Biopolymer-Based Sustainable Food Packaging Materials: Challenges, Solutions, and Applications

1The use of biopolymers as packaging materials is becoming an emerging trend worldwide due to their major benefits over plastics, such as biodegradability, eco-friendly nature, nontoxicity, and biocompatibility. These natural biopolymers have excellent film-forming cohesive structures and thin protective layers of film.

2Biopolymers used as food packaging materials are mainly polysaccharides, proteins, and aliphatic polyesters, which can maintain food quality and increase the shelf-life of the product. These packaging materials have barrier properties that control the exchange of gases, moisture, aroma, and lipids from the external environment and vice versa, possess antimicrobial activity that can protect the food product from the external environment, and prevent the loss of desirable compounds such as flavor and texture. Biopolymers such as starch, cellulose, and polylactic acid (PLA) are currently used for food packaging materials. However, the main limitation of using biopolymers in food packaging is their weak mechanical strength and high sensitivity to moisture. The merits and demerits differ depending on the type of biopolymer used for food packaging. Table 1 shows the advantages and disadvantages of different biopolymers used in food packaging. To overcome the weaknesses of biopolymers, many studies have been performed with the addition of reinforcing agents such as nanofillers, biopolymers, plasticizers, and natural agents such as essential oils. Furthermore, biopolymer matrices act as carriers for antimicrobial substances, antioxidants, flavor agents, vitamins, or nutrients, thereby aiding in improving food quality, safety, nutritional value, and sensory properties. An overview of biopolymers in food packaging is presented in Figure 1. Due to the numerous advantages, biopolymers have been proposed as an alternative to synthetic polymers such as plastic, which reduces the harmful impact on the environment. As the use of biopolymers in food packaging materials is increasing, it is important to upgrade the biopolymer industry to a large scale. Strategies for sourcing biopolymers include utilizing agricultural waste, instituting efficient cultivation practices, and researching innovative biopolymer production technologies.

3Despite numerous works reporting on the use of biomaterials for packaging, the novelty of this review lies in the extensive explanation of each material’s unique qualities that make it appealing for packaging a specific food product. This review article also describes various challenges and possible solutions associated with food packaging materials. It examines the current state of research and industrial application, including the advantages and disadvantages of various biopolymer-based food packaging. Finally, a SWOT (strengths, weaknesses, opportunities, and threats) analysis is performed on biopolymers, and future trends are discussed. Thus, this review will be useful in the decision-making process to develop biopolymer-based packaging materials.

4Plastic, a petroleum-based, diverse, and ubiquitous material, is widely used in food packaging due to its lightweight, cost-effective, transparent, versatile, and easy-to-process properties. These synthetic polymers possess excellent mechanical, thermal, and barrier characteristics, while ultra-thin layers extend the shelf-life of packaged products and reduce food waste. Consequently, plastics provide direct economic benefits by lowering transportation costs.

5Global plastic production has increased significantly, with 40% of all produced plastic being used for packaging, and nearly half of that for food packaging. Europe’s plastic distribution demand is dominated by packaging at 39.6%. However, plastic’s high production volume, short usage time, non-biodegradable nature, and inadequate management have raised concerns worldwide, with recycling challenges arising from multilayer plastics.

6Plastics account for about 6% of global oil consumption, projected to increase to 20% by 2050. Plastic waste damages terrestrial environments and pollutes aquatic ones, accumulating due to prolonged degradation. Landfill plastics release harmful substances during abiotic and biotic degradation, contaminating soil and water. Chlorinated plastics leach toxic chemicals, polluting ecosystems, while plastic degradation in water releases chemicals such as polystyrene and Bisphenol A, causing water pollution. Methane and CO2 emissions during plastic microbial digestion contribute to global warming. Animals are exposed to plastic waste through ingestion and entanglement, with detrimental consequences.

7Countries are addressing plastic pollution through waste reduction, production reduction, recycling, and alternatives. Governments have adopted policy initiatives to reduce plastic pollution, with global legislation focusing on protecting territorial and marine environments. The United Nations Convention on the Law of the Sea (UNCLOS) in 1982 was the first international legislation agreement on plastic waste. Other conventions include the International Convention for the Prevention of Pollution from Ships (MARPOL) in 1973, the London Convention (1972), the Global Program Action for the Protection of the marine environment from land-based activities (GPA) in 1995, and the Global Partnership on Marine Litter (GPML) formed in 2012.

8The 17 Sustainable Development Goals (SDGs) by the United Nations General Assembly in 2015 aim to promote sustainability, protect ecological life support systems, and reduce waste and pollution by 2030. The Basel Convention (1989), Rotterdam Convention (2004), and Stockholm Convention (2004) address the safe disposal and management of hazardous substances associated with plastic disposal. Legislation on global warming includes the United Nations Framework Convention on Climate Change (1992) (UNFCCC) and the Montreal Protocol (1987).

9The European Union (EU) combats plastic pollution through strategic legislation, including the EU action plan in 2015, the Regional Strategy for Plastics in a Circular Economy in 2018, and the directive on the reduction in the impact of certain plastic products in 2019. The latest update in 2020 focuses on the regulation of recycled content, waste reduction, and product labeling.

10The growing environmental concerns surrounding plastics have prompted research into alternative food packaging materials. Biodegradable materials, such as biopolymers, bioplastics, bio-nanocomposites, and edible coatings, are being developed to replace plastics.

11Biodegradable polymers are renewable, nontoxic, biodegradable, biocompatible, reproducible, versatile, abundantly available, and boast a low carbon footprint. However, issues such as viscosity, hydrophobicity, crystallization activity, brittleness, water sensitivity, thermal stability, gas barrier properties, mechanical strength, processing difficulty, and cost have hindered their widespread industrial adoption. Biodegradable polymers can be classified as polysaccharides (starch, cellulose, chitosan, etc.), proteins (soy protein, collagen, zein, etc.), and aliphatic polyesters (polybutylene adipate terephthalate (PBAT), PLA, etc.).

12To address these issues, biodegradable polymers can be blended with other biodegradable polymers, plasticizers (e.g., glycerol), and compatibilizers (e.g., essential oils). The biopolymer packaging market in Europe increased from 1743.9 million m2 in 2016 to 2427.1 million m2 in 2021. Bioplastics are bio-based and/or biodegradable plastics that share properties with traditional plastics and offer additional benefits such as renewability and biodegradability.

13Bio-nanocomposites, which consist of a bio-based polymer matrix and an organic/inorganic filler with at least one nanoscale material, are suitable as active and/or intelligent packaging materials due to their enhanced mechanical, thermal, barrier, antimicrobial, and antioxidant properties. These materials focus on extending shelf-life and reducing microbial growth in food products.

14Biopolymer-based edible films, formed from polysaccharides or blends of polysaccharides containing proteins, lipids, and food-grade additives, are suitable for human consumption and can increase the shelf-life and quality of food products. Despite their potential, these packaging techniques confront obstacles such as poor elongation, safety and health concerns, high cost, processing difficulties, lack of awareness, cultural concerns, and customer acceptance.

