Recent developments in natural biopolymer composites for active food packaging

Cai, Y., Sun, N., Lin , Q., Liu , J., and Chen, Y. (2026). "Recent developments in natural biopolymer composites for active food packaging," BioResources 21(3), 9137-9220.

Abstract

The transition toward a circular economy has established biodegradable polymer composites as a critical platform for active food packaging. This review systematically examines the structural design, functional mechanisms, and application performance of natural biopolymer matrices, including polysaccharides and proteins. Physicochemical coupling among polymer-network architecture, interfacial interactions, and active-agent dispersion governs the integration of antimicrobial, antioxidant, gas-barrier, UV-shielding, moisture-regulating, and stimuli-responsive functions. Particular emphasis is placed on controlled mass transfer and release kinetics at active packaging interfaces. Active-agent delivery is governed by molecular diffusion, polymer-network relaxation, carrier structure, and microenvironmental triggers such as pH, humidity, and temperature, which collectively determine the effective concentration and duration of antimicrobial and antioxidant activity. These structure–release–function relationships are further evaluated in high-moisture foods, respiring fruits and vegetables, and low-moisture or lipid-rich products. In addition, this review discusses the major constraints on industrial translation, including the migration and regulatory compliance of intentionally and non-intentionally added substances, nanoparticle safety, environment-dependent biodegradation, life cycle impacts, and thermomechanical challenges associated with continuous processing. Future development should move beyond passive material substitution toward the integrated design of active and intelligent packaging, scalable manufacturing, food-specific performance validation, and multi-objective optimization of functionality, safety, cost, and end-of-life behavior.

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Recent Developments in Natural Biopolymer Composites for Active Food Packaging

Yawei Cai,^a,c,* Na Sun,^b,c Qixuan Lin,^a Jianghe Liu,^d and Yongjun Chen ^a,*

DOI: 10.15376/biores.21.3.Cai

Keywords: Active food packaging; Biodegradable polymer composites; Controlled release kinetics; Food preservation; Life cycle assessment

Contact information: a: Packaging Materials Testing Laboratory, Shenzhen Polytechnic University, Shenzhen 518055, Guangdong, China; b: Huzhou Key Laboratory of Green Energy Materials and Battery Cascade Utilization, Huzhou University, Huzhou 313000, Zhejiang, China; c: School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150080, Heilongjiang, China; d: Industrial Training Center, Shenzhen Polytechnic University, Shenzhen 518055, Guangdong, China;

* Corresponding authors: [email protected]; [email protected]

INTRODUCTION

Extending food shelf life and ensuring food safety impose multi-dimensional performance requirements on modern packaging materials (Ablegue et al. 2025). Traditional petroleum-based polymers dominate the food packaging sector because of their low cost, excellent processing rheology, and high gas barrier properties. However, their inherent recalcitrance to degradation has caused severe ecological burdens, including solid waste accumulation, microplastic pollution, and the depletion of finite fossil resources. Consequently, developing novel alternative materials that integrate environmental sustainability with functional efficacy has become an inevitable trend in the transition toward a circular economy (Geyer et al. 2017; Barrowclough and Birkbeck 2022).

Biodegradable polymers—encompassing natural macromolecules such as starch, cellulose, chitosan, alginate, and proteins, alongside certain bio-based synthetic polyesters—are regarded as highly promising matrices for packaging materials due to their renewability and biocompatibility (Atta et al. 2022; Dutta and Sit 2024; Megha et al. 2024). Nevertheless, neat natural polymer networks typically contain dense arrays of polar groups (e.g., hydroxyl and carboxyl groups), resulting in pronounced hydrophilicity. This characteristic leads to significant attenuation of mechanical strength in the wet state, high water vapor transmission rates, and restricted thermal processing windows. To overcome these inherent deficiencies and meet the physical performance standards of commercial packaging, it is imperative to remodel the interfacial interactions and network topology of the materials through multi-scale composite engineering, such as nanofiller blending, chemical cross-linking, and multilayer assembly (Amin et al. 2022; Stoica et al. 2024). Broader studies of natural-fiber hybrid composites likewise indicate that fiber–matrix adhesion, reinforcement architecture, and defect evolution govern stress transfer and mechanical failure (Saleem et al. 2018, 2023, 2024a,b; Manikandan et al. 2026).

Building upon this foundation, active packaging refers to packaging systems that are intentionally designed to interact with the food or package headspace by releasing active compounds, absorbing or scavenging undesirable substances, or regulating the local microenvironment to maintain food quality, improve safety, or extend shelf life. This category includes antimicrobial- and antioxidant-releasing systems, oxygen and ethylene scavengers, moisture regulators, and stimuli-responsive delivery systems. In contrast, packaging that provides only containment, mechanical support, or passive gas and moisture barriers without a deliberately designed interaction with the food or headspace is not classified as active packaging. Intelligent packaging that solely monitors food condition is also conceptually distinct unless it is integrated with an active intervention function.

Within this framework, a central focus of this review is the controlled release of active agents, because preservation efficacy depends not only on the intrinsic activity of the incorporated compounds but also on their spatial and temporal delivery at the food–package interface. By incorporating essential oils, natural polyphenols, inorganic nanoparticles, or microporous framework carriers such as metal–organic frameworks (MOFs) and zeolitic imidazolate frameworks (ZIFs) into biodegradable matrices, composite systems can establish dynamic protection mechanisms at the food-contact interface (Angeli et al. 2025; Jiang et al. 2025b; Zhang et al. 2024d). These mechanisms involve multiple physicochemical processes. Antimicrobial activity may be achieved through cell-envelope disruption and the induction of reactive oxygen species (ROS), whereas oxidative deterioration can be suppressed through radical scavenging, ultraviolet (UV) shielding, and the catalytic or adsorptive removal of undesirable headspace gases, including oxygen and ethylene (Alfei et al. 2024; Bai et al. 2024). The duration and effectiveness of these functions are strongly governed by mass-transfer and controlled-release processes, including molecular diffusion, polymer-network relaxation, carrier–matrix interactions, and responses to microenvironmental stimuli such as pH, relative humidity, and temperature (Kuai et al. 2021; Ahmed et al. 2022).

For heterogeneous food systems, the structural design of active packaging must be precisely tailored to their specific physiological and metabolic characteristics. For high-moisture and lipid-rich meat and seafood products, the design of the packaging network focuses on exudate control, the stable release of interfacial antioxidants, and broad-spectrum antimicrobial activity (Constantin et al. 2026). Conversely, for fresh-cut fruits and vegetables with highly active respiratory metabolism, it is necessary to optimize the gas permeation selectivity of coatings or films, establishing a thermodynamic balance among water transpiration, O₂/CO₂ exchange rates, and ethylene scavenging (Faisal et al. 2025; Bin et al. 2026). This quantitative matching of “matrix structure to preservation function” is central to achieving effective packaging intervention.

Although laboratory-scale solution casting studies have extensively validated the feasibility of the above-mentioned strategies, the industrial translation of biodegradable active packaging remains constrained by multi-dimensional factors. First, the incorporation of functional components induces complex interfacial substance migration issues, necessitating strict adherence to regulatory frameworks to evaluate the compliance of intentionally added substances (IAS) and non-intentionally added substances (NIAS) generated from polymer degradation (Miralles et al. 2025). Second, the environmental fate of the materials cannot be simply equated with “biodegradable,” but must be systematically quantified by integrating degradation kinetics in specific end-of-life pathways (e.g., soil degradation, industrial composting) with life cycle assessment (LCA). Additionally, the scale-up of the manufacturing process faces significant thermomechanical challenges (Shen et al. 2023b; Pamakštys et al. 2026). Specifically, when transitioning solution-based formulations to continuous melt extrusion processes (e.g., film blowing, cast extrusion) that entail high-temperature and high-shear flow fields, it is critical to effectively suppress the volatilization loss and thermal degradation of active components, as well as phase separation within the matrix (Patil et al. 2024).

To ensure a focused and up-to-date review, relevant studies were mainly identified from the Web of Science, Scopus, and PubMed databases using keywords related to natural biopolymers, active food packaging, controlled release, antimicrobial and antioxidant functions, biodegradation, and food preservation. Peer-reviewed studies directly addressing food-packaging applications and reporting relevant material properties or preservation performance were included, whereas duplicate, non-peer-reviewed, unrelated, or insufficiently documented studies were excluded.

Against this background, this review systematically outlines recent advances in biodegradable polymer composites within the active food packaging domain. This article first summarizes the structural characteristics and composite modification strategies of representative natural biopolymer matrices. Particular emphasis is then placed on controlled mass transfer and release kinetics at active packaging interfaces, including the effects of molecular diffusion, polymer-network relaxation, carrier architecture, and pH-, humidity-, and temperature-responsive behavior. The associated antimicrobial and antioxidant mechanisms are subsequently discussed in relation to the availability and duration of active compounds. The review further evaluates the preservation performance of these systems in heterogeneous foods, including high-moisture products, respiring fruits and vegetables, and low-moisture or lipid-rich foods. Finally, it systematically examines the critical bottlenecks constraining technological translation, including substance-migration compliance, environmental degradation kinetics, and thermomechanical scale-up challenges, with the aim of providing a theoretical basis for the development of multifunctional packaging materials with high industrial viability and environmental sustainability.

