN110141529A	[198]

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9. Challenges, Limitations, Innovative Trends, and Future Prospects

9.1. Challenges in Starch Extraction and Modification

Starch modification presents several challenges that affect its efficiency and applicability in various fields. Its complex and varied structure makes it difficult to achieve precise modifications, often leading to inconsistent performance. Many existing techniques do not consistently deliver the desired functional properties, thereby limiting their usability across various industries. Optimising processing conditions, such as temperature, pH, and reagent concentration, is crucial because any imbalance may cause degradation. Environmental concerns also arise due to the use of chemicals that can be hazardous and contribute to pollution. The high production cost, which involves expensive reagents and energy-intensive processes, further restricts large-scale adoption. Moreover, the regulatory requirements in the food and pharmaceutical sectors impose strict quality and safety standards, limiting the acceptance of modified starch. Another issue is that certain modifications reduce the natural biodegradability of starch, thereby affecting its role in sustainable applications. Addressing these challenges is crucial for enhancing starch modification techniques and broadening their industrial potential [199].

9.2. Limitation

Starch quality is influenced by factors such as the plant source, seasonal variations, and the location of production. The production process is characterized by high energy, water, and chemical demands, which contribute to elevated production costs. Native starch often demonstrates inadequate mechanical strength, solubility, and thermal stability. Additionally, there are challenges related to managing hazardous waste and byproducts. The market faces competition from more affordable synthetic alternatives and limited consumer adoption. Advanced processing techniques necessitate costly equipment and specialized expertise. Furthermore, stringent standards are in place for applications in food-grade and biodegradable products.

9.3. Innovative Trends and Future Prospects

Advancements in green chemistry for starch modification: Integrating green chemistry principles into starch modification processes enhances the efficiency of these methods and reduces their environmental impact. For instance, using biocatalysts, such as enzymes, allows for more selective modifications of starch without the need for harsh chemicals or extreme conditions. This results in products that maintain their natural properties while being tailored for specific applications, such as improved solubility and enhanced thickening capabilities. Furthermore, researchers are investigating the use of renewable solvents derived from natural sources to replace traditional organic solvents, thereby minimizing toxic waste and promoting a more sustainable production cycle.

Development of sustainable starch-based products: The trend toward sustainability is driving innovation in the development of starch-based products that cater to eco-conscious consumers. For example, starch is used to create biodegradable packaging materials that decompose naturally, thereby reducing plastic waste in landfills and oceans. Companies are also exploring the use of starch in food packaging, which helps preserve food quality and minimize environmental impact. Additionally, starch-based adhesives and coatings are being developed as alternatives to synthetic options, providing similar performance while being more environmentally friendly. These sustainable products are gaining traction in various industries, including food, cosmetics, and construction, as businesses seek to align their products with consumer preferences for greener alternatives. Potential applications in emerging fields: Starch’s versatility opens up exciting opportunities in various emerging fields. In 3D printing, starch-based materials are formulated to create complex, lightweight, and biodegradable structures. This innovation is particularly relevant to producing prototypes and custom designs in industries such as fashion and architecture.

10. Conclusions

Starch, a renewable and biodegradable polymer, holds significant promise across various sectors, including food, pharmaceuticals, and sustainable packaging. Its adaptability has been demonstrated as a thickening agent, stabilizer, and biodegradable material. Nonetheless, the inherent limitations of native starch, such as inadequate thermal stability and weak mechanical strength, require modifications to improve its functionality. Ongoing research and industrial adoption are crucial to unlocking the full potential of starch as a cornerstone of sustainability in various fields. The resource-intensive nature of starch extraction, environmental concerns related to water and energy usage, and high costs of advanced modification techniques remain barriers to its widespread adoption. Furthermore, native starch often lacks mechanical performance and resistance to extreme conditions, necessitating further advancements in its modification techniques. Emerging technologies, such as green chemistry, CRISPR-based genetic engineering, and renewable solvent systems, offer promising solutions to these issues, aligning with global sustainability goals. The role of starch in the transition to a circular economy is vital. The potential of replacing synthetic materials with bioplastics, adhesives, and food coatings supports efforts to reduce plastic waste and carbon emissions. Moreover, the adaptability of starch for use in novel fields such as bioethanol production, sustainable textiles, and innovative materials ensures its relevance in addressing both industrial demands and environmental challenges. Developing efficient, eco-friendly starch-based products can significantly contribute to achieving a more sustainable future by fostering collaboration among research institutions, industries, and policymakers.