15During biopolymer biodegradation, the polymers are first converted to monomers, and they are then mineralized. The mineralization of the organic material takes place by microorganisms (e.g., fungi, archaea, and bacteria) eventually resulting in carbon dioxide, water, and biomass. The reactions occurring during biopolymer biodegradation are as below:

16The biodegradation of the large molecules of the biopolymers takes place by extracellular enzymes in microorganisms, while the smaller molecules are transported into the microorganism digestion by endoenzymes. For the biodegradation of a biopolymer substrate, most microorganisms use multiple enzyme systems. The biopolymer biodegradation takes place either through oxo-biodegradation or hydro-biodegradation. Oxo-biodegradation takes place in natural polymers such as rubber, humus, and lignin. During this process, loss of the mechanical properties of carbohydrate polymers takes place by the peroxidation process, which is initiated by heat/light, resulting in oxocarboxylic acid molecules, aldehydes, ketones, and alcohols. After that, the biopolymers undergo bio-assimilation with the aid of enzymes of microorganisms into the water, carbon dioxide, and biomass. The hydro-biodegradation process takes place in cellulose, starch, and aliphatic polyesters. The biopolymers are converted into monomers through the enzymatic digesting of microorganisms. The hydrolysis of ester bonds in monomers is performed by the extracellular enzymes of microorganisms. The aliphatic polyesters and carbohydrate polymers are hydrolyzed and bio-assimilated rapidly in an aqueous medium.

17The rate of biodegradation depends upon different factors such as (1) polymer characteristics (chemical bonds, branching, hydrophilicity/hydrophobicity, stereochemistry, molecular weight, chain flexibility, crystallinity, interactions with polymers, coatings, surface area, mobility, and addition of plasticizers/additives/active agents), (2) microorganism type (aerobic and anaerobic facultative, co-metabolism, nature, enzymes, enzyme level, enzyme location, enzyme kinematics, and inhibitors/ inducers), and (3) environment conditions (temperature, humidity, oxygen, salts, metals, trace nutrients, pH, redox potential, stability, pressure, alternate carbon, and light). When the above conditions are present appropriately, the rapid degradation process occurs. During industrial composting, the bioplastics are biodegraded in approximately 6–12 weeks.

18To access the biodegradability of a biopolymer, laboratory tests, simulation tests, and field tests are carried out. The laboratory tests applied include enzyme tests, clear zone tests, Sturm tests, and synthetic environment-defined conditions. Stimulation tests are performed using laboratory reactors, water, soil, compost, and material from landfills with complex environments in defining conditions. Finally, field tests are performed in nature, water, and soil/compland fill under a complex environment in variable conditions.

19The properties of the packaging materials, such as barrier, mechanical, chemical, and thermal properties, play an important role in increasing the shelf-life and maintaining the quality of the food products. The barrier properties of a biopolymer used in food packaging are the main parameter for extending the shelf-life of the packed food product. Barrier properties such as gas, water vapor, organic vapors, and liquids are essential for food packaging to separate the food product from the external environment. In addition, these products differ in the different biopolymers used in food packaging. Thus, the loss/gain of oxygen and water plays a major role in food deterioration. The barrier properties play a crucial role in packaging since gas/water vapor may pass through the walls of the biopolymer, resulting in changing the food product quality and shelf-life.

20The gas permeability of the packaging material depends on the parameters; transmission rate, permeance, and permeability. However, the barrier properties of materials not only depend on these factors but also on environmental conditions such as temperature, pressure, and relative humidity. Further, the rating of the barrier properties also depends on the nature of the food products that are to be packaged. As a result, food packaging materials can prolong the shelf-life of food products by improving the barrier properties.

21The oxygen barrier properties of a packaging material play an important role in the preservation of fresh food products. The oxygen permeability is quantified by the oxygen transmission rate and oxygen permeability. This measures the amount of oxygen in the packaging system. When the oxygen permeability is reduced, the oxygen pressure in the packaging system drops, resulting in an extended shelf-life of the food product.

22The water vapor barrier properties are of great significance for food products to maintain physical or chemical deterioration concerning the moisture content. The water vapor barrier properties are quantified by the water vapor permeability of the packaging material by the ASTM E-96-95 standard method and the water vapor transmission rate. The water vapor permeability depends upon the solubility and the diffusion of the water in the polymer material. The shelf-life of some food products is directly related to the water exchange rate between the external and internal environment; thus, the water transfer should be reduced to protect the food product from moisture.

23The UV barrier properties of packaging material are quantified by the optical properties of a film using a spectrophotometer. The UV barrier properties are essential to prevent the loss of nutrient value and the change in the color of food.

24Mechanical properties of the packaging system are essential to secure the food during stressful conditions such as storage, handling, and processing of the food. The architecture of the polymer matrix is the key factor that determines the mechanical properties of the biopolymer. The mechanical properties of packaging material are determined by tensile properties such as tensile strength, elongation at break, and elastic modulus.

25Chemical resistance is important because the food in the package may be acidic and combine with the packaging material. For safety reasons, it is important to find out what the food is made of chemically before packing it. When these chemicals combine with and become absorbed by the biopolymer matrix, the mechanical properties of the material may change.

26The thermal properties of the packaging material are determined by thermogravimetric and differential scanning calorimetry. Thermal properties and thermal stability are essential for the heat resistance of the packaging material. Thus, the thermal properties allow us to store and transport the food packaging at the temperature essential for the food products.

27Polysaccharide-based biopolymers are nontoxic, abundantly available natural components that are highly suitable as food packaging materials. They have excellent mechanical and structural properties while being selectively permeable to carbon dioxide and oxygen. However, they have poor water vapor barrier properties.

28The biodegradable films from biodegradable polymers have been modified by the addition of various reinforcement agents to produce a packaging system that has beneficial properties and is suitable for industrial applications. Such films may include polymer blending/hybrid films, plasticizers, and/or nanoparticles (NPs). The addition of antioxidants, antimicrobials, nutrients, and color change indicators such as essential oils, phenolic compounds, and plant extracts to biopolymers make them attractive, active, and intelligent packaging, increasing the shelf-life of food. The addition of plasticizers (such as glycerol/sorbitol) to biopolymers can modify their brittleness, increase their processing ability, increase the mobility of starch chains, and decrease moisture absorption. Unfortunately, the incorporation of plasticizers into biodegradable polymers decreases their mechanical properties.