Natural Biopolymer Platforms and Structural Engineering

Starch matrices

As one of the most abundant natural macromolecular carbohydrates on Earth, starch is primarily extracted from plant tissues such as corn, potato, cassava, and wheat. Chemically, starch is a polysaccharide that is made up of polymerized D-glucopyranose units, mainly comprising two macromolecular conformations: amylose and amylopectin. Amylose, connected primarily by α-1,4-glycosidic bonds, forms a relatively linear helical structure and serves as the core component providing the matrix with excellent film-forming properties, flexibility, and mechanical strength. Amylopectin, containing numerous α-1,6-glycosidic branches on the main chain, possesses a highly branched structure that typically leads to poor film-forming ability but significantly influences the viscosity, crystallization behavior, and gelation process of the system. The inherent differences in the ratio of amylose to amylopectin among different botanical sources (amylose content typically ranges from 15% to 30%) fundamentally determine their baseline film-forming characteristics. Furthermore, native starch exists as semi-crystalline granules that are insoluble in cold water. To transform it into a continuous film matrix, heating and shearing in the presence of plasticizers (such as water, glycerol, or sorbitol) are usually required. This gelatinization process effectively disrupts the hydrogen bond network within the starch granules, allowing the polymer segments to disentangle and rearrange, thereby forming thermoplastic starch (TPS), which has processing potential or homogeneous film-forming solutions.

Based on these material properties, starch has become one of the most widely used matrices among natural polysaccharide food packaging materials, owing to its abundant sourcing, low cost, complete biodegradability, and high formulation compatibility. Its structural characteristics make it highly suitable as a loading platform for essential oils, polyphenols, plant extracts, and nanofillers. However, because the starch polymer chains are rich in hydroxyl groups, pure starch films generally exhibit strong hydrophilicity, high water solubility, and poor wet mechanical stability. This limits their application in practical packaging scenarios that require a comprehensive balance of mechanical properties, barrier performance, and storage stability. Therefore, recent research focus has gradually shifted from exploring single film-forming capabilities to enhancing the structural stability of the matrix through composite modification strategies and endowing it with active preservation and controlled-release functions.

For essential oil-incorporated active starch films, Wang et al. (2022) demonstrated using a cassava starch/geranium essential oil system that as the essential oil content increased to 2%, the tensile strength of the films decreased from 8.12 ± 0.30 MPa to 3.09 ± 0.11 MPa, while the elongation at break increased from 41.59 ± 1.67% to 72.84 ± 3.55%. Concurrently, the inhibition zone areas against Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes reached 99.14 ± 3.21, 125.31 ± 2.58, and 126.57 ± 2.45 mm², respectively. Criollo-Feijoo et al. (2024) introduced oregano essential oil into cassava starch and cassava bagasse starch films. Their results indicated that at an essential oil content of 3%, the water vapor permeability values of the two types of films were 6.32 × 10⁻¹⁴ and 5.73 × 10⁻¹⁴ kg·m/(m²·s·Pa), with maximum stresses of 0.19 and 0.39 MPa, respectively; the total phenol content and antioxidant activity were significantly enhanced, exhibiting obvious inhibitory effects against pathogenic bacteria. Bhatia et al. (2025) observed significant improvements in DPPH and ABTS scavenging rates after adding juniper berry essential oil to potato starch/pectin films, along with inhibitory effects on strains such as Pseudomonas aeruginosa. Furthermore, Chysirichote et al. (2025) constructed active films using acetylated rice starch (degree of substitution, DS = 1.8) and essential oil, which reduced the system’s water solubility to 15.3% and water vapor permeability to 10 × 10⁻¹¹ g·m⁻¹·s⁻¹·Pa⁻¹, and extended the shelf life of fried pork rind at 30 °C from 37.8 days to 57.7 days. These results indicate that the incorporation of essential oils primarily endows starch films with antimicrobial and antioxidant functions while increasing matrix flexibility; however, without interfacial compatibilizers or cross-linking designs, it typically results in a reduction of the mechanical strength of the matrix.

The introduction of polyphenols and plant extracts is frequently used to simultaneously improve the antioxidant properties, UV-shielding capability, and interfacial compactness of the films. Luo et al. (2022) introduced tea polyphenols and MgO nanoparticles into potato starch films, which significantly improved the moisture content (decreased to 11.21%), water solubility (decreased to 16.56%), and water vapor permeability (decreased to 9.07 × 10⁻¹¹ g·m⁻¹·s⁻¹·Pa⁻¹) of the films. Miao et al. (2021) developed active films via a “tea polyphenol-loaded porous starch” strategy, discovering that the incorporation of porous starch resulted in a tea polyphenol release of 83% at 240 min, demonstrating a superior sustained-release effect compared to the direct addition system (which released 88% at 180 min). Moreover, the composite film containing 10% tea polyphenols exhibited the best comprehensive physicochemical properties. These two studies indicate that starch can not only serve as a continuous phase matrix but also participate in regulating the delivery behavior of active molecules through its microscopic pore structure.

Regarding natural pigments and fruit/vegetable byproduct extracts, Luz et al. (2023) prepared starch films containing jabuticaba peel phenolic extracts, presenting distinct integrated active and intelligent features. The optimized films exhibited a DPPH scavenging percentage of 91.01 ± 0.5%, a tensile strength of 16.3 ± 0.7 MPa, and an elongation at break of 79.7 ± 3.1%, while also possessing high transparency, UV-shielding properties, antimicrobial activity, and pH-responsive color-changing capabilities. Zhang et al. (2024c) introduced sweet potato peel polyphenols into sweet potato starch films, finding that under the optimized formulation, the water solubility of the pure film decreased from 90.4% to 45.9%, and the water contact angle increased from 51.7° to 82.3°. Concurrently, the water vapor and oxygen permeability significantly decreased, and the antioxidant activity substantially increased, extending the preservation period of cherry tomatoes at 4 °C to 7 days. This suggests that polyphenolic substances from food processing byproducts help to improve the hydrophobicity, gas barrier properties, and functional activity of the films.

The introduction of natural second-phase fillers is another effective approach for optimizing the starch matrix structure. Chen et al. (2024b) found that the water contact angle of a laver-reinforced starch film (optimized sample S7-3) increased to 114.98 ± 1.28°, and its water solubility decreased to 15.38%; meanwhile, its tensile strength, elongation at break, and Young’s modulus reached 32.5 MPa, 19.0%, and 607 MPa, respectively. Raajeswari et al. (2025) fabricated composite films using tapioca starch, carboxymethyl cellulose (CMC), citric acid, and basil essential oil. The ultimate load of their optimized formulation reached 85.39 ± 0.26 N, with a tensile strength of 6.28 ± 0.17 MPa. In food packaging tests, the composite films containing basil oil exhibited the lowest total viable count (3.1 × 10¹ CFU/g) on day 120 and completely degraded in soil within 24 days. Such studies validate the coupled relationship among structure, properties, and functions, wherein compatibilizers and cross-linkers optimize the matrix structure, while active substances provide functional properties. Notably, introducing novel two-dimensional nanomaterials offers considerable engineering potential for overcoming the mechanical and barrier limitations of starch matrices. Recently, Dong et al. (2024) introduced Ti₃C₂Tₓ MXene nanoplatelets into a starch matrix for the first time, developing fully biodegradable nanocomposite films with exceptional water and oxygen barrier properties. As illustrated in Fig. 1, the hydrophilicity of the composite film was significantly suppressed with increasing MXene content.

Fig. 1. (a) Moisture content; (b) moisture absorption; (c) water solubility; (d) water contact angle; and (e) soil burial test process of pure starch films and composite films with different MXene loadings. (Reproduced from Dong et al. (2024), CC BY 4.0).

At a 10 wt% addition level, the water contact angle of the film increased from 55.3° (pure starch film) to 84.8°, while the moisture content, moisture absorption, and water solubility exhibited systematic reductions (Figs. 1a–d). More crucially, benefiting from the dense hydrogen bond network formed within the matrix and the physical labyrinth effect (highly tortuous paths) constructed by the 2D nanosheets, the water vapor and oxygen permeability of the composite film plummeted by 92.9% and 74.0%, respectively. Mechanically, its Young’s modulus surged from 456.5 MPa to 1923.6 MPa, and the tensile strength improved from 9.9 MPa to 19.1 MPa. Soil burial tests (Fig. 1e) further confirmed that the composite films could completely degrade within 6 weeks. This work demonstrates that the rational utilization of the geometric characteristics and surface chemistry of 2D nanofillers can achieve a simultaneous improvement in the “high mechanical-high barrier” performance of starch matrices, without sacrificing the natural biodegradability of the materials.

Research by Sousa et al. (2025) on monolayer films of TPS and olive leaf extract demonstrated that natural polyphenols could improve material performance while maintaining the continuous structure of the matrix. With the addition of 5% and 10% extract, the Young’s modulus of the films increased from 0.95 ± 0.11 GPa to 1.11 ± 0.10 and 1.17 ± 0.08 GPa, respectively, and the tensile strength also increased. Fresh-cut pear preservation experiments showed that the extract-modified films could significantly reduce the browning index of the fruit. On the other hand, Cvetković et al. (2025) found that although the introduction of wild blackberry extract endowed the films with pH responsiveness and high antioxidant activity, it also exacerbated the hydrophilicity of the starch matrix, leading to significant increases in film moisture content, swelling capacity, and water solubility. This suggests that when designing smart responsive starch films, it is essential to comprehensively balance the matching degree between responsive functions and matrix water resistance, rather than solely relying on the “lowest permeability” as the guiding metric.

