Recent progress in properties and application of antibacterial food packaging materials based on polyvinyl alcohol

3.1 Mechanical properties

Mechanical properties play important roles in food packaging, which ensure the food quality by influencing the resistance to deformation or breakage. The elongation at break (EB) and TS show the toughness and strength of the film, respectively. Measurement of the mechanical properties of PVA-based films can evaluate the feasibility of their practical use as food packaging materials. As shown in Table 1, mechanical properties are remarkable parameters for developing food packaging materials combined with different antimicrobials.

Mechanical strength of the PVA film was highly improved after the incorporation of 2.5 wt% calcium propionate (35) compared with pure PVA film (31). This may be due to the uniform distribution of calcium propionate in the film and the interaction with PVA molecular chains, which enhanced the strength and toughness of the film. Among all the films prepared, the PVA/carboxymethyl CS composite film with CA showed highly improved mechanical properties (36). In another study, the EB of PVA/CS films was 223.89 ± 7.50%, and it increased to 281.10 ± 24.69% upon the addition of modified bacterial nanocelluloses (mBNCs) and 4-hexylresorcinol (4-HR) (11). EB raises as the concentration of mBNCs and 4-HR increases, but the composite films show a decrease in TS. Likewise, the solution casting method for the preparation of PVA films containing cinnamic and ferulic acids showed enhanced TS and elastic modulus compared to the pure PVA films, and EB was significantly enhanced for the films after thermo-processing. Moreover, the solution casting method was used to prepare PVA films containing cinnamic and ferulic acids, which demonstrated enhanced TS and elastic modulus compared to pure PVA films. Furthermore, EB was significantly improved for the films after thermo-processing. In addition, the TS of the films increased, while the EB tended to decrease with the addition of piperic acid, and the results indicated the suitability of the composite films for food packaging (37). The TS of composite films prepared from PVA/ST was increased up to 31.83 ± 0.17 MPa compared to neat films, which is 18.05 ± 0.04 MPa, depending on the nanoparticle filler concentration (38).

3.2 WVP

WVP is the main parameter to evaluate water transfer between the internal and external atmosphere of food packaging, which is considered to be an important parameter of food packaging materials. The difference between the relative humidity in the external environment and the water activity of the food itself can lead to moisture or dehydration during the storage of food, so it is necessary to explore the effect of WVP of the film on food packaging. The WVP of PVA-based films containing different antimicrobial agents are shown in Table 1.

The moisture content (MC) and WVP of the PVA/CS composite films were improved with the addition of mBNCs and 4-HR, while water solubility was reduced (12). The WVP and oxygen permeability of the PVA films containing cinnamic and ferulic acids were significantly reduced (39). The incorporation of AgNPs decreased the WVP of the PVA films, which is in line with that reported in previous studies, suggesting that the addition of nanoparticles enhances the vapor barrier properties of the films (40). This is also consistent with another study which found that the WVP of PVA/CS nanocomposite films incorporated with TiO₂ were observed to decrease the WVP property ranging from 6.57 to 4.36 × 10⁻¹² g·cm·cm⁻²·s⁻¹·Pa⁻¹ (41). The addition of CA into PVA/carboxymethyl CS composite films can induce a decrease in WVP values (36). The presence of nanoparticles reduced the intermolecular spacing within the films, thus reducing the WVP through the film (42). Another study also confirmed that the incorporation of CA into the PVA for the fabrication of food packaging films can decrease the WVP up to 1.28 × 10⁻¹⁴g·m⁻¹·s⁻¹·Pa⁻¹ compared to control composites without CA having WVP of 4.02 × 10⁻¹⁴g·m⁻¹·s⁻¹·Pa⁻¹ (43).

According to Chen et al. (44), the WVP significantly decreased from 3.13 × 10^–14 to 1.43 × 10⁻¹⁴ g·(cm⋅s⋅Pa)⁻¹ for PVA/ST film with the addition of clove oil (CO). The addition of CO would structure a zigzag route at the hydrophilic hydrophobic interface, which decreased the diffusion capability of WVP.

3.3 Transparency

The transparency of PVA-based food packaging is of great importance. Transparent PVA-based packaging offers several benefits, including expanded product visibility, increased safety assurance, improved food quality assessment, and a platform for promoting eco-friendly materials and sustainability initiatives by manufacturers. PVA-based transparent packaging can contain environmentally friendly packaging materials and promote sustainable development efforts of manufacturers.