29To improve the properties of the polysaccharides and develop them into an industrially used active/smart packaging system, a combination of polysaccharides, lipids, and NPs are utilized as explained in detail below in the different sub-sections of polysaccharides (Table 2). The mechanical properties of some of the studies depicted in Table 2 have been taken, and a scatter plot has been drawn for a better understanding of the properties, which can be seen in Figure 2. The active polysaccharides can be extracted using different methods, such as hot water extraction, acid–base extraction, enzyme extraction, ultrasonic extraction, ultrahigh pressure extraction, microwave extraction, and supercritical fluid extraction. Currently, starch blends and cellulose are used in industrial applications. Products such as cups, plates, cutlery, and food packs are produced from thermoplastic starch. Companies such as Plantic Technologies (Plantic, USA), Rodenburg Biopolymers (Solanyl, Tokyo, Japan), Biotec (Bioplast, Bristol, PA, USA), Biop (Biopar, Schwalbach am Taunus, Germany), Novamont (Mater Bi, Bottrighe, Italy/Waltham, MA, USA), KINGFA (ECOPOND®, Guangzhou, China), and Biome Bioplastics Limited (BIOME Bioplastics, Southampton, UK) manufacture starch-based films. Additionally, cellulose is used in industries to make bags, wraps for food, and films. Companies such as Nature Works LLC (BioMass Packaging®, Richmond, CA, USA) and Nature Flex™ (Innovia Films, Wigton, UK) produce these cellulose biopolymers on a large scale. Nature Flex™ manufactures cellulose-based products such as coffee and tea packaging, compostable snack bags, packaging for dried foods, compostable stick packs, packaging for chocolate and candy, compostable packaging, packaging for bakeries, custom packaging for food service, and compostable bags. In addition, cellulose and chitosan-lined paper bags and cups are also produced at the industrial level.

30Starch is a polysaccharide composed of linear (amylose) and branched (amylopectin) sections, which are extracted from maize, potato, cassava, and cereal grains. It is regarded as one of the most promising biodegradable polymers for use in food packaging due to its many advantageous properties, such as biodegradability, low cost, abundance, transparency, colorlessness, flavorlessness, tastelessness, reduced water sensitivity, excellent oxygen barrier properties, renewability, edibility, and being an excellent film-forming biopolymer. Nevertheless, starch alone is not a suitable food packaging material as it lacks basic important properties such as vapor barrier, mechanical, and thermal properties. It is also found to be brittle due to the massive inter- and intra-molecular interactions between starch chains and is hydrophilic. The two main techniques, the dry process, and the wet process, are used for the development of starch biofilms.

31Some limitations of using starch as a packaging material can be overcome by chemical or physical modification of native starch. Chemical modification has limitations since it is a complex, time-consuming process that can be toxic. The physical modification of starch such as microwave treatment, pulsed electric field processing, and high-pressure and irradiation treatments has yielded promising results. Thermoplastic starch (TPS) is developed by transforming the starch into a melted material by adding a plasticizer. However, TPS also has poor mechanical and water vapor barrier properties, which make it unsuitable for food packaging without the addition of other components. Another modification of starch is the development of starch-based aerogels, which have been highly studied and are still in the basic research stage. These aerogels are environmentally friendly, biodegradable, and have many unique properties. The two main fabrication routes of starch-based aerogels based on their shapes are monolith and microsphere. Moreover, starch nanocrystals are produced from native starch, which has many merits, such as high surface area, robust mechanical properties, and intriguing self-assembly properties. Starch foam packaging is an alternative packaging that was developed for polystyrene foam in the initial research phase.

32The incorporation of starch with other biodegradable polymers or synthetic polymers allows for better packaging material. Recent studies by Lan et al. focused on encapsulating Lactococcus lactis into a starch-carboxymethyl cellulose matrix to form an antimicrobial edible film as shown in Figure 3 with low moisture content. The film containing 1.5% L. lactis had the lowest water vapor transmission rate (5.54 g/m s Pa) and retained a viable count of 5.64 log CFU/g of L. lactis after 30 days. After 8 days, the film containing 1.5% L. lactis had the maximum nisin release (3.35 mg/mL) and antibacterial efficacy against Staphylococcus aureus (53.53%).

33The incorporation of NPs such as cellulose nanofibers, cellulose nanocrystals, and ZnO also improves the properties of starch. Tibolla et al. developed a bio-nanocomposite film by using cellulose nanofibers isolated from the unripe banana peel by acid hydrolysis as reinforcement agents in a matrix of banana starch. The cellulose nanofibers incorporated into starch films showed high elongation at break (30.6%), good tensile strength (12.3 MPa), low moisture (13.66%), solubility in water (24.1%), and inferior UV/light transmission. Coelho et al. formed a bio-nanocomposite film by embedding pomace pre-treated cellulose nanocrystals into a starch matrix by casting technique. The incorporation of cellulose nanocrystals reduced the water vapor permeability of the starch films from 7.5 ± 0.35 g × h·m·Pa−1 to 4.25 (1% cellulose nanocrystals) and 4.55 × 10−7 g × h·m·Pa−1 (1% cellulose nanocrystals). Films containing 5 to 15% cellulose nanocrystals were more opaque and degraded faster when exposed to light, while the mechanical, and barrier properties were unaffected.

34The combination of cinnamon essential oil and TiO2 NPs was incorporated into a Sago starch matrix to form packaging for fresh pistachios. The addition of essential oil into the starch matrix enhanced the permeability of starch films to oxygen and water vapor, while increasing the concentration of TiO2 NPs lowered the barrier properties. Further, the moisture content of starch films was reduced from 12.96% to 8.04%, and water solubility declined from 25% to 13.7%. Starch-based films have been developed to become smart packaging systems along with antioxidant activity and color changes at different pH as for the study by Ceballos et al. on yerba mate extract. Extrusion and compression molding were used to make native or hydrolyzed starch and yerba mate extract films. The developed film was hydrophobic with an increased plasticizer effect and disintegrated after 10 weeks of soil burial.

35In the recent study of Li et al. lactic acid bacteria (probiotic) and sodium carboxymethyl cellulose were incorporated into starch to form an edible film. To boost the film’s probiotic activity, two lactic acid bacteria species (Lactiplantibacillus plantarum and Pediococcus pentosaceus) with high exopolysaccharide yield were used from a pickled water sample. The composite film’s antioxidant activity was greatly increased, with the highest activity of 48.1%. The water vapor and light transmission of the film were reduced, thus resulting in lipid oxidation deterioration and leading to increased shelf-life of banana.

36Chitosan is a nontoxic, biodegradable polycationic copolymer derived from chitin by deacetylation. It is insoluble in water and organic solvents but forms polycations in media with a pH less than 6.5. Chitosan is a highly researched biodegradable biopolymer due to its attractive properties, which include biocompatibility, film-forming ability, antioxidant activity, antimicrobial activity, mechanical properties, selective permeability to CO2 and O2, UV barrier properties, good optical properties, transparency, flexibility, and fat and oil resistance. A chitosan-based packaging system increases the emulsifying effect, the natural flavor, the texture setting, the deacidification, and the color stabilization of food products, thereby enhancing their quality, safety, and shelf-life. However, the limitation of pure chitosan in food packaging is found to be weakened water vapor barrier properties; thus, it is highly sensitive to moisture, and a film developed from chitosan is found to be brittle with low elasticity.

37Chitosan has been blended with many biopolymers in studies to increase the relevant properties. The non-covalent bond formation between chitosan and alginate makes them one of the most compatible biopolymers for food packaging, while starch–chitosan is also considered a promising blend film. Further, polymer blends with pectin make packaging material transparent with increased mechanical properties. Some studies in recent years have demonstrated that the addition of NPs to the chitosan matrix increases the antimicrobial properties of the film while prolonging the shelf-life of the food product. A study by Kaewklin, Siripatrawan, and Suwanagul shows that TiO2 NPs exhibited ethylene photodegradation while delaying the ripening process and enhancing the quality of the tomatoes. In this study, TiO2 NPs were incorporated into a chitosan matrix to form a packaging film. Paiva et al. reinforced graphene oxide NPs into chitosan to form packaging bags by the solvent casting method. The film decreased water vapor permeability and increased tensile strength and Young’s modulus while prolonging the shelf-life of melon fruits.