To improve wet stability, Mylkie et al. (2025) utilized boronated chitosan to cross-link starch films containing cannabidiol (CBD) oil, decreasing the water vapor transmission rate to 3 g·m⁻²·day⁻¹. Under wet conditions, the attenuation of tensile strength in the cross-linked films (CS-FPBA-CBD-S) was significantly lower than that of the uncross-linked group, and they exhibited a higher free radical scavenging capacity. In contrast, Silveira et al. (2025) prepared low-cost bioplastic films using starch extracted from cassava processing waste. Although they demonstrated good antimicrobial ability and elongation at break (32.9%), the tensile strength was only 0.17 MPa. The results indicate that chemical cross-linking can effectively mitigate the structural instability of starch films under high-humidity conditions, whereas agricultural waste starch is more suitable as a substrate for single-use or short-lifespan active packaging.

The construction of inclusion complexes and edible coating technologies has further diversified the application forms of starch-based materials. Frangopoulos et al. (2025) prepared starch inclusion complex films loaded with carvacrol and ascorbic acid. In minced meat refrigeration experiments, they found that ascorbic acid helped maintain the redness of the meat, while carvacrol was more effective in inhibiting microbial proliferation. Ramadoss et al. (2025) developed active coatings based on pectin, potato starch, and pyrogallol, extending the shelf life of tomatoes to 21 days while effectively controlling weight loss and quality deterioration. This demonstrates that starch systems can achieve interfacial regulations more aligned with food degradation pathways through inclusion complexes or coating structures.

In summary, representative studies from recent years indicate that: (1) the starch matrix possesses core advantages including renewability, ease of film formation, and high compatibility with natural active substances; (2) the wet mechanical attenuation and insufficient storage stability caused by its strong hydrophilicity remain its primary application bottlenecks, making composite modification a prerequisite for meeting practical application demands; (3) current design strategies are no longer limited to merely increasing the loading of active substances, but rather focus on achieving a coordinated optimization of the “structure–property–function” relationship through extract/essential oil functionalization, second-phase reinforcement, cross-linking stabilization, and inclusion complex-based controlled release techniques. In terms of application scenarios, starch-based composite films are currently best suited for fruits and vegetables, baked goods, and short-shelf-life cold chain foods; for supply chain conditions with high humidity or substantial mechanical stress loads, they typically require further compounding with cellulose, proteins, or biodegradable polyesters.

Cellulose and its derivatives

Cellulose-based materials used in active food packaging include native cellulose, nanocellulose, regenerated cellulose, bacterial cellulose, and a variety of chemically modified derivatives of cellulose. Their functions are closely related to their molecular organization and processing form. Native cellulose consists of β-1,4-linked D-glucopyranose chains assembled into highly ordered fibrillar structures through extensive intra- and intermolecular hydrogen bonding. This hierarchical organization provides high crystallinity, mechanical rigidity, and thermochemical stability, but it also results in poor solubility and limited thermoplastic processability. Consequently, native cellulose, cellulose nanofibers, and cellulose nanocrystals are commonly employed as reinforcing or network-forming phases in composite films. Chemical substitution of hydroxyl groups partially disrupts the dense hydrogen-bonding network, producing derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methylcellulose, and methylcellulose with improved solubility and film-forming ability. Regenerated cellulose and bacterial cellulose can additionally form continuous films or three-dimensional networks, thereby extending the role of cellulose from a reinforcing component to a self-supporting packaging matrix.

The engineering performance of these cellulose-based systems is further governed by their cross-scale hierarchical assembly. As highlighted by Liu et al. (2022), cellulose structures extend from macroscopic plant tissues and cell walls to fibrils, crystalline and disordered domains, and molecular chains. As illustrated in Fig. 2, the coexistence of ordered crystalline regions and relatively disordered domains influences the rigidity, accessibility, and processability of cellulose. Mechanical or chemical deconstruction produces cellulose nanofibers and cellulose nanocrystals with high aspect ratios and mechanical strength, whereas microbial biosynthesis generates bacterial cellulose with a dense three-dimensional network. These structural differences provide the basis for using cellulose-based materials as reinforcing phases, continuous films, or network-forming components in active packaging systems.

Based on the material fundamentals, cellulose and its derivatives constitute a matrix system with significant structural engineering potential in natural polysaccharide-based food packaging materials. Compared to starch, cellulose matrices typically exhibit stronger intermolecular physical cross-linking, higher structural order, and superior intrinsic oxygen barrier properties, thus presenting distinct advantages in mechanical support, transparency retention, and film-forming integrity. Furthermore, these materials are easily used in combination with polyphenols, natural pigments, antimicrobial peptides, nanocellulose, and inorganic nanoparticles to construct multifunctional composite films. However, most water-soluble cellulose derivatives retain strong hydrophilicity, which limits their water vapor barrier performance and dimensional stability under high-humidity conditions. Consequently, the current research focus has gradually shifted from merely “using cellulose to replace traditional plastics” to introducing antimicrobial, antioxidant, UV-shielding, and controlled-release functions while prioritizing the improvement of moisture resistance, all while maintaining its high-strength skeletal advantages.

Although developed for structural composites rather than food-contact films, these studies provide transferable evidence that reinforcement architecture and interfacial integrity govern stress transfer and failure. Acoustic-emission analyses of hybrid laminates and banana/ramie/epoxy composites identified matrix cracking, fiber–matrix debonding, delamination, and fiber fracture as key failure modes (Saleem et al. 2018, 2023, 2024a,b); hybrid stacking increased load-carrying capacity, energy absorption, and stiffness by 30.6%, 26.8%, and 35.2%, respectively (Saleem et al. 2024b). Biomass-derived carbon quantum dots also improved the mechanical performance of pineapple/ramie/epoxy laminates (Manikandan et al. 2026). In food-packaging systems, these interfacial principles must additionally be evaluated together with barrier, migration, release, and biodegradation requirements.

Carboxymethyl cellulose (CMC) is currently one of the most widely used cellulose-based active packaging materials. Roy and Rhim (2021) constructed functional films based on CMC/agar. They found that the incorporation of alizarin and grapefruit seed extract (GSE) enhanced the mechanical strength and water resistance of the films by approximately 20% and 40%, respectively, while exhibiting excellent UV-shielding, antioxidant, antimicrobial, and pH-responsive color-changing capabilities. Subsequently, Roy et al. (2021) further introduced cellulose nanocrystals (CNCs) and shikonin into the CMC/agar system; the resulting smart composite film achieved a tensile strength of 61.7 MPa, combining high transparency, enhanced UV-shielding performance, and significant inhibitory effects against Listeria monocytogenes and Escherichia coli. These studies indicate that polysaccharide composite systems such as CMC/agar can achieve a coordinated improvement in transparency, mechanical strength, and smart responsive activity through the introduction of appropriate amounts of active molecules and nano-reinforcement phases.

Utilizing natural agricultural/forestry byproducts or constructing multiphase cross-linked networks represents a crucial pathway in recent years to enhance the antioxidant and moisture-proof properties of CMC matrices. Lawal et al. (2023) introduced date seed powder into CMC films, which increased the system’s thickness (from 0.11 mm to 0.15 mm), decreased water solubility (from 95.3% to 77.2%), and imparted significant free radical scavenging capacity (DPPH and ABTS scavenging rates reached 52.0% and 84.6%, respectively). Although the tensile strength slightly decreased (from 7.66 to 5.12 MPa), the elongation at break increased to 86.0%, and the composite film exhibited broad-spectrum antimicrobial activity against pathogenic bacteria, particularly showing significant inhibition against Gram-negative bacteria (such as Salmonella typhimurium) at high addition levels. Wang et al. (2025b) physically and chemically cross-linked CMC/polyvinyl alcohol (PVA) composite films using cinnamaldehyde-tannin-metal nanoparticles, resulting in a composite film with a tensile strength of 69.8 MPa, an elongation at break of 104%, a water contact angle increased to 119°, and a maximum DPPH scavenging percentage of 89.4%. On the application side, Doveri et al. (2025) developed active pectin/CMC composite films with a thickness of approximately 40 to 65 μm for bread packaging, which demonstrated excellent O₂/CO₂ barrier properties. In anti-mold tests, the mold inhibition rate of the dual-active phase composite system reached 99.97%–99.998%, with active component migration well below 2.0 mg/slice. These results demonstrate that CMC is suitable as a continuous phase skeleton in multiphase composite systems, effectively compensating for its intrinsic lack of moisture resistance through cross-linking with polysaccharides, synthetic polymers, natural particles, or active nanonetworks.

Hydroxyethyl cellulose (HEC) offers unique advantages in flexibility tuning and multicomponent compatibility. It is frequently used to construct integrated films with high strength, antimicrobial, and UV-shielding functions. An HEC/PVA/ε-polylysine composite film prepared by Zhang et al. (2022) achieved a maximum tensile strength of 95.9 ± 4.1 MPa and an elongation at break of 148.8 ± 2.6%, alongside translucency, efficient UV shielding, and good antimicrobial activity. Cen et al. (2023) investigated an HEC/carboxymethyl chitosan (CMCS)/nano-ZnO antimicrobial film, discovering that the combined effects of CMCS and ZnO reduced the film’s water solubility by 94.3% and improved its UV shielding capability by 45.7%, while achieving over 99.99% inhibition against L. monocytogenes and Pseudomonas aeruginosa. Simultaneously, the elongation at break and maximum load capacity of the film were enhanced by 494% and 142%, respectively. Furthermore, Chen et al. (2024a) incorporated sulfated rice bran polysaccharides (SRBP) into HEC films, showing that as the SRBP content increased from 0 to 20%, the tensile strength increased from 12.66 ± 0.33 MPa to 33.04 ± 0.47 MPa, water vapor permeability decreased from 4.21 × 10⁻¹⁰ to 1.15 × 10⁻¹⁰ g·m⁻¹·s⁻¹·Pa⁻¹, and both water solubility and moisture content were significantly reduced. Concurrently, the DPPH scavenging percentage increased to 77.83 ± 1.12%, forming distinct inhibition zones. This indicates that HEC not only can serve as a mechanical load-bearing skeleton, but it also can achieve simultaneous enhancement of mechanical strength, barrier properties, and biological activity through combination with natural polysaccharides, chitosan derivatives, and inorganic nanophases.