The addition of 2–6 wt% of CNC to PVA improved interfacial interactions, yielding clear micro-structures. The bio-nanocomposite films maintained high transparency (90% transmittance in UV-vis), indicating good CNC dispersion. These eco-friendly composites are promising for food packaging (45). The light transmittance of the PVA/starch/glycerol/halloysite nanotube (HNT) nanocomposite films decreased linearly by 26.90% as the HNT content increased from 0 to 5 wt%, making them suitable for sustainable food packaging, especially for lipophilic and acidic foods (46). The transparency of PVA-based films decreased with higher loading of TiO₂ and MMT nanoparticles in the nanocomposite films prepared using the solution casting method (47). Pure PVA had better light transmittance than PVA/xanthan gum (XG) composite films, suggesting better transmittance in pure PVA due to the composite film’s internal structure affecting light transmission and scattering. It is worth mentioning that all samples exhibited over 85% transmittance, demonstrating good uniformity and transparency (48).

In summary, the transparency of PVA-based food packaging not only meets practical goals such as product visibility and safety, but also plays a key role in marketing, branding, sustainability, and overall consumer satisfaction. This meets consumers’ desire for transparency and helps build trust in food products and their packaging.

4.1 Organic antimicrobial agents

Organic antimicrobial agents largely disrupt cell membranes by releasing antimicrobial substances, which causes sulfhydryl acidification and protein denaturation. It blocks DNA synthesis and cellular metabolism and inhibits the reproduction of bacteria and fungi. The antimicrobial agent not only has a superior antimicrobial ability, abundant source, fast bactericidal speed, wide antibacterial range, and good bactericidal effect but also has poor safety, poor stability, common drug resistance, and relatively weak effect on bacteria (49). The organic antibacterial agents typically added in PVA substrates includes potassium sorbate (50), calcium propionate (35), CA (36), sodium lactate (51), and caffeic acid (52).

The film material of PVA with calcium propionate additive of 2.5 wt% produced certain antimicrobial effects on Bacillus cereus, E. coli, and Aspergillus oryzae (35). CA was discovered to have a substantial inhibitory impact on S. aureus at a certain dose in PVA/carboxymethyl CS packaging film (36). A study (52) of solid caffeic acid and β- or γ-cyclodextrin inclusions embedded in PVA nanofibers demonstrated high antibacterial activity against both E. coli and S. aureus. This study used a sodium lactate-loaded PVA/CS/MMT composite film with excellent inhibition activity against E. coli. PVA/piperic acid composite films demonstrated strong antimicrobial action against the Fusarium solani, Penicillium, and Aspergillus foodborne pathogens (33). Food can be shielded from browning and exposed to less UV light thanks to antibacterial films containing PVA/N-acetylcysteine (NAC) ability (45). At 85°C and when exposed to moisture, the released NAC significantly slowed the growth of S. aureus and E. coli.

Meanwhile there are some lipid compounds, halides, and organometallics added as antibacterial agents in food packaging film materials. The growth of four major food pathogens, including Campylobacter jejuni, E. coli, Listeria monocytogenes (L. monocytogenes), and Salmonella typhimurium, was inhibited by PVA/CS conjugate films (34), and the best antibacterial effect was seen for films with 5% and 10% ethyl lauroyl arginate content. Additionally, food packaging films with strong antibacterial activity and severe sensitivity to E. coli and L. monocytogenes were made using PVA grafted ethylene radical alteration and N-haloamines (53). The zeolite imidazole skeleton-8 (ZIF-8) metal-organic skeleton, along with PVA and quaternary ammonium CS, constructs ZIF-8 films. These composite films possess high bacterial filtering capabilities and demonstrate effectiveness in eradicating both E. coli and S. aureus (54).

4.2 Inorganic antimicrobial agent

Inorganic antimicrobial agents are broadly used in medical materials, agricultural antimicrobial agents, optical materials, and semiconductor materials. It is one of the top research hotspots for antibacterial materials because of its high antibacterial efficiency and durability, low drug resistance, high safety, and UV-barrier properties. Pursuant to the inverse antibacterial mechanism, inorganic antibacterial agents can be categorized into two types: dissolution type and photocatalytic type. The soluble type is loaded with inorganic carriers such as Ag, Cu, and Zn; the photocatalytic type consists of inorganic oxides such as TiO₂ and ZnO, which have relatively high heat resistance, but have bactericidal effects only in the presence of UV light, oxygen, or water. A wide range of antibacterial agents have been reported in the literature as metal nanoparticles (e.g., Ag, Cu, etc.) (55,56), metal oxide nanoparticles (e.g., TiO₂, ZnO, CuO, Cu₂O, etc.) (54,57,58,59).