38To overcome the shortfalls of the pure chitosan natural plant extracts such as olive pomace, purple-fleshed sweet potato extract, apple peel, black soybean seed coat extract, and Chinese chive root extract have been used, which exhibit good antioxidant and antimicrobial activity. Further, some of these plant extracts (soybean seed coat extract and purple-fleshed sweet potato extract) were studied for pH-sensing ability, thus forming a smart food packing material.

39Glycerol/sorbitol is added to the chitosan matrix as plasticizers making the film less soluble in water, with increased optical property and less brittleness Further, studies have been conducted using a combination of other biopolymers, NPs, and plant extracts together on the chitosan matrix. Jha developed a packaging material with the combination of chitosan–starch–nanoclay and different ratios of grapefruit seed extract. The film containing 1.5% grapefruit seed extract showed increased mechanical (tensile strength of 19.6 MPa and 55.8% elongation at break), thermal, and water barrier properties. Further, this film showed a higher zone of inhibition against A. niger and high antifungal activity in stored bread at 25 °C for 20 days. Lin et al. developed a functional food packaging material of chitosan–nano-silicon aerogel films incorporated with Okara powder by the casting method as shown in Figure 4. The produced films in general had increased flexibility, while the increased chitosan concentration of the film resulted in increased tensile strength. Further, the increased chitosan content led to a significant decrease in the water contact angle. The film also showed strong antibacterial activity against E. coli and S. aureus.

40Further, a chitosan-based food packaging system with NPs was formed by Panariello, Coltelli, and Buchignani with the incorporation of nanostructured chitin and cellulose. Here, chitosan and nanostructured chitin-based films were prepared in combination with cellulose by using the solution casting method.

41Carrageenan is a linear, sulfated water-soluble polysaccharide that is extracted from red seaweeds belonging to the Rhodophyceae family. It is widely used as a food additive. The commercial production of κ-carrageenan developed by CP Kelco is GENUGEL®, which is used as a thickening, stabilizing, gelling, and texturizing agent in food applications. Carrageenan has a scope as a food packaging material due to its excellent film-forming ability, thermal stability, antibacterial properties, barrier properties, and biodegradability. However, it has limited application due to undesirable mechanical and water resistance properties. The addition of other polysaccharides such as starch significantly increases the physical, thermal, and mechanical properties of the film. Further to their studies, Sun et al. designed an antioxidant and pH-responsive κ-Carrageenan-hydroxypropyl methylcellulose film with the incorporation of Prunus maackii juice. With the increasing Prunus maackii concentration, antioxidant activity reached 28.76%, and elongation at break was 48.64%. The lowest oxygen permeability was 1.63 cm3 mm m−2 day−1 atm−1, and the least water vapor permeability was 0.37 ± 0.01 g m−1 s−1 Pa−1 × 10−12. When the volatile base nitrogen content in the pork was 19.26 mg/100 g, the film turned from red to blue, indicating the monitoring of pork freshness.

42Recently, further studies have been conducted using carrageenan biopolymer and nanofillers—carrageenan-CuSNPs, κ-carrageenan-Zataria multiflora extract—nanoclay, and κ-carrageenan-glycerol-cellulose nanocrystals. Nanoclay, 1–3% v/v Zataria multiflora plant extract, and glycerol as a plasticizer were used to develop a biodegradable carrageenan nanocomposite film by using two different methods (adding glycerol before the formation of film-forming solution and after film-forming solution formation). The addition of glycerol to the carrageenan solution before the film formation solution increased tensile strength by 56% while lowering elongation at the break by 61%. All films were effective against E. coli and P. aeruginosa.

43Additionally, Liu et al. developed an active intelligent food packaging material using κ-carrageenan with the incorporation of pomegranate flesh or peel extracts. The incorporation of pomegranate flesh and or peel extracts enhanced the tensile strength from 24.73 MPa (pure κ-carrageenan film) to a maximum of 30.94 MPa and reduced water vapor permeability from 8.32 × 10−11 g m−1 s−1 Pa−1 (pure κ-carrageenan film) to a minimum of 3.47 × 10−11 g m−1 s−1 Pa−1. Furthermore, due to the abundance of anthocyanins, pomegranate-flesh-extract-containing films demonstrated pH-sensitive properties.

44To develop a less expensive film, semi-refined carrageenan has been produced. However, they have poor water vapor permeability and relatively poor mechanical properties. Due to its inferior optical properties, it can be used for packaging applications such as food containers and cups. The mechanical and water barrier properties of semi-refined carrageenan film samples can be enhanced by photo-crosslinking with UV light to produce a low-cost food packaging material.

45Cellulose is the most abundant natural organic compound widely present in plants and bacteria. Cellulose is the agro-industrial waste that is mostly reused. The cellulose molecule (C6H10O5) n) has a linear ribbon-like conformation, and its compounds are bound together by the so-called β1-4, glycosidic bonds. It is widely used as raw materials for biodegradable films and edible films that are renewable, low cost, nontoxicity, biocompatible, biodegradable, odorless, tasteless, and chemically stable. Further, it has increased oxygen, hydrocarbon barrier properties, and water vapor permeability.

46The most used cellulose derivatives in food packaging are methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), hydroxypropyl cellulose (HPC), and carboxymethyl cellulose (CMC); however, due to their hydrophilic nature, they have poor water vapor barriers. In addition to the above demerits, cellulose has low mechanical strength and has opacity.

47As per the study of Tavares et al., they formed films through the solvent casting method by increasing the carboxymethyl cellulose concentration to form a neat starch film. There was an increase in the mechanical (elastic modulus was 14.5 times higher) and water vapor barrier properties of films by reducing the water vapor permeability by 56% (40% carboxymethyl cellulose incorporated film). However, there is a slight reduction in thermal stability from 294 °C for the pure starch film to 253 °C for the 40% carboxymethyl cellulose incorporated film. Further, studies were carried out on carboxymethyl cellulose by where glycerol, mucilage from Dioscorea opposita, and Ag NPs were incorporated into a carboxymethyl cellulose matrix by the casting method. With the decreasing concentrations of carboxymethyl cellulose in the film, tensile strength reduced from 18.30 MPa to 6.78 MPa, while the elongation at break increased from 38.52% to 62.33%. The water vapor permeability reduced from 25.06 g·mm/m2·d·kPa to 19.87 g·mm/m2·d·kPa. The film showed significant antibacterial activity against S. aureus and E. coli.