Hydroxypropyl methylcellulose (HPMC) and methylcellulose (MC) are commonly utilized to construct composite films with stable interfaces and controlled-release capabilities for active molecules. Cabrera-Barjas et al. (2025), working with an HPMC/fungal chitin nanofiber/ferulic acid system, noted that at a 5 wt% addition of chitin nanofibers, the film exhibited a tensile strength of approximately 15 MPa, plasticity of around 52%, and a water vapor permeability of 0.94 × 10⁻⁹ g·m⁻¹·s⁻¹·Pa⁻¹; however, excessive nanofibers led to phase separation, thereby weakening tensile and barrier properties. This confirms that the reinforcing effect of nanofillers in a cellulose matrix is highly dependent on interfacial compatibility and network continuity. Dag et al. (2024) introduced cellulose nanofibers (CNF) and propolis-loaded zein nanoparticles into HPMC films for cheddar cheese storage, verifying that this combination could jointly improve the system’s compatibility, hydrophobicity, gas barrier, and active substance release behaviors. In MC systems, Madihalli et al. (2025) incorporated L-arginine into methylcellulose films; the optimized film reached a tensile strength of 41.11 ± 1.03 MPa, an elongation at break of 14.11 ± 0.53%, a reduced oxygen permeability of 9.6 × 10⁻⁵ cc·m⁻¹·24 h·atm, and a DPPH scavenging percentage of 72.28 ± 0.28%, effectively controlling weight loss and browning when used for grape packaging for 17 days. Khater et al. (2023) demonstrated that incorporating AgNPs and TiO₂-NPs into HPMC substantially increased tensile strength from 39.2 to 144 MPa and 158 MPa, effectively decreased water vapor permeability. The films exhibited antimicrobial ability against Bacillus cereus. Moreover, Mohammadi et al. (2024) optimized a CMC/pectin (CMP)/chitosan nanofiber (CHNF) composite system via response surface methodology (optimal formulation: CMC 1.5 wt% + CMP 0.25 wt% + CHNF 0.75 wt%), where the introduction of nanofibers not only reduced the film’s porosity and water vapor permeability but also significantly enhanced the system’s ultimate tensile strength (UTS) and antimicrobial properties.

Fig. 2. Cross-scale hierarchical structure and morphological characteristics of cellulose: (a) Schematic of the hierarchical assembly of plant-derived cellulose from macroscopic tissues to molecular chains; (b) Micro-morphology and macroscopic hydrogels of bacterial cellulose; (c) Molecular arrangement configuration of crystalline and disordered regions in cellulose chains; and (d-f) Electron microscopic images of different forms of nanocellulose (e.g., CNC, CNF, and bacterial cellulose networks). (Reproduced from Liu et al. (2022), CC BY 4.0).

When selecting material systems from sustainable sources in an attempt to achieve high intrinsic mechanical properties, regenerated cellulose, cellulose-lignin films, and nanocellulose films present enormous potential. Cellulose-lignin composite films developed by He et al. (2023) maintained a high tensile strength of 75.9 MPa even at a lignin content of up to 30%. When combined with 3% ε-polylysine, the bactericidal percentage approached 100%, demonstrating excellent UV shielding, hydrophobicity, and water/oxygen barrier performance. Concurrently, Han et al. (2024) also validated the broad application prospects of all-cellulose composites in the development of antimicrobial and degradable active packaging. Qi et al. (2025) prepared grape preservation films using wheat straw-derived CMC, glycerol, and polymalate, achieving a tensile strength of 28.4 MPa, an elongation at break of 142.1%, and a water vapor permeability as low as 0.55 × 10⁻¹² g·m/(m²·s·Pa), effectively maintaining the storage quality of grapes. Paudel et al. (2025) utilized grapevine waste to extract cellulose for preparing transparent films, which achieved a transmittance of 83.7% to 84.30% mm⁻¹, a tensile strength of 15.4 to 18.2 MPa, and complete degradation in soil within 17 days. Furthermore, Lovely et al. (2025) optimized CNF films via a low-pressure homogenization process, showing that homogenization reduced the oxygen transmission from 0.48 to 0.25 cc·μm/(m²·day·kPa) (at 50% RH), increased tensile strength from 94 to 157 MPa, raised Young’s modulus from 2630 to 3840 MPa, lowered surface roughness (S_a) from 4.73 to 2.64 μm, and maintained crystallinity at approximately 64%. These studies collectively indicate that the “structural refinement” processing technique itself can significantly enhance the strength and oxygen barrier properties of cellulose materials, making them highly suitable as high-performance load-bearing skeletons for active packaging.

In summary, current representative studies indicate that, compared to starch, cellulose and its derivatives have more prominent mechanical support and oxygen barrier potential. Their tensile strength typically ranges from 12–15 MPa to 60–95 MPa, reaching up to 157 MPa in highly dense nanocellulose films. Concurrently, by compounding with lignin, polyphenols, polysaccharides, ε-polylysine, inorganic nanoparticles, or carbon dots, their antioxidant, antimicrobial, and UV-shielding functions can be significantly enhanced. However, such systems are generally constrained by inherent hydrophilicity and limited water vapor barrier capacity. Therefore, in high-humidity environments and long-cycle supply chain scenarios, cellulose-based composite films are more suitable as mechanical support layers, oxygen barrier layers, or functionally active layers in multilayer packaging structures, rather than independently bearing the sole responsibility of moisture protection. In short, the core application value of cellulose and its derivatives lies not in simply replacing traditional plastics, but in providing a skeletal platform that combines high mechanical support, sustainability, and multifunctional potential for degradable active packaging.

Chitosan matrices

Chitosan (CS) is one of the materials with potential for “active packaging” applications among natural polysaccharide matrices. Compared to starch and most cellulose derivatives, the chitosan macromolecular skeleton contains a large number of protonatable primary amino groups. This chemical structure provides the system with film-forming properties and intrinsic antibacterial ability, while also exhibiting certain oxygen barrier potential and interfacial reactivity. Chitosan can be directly used as a food contact layer or as a carrier for active molecules, polyphenols, nanoparticles, and polysaccharide reinforcing phases. However, the chitosan matrix has physical limitations such as relatively strong hydrophilicity, susceptibility to swelling in wet states, insufficient long-term water resistance stability, and relatively high brittleness of pure films. Therefore, recent research has primarily focused on balancing its structural stability and active functions through strategies such as chemical cross-linking, nanocompositing, the introduction of plant extracts, and the construction of edible coatings.

In terms of structural modification, cross-linking and the introduction of natural phenolic substances are commonly used strategies. Westlake et al. (2023a) utilized vanillin-cross-linked chitosan to construct active packaging films loaded with green tea polyphenols. As shown in Fig. 3, the formation of the Schiff base cross-linked network reduced the water solubility and moisture content of the system, achieved a tensile strength of 20.9 ± 3 MPa, and altered the release kinetics of the polyphenols. In food simulants (Fig. 3A), green tea polyphenols exhibited burst release characteristics within the initial 8 h (releasing approximately 70%), followed by a steady release phase lasting up to 400 h. Electron microscopic images (Fig. 3B) showed the gradual formation of microscopic diffusion channels in the film cross-section over immersion time, indicating a matrix network-mediated Fickian diffusion mechanism. The film also demonstrated a 100% UV shielding rate. Experimental data demonstrate that altering the polymer network structure via covalent cross-linking allows for the quantitative regulation of the active molecule’s release cycle. Hu et al. (2022) introduced persimmon peel extract (PPE) into chitosan films. When the PPE addition was 10%, the water vapor permeability (WVP) of the film decreased from 5.78 ± 0.23 × 10⁻³ g·mm/(m²·s·Pa) for the pure film to 3.12 ± 0.04 × 10⁻³ g·mm/(m²·s·Pa). The DPPH scavenging rate increased from 11.82 ± 1.02% to 73.43 ± 3.29%. In banana preservation tests, the weight loss rate of the CS-PPE 10 packaging group at the end of storage was 4.78%, which was lower than the 8.98% of the unpackaged group. Hamed et al. (2024) added 4% purified Moringa oleifera flavonoids to chitosan films, decreasing the WVP from 8.85 to 2.47 g·mm/(m²·s·Pa), increasing mechanical properties and antioxidant activity, and inhibiting the proliferation of pathogenic bacteria in hamburger meat. Studies indicate that constructing hydrogen bonds or Schiff base networks via aromatic aldehydes, polyphenols, and plant flavonoids can improve the gas/moisture barrier properties and service-life stability of chitosan films.