Inorganic metal nanometer antimicrobial agents treated with nanotechnology have a wide range of highly effective antibacterial bactericidal properties, AgNPs are most widely used among them. PVA-based film materials enriched with AgNPs exhibited significant inhibition of Salmonella typhi (60), E. coli (53), S. aureus (61), and Aspergillus niger (40). Salmonella typhi and S. aureus growth was greatly slowed down by PVA/boiled rice starch (BRS)/AgNPs composite films. In comparison with the control PVA/BRS composite films, the nanocomposite showed improved mechanical and optical properties and had a lower water sensitivity. Moreover, PVA/BRS/AgNP films function better against environmental microbes (60). Pure PVA film containing AgNPs showed significant inhibition of Aspergillus niger (40). In the alternative, the addition of nanocellulose also enhanced the inhibition of E. coli and S. aureus by PVA/AgNPs film materials (62).

Plant extracts majorly contain polysaccharides, polyphenols, alkaloids, aldehydes, proteins and amino acids, which can be used as reducing and stabilizing agents for the biosynthesis of AgNPs by reaction with silver nitrate solution, and have significant effects on the biosynthesis of AgNPs. AgNPs synthesized by the reaction of cynodon dactylon (CD) leaves extract with silver nitrate were added to PVA film-forming solution to prepare antibacterial film materials, which showed significant inhibition of Pseudomonas fluorescens. The addition of biosorbed-AgNPs improved the physical and antibacterial properties of the films (63). Ginger extract was reacted with silver nitrate to synthesize AgNPs and the prepared PVA/MMT/AgNPs composite film materials showed strong antibacterial effect against pathogenic bacteria S. typhimurium and S. aureus (64). The significant increase in TS of the nanocomposite films could be attributed to the high compatibility between nanofillers (MMT and AgNPs) and PVA. The effective dispersion of nanofillers in the polymer matrix helps to control the stress transfer at the interface between the filler and matrix, which ultimately leads to the increase in TS of the nanocomposites. The increase in Young’s modulus (YM) of the nanocomposite blended films may be due to the interaction between the filler and matrix, resulting in the limitation of matrix motion and stiffness. On the other hand, the EB of pure PVA films was found to decrease after blending with ginger extract, MMT, and AgNPs. Similarly, AgNPs synthesized by the reaction of capparis zeylanica leaf extract with silver nitrate were added to PVA/polyethylene glycol film-forming solution to make films, and the composite films showed better inhibition of Pseudomonas aeruginosa (65). Other AgNPs such as periwinkle (59,66), sodium citrate dihydrate (67), oregano essential oil (OEO) (42), morinda citrifolia leaf extract (68), CS (69), and glucose (70) synthesized by reaction with silver nitrate were added to PVA film-forming solution to prepare antibacterial film materials.

The metal oxides that have been reported for antibacterial packaging of PVA substrates are TiO₂, ZnO, CuO, Cu₂O, etc. E. coli, Salmonella enterica, L. monocytogenes, and S. aureus were all significantly inhibited by PVA/CS composite films containing TiO₂, and the inhibition of the first three bacteria by the composite film materials increased with the increase in the TiO₂ concentration (41). Other studies discovered that film materials made of PVA/corn starch and PVA/carboxymethylcellulose (CMC) that contained ZnO nanoparticles both demonstrated strong antibacterial activity against E. coli and S. aureus (24,71), while PVA/corn starch film with outstanding UV-shielding capability meanwhile retaining highly optical transparency (approximately 90%) (24).