48A pH-sensitive active film was produced from methylcellulose with the incorporation of anthocyanins present in jambolão (Syzygium cumini) skin by the casting technique. When compared to the pure methylcellulose film, the tensile strength improved from 16.10 MPa to 21.4 MPa (methylcellulose film + 50% jambolão extract), while elongation at break increased from 14.2% to 37.5% (methylcellulose film + 50% jambolão extract). As a result of the pH-sensitive structure of anthocyanins, color variations were observed in films when the pH was altered. Methylcellulose exhibited no radical scavenging activity, whereas increasing concentrations of jambolão jambolo extract increased radical scavenging activity. The films biodegraded in 2 days in sea water and 15 days in soil. Additionally, studies have also been performed with the addition of a nanofiller to a cellulose matrix; examples are cellulose-lignin-cellulose nanocrystals, carboxymethyl cellulose-chitosan-ZnO NPs, and carboxymethyl cellulose-guanidinylated chitosan enriched with TiO2 NPs. These packaging materials are considered potential active packaging materials with improved thermal stability, mechanical and UV barrier properties, and antimicrobial activity.

49Agar is a heterogeneous gelatinous polysaccharide extracted from marine red algae. The agar chain consists of D-galactopyranose and 3,6-anhydro-L-galactopyranose with alternating (1, 4) and (1, 3) linkages. Agar is insoluble in cold water and soluble in hot water, while it is stable in a different environment with low pH and high temperature. It is used as a biodegradable film in food packaging because of its desirable film-forming ability, nontoxicity, stability in different environmental conditions, continuity, and transparency. However, its application in food packaging is limited due to poor water vapor barrier properties, mechanical properties, brittleness, thermal stability, and strong hydrophilic characteristics. A considerable amount of research has been conducted on applications of agar in food packaging by the incorporation of reinforcement agents, for example, nanomaterials, other biopolymers, plasticizers, or antimicrobial agents.

50The incorporation of other polymers such as maltodextrin–beeswax–liquid paraffin, maltodextrin–beeswax, starch, and gelatin considerably increase the properties of agar. Fekete et al. developed agar-based packaging films by casting or melt blending with a high glycerol concentration after agar was added to thermoplastic corn starch in a high concentration. The addition of agar to the starch matrix significantly increased the stiffness and strength of the film. Further, young’s modulus and tensile strength increased with the increasing concentrations of agar. Zhang et al. developed an agar–maltodextrin–beeswax pseudo-bilayer edible film with different homogenizing speeds for mixing. The film was homogenized at a speed of 8000 rpm for 1 min and had the maximum tensile strength (20.57 MPa), young’s modulus (640.60 MPa), and contact angle (92.9°) and the minimum water vapor permeability (2.18 × 10−12 g m−1 s−1 Pa−1).

51Melanin NPs, sodium alginate-nano-SiO2, and montmorillonite-gellan gum all improve the UV-blocking activity, hydrophobicity, mechanical properties, water vapor barrier, and thermal stability of agar, which makes them effective materials for food packing. Roy and Rhim utilized melanin NPs isolated from sepia ink as the reinforcement agent for an agar-based packaging film. There was a decrease in the UV and visible light transmittance in the agar–melanin NPs film when compared to the pure agar film. The tensile strength (from 34.8 MPa to 39.8 MPa) and elongation at break (from 11.8% to 16.1%) of agar increased when 0.25% of melanin NPs was added. Lee et al. combined another biopolymer gellan gum and montmorillonite nanoclay into an agar matrix to form a ternary nanocomposite film via the solution casting method. This film had improved thermal stability (119.4–174.7 °C) and tensile strength (29.9–44 MPa) upon the addition of montmorillonite. Furthermore, there was a decrease in the water barrier (1.9–1.7) and contact angle (56.8–49.4°) upon the incorporation of the montmorillonite nanoclay.

52Pectin is a natural, renewable, and abundant polysaccharide in plant cell walls consisting of α (1–4) galacturonic acid monomers with different degrees of esterification. It is an acid and water-soluble polymer that is used in industry as a stabilizing thickening, encapsulating, and gelling agent. Pectin’s beneficial characteristics, such as being biodegradable, renewable, cheap, gas permeable, and film-forming, make it a good material for edible films, biodegradable films, or gels used in food packing. However, pectin has certain characteristics that are not beneficial, such as negative mechanical properties, brittleness, low thermal stability, high solubility in water, and no antimicrobial properties.

53Priyadarshi, Kim, and Rhim, developed a hybrid biopolymer active food packaging material, pectin–pullulan, with different ratios of polymers through the solution casting method. The blend with the 50:50 ratio of pectin and pulullan exhibited the highest thermal stability, surface hydrophobicity, smallest water contact angle of 63.4°, and oil absorption value of 6.33 g m−2.

54The thermal and oxidative stability and oxygen barrier properties of pectin have been improved by the addition of nanofillers into the matrix pectin–cocoa bean shell waste extract–ZnO-Zn-NPs. Dash, Ali, and Das also developed an edible film with lemon-waste pectin and sweet potato starch with TiO2 NPs by using the casting method. The film exhibited improved mechanical (tensile strength increased from 22.34 MPa to 26.16 MPa), moisture barrier, and UV barrier properties with the addition of TiO2 NPs. In recent years, studies have been performed on pectin modification such as pectin chemically modified with polycaprolactone, which reduces pectin’s hydrophilicity, pectin films activated by copaiba oil nanoemulsions that improve physicomechanical and antimicrobial properties, and thermoplastic pectin, which increases water resistance and mechanical properties.

55Alginate is a natural polysaccharide extracted from brown algae, consisting of a (1–4) chain of a-L-guluronate and R-D-mannuronate. Alginate is regarded as a food safety additive by the FDA (US Food and Drug Administration) and EFSA (European Food Safety Authority). Commercially, alginate is used as a thickener, stabilizer, and gelling agent in foods such as deserts, sauces, and beverages. Alginate can produce a strong insoluble polymer that has improved water barrier properties, mechanical properties, cohesiveness, stiffness, flavor maintenance, and slower fat oxidation. It has poor moisture barriers, and its hygroscopicity slows the dehydration of food. Alginate is brittle, has poor water resistance, and is easily dissolved in water at room temperature. Alginate packaging materials have been modified in recent years with the addition of other biopolymers such as sodium alginate–carboxymethyl cellulose–epigallocatechin gallate, and sodium alginate–pectin–citric acid–tartaric acid; active agents such as sodium alginate–oregano essential oil and alginate–sepiolite modified with myrtle berries extract; and nanofillers such as alginate-Zn-MgO NPs and sodium alginate-cellulose nano whisker-CuO NPs. Singh et al. developed a pectin (extracted from the waste pineapple shell)–sodium alginate (extracted from seaweed)-based film by crosslinking with citric acid and tartaric acid. The film was found to be a suitable edible packaging material through the studies of mice feed, plant growth substrate, and vermicomposting. Cheikh et al. utilized the solution casting to make alginate nanocomposite films comprising sepiolite modified with polyphenol-rich myrtle berry extract. When compared to the control film, the hybrid films improved elongation at break (from 3.8% to 5.6%), tensile strength (from 38 MPa to 87 MPa), water vapor, and UV barrier properties. The films’ antioxidant activity was greatly improved and boosted as the myrtle berry extract content was increased.