In composite system design, chitosan exhibits structural compatibility with various reinforcing phases. Subramani and Manian (2024) introduced bio-based vanillin and kaolin into chitosan films, increasing the DPPH free radical scavenging percentage from 55.6% (pure film) to 80%, with an inhibition of approximately 90% against Escherichia coli and Staphylococcus aureus. Souza et al. (2021) investigated the mechanical effect of ZnO nanoparticles (NPs) on chitosan films. After adding 0.5%, 1.0%, and 2.0% ZnO NPs, the tensile strength of the system (46.7 MPa for the pure film) was decreased by 30.8%, 22.5%, and 34.9%, respectively. This result indicates that ZnO NPs synthesized from food by-products acted as a toughening and plasticizing agent in this system, transitioning the material from brittleness to ductility while maintaining gas barrier properties. To reduce the degree of swelling under high-humidity conditions, Zhao et al. (2025a) constructed a CS-CNF/VA25-Ca1.5 multiple cross-linked film. This system remained intact after immersion in room-temperature water for over 32 days and did not disintegrate in 60 °C water for 24 h (pure chitosan film dissolved completely within 3 min); its oxygen permeability was 0.9 cm³·μm/(m²·d·kPa), the DPPH scavenging percentage was 93.6%, and the shelf life of strawberries at room temperature was extended to 7 days. This demonstrates that multiple cross-linking and nanocomposites can effectively inhibit the rapid swelling of the film layer. Deep-eutectic-solvent-assisted pullulan/carboxymethyl-chitosan films containing zein–nisin nanofillers also showed improved physicomechanical and antimicrobial performance (Ashraf et al. 2026b).

The chitosan matrix is also widely applied in edible coatings and fruit/vegetable preservation research. Yan et al. (2024) introduced trans-cinnamaldehyde essential oil into a chitosan/diepoxy-poly(ethylene glycol) system. The prepared cross-linked coating exhibited changes in tensile properties, light transmittance, water vapor barrier, and antibacterial properties; in banana storage applications, the coating reduced the respiration rate and weight loss rate of the fruit, extending the preservation period to 24 days. A chitosan/ascorbic acid/curcumin composite coating (CS-AA-Cur 20) constructed by Zhou et al. (2025) reduced the weight loss rate, decay rate, and accumulation of malondialdehyde (MDA) and H₂O₂ in strawberries refrigerated at 4 °C, extending the shelf life to 15 days. Soni et al. (2025) used an Ocimum gratissimum essential oil nanoemulsion to construct a chitosan coating. The coating showed minimum inhibitory concentrations (MIC) against five tested fungi ranging from 0.05 to 0.25 μL/mL. In room-temperature strawberry preservation experiments, the weight loss rate of the treated group was reduced by 49.7%, and the basic quality of the fruit was maintained for 8 days. Test results indicate that chitosan can act as a matrix carrier to be compounded with antioxidants and essential oils to regulate moisture volatilization and microbial activity on the surface of fruits and vegetables.

For meat and poultry food preservation, the chitosan matrix is frequently used as a release layer for antibacterial and antioxidant components. Shiryanpour et al. (2025) loaded essential oil and anthocyanin in the form of a double nanoemulsion (DNE) into chitosan films for chicken breast preservation. After 16 days, the pH value (6.23), total volatile basic nitrogen (18.5 mg N/100 g), and total viable count (4.6 log CFU/g) of the DNE-treated group were lower than those of the control group (6.85, 31.2 mg N/100 g, and 7.8 log CFU/g, respectively), extending the shelf life within the test period. Tan et al. (2025) introduced caffeic acid-grafted inulin into chitosan films, observing increases in tensile strength, elongation at break, UV shielding capability, and antibacterial performance, and a reduction in the decay rate of tested strawberries. In composite systems containing metal nanoparticles, Deb et al. (2025) introduced Indian gooseberry extract and silver nanoparticles (AgNPs) into chitosan films. The tensile strength increased from 29.29 ± 1.04 MPa for the pure film to 46.62 ± 0.82 MPa, and the elongation at break increased from 36.21 ± 1.87% to 89.39 ± 1.11%; water absorption, water vapor transmission rate (decreased to 313.94 ± 1.81 g/m²/day), and water solubility all exhibited downward trends. Degradation tests showed that the pure chitosan film lost approximately 93.0% of its mass in the first 3 weeks, whereas the composite film lost 34.8% of its mass in the first month, reaching 93.4% by the end of the second month. This illustrates that the composite of inorganic nanoparticles and cross-linked networks can alter the service-life and degradation kinetics of the material.

Fig. 3. (A) Cumulative release profiles of green tea polyphenols from vanillin cross-linked chitosan films (inset shows the initial burst release phase); (B) Microstructural evolution of the film cross-section during the release process (t = 0 to t = 240 h). (Reproduced from Westlake et al. (2023a), CC BY 4.0).

In summary, recent experimental data indicate that chitosan has potential for application in active contact layers, edible coatings, and barrier functional layers. Its structural optimization primarily focuses on: (1) utilizing vanillin, cinnamaldehyde, etc., to construct cross-linked networks to improve mechanical stability and water resistance; (2) introducing polyphenols, flavonoids, essential oils, and plant extracts to increase antioxidant and antibacterial activity; (3) utilizing nanoparticles and emulsion systems to construct controlled-release networks for active substances. Its primary physical limitation remains its swelling behavior under high-humidity conditions. In practical packaging structure design, chitosan is frequently used as an inner layer or functional coating, undergoing multilayer compounding with starch, cellulose, protein, or biodegradable polyester materials.

Alginate and pectin matrices

Before discussing the composite modification strategies for use in packaging materials, it is necessary to briefly outline the molecular structural characteristics and intrinsic gelation mechanisms of alginate and pectin. Alginate, which is primarily extracted from natural brown algae, is a linear anionic polysaccharide copolymerized by (1→4)-linked β-D-mannuronic acid (M units) and α-L-guluronic acid (G units) in various sequences (M-blocks, G-blocks, and alternating MG-blocks). Its core mechanism for film formation and crosslinking lies in the specific coordination and chelation of divalent cations (e.g., Ca²⁺, Fe²⁺) with the G-blocks on adjacent polymer chains, forming the classic three-dimensional “egg-box” gel network. Pectin, widely present in the primary cell walls and middle lamella of higher plants, features a structural backbone primarily composed of a homogalacturonan chain of α-(1→4)-linked D-galacturonic acid. Based on the degree of esterification (DE) of its carboxyl groups, pectin is generally classified into high-methoxyl pectin (HMP, DE > 50%) and low-methoxyl pectin (LMP, DE < 50%). The gelation mechanism of LMP is highly similar to that of alginate, as it can also form the “egg-box” conformation through the interaction between free carboxyl groups and divalent cations. This characteristic molecular structure based on uronic acid residues and the capability for metal ion coordination constitute the underlying chemical foundation for these two polysaccharides to undergo liquid-solid phase transitions and form edible interfaces under mild conditions.

Building upon these structural properties, alginate and pectin, as typical natural anionic polysaccharide matrices, exhibit macroscopic material characteristics such as broad availability, edibility, biodegradability, and relatively high transparency. Compared to starch and chitosan, their primary advantages in the field of active packaging include mild film-forming conditions, facile ionic crosslinking, and excellent physicochemical compatibility with polyphenols, essential oils, and plant extracts. However, because their polysaccharide backbones are rich in hydroxyl and free carboxyl groups, the materials themselves are highly hydrophilic. In environments with high relative humidity, they are prone to water absorption and plasticization, leading to a severe decline in mechanical strength and water vapor barrier performance. Addressing these intrinsic shortcomings, recent research has focused on establishing a more stable balance among structural integrity, barrier properties, and the release kinetics of active agents through ionic crosslinking, compounding with plant extracts, second-phase reinforcement, and dual-network structural design.

In alginate systems, incorporating natural by-products or essential oils to fabricate active composite films is an effective strategy for enhancing overall material performance. Khwaldia et al. (2023) introduced date palm pit extract (DPPE) into an alginate matrix, demonstrating that the addition of 10% DPPE significantly improved the water vapor barrier properties of the films, while increasing the tensile strength (TS) and elongation at break (EAB) by over 50% and 45%, respectively; simultaneously, the water solubility of the films decreased by 37% to 64%, and the surface wettability was reduced by 72% to 111%. This indicates that polyphenol-rich plant by-products not only impart antioxidant activity to the matrix but also effectively mitigate the polarity and water absorption of alginate (Khwaldia et al. 2023). Yun and Liu (2024) further directly incorporated 12 varieties of mandarin peel powder into sodium alginate films. The resulting composite films exhibited thicknesses of 118 to 152 μm, moisture contents of 16.4% to 23.6%, water contact angles of 26.0° to 90.8°, WVPs of 5.38 to 8.31 × 10⁻¹¹ g·m⁻¹·s⁻¹·Pa⁻¹, oxygen permeabilities of 5.26 to 12.91 × 10⁻²⁰ m²·s⁻¹·Pa⁻¹, TS values of 4.87 to 7.90 MPa, and EAB values of 13.4% to 24.6%. Microstructural analysis revealed that higher pectin and lipid contents in the mandarin peels facilitated the formation of a dense matrix, whereas excessive crude fiber content tended to induce internal microcracks, thereby compromising the mechanical and barrier properties. These data confirm that the performance of composite films depends not merely on the loading amount of the active agents, but is highly reliant on the compatibility and spatial arrangement of the second-phase components within the polysaccharide network.