The antibacterial activity of PVA/CS was further enhanced by the addition of Cu₂O@NCs, with 2% Cu₂O@NCs achieving 72% and 66% inhibition against S. aureus and E. coli, respectively (59). Similarly, it was found that the introduction of CuO@ZIF-8 nanoparticles into the PVA/quaternary ammonium CS as the inner layer exhibited better antibacterial ability against S. aureus and E. coli (54). Meanwhile, the films provided low WVP and strong UV-barrier ability. There were also PVA/CS/ZnO-SiO₂ composite film materials made by adding different ratios (0.50%, 1.0%, 3.0%, and 5.0%) of ZnO-SiO₂ (72) to the PVA/CS mixture, which exhibited better antibacterial properties against E. coli and S. aureus. The addition of ZnO-SiO₂ nanocomposites substantially reduced the WVP of the films, with values of 954.19, 890.38, 890.38, and 500.60 g·(m²·day)⁻¹, respectively, compared to 980.86 g·(m²·day)⁻¹ for PVA/CS films (72).

4.3 Natural antimicrobial agent

Natural antimicrobial agents can be grouped into three main categories in terms of their main sources: natural antimicrobial agents of plant origin, natural antimicrobial agents of microbial origin (73), bacteriocins (nisin, Lantibiotics, antibiotics, etc.) (74,75,76), biopolymers (CS) (77,78), and enzymes (lysozyme) (79). Section 4.3.1 focuses on the more studied plant-derived antimicrobial agent, streptococin lactate.

5.1 Release factors

By altering the environmental conditions such as temperature and humidity or by adjusting the concentration of antimicrobial agents, researchers have changed the release ability of antimicrobial agents. Figure 4 shows the release of antibacterial agents in the packaging system. For illustration, the release process of thymol from PVA-based films was investigated at different temperatures (4°C, 25°C, and 40°C) using thymol as an antimicrobial agent (108). The release process of CEO at three different temperatures made it clear that the release rate of CEO increases proportionally with the increase in temperature and relative humidity (109). Nisin was added to PVA/AHSG films and its release rate in 50% ethanol food simulants was regulated by varying the concentration or temperature (4°C, 25°C, and 40°C) and time of nisin release, and the results showed that the migration of nisin from PVA/AHSG films to food simulants accelerated with the increasing temperature (110). When the release of sodium lactate from active antimicrobial packaging with PVA and CS as substrates was also explored, its diffusion from the membrane was found to be influenced by the pH and ionic strength of the aqueous solution (51).

Figure 4

Application of PVA-based food package film in different fields: (a) strawberries (38), (b) mushroom (119), (c) pork (121), and (d) cheese (Karish) (12).

In another study (95), nisin in the PVA/CS film material increased from 0% to 10%, the relative concentration of S. aureus decreased sharply from 100% to 11.65%, and then gradually decreased. With the increase in nisin content in the film, the release of nisin in the bacterial suspension increased, thus effectively inhibiting the growth of S. aureus. The increase in nisin content had no significant effect on the antimicrobial activity when the nisin content was higher than 10%. The release rate during the release of NAC was proportional to the square of the amount of NAC in the membrane at each moment (111). Other researchers (71) investigated the release process of ZnO nanoparticles in CMC/PVA films, and the release of nanoparticles in the simulants ethanol and acetic acid was related to the concentration of Zn²⁺ in the film. The PVA/MMT/potassium sorbate active packaging materials were prepared by flow casting method, and it was found that adjusting the MMT concentration changed the release effect of potassium sorbate in fatty food simulants. The release process of OEO and CEO in 10% ethanol and 50% ethanol food simulants within PVA composite films at room temperature was found to be higher than OEO release for the same concentration of CEO (83). Antimicrobial food packaging films were synthesized by mixing PVA, starch, and glycerol with embedded CuO and ZnO nanoparticles, and the release of Cu²⁺ and Zn²⁺ metal ions from the films with embedded nanoparticles was explored (38).

Parameters such as pH, temperature, and antimicrobial agent concentration affect the antimicrobial activity of the film, and each of these parameters has a strong influence on the bioactivity, compatibility, and stability of the antimicrobial agent and its rate of release from the film matrix. Regulation of the release of antimicrobial agents from packaging films under different circumstances is therefore necessary.

5.2 Release kinetics

Modeling the release of antimicrobial agents is useful to further explore and predict the release behavior of antimicrobial agents in film materials and to evaluate the diffusion ability and distribution behavior of antimicrobial agents within the film materials to the food products inside, so as to optimize the antimicrobial packaging system and reduce the experimental cost. In the process of exploring the kinetics of antimicrobial agent release, the commonly used model in PVA substrates is the Fickian model (112).