56Gums are polysaccharides found in microbial production with a few different types. Arabic gums are found in the stems of various Acacia species, and it shows excellent film-forming ability, encapsulation properties, and unique emulsification. Xanthan gum is an exopolysaccharide synthesized by Xanthomonas campestris. Xanthan gum is used as a food stabilizer, thickener, and emulsifier. It forms a stable viscous solution in hot/cold water at different ranges of temperature and pH. Gellan is a polysaccharide produced by Sphingomonas elodea. Gellan is used as a gelling agent, texturizer, and carrier for food additives in the food industry. Gum biopolymers have a controlled viscosity, good biocompatibility, and low cytotoxicity. However, it has limited application in food packaging due to the high cost of production and low rheological, mechanical, and barrier properties. Recently, studies of xanthan gum biopolymers have been performed in developing xanthan gum–polyvinyl alcohol (PVA)-red grape pomace and xanthan–curdlan packaging materials, which were able to improve mechanical strength and antioxidant and antimicrobial activity. Lee et al. developed ternary composite films from gellan gum–agar–montmorillonite via the solution casting method. The incorporated montmorillonite was able to improve thermal stability by 46.3%, tensile strength by 47.1%, and rheological properties. Further studies on the gellan gum intelligent food packaging material were performed by Wei et al., which improved mechanical properties, water resistance, and antioxidant activity with the potential to detect the spoilage of protein-rich foods caused by bacteria growth. Finally, the studies of Rukmanikrishnan, Ismail, and Manoharan were performed with the combination of two gum biopolymers and a nanofiller—gellan gum–xanthan gum–zinc oxide NPs—by using a solvent evaporation method. This combination improved tensile strength by 60.6%, thermal stability, and UV barrier properties. The water vapor permeability decreased by 39.7%, while moisture content values decreased by 38.0%.

57Lignin is a complex phenolic compound that is abundantly found in the plant cell wall. It has good antioxidant properties and is a natural UV blocker. However, lignin has low mechanical and barrier properties. The combination with agar enhances the water vapor barrier and mechanical and thermal stability of the film while reducing the swelling ratio, transparency, and moisture content. Limited studies have been performed on lignin biopolymers where lignin is combined with other biopolymers; lignin–gellan gum–hydroxyethyl cellulose and alkali lignin–lignosulfonate–soy protein isolate were tested to improve their UV barrier properties. Rukmanikrishnan, et al. used the solvent casting process to make composite films using gellan gum, hydroxyethyl cellulose, and lignin (0, 1, 5, and 10 wt%). The addition of 10 wt% lignin increased the tensile strength of the film by 59.2%. This film showed 100% protection against UVB and 90% protection against UVA. The UV barrier properties of lignin were also observed in the studies of Zadeh, O’Keefe, and Kim examining an alkali lignin–lignosulfonate–soy protein isolate film. Moreover, this film showed increased mechanical and thermal stability.

58Pullulan is a natural and biocompatible microbial polymer obtained from Aureobasidium pullulans. It has an alternation of α-(1,4) and α-(1,6) glycosidic bonds. Pullulan is currently used as a low-calorie component in food, coagulating agents, coating and wrapping material, and binders for fertilizers. It has many beneficial characteristics that can be used in food packaging such as being biodegradable, nontoxic, odorless, colorless, heat-sealable, water permeable, transparent, low in oxygen, oil permeable, and flexible. Further, it is also palatable and water-soluble, making it a suitable edible film material. However, it has high moisture sensitivity, affecting food packaging performance, in addition to low mechanical properties and brittleness.

59The undesirable properties of pullulan were overcome in the study of Yeasmin et al. by the addition of montmorillonite and tempo cellulose nanofibrils to a pullulan matrix. This film showed great optical transparency, moisture resistance, tensile strength (the highest 45.9 MPa was observed for 5 wt.% montmorillonite-containing films), and thermal properties. In addition to this study, Silva, Vilela, and Almeida also developed a packaging material with pullulan–lysozyme nanofibers by a simple solvent casting technique from aqueous suspensions. This film showed improved mechanical properties (young’s modulus = 1.91–2.50 GPa), thermal stability, 77% DPPH scavenging activity, and antimicrobial properties. Studies on a potential edible film from pullulan—egg white were performed by Han, Liu, and Liu.

60Curdlan is nontoxic, biodegradable, colorless, odourless, has a high absorption/retention of moisture, can withstand extreme cold conditions, is insoluble in water, and is thermally stable. Nonetheless, it possesses weak mechanical properties. Studies of curdlan are extremely limited in food packaging applications, although it can be used as a suitable copolymer due to its characteristics. Zhang et al. developed a packaging material based on curdlan-PVA-thyme essential oil. The curdlan: PVA film ratio of 4:1 had the highest tensile strength of 11.81 MPa and an elongation at break of 189.31%. The antioxidant properties of the film were improved by the addition of thyme essential oil, and the shelf-life of chilled meat was extended up to 10 days.

61Protein biopolymers are made up of amino acid copolymers and can be divided into plant-origin proteins (e.g., gluten and soy) and animal-origin proteins (e.g., whey, collagen, and keratin). Protein biopolymers have many beneficial properties such as good mechanical properties, excellent gas barrier properties, good film-forming ability, nutritional value, and elasticity, thus making them suitable for food packaging applications. However, these proteins are hydrophilic, making them have poor water barrier properties. Protein-based biopolymers have potential applications in biomedicine and food packaging. Protein-based polymers including whey protein, gelatin, wheat gluten, corn, zein, and soy protein have been used to produce edible films in food packaging, improving their mechanical and barrier properties. Further, biopolymers such as keratin, casein, zein, gelatin, and soy protein play an important role in the preparation of various industrial products such as shopping bags, protection film, and sanitary products. The mechanical properties and other properties of protein biopolymers can be further enhanced by blending them with other biopolymers (protein/non-protein) or with other reinforcement agents as shown in Table 3. The mechanical properties of some of the studies depicted in Table 3 have been taken, and a scatter plot has been drawn for a better understanding of the properties, which can be seen in Figure 5. Protein biopolymers act as coating films in food packaging. WHEYLAYER and THERMOWHEY are European initiatives designed to develop coatings based on protein biopolymers. These initiatives developed oxygen barrier coatings for reusable multilayer packaging materials as an alternative to synthetic polymers.

62Whey protein is a byproduct of the manufacturing of cheese. It is inexpensive, abundant, biodegradable, nutritious, film-forming, nutrient-rich, and has gas barrier properties. However, it has poor tensile strength and moisture resistance. Recent studies have been conducted in blended biopolymers such as whey protein–furcellaran–yerba mate–white tea extracts. The incorporation of nanofiller such as whey protein–corn oil-TiO2NPs and whey protein–chitosan nanofiber–nano-formulated cinnamon oil has also been examined. Finally, the incorporation of active agents such as whey protein–nanoemulsions of orange peel (Citrus sinensis) essential oil has been studied.