The combined use of ionic crosslinking and ultrasonic emulsification is another critical pathway for optimizing the performance of alginate-based packaging. Asmadi et al. (2025) prepared active sodium alginate films by combining sonication, internal crosslinking with 2% CaCl₂, and the incorporation of 1% patchouli essential oil (PEO). The optimal formulation (S5/C2/PEO) achieved a TS of 31.8 MPa, a WVP reduced to 2.11 × 10⁻¹¹ g·m⁻¹·h⁻¹·Pa⁻¹, and exhibited excellent thermal stability. In storage trials with cherry tomatoes, this packaging significantly inhibited mold growth over 4 d. Wardak et al. (2024) loaded kiwifruit seed essential oil (KSO) into sodium alginate coatings and found that the KSO30 formulation possessed an excellent combination of structural integrity, hydrophobicity, barrier, and mechanical properties. When applied to persimmon preservation, the KSO30-treated group showed a weight loss of only 5.1% at the end of storage (compared to 6.8% for the control) and a pH of 6.3 (compared to 6.1 for the control), effectively delaying the loss of fruit firmness and the onset of the respiratory peak. Furthermore, the SA/QKC (sodium alginate (SA) with quaternary ammonium lignin-cinnamaldehyde (QKC) composite) antibacterial coatings developed by Miao et al. (2025) demonstrated that with 5 wt% QKC, the TS of the sodium alginate coating increased from 11.5 to 24.4 MPa, and the WVP decreased by 35.4%. The inhibition percentages against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) reached 96% and 65%, respectively, effectively reducing weight loss and decay in persimmons and citrus fruits during storage. These studies indicate that through crosslinking and emulsification-dispersion technologies, alginate can be efficiently transformed into an active physical barrier with tunable functions.

Beyond serving as physical barriers, the multiscale structural design of alginate matrices facilitates the integration of smart indicating and advanced active functionalities. As illustrated in Fig. 4, recent modifications emphasize environmentally friendly chemical grafting and the incorporation of nanocarriers. Zhang et al. (2024b) developed a polyvinyl alcohol/sodium alginate (PVA/SA) composite film loaded with ZIF-8-alizarin (PVA-SA-ZA). The alginate backbone was covalently grafted with 4-phenylsemicarbazide and subsequently crosslinked via Ca²⁺ to stably anchor the MOF nanocarriers (Fig. 4a). During refrigerated beef storage, the film’s color difference exhibited a linear correlation with total volatile basic nitrogen (TVB-N) concentrations, providing visual feedback for ammonia release (Figs. 4b, 4c). In the realm of active preservation, incorporating Pickering emulsions and multilayer networks further enhances the physical isolation capacity of alginate. For instance, incorporating a baobab seed oil pickering emulsion (BOPE) into an alginate/guar gum matrix restricted cross-interfacial moisture migration and delayed epidermal browning in Agaricus bisporus mushrooms over 30 d (Fig. 4d) (Yang et al. 2024a). Similarly, bilayer composite films incorporating TiO₂ NPs effectively inhibited mold proliferation across various temperature gradients of 4 °C, 10 °C, and 25 °C (Fig. 4e) (Yang et al. 2024b). These results demonstrate that combining molecular-level modification with nanocarrier blending allows alginate matrices to simultaneously achieve environmental responsiveness and long-term microbial inhibition.

In contrast, the physicochemical behavior of pectin-based materials exhibits a prominent coupling characteristic of “source variance–structural variance–performance variance”. Jiang et al. (2023a) systematically evaluated the film-forming properties of pectin extracted from pomelo, lemon, and white-fleshed pitaya peels. The results showed that the WVPs of the three pectin films were 1.67 ± 0.30, 1.63 ± 1.35, and 1.65 ± 1.06 × 10⁻⁹ g·m⁻¹·s⁻¹·Pa⁻¹, respectively; their TS values were 22.25 ± 1.52, 31.26 ± 2.30, and 32.40 ± 1.65 MPa, respectively, with the white-fleshed pitaya peel pectin film exhibiting the highest EAB (10.95 ± 1.51%). Such significant macroscopic differences in mechanics and barrier properties are primarily attributed to the source-dependent heterogeneity in monosaccharide composition, DE, and crystallinity. This implies that in practical packaging applications, the selection of a pectin matrix must be specifically matched according to its botanical origin and extraction process.

For pectin-based active packaging, essential oil encapsulation and functionalization with natural polyphenols are the core strategies to enhance material activity. Pectin films loaded with lemon essential oil microcapsules, reported by Akachat et al. (2025), showed that the incorporation of the essential oil increased the EAB from 11.52 ± 0.12% to 20.05 ± 0.78%, improved the TS from 12.28 ± 1.27 MPa to 14.68 ± 1.42 MPa, and surged the DPPH radical scavenging percentage from 21.37 ± 0.001% to 63.60 ± 0.001%. Morphological analysis indicated that essential oil loading transitioned the film surface from a smooth state to a rough topography containing spherical structures and interconnected channels, reflecting the structural reconfiguration of the hydrophobic phase within the hydrophilic pectin network. The apple pectin–ε-polylysine–luteolin (APPL-Lu) composite coating developed by Li et al. (2026) further verified the combined effects of multiple components. The addition of luteolin significantly increased the water contact angle of the films from 66.9° (pure AP) and 60.5° (APPL) to 118.0°, achieving effective surface hydrophobic modification. Mechanical testing revealed that at a luteolin concentration of 0.15%, the EAB was increased to 38.6%, which was 90.1% and 40.4% higher than those of the AP and APPL films, respectively. In fresh-cut apple preservation tests, the APPL-Lu treated group maintained a firmness of 10.7 N at the end of storage (a mere 6.2% decrease from the initial value, and 41.5% higher than the control group), with a weight loss of only 0.12% (compared to 1.5% for the control). This series of studies confirmed that the molecular-level combined action of antimicrobial peptides and natural polyphenols can endow pectin coatings with excellent interfacial adhesion, hydrophobicity, and antidegration efficacy.

For dual-component composite systems of pectin and alginate, constructing dual-network and multiple-crosslinking structures is a critical approach to overcoming the bottleneck of intrinsic hydration sensitivity. He et al. (2024) fabricated pectin/sodium alginate (PS) composite films by introducing tannic acid (TA) and Fe³⁺ to build metal-phenol networks. The study found that this coordination network increased the film thickness from 45.00 ± 3.53 μm to 63.89 ± 3.66 μm (with TA) and 67.63 ± 3.07 μm (with TA-Fe³⁺), reduced water permeability by 59.8% and bestowed the material with superior UV-blocking capabilities and a denser crosslinked microstructure. When applied as a coating for golden passion fruit, this composite film significantly reduced the fruit’s water loss rate and maintained its freshness. Hoque et al. (2024) further investigated the reinforcement mechanism of microcrystalline cellulose (MCC) and geraniol in PEC/SA composite systems. In a system crosslinked with 2.0% CaCl₂, the addition of 10% MCC significantly enhanced the TS of the films; with the subsequent incorporation of geraniol at various concentrations (2.5%, 5.0%, 7.5%, 10.0%), the water solubility of the composite films notably decreased, water vapor and oxygen barrier properties were substantially strengthened, and complete inhibition of E. coli and Bacillus cereus was achieved within 24 h. Thermogravimetric analysis (TGA) demonstrated that the blending of MCC and geraniol increased the onset thermal decomposition temperature of the system from 195 °C to 221 °C, and elevated the temperature of the maximum thermal degradation rate (T_max) from 237 to 260 °C. This evolutionary process demonstrates that through the multidimensional integration of ionic crosslinking, metal-phenol networks, and cellulose reinforcing phases, highly hydrophilic and easily plasticized anionic natural polysaccharides can be effectively transformed into advanced packaging interfaces with high mechanical integrity and active protective functions.

Fig. 4. Modification mechanisms and comprehensive applications of sodium alginate-based packaging materials: (a) Schematic representation of the chemical grafting and Ca²⁺ cross-linking mechanism; (b, c) Colorimetric response of PA-SA-ZA smart indicator films during beef refrigeration; (d) Preservation effect of BOPE-incorporated composite films on Agaricus bisporus mushrooms; and (e) Inhibition of target spoilage by composite films under different temperatures. Adapted from Wang et al. (2025e), Figs. 12 and 17, under CC BY 4.0.

In summary, within the realm of natural biopolymer systems, alginate and pectin are positioned as anionic polysaccharide platforms characterized by mild film-forming conditions, facile crosslinkability, and high functionalization potential. Alginate, relying on Ca²⁺/Fe³⁺ ion coordination to rapidly form stable networks, holds immense engineering application potential for fresh produce preservation coatings and edible active packaging layers; pectin, owing to its excellent matrix dispersibility, is more suitable as a carrier substrate for polyphenols, essential oils, and antimicrobial peptides. Addressing their mutual plasticization issues in high-humidity environments, a more promising future research paradigm should not be limited to the simple substitution of traditional plastics. Instead, it should focus on multilayer composite technologies incorporating nanocellulose, proteins, lipid phases, or biodegradable polyesters, enabling the polysaccharide matrices to precisely assume specific roles in structural support, functional release control, or interfacial regulation within complex packaging architectures.