The expression of Fickian’s second law is as follows:

where D _P is the diffusion coefficient of antimicrobial agent in the packaging material (cm²·s⁻¹); C is the concentration of active substance (mg·cm⁻³); l is the distance in the direction of release (cm); and t is the active substance release time (s).

The limited packaging-limited food system considers a limited volume of packaging and a limited volume of food. At this time

where M _F,t is the amount of active substance released into the food/simulation fluid at time t, mg; M _F,∞ is the amount of active substance released into the food/simulation fluid at equilibrium, mg; q _n is the non-zero positive root of the equation tan q _n = −αq _n

The diffusion coefficient (D _P) during the release of potassium sorbate to 95% ethanol in PVA/MMT films ranged from 0.08 × 10^–11 to 30.3 × 10^–11 cm²·s⁻¹ when the ambient temperature was increased from 4°C to 60°C (50). The D _P of lactobacillus peptides in membranes was determined by adding lactobacillus peptides to PVA/AHSG films, and the D _P increased from 2.04 × 10^–13 cm²·s⁻¹ to 1.51 × 10^–12 cm²·s⁻¹ as the temperature increased from 4°C to 40°C (110). Fickian equation was used to describe the D _P of sodium lactate in PVA and CS-based active antimicrobial packaging in aqueous solutions with different pH and NaCl concentrations, and it was found that D _P increased with the increase in pH, while higher NaCl concentrations inhibited the movement of ions, especially at pH 7 and NaCl concentration of 0, where D _P was maximum at 12.52 × 10^–7 cm²·s⁻¹, while the D _P is minimal at a NaCl concentration of 0.10, 2.47 × 10^–7 cm²·s⁻¹ (51). In kinetic studies of silver ion release from starch/PVA films into polar food simulants distilled water, ethanol, and acetic acid, the D _P of silver ions was 3.37 × 10^–11 cm²·s⁻¹ in distilled water, 3.2 × 10^–11 cm²·s⁻¹ in ethanol, and 2.88 × 10^–11 cm²·s⁻¹ in acetic acid (113). A study to investigate the release kinetics of rosemary polyphenols from PVA electrospun nanofibers in three food simulants revealed that the D _P of polyphenols showed similar results in hydrophilic and acidic media (114). The diffusion rate of polyphenols was similar in the PVA base layer, while the D _P in the lipophilic simulant was the largest at 1.37 × 10^–14 cm²·s⁻¹ containing 4% tea polyphenols in a polypropylene/PVA/polypropylene multilayer active film, the D _P increased from 2.06 × 10^–11 to 8.06 × 10^–11 cm²·s⁻¹ with the increase in the film pore size in 50% ethanol (115). Table 2 summarizes the release effects and diffusion coefficients of some different antimicrobial agents in food simulants.

6.1 Application in fruits and vegetables packaging

Antimicrobial films or coatings formulated by adding antimicrobial agents to PVA substrates were used to package fruits and vegetables to elongate the shelf life of strawberries (10,23,38,116,117), cherry tomato (59,118), bananas (17), grapes (40), lemons (21), mushrooms (119), etc. According to Wen et al. (10), PVA/β-cyclodextrin/CEO nanofiber films used for strawberry preservation not only increased the shelf life of strawberries but also preserved their color and look while being stored. Similar to this, strawberries that were wrapped in PVA/starch films with CuO and ZnO nanoparticles demonstrated improved shelf life and kept their fruit’s nutritional value (38). As reported by Shao et al. (117), PVA/permutite fibrous/CEO electrostatic spinning films increased the shelf-life of packaged strawberries.

An active nanocomposite coating made by co-blending PVA, agar, and maltodextrin, along with AgNPs, sprayed onto the surface of bananas, significantly extended the shelf life of bananas (17). The novel antimicrobial agent CuO@ZIF-8 was introduced into a composite bilayer film with poly (lactic acid) and PVA-quaternary ammonium CS as the outer and inner substrates, and the bilayer film had good antimicrobial activity and the composite film inhibited the growth of harmful microorganisms on the surface of sainfoin fruits (54). It was also found that the addition of Cu₂O@NCs prolonged the shelf life of sainfoin fruits (59). When compared to PE cling film, PVA/CEO/β-cyclodextrin electrostatically spun nanofiber films improved the hardness and retained a better color for the mushrooms, but the rate of weight loss was slower (119).