63Pluta-Kubica et al. developed a whey protein films–furcellaran-based edible film with the incorporation of yerba mate and white tea extracts by using the casting method as shown in Figure 6. The permeability of water vapor, water content, solubility, modulus elasticity, and thermal stability of the film were all increased by yerba mate. During storage, the water content and activity of cheese packed in each type of biopolymer film reduced along with the coliform total bacterial count. Montes-de-Oca-Ávalos et al. developed a TiO2NPs-incorporated corn oil–whey protein-based edible film with varying concentrations of whey proteins. The TiO2NPS-loaded bio-nanocomposite film had the highest elastic modulus (19.2 MPa), Young’s modulus (19.4 MPa), and elongation at break (119%).

64Gelatin is a renewable, sustainable protein source that is mostly found in the skin and bones of an animal. Collagen, in its natural form, has little use for application. Therefore, one chooses to extract the gelatin present in its composition for use. To obtain the gelatin, it is necessary for the collagen to undergo a hydrolysis process (acidic, alkaline, or enzymatic), associated with high temperatures to break the covalent bonds, releasing the gelatin molecules through denaturation of the helix triple. After cooling the solution, the chains absorb the water, forming gelatin. The two types of collagen (A and B) can be obtained from partial hydrolysis or thermal degradation of collagen. It is currently used in the food, pharmaceutical, and photographic industries due to its nontoxicity, renewability, biodegradability, and excellent film-forming ability. Furthermore, gelatin is biocompatible, adhesive, abundantly available, flexible, and transparent. It also is cheaper to manufacture while it has excellent water, aroma, and oxygen barrier properties. However, it is not suitable as a food packaging material alone due to its poor mechanical properties and processability. Recent research has examined the blending of different biopolymers, such as Gelatin–PLA, Gelatin–chitosan-3-phenylacetic acid, and Gelatin–agar bilayer vine leaves. The studies of Nilsuwan, Guerrero, and Caba focused on developing a bilayer fish gelatin film incorporated with epigallocatechin gallate and laminated with PLA by thermo-compression molding. These films had high lipid oxidation retardation ability and thus can be used for the packaging of high-lipid-content foods. Ge et al. also developed a green nanocomposite film with pH sensitivity and antioxidant activity using gelatin–chitin nanocrystals–anthocyanins that can be used for the freshness monitoring of high-protein foods. In addition, the bio-nanocomposite Gelatin–grapefruit seed-TiO2 NPs was developed by Riahi et al. via the solution casting method. The film had improved mechanical properties, water contact angle, and antimicrobial and antioxidant activity, while it prevented UV light transmission completely.

65Soy proteins are abundant, renewable, and highly biodegradable proteins. Soy proteins consist of a high amount of polar amino acids such as cystine, arginine, lysine, and histidine. Thus, it has improved the mechanical strength, oxygen and lipid barrier, high water vapor permeability, and thermal properties in addition to flexibility, low cost, sustainability, biocompatibility, film-forming capacity, smoothness, and transparency. However, soy proteins have low water resistance, low thermoplasticity, brittleness, low mechanical properties, low film gloss, and low tensile strength. Soy proteins are available in three types—soy flour, soy protein concentrate, and soy protein isolate. Soya protein isolates are easily biodegradable but have poor plasticity, brittleness, and water vapor permeability.

66Zein is the main protein of corn endosperm and the chief byproduct of the bioethanol industry. It is a polyamine that has a high content of hydrophobic amino acids. Zein is soluble in ethanol and insoluble in water. Zein has great qualities for film-forming in the food packaging industry, such as hydrophobicity, antimicrobial potential, antioxidant activity, adhesive film-forming ability, and extreme resistance to moisture and oxygen. Further, Zein is also considered a safe material for the food system by the Food and Drug Administration (FDA). However, it breaks easily and has poor processability, mechanical properties, elongation at break, and thermal properties. Thus, it is unable to be used as a packaging material in its pure form. Plasticizers such as linoleic acid, palmitic acid, oleic acid, poly (ethylene glycol) (PEG), poly (propylene glycol) (PPG), poly (tetramethylene glycol) (PTMG), and glycerol has been added to zein films to increase brittleness, elasticity, and flexibility. Recently, the properties of zein proteins have been enhanced by combining polymer blends and nanoparticles; studies have shown that the following combinations improve the properties: Zein–potato starch–chitosan NPs incorporated with curcumin, zein–chitosan–cinnamodendron dinisii Schwanke essential oil, zein–sodium alginate-TiO2 NPs-betanin, zein–pomegranate peel extract–chitosan NPs, and zein-TiO2 nanofibers. Xin et al. developed a zein–starch-based film with the incorporation of curcumin-loaded chitosan NPs by using the solution casting method. The highest tensile strength (13.1 MPa) and elongation at break (50.3%) were observed in the films with the lowest zein concentration (30%). These films were able to prolong the Schizothorax prenati fillets’ shelf-life up to 15 days. On the other hand, Amjadi, Almasi, and Ghorbani used electrospinning technology to create novel nanofibers based on zein–sodium alginate integrated with TiO2 NPs and betanin for food packaging. The film showed acceptable mechanical properties, high surface hydrophobicity, and a DPPH scavenging activity of 64.42%. It also showed antimicrobial activity against S. aureus and E. coli.

67Keratin is a natural protein found in bird feathers, wool, or other natural resources. Keratin is a biodegradable, biocompatible, and hydrophobic compound with greater absorption properties. However, keratin has very poor mechanical properties, making it not a suitable packaging material to be used in its pure form. A limited number of studies have been performed on keratin-based food packaging materials. In recent years, Ramirez et al. developed a keratin–citric acid-based food packaging material by using the casting method. This film showed an improved biocidal effect and a 600% elongation at the break. It can prolong the shelf-life of carrots when compared to commercial film. Further, Ramakrishnan et al. also designed a keratin–glycerol-based biodegradable packaging material from keratin extracted from chicken feathers. The best mechanical and thermal properties are found in keratin films with 2% glycerol. Biodegradability tests have shown that all produced bioplastics films are biodegradable.

68Collagen is a naturally abundant, biocompatible, and biodegradable protein found in animals. It is industrially produced from the skin and bones of swine, cattle, and fish skin. Collagen has a great film-forming ability, antioxidant properties, moisture and oxygen barrier, and structural integrity. However, its high water vapor transmission rates and poor mechanical properties give collagen limited applications in the food packaging industry. Thus, very limited studies have been performed on collagen food packaging. Jiang et al. fabricated a food packaging material with a collagen matrix by using the solvent casting method, where the chitosan–lemon essential oil NPs were incorporated. The film had improved tensile strength, elongation at break from 65.41% to 104.34% (30% chitosan–lemon essential oil NPs), and reduced oxygen permeability from 0.57 cm3 mm m−2 d−1 kPa−1 to 0.39 cm3 mm m−2 d−1 kPa−1 (30% chitosan–lemon essential oil NPs). With regard to the shelf-life study, when the pork was stored at 4 °C for 21 days, films significantly prevented lipid oxidation, reduced microbial multiplication, and prolonged the deterioration of pork.