Protein-based matrices

Compared to polysaccharide systems, the molecular chains of protein-based matrices contain amino, carboxyl, hydroxyl, and sulfur-containing groups, allowing for network reconfiguration through chemical or physical methods such as heat-induced denaturation, enzymatic cross-linking, metal-polyphenol coordination, Schiff base reactions, and pH-driven self-assembly. This structural characteristic endows protein matrices with film-forming, active substance-loading, and interfacial adhesion capabilities, making them frequently applied in packaging systems for meat, seafood, and fresh-cut fruits and vegetables. However, natural protein films exhibit physical limitations such as high moisture sensitivity, limited water vapor barrier capacity, and narrow processing windows. Recent research has primarily focused on compounding proteins with polysaccharides, nanofillers, hydrophobic active agents, or smart indicator components to construct multiscale cross-linked networks, thereby regulating the mechanical properties, barrier capacities, and release kinetics of active substances.

Animal-derived proteins: Gelatin and whey protein

Among animal-derived proteins, gelatin and whey protein are commonly used film matrices in active packaging. Gelatin possesses good film-forming properties and transparency, and exhibits structural compatibility with meat surfaces, making it suitable for constructing adherent active films or coatings. Experiments have demonstrated that compounding gelatin with hydrophobic proteins, essential oil carriers, or nanoparticles alters its hygroscopicity and controlled-release behavior. Wu et al. (2023) developed an electrospun gelatin/zein nanofiber film co-loaded with cinnamaldehyde and thymol for strawberry packaging. The film showed improved hydrophobicity and barrier performance, with a water contact angle of 85.1° and a water vapor transmission rate of 3.1 × 10⁻⁸ g·mm⁻¹·h⁻¹·Pa⁻¹. It also retained good mechanical properties, with a tensile strength of 1.30 MPa and an EAB of 185%. Hong et al. (2024) introduced cinnamon essential oil-loaded metal-organic frameworks (MOFs) into a gelatin/pullulan composite film; in meat preservation tests, the inhibition approached 99.9%, and the pH variation and weight loss of the samples were mitigated. Xu et al. (2025a) reinforced gelatin films with zein-quercetin NPs, resulting in a composite film with a tensile strength of approximately 3.2 MPa, an EAB of about 142%, water vapor and oxygen transmission rates decreased by 78.4% and 76.9%, respectively, a water contact angle of 112.0 ± 0.6°, and a DPPH radical scavenging rate of 64.9 ± 0.7%. Khan et al. (2023) incorporated green tea carbon dots into a chitosan/gelatin system for pork preservation, similarly validating the loading capacity of the gelatin network for natural antioxidant factors.

Constructing active delivery networks via emulsion or vesicle structures is another pathway for gelatin modification. A Schiff-base-crosslinked β-cyclodextrin/gelatin–carrageenan film has been found to enable controlled carvacrol release for ready-to-eat food preservation (Cui et al. 2023). Ran et al. (2024) introduced doubly stabilized clove essential oil chitosomes into gelatin/polyvinyl alcohol (PVA) films; the addition of composite nanoparticles reduced the swelling index of the films from 964% to 495%, regulated the release rate of the essential oil, and extended the shelf life of marinated steaks from 3 days to 7 days. Acharya et al. (2025) designed a Pickering emulsion-based pH-responsive gelatin film, utilizing bacterial cellulose nanocrystal-nanochitosan (BCNC-nCS) composite particles to stabilize the emulsion and load black pepper essential oil for duck meat preservation. The study demonstrated that the gelatin network can achieve targeted release triggered by environmental pH via emulsion microstructures. Lima et al. (2025) introduced tea tree essential oil into gelatin-based packaging, which produced inhibition zones of 17 mm and 9 mm against Pseudomonas aeruginosa and Salmonella enterica, respectively, with an established minimum inhibitory concentration (MIC) range of 10% to 15%.

Whey protein isolate (WPI) possesses intrinsic oxygen and lipid barrier properties due to its intramolecular disulfide bonds and conformational characteristics. Dai et al. (2024) loaded chlorogenic acid into a sweet whey/starch composite film; the UV shielding rate at 315 nm was increased by 54.6%, the inhibition rate against E. coli increased by 47.5%, and the ABTS scavenging rate improved by 74.5%. Gao et al. (2024) analyzed the release kinetics of cinnamaldehyde in whey protein/HPMC films, showing that its release behavior was adequately described by the Fickian power-law and Weibull models. In smart indicator systems, Kiani-Salmi et al. (2025) constructed a chitosan/WPI/betacyanin/carbon dot composite film with inhibition zones of 20 ± 1.2 mm and 15 ± 0.36 mm against S. aureus and E. coli, respectively. The TS ranged from 79.4 to 91.7 MPa, and the WVP decreased from 6.90 × 10⁻¹¹ to 2.54 × 10⁻¹¹ g·m/(m²·s·Pa). Using chitosan and transglutaminase-modified whey protein as film-forming substrates, Liu et al. (2025c) prepared UV-resistant alizarin/curcumin-based pH indicator films for shrimp freshness monitoring, demonstrating that enzymatic cross-linking alters the water resistance and mechanical stability of the whey protein network. Leaching-resistant anthocyanin bigels and chitosan–quercetin films have also been used for colorimetric monitoring of volatile amines and fish spoilage, respectively (Zhai et al. 2022; Wu et al. 2025). Together, these studies indicate that WPI-based composite networks can integrate barrier and antimicrobial functions with colorimetric freshness monitoring. The reliability of the sensing response is closely related to the stability of the pigment within the polymer microenvironment. Betacyanins, alizarin, and curcumin may undergo light-, oxygen-, temperature-, or moisture-induced changes during storage, while film thickness, pigment distribution, polymer–pigment interactions, and headspace humidity can alter the initial color and response range. Consequently, color responses obtained in buffer solutions or model headspaces need to be correlated with food-specific spoilage indices, such as pH, total volatile basic nitrogen, microbial counts, or biogenic amine concentrations, under realistic storage conditions. Response time, instrumental color difference, repeatability, and pre-use storage stability are therefore important parameters for evaluating sensing accuracy. At the package level, indicator migration, batch-to-batch variation in natural pigments, standardized visual or smartphone-based color acquisition, and compatibility with scalable coating or printing processes will further determine the transition of these systems from laboratory prototypes to practical packaging applications (Stoica et al. 2024; Yang et al. 2025a).

Plant-derived proteins: Zein and soy protein

In the domain of plant-derived proteins, zein and soy protein isolate (SPI) are two primary film matrices. Zein possesses high surface hydrophobicity and is frequently utilized as a carrier for lipid-soluble essential oils and hydrophobic antimicrobial agents. SPI features numerous side-chain reactive sites, making it suitable for network cross-linking via chemical or physical modifications. Research on zein has primarily focused on the construction of electrospun nanofiber mats and nanocomposite films. A zein film containing pomegranate-peel-extract-loaded chitosan nanoparticles achieved sustained active release with inhibition of L. monocytogenes in pork (Cui et al. 2020). Khalil et al. (2024) prepared zein electrospun mats loaded with nisin to control Listeria monocytogenes on peach surfaces, testing the sustained release behavior of the nanofibers. Gholizadeh et al. (2024) introduced geraniol nanoliposomes into zein nanofiber mats, achieving the encapsulation and release of hydrophobic active substances. Yi et al. (2024) and Zhang et al. (2025b) constructed active zein films utilizing gallic acid-loaded γ-CD-MOFs and composite AgNPs, respectively. Zhang et al. (2025b) reported that the composite film exhibited inhibition rates of 44.6% to 78.0% and 28.4% to 59.5% against E. coli O157:H7 and Salmonella enterica, respectively, maintained antioxidant activity for approximately 100 days, and extended the shelf life of refrigerated pork by 9 days.

Cross-linking modifications can alter the mechanical and barrier properties of zein systems. Wei et al. (2025a) applied citric acid vapor-assisted cross-linking to nisin-embedded zein/PEG composite nanofiber membranes. The film exhibited a water vapor transmission rate of 150.47 ± 7.14 g·m⁻²·24 h⁻¹, an oxygen transmission rate of 59.74 ± 3.10 cm³·m⁻²·24 h⁻¹, and inhibition zones of 11.52 ± 0.44 mm and 10.67 ± 0.46 mm against E. coli and S. aureus, respectively. After 10 days of cooled goose meat preservation, the pH, TVB-N, and total viable count (TVC) of the samples were approximately 5.7, 11.3 mg/100 g, and 5.01 ± 0.69 log CFU/g, respectively. Kazemi et al. (2026) noted that under specific concentration, voltage, and flow rate conditions, the zein spinning system produced an inhibition zone of 12.2 mm against L. monocytogenes and retained approximately 38.2% of its DPPH scavenging ability. Cheng et al. (2024) confirmed that the addition of TiO₂ nanotube arrays also altered the mechanical strength and structural compactness of zein films.

SPI research has emphasized the construction of covalent or non-covalent cross-linked networks. Sun et al. (2024) introduced a starch aldehyde–quercetin conjugate into SPI; the resulting films achieved DPPH and ABTS scavenging percentages of 79.8% and 62.1%, respectively, alongside changes in light shielding, thermal stability, and surface hydrophobicity. Choo et al. (2024) incorporated phage CAM-21 into SPI films; the phage remained active under pH 3 to 11 and 55 °C conditions and inhibited E. coli O157:H7 in beef test groups. Ren et al. (2024) added 10% tara pod extract to SPI films, increasing tensile strength by 56.4%; after 90 days of beef tallow packaging, the peroxide value was 0.002 g/100 g (compared to 0.0835 g/100 g for the polyethylene control film).