6.2 Application in fresh meat packaging

Microbial contamination and protein oxidation are the main problems in food safety and quality deterioration of fresh meat products. The packaging materials and technologies have a significant impact on the meat quality and safety characteristics. Therefore, it is highly justified to conducting further research in this area. PVA-based films or coatings prepared by adding antimicrobial agents were used for packing chicken (120), pork (121), beef (11), lamb, fish (122), and shrimp (107) to the extension of their shelf life.

Active food packaging materials containing essential oils were prepared by electrostatic spinning from two commonly used spices (laurel and iteranum Laurus nobilis and Rosmarinus officinalis) and applied to chicken breasts, which improved the shelf life, decreased lipid oxidation, and reduced the number of L. monocytogenes during refrigeration (20). In a study, the combination of 4-HR and mBNC in the PVA/CS composite film was found to effectively suppress spoilage bacteria in vacuum-packed chilled raw beef (9). This innovative approach holds promise for enhancing meat preservation and preventing bacterial growth, thus contributing to the extension of its shelf life (11).

Changes induced by rose petal extract (RPE) have been effectively studied in films using PVA/CMC, the study indicated that the total bacterial count, pH, total volatile alkaline nitrogen, and thiobarbituric acid reactive substances of fish were higher in PVA/CMC composite film compared to the RPE film. This finding suggests that the RPE film exhibits better performance in terms of controlling bacterial growth and maintaining the quality of the fish by reducing the accumulation of volatile alkaline nitrogen and thiobarbituric acid reactive substances (122). Antimicrobial food packaging films prepared from PVA/polyacrylic acid combined with aminoethyl radicicicin aminoethyl-phloretin showed significant inhibition of L. monocytogenes and S. aureus and potently extended the shelf life of pork by 4 days at 25°C (121).

Proanthocyanidins (PC) as an active ingredient have also exhibited potent antibacterial properties in food packaging materials. However, it is important to note that PC is susceptible to acid hydrolysis. The CS-graft-PVA film containing PC was used for the preservation of salmon muscle and showed the potential ability to prevent microbial contamination and texture deterioration within 10 days. It is suggested that CS-grafted PVA films had good prospects for future food packaging applications (123).

6.3 Application in other types of food packaging

The physical appearance of bread packed with this bio-nanocomposite film was significantly improved when ZnO-SiO₂ were utilized in PVA/CS nanocomposites (72). The presence of anthocyanins and limonene was added to the composite of PVA/potato starch, which showed good color development and antibacterial activity against pasteurized milk (88). In other study, the effect of TiO₂ on PVA/CS film antimicrobial properties were investigated. The results showed that the weight loss of the cheese was reduced, the sensory properties was enhanced, and the shelf life was extended due to the nanomaterials during a storage period of 25 days. Among the different compositions tested, the composite containing 3% TiO₂NPs exhibited the highest effectiveness in terms of preserving the quality and prolonging the shelf life of the cheese (12). When PVA/20% sorbitol film-forming solution containing Salmonella enterica phage PBSE191 was applied to the surface of eggshells, the PVA coating containing PBSE191 on the eggshell surface showed significant anti-Salmonella activity within 24 h (124).

Figure 4 presents the application of PVA-based food package film in different fields. Table 3 summarizes the antimicrobial activity of PVA-based packages of different antibacterial agents.

6.4 Degradation of the PVA-based films

PVA is a water-soluble synthetic polymer that can degrade under various environmental conditions. The dominant factor is the water solution of the film in the initial stage of degradation, the phenomenon might result from the hydrophily of the main component, then the moisture in the soil comes in contact with the surface of films which results in the solution, swelling, and the further osmosis of moisture into the polymer network. As PVA chains break, smaller, water-soluble PVA fragments are formed. These fragments dissolve in water. Microorganisms absorb these water-soluble fragments and use them as a carbon and energy source for growth and metabolism. As long as suitable conditions exist, microorganisms continue producing PVA enzymes and breaking down PVA, allowing them to grow and reproduce. The rate and efficiency of degradation depend on factors like the type of microorganisms, environmental conditions, and the specific PVA material (125).

The PVA/starch/glycerol/HNT films become less degradable and less transparent as the HNT content goes up from 0 to 5 wt% as a biodegradable material (46). PVA/XG composite films can be fully decomposed in soil and water within 12 h, much faster than regular plastic bags and other biodegradable materials (48). This makes it a promising option for eco-friendly, renewable, and sustainable food packaging, potentially replacing traditional plastic bags.