69Aliphatic polyesters are biopolymers composed of repeating structures that, upon degradation, produce metabolites such as poly(beta-hydroxy alkanoate)s and poly(alpha-hydroxy alkanoate)s. They are easily biodegradable because of the presence of ester bonds in the soft chains making them sensitive to hydrolysis. Aliphatic polyesters have been used as commercial products as an alternative to synthetic properties due to their similar properties; however, they lack mechanical and thermal properties. Some of the aliphatic polyesters that are used in food packaging are PLA, PBAT, polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), polyhydroxybutyrate (PHB), and polycaprolactone (PCL), and their properties are shown in Table 4. The mechanical properties of some of the studies depicted in Table 4 have been taken, and a scatter plot has been drawn for a better understanding of the properties, which can be seen in Figure 7.

70Aliphatic polyesters amount for most of the bioplastics, which amount to 2.11 million tonnes of global production in 2020, out of which the highest market segment is the packaging market, which accounts for 47% (0.99 million tonnes). As for the European Bioplastic PBAT, PLA, PBS, and PHA are currently in use in the rigid and flexible packaging marketing sector.

71Poly lactic acid (PLA) has become one of the most significant commercial polymers that are biodegradable and bio-based thermoplastics. PLA is made up of alpha-hydroxy acids, which include polyglycolic acid or polymandelic. PLA is derived by depolymerization of the lactic acid monomer obtained from sugar cane, corn starch, or tapioca. Companies such as Ingeo (Nature Works, Plymouth, MN, USA), PURAC (PURAC Co., Rayong, Thailand), BIOFRONT (Teijin, Tokyo, Japan), HiSun (Revoda, Stoney Creek, ON, Canada), and Pyramid (Tate and Lyle, Pinckneyville, Denmark) manufacture biodegradable PLA films. These produced biopolymers are used in a wide variety of industrial applications such as disposable household items (drinking cups, cutlery, trays, food plates, and food containers), food packaging, waste bags, shopping bags, agriculture (soil retention sheeting and agriculture films), drug delivery systems, biomedical devices disposable garments, feminine hygiene products, and diapers. PLA is used in commercial food packaging for manufacturing caps (PLA blends), coffee capsules/pouches (PLA/PHB), shopping/waste bags (Blends of PLA/PHA/PBAT), clear films for fruits and vegetables (PLA/Blends of PLA/Bio-PET), and teabags (PLA blends).

72PLA shows incredible properties for films for food packaging applications such as mechanical strength, light transmission, transparency, rigidity, low cost, high stiffness, resilience, biodegradability, excellent barrier properties, and biocompatibility. However, it is brittle, has low melt strength, and has low thermal stability.

73In recent years, many different types of nanofillers have been incorporated into the PLA matrix. Kostic et al. incorporated alginate microbeads containing AgNPs into a PLA matrix to form a nanocomposite film by using the solvent casting method. Here, the PLA matrix acted as a diffusion barrier by lowering the Ag migration levels within the allowed limit of 0.05 mg kg−1 after 10 days. Further, the films had inhibitory effects against S. aureus. While the incorporation of modified carbon nanostructures in the PLA matrix increases the thermal and mechanical properties of the film. On the other hand, the studies of Andrade-Del Olmo et al. focused on forming a layer-by-layer bio-nanocomposite film of PLA-ZnONPs–chitosan-β-cyclodextrins. Here, PLA was blended internally with ZnONPs, and it was superficially modified by the deposition of chitosan and cyclodextrins. The microbial properties of treated surfaces were improved as a result of increased surface hydrophilicity. The multilayers appear to be acceptable substrates for carvacrol loading and release, with maximum release occurring during the first 14 days of exposure.

74Further, the incorporation of active agents’ thymol, kesum, and curry into a PLA to form an active film through the solvent casting method was carried out in. The films showed antimicrobial activity against S. aureus. All active-agent-loaded PLA films successfully kept chicken flesh in good condition during storage for up to 15 days. Yang et al. developed a packaging film by grafting star-like lignin microparticles onto PLA via the ring open polymerization of l-lactide, which began with the hydroxyl groups on the lignin microparticle surface. With the addition of lignin microparticles, elongation at break increased up to 236%, and there was excellent UV resistance behavior, antioxidant activity, and low migration level, making it a suitable packaging material.

75Poly (butylene adipate terephthalate) (PBAT) is an aliphatic-aromatic copolyester obtained from the poly-condensation of butanediol, adipic acid, and terephthalic acid. It has been used for applications in agricultural, food packaging, and biomedical areas. The major commercially available PBAT biopolymers are manufactured in BASF (ECOFLEX®, Ludwigshafen, Germany), KINGFA (ECOPOND®, Guangzhou, China), NOVAMONT (Origo-Bi®, Novara, Italy), TUNHE (Beijing, China), XINFU (Beijing, China), and JINHUI (ECOWORD®, Lvliang, China). Shopping bags have been developed using Starch-PBAT blends by KINGFA, which is widely used in Chinese supermarkets.

76PBAT has good mechanical and biodegradable properties. However, it has poor photostability, which leads to a decline in its mechanical performance during the application. Furthermore, it has high melt viscosity, low crystallization rate, low tensile strength, and high production cost. Therefore, it is usually used in an application with blended polymers, nanofillers, or other natural compounds. Thus, blended products of starch-PBAT and PLA-PBAT have been developed by KINGFA, China, to improve the mechanical properties and production cost.

77Recent studies have been performed with PBAT blended polymers. Sharma et al. developed a PLA-PBAT–ferulic acid, and this film was incorporated with ferulic acid by using the solvent casting method. The thickness of the film was raised by 1.5–10%, and tensile strength increased to 10.78 MPa from 5.42 MPa (control film) when ferulic acid was added to the film. The film also showed antimicrobial activity against Listeria monocytogenes and E. coli.

78Further studies have been performed by incorporating lignin or melanin or lignin–melanin core-shell into a PBAT matrix as shown in Figure 8. At 0.5 to 5 wt% NP concentrations, all of these films had outstanding UV-blocking capacity, blocking nearly all UV-A and more than 80% of UV-B light while maintaining reasonable optical transparency.

79Polycaprolactone (PCL) is a biodegradable polyester with a low melting point of 60 °C and a glass transition temperature of −60 °C. It is prepared by the ring-opening polymerization of ɛ-caprolactone. It has poor mechanical and thermal properties, high solubility, and an excellent ability to form blends. Lukic, Vulic, and Ivanovic, developed a blend packaging material PCL-PLA–thymol–carvacrol by using the solvent casting method. The thymol and carvacrol were loaded into the PCL-PLA mixture by utilizing supercritical CO2 at 40 °C and 10 MPa for 5 h. The PCL-PLA film loaded with the thymol and carvacrol mixture had the highest total polyphenol content (128.05 mg GAE/g film) and antioxidant activity (7590.0 μmolTrolox equivalent/g film), acceptable physical properties, and the lowest release rate of 44.51 mg/L released after 6 weeks.

80Polybutylene succinate (PBS) is a thermoplastic biodegradable aliphatic polyester formed by polycondensation. It has properties similar to polypropylene with high crystallinity and good thermal and mechanical properties. PBS has been used as an additive with other biopolymers such as PLA. A blended film of PBS-PLA was developed with the incorporation of carvacrol and thymol by the extrusion casting method. The inclusion of active compounds increased the ductility and flexibility of PLA-PBSA-based active films. PLA-PBSA films with carvacrol or