In constructing multiphase structures to regulate the release of volatile active substances, the introduction of high internal phase (HIP) emulsions provides a novel interfacial design strategy for SPI films. Zhao et al. (2024b) prepared an oil-in-water (O/W) HIP emulsion and incorporated it into an SPI film-forming solution to load thymol. As illustrated in Fig. 5, confocal laser scanning microscope (CLSM) images demonstrated that within the HIP emulsion system, oil droplets were smaller and more uniformly distributed within the film-forming solution and the final films (Figs. 5a, 5b), reducing the migration degree of the oil droplets. Physicochemical analyses revealed (Fig. 5c) that the HIP emulsion films containing 30% oil phase exhibited the lowest WVP (1.15 × 10⁻¹⁰ g·m⁻¹·s⁻¹·Pa⁻¹), glass transition temperature (40.9 °C), and TS (4.47 MPa), alongside the highest transparency value (12.9) and EAB (161%). Further antimicrobial tests demonstrated that, compared to conventional O/W emulsion or pure oil systems, the HIP-based SPI films exhibited a higher thymol encapsulation efficiency (Fig. 5d) and more pronounced sustained-release characteristics, thereby achieving more prolonged growth inhibition against the tested microbes. This study confirmed the regulatory role of high internal phase emulsions on the mechanical flexibility of the SPI matrix and the controlled release of hydrophobic active molecules.

Fig. 5. Micro-morphology and physicochemical properties of SPI films modified by high internal phase (HIP) emulsions loaded with thymol: (a) Confocal laser scanning microscope (CLSM) images of conventional oil-in-water (O/W) emulsions and HIP emulsions in film-forming solutions and films; (b) Particle size distribution curves of the oil droplets; (c) Schematic illustrating the formation of SPI films with varying oil droplet distribution characteristics; (d) Comparison of thymol encapsulation efficiency among the SPI-based emulsion films. (Zhao et al. (2024b), CC BY-NC 4.0).

In fruit and vegetable preservation applications, Zhao et al. (2024a) introduced pomegranate peel extract into SPI/Artemisia sphaerocephala Krasch. gum composite films. The film thickness, TS, and EAB were increased by 24.5%, 58.8%, and 30.5%, respectively, while water vapor and oxygen transmission rates were decreased. Xue et al. (2024) constructed preservation films for cherry tomatoes using SPI-polyphenol conjugates loaded with rose essential oil. Focusing on metal-phenolic networks (MPNs), Cheng et al. (2025) introduced Schiff base-metal phenolic networks into an oxidized corn starch/SPI system, increasing TS by approximately 72% and decreasing water vapor transmission rate by about 35%. Wang et al. (2025a) reported that MPN-modified SPI films exhibited >80% antimicrobial efficiency on blueberries and delayed fruit quality degradation in a 10-day test. Test results indicate that zein systems are frequently used to construct carriers for hydrophobic active substances and nanofibers, whereas SPI generally serves as a reactive cross-linked network platform in the design of composite films.

**Structural Tailoring via Secondary/Tertiary Structure Modulation**

The mechanical strength, moisture resistance, surface hydrophobicity, and active substance release behaviors of protein-based films are directly influenced by the conformational rearrangement of macromolecular chains. Thermal denaturation promotes the exposure of buried hydrophobic groups and partial sulfhydryl groups, affecting intermolecular hydrophobic association and disulfide bond recombination. Enzymatic cross-linking alters the topological structure of intermolecular covalent connections. Polyphenols, metal ions, and deep eutectic solvents influence the local structural order and free volume distribution of the protein matrix through hydrogen bonding, coordination, and conformational plasticization.

Regarding the reorganization of protein disulfide networks, the introduction of reducing agents directly alters the processing rheological characteristics of the system and intermolecular forces during film formation. Jiang et al. (2023b) systematically analyzed the effects of cysteine pretreatment on the physicochemical properties of SPI film-forming solutions and films (Fig. 6). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis (Fig. 6a) indicated that cysteine cleaved the disulfide bonds linking the α and α’ subunits of SPI, thereby reducing the apparent viscosity of the film-forming solution from 41.6 to 12.8 mPa·s (at a 1 mmol/L concentration), which improved the processing fluidity of high-concentration film-forming solutions. During the film drying process, the cleavage of disulfide bonds promoted the exposure of internal hydrophobic groups, leading to an increased proportion of hydrophobic interactions within the film (Fig. 6b). This molecular rearrangement based on tertiary structure unfolding decreased the water solubility of the film from 70.4% to 57.6%, improving the water resistance of the material without altering its tensile strength. However, when the cysteine concentration reached 4 mmol/L and above, X-ray diffraction (XRD, Fig. 6c) and scanning electron microscopy (SEM, Fig. 6d) results revealed that excessive cysteine formed crystalline aggregates on the film surface, resulting in a decrease in elongation at break. This study confirmed that regulating the thiol/disulfide exchange reactions of proteins via small-molecule reducing agents can quantitatively tune the rheological properties of film-forming solutions and the structural compactness of the final films.

Studies on the conformational evolution of SPI systems confirm the aforementioned mechanisms. Kang et al. (2024) analyzed the effect of transglutaminase (TGase) on the film-forming behavior of soy protein; spectroscopic data indicated that TGase promoted the transition of proteins from β-turns/random coils to β-sheets, thereby altering the structural order and water stability of the film network. Research by Wang et al. (2023) on MPN-modified SPI demonstrated that polyphenol networks intervened in intermolecular protein interactions and interfacial adhesion. Zheng et al. (2025) plasticized SPI films using a β-cyclodextrin supramolecular deep eutectic solvent; conformational analysis revealed an increase in α-helix and β-turn content and a decrease in β-sheets, with the films reaching DPPH and ABTS scavenging percentages of 28.94% and 24.29%, respectively. This indicates that the introduction of plasticizers is accompanied by the resetting of local conformations and free volume within the protein matrix.

In the regulation of active substance loading and release, Li et al. (2025d) achieved the pH-triggered release of tannic acid by utilizing changes in the spatial conformation of SPI induced by environmental pH variations. This mechanism controls release kinetics by modulating intermolecular protein spacing and the exposure of binding sites, and was applied in shrimp preservation tests. Previously, Li et al. (2022b) introduced curcumin into SPI films via an organic solvent-free pH-driven system; results showed that curcumin was dispersed in an amorphous state and embedded into the protein network through hydrogen bonding and hydrophobic interactions. The resulting films had an EAB of 122 ± 6% and a WVP of approximately 1.70 × 10⁻¹⁰ g·m/(m²·s·Pa). These data indicate that pH-driven reconstitution affects the solid-state dispersibility of active substances and the toughness of the composite network.

For mixed protein systems, structural tailoring involves the control of microphase separation in multiphase systems. Phase separation occurs when compounding hydrophobic zein with hydrophilic proteins such as gelatin. Zulfikar et al. (2025) systematically analyzed the phase separation characteristics and structure-property correlations in gelatin/zein films. The results demonstrated that the final physical properties of the blended films are jointly governed by phase-domain scale, interfacial adhesion forces, and macromolecular segment migration behavior. Physicochemical characterization results indicate that quantitative interventions in the rheology, interfacial adhesion, gas barrier, and active delivery characteristics of protein matrices can be achieved by controlling the conformational rearrangements of secondary and tertiary structures.

To facilitate a quantitative comparison among the natural biopolymer matrices discussed above, Table 1 summarizes representative mechanical, barrier, and active properties reported for selected composite systems.

Because these data were obtained using different formulations, film dimensions, conditioning procedures, and analytical protocols, the absolute values primarily reflect the performance achieved under the specific conditions of each study. In particular, mechanical and barrier properties are sensitive to film thickness and environmental conditioning, whereas antimicrobial and antioxidant results depend strongly on the selected evaluation method. Therefore, comparisons are more meaningful when based on the relative changes between the modified and control films within the same study, while differences among independent studies should be interpreted as general performance trends rather than as a strict ranking of the polymer matrices.

Fig. 6. Effects of cysteine pretreatment on the microstructure and intermolecular forces of SPI films: (a) SDS-PAGE protein patterns of films under different cysteine concentrations; (b) Proportion distribution of chemical bonds (ionic bonds, hydrogen bonds, hydrophobic interactions, and disulfide bonds) in the films; (c) XRD patterns of SPI films; (d) SEM images of the film surfaces (showing cysteine crystalline aggregates). (Jiang et al. (2023b), CC BY-NC-ND 4.0).

The mechanical response to active-agent incorporation is determined by the competition among reinforcement, plasticization, and defect formation rather than by the presence of the active component alone. At low or optimized loadings, hydrogen bonding, electrostatic interactions, hydrophobic associations, ionic or covalent crosslinking, and strong filler–matrix adhesion can restrict chain slippage and improve stress transfer, thereby increasing tensile strength or modulus. In contrast, liquid essential oils and some low-molecular-weight extracts may act as plasticizers by increasing chain mobility and free volume, commonly decreasing tensile strength while increasing elongation at break. When the loading exceeds the compatibility or dispersion capacity of the matrix, aggregation, phase separation, microvoids, and interfacial debonding interrupt stress transfer and promote premature fracture. The resulting mechanical properties are also affected by filler aspect ratio, crosslink density, crystallinity, porosity, plasticizer content, moisture conditioning, film thickness, and testing conditions. Consequently, improvements or deterioration should be interpreted as formulation- and condition-dependent outcomes rather than as universal effects of a specific active agent (Wang et al. 2022; Dong et al. 2024; Yun and Liu 2024; Cabrera-Barjas et al. 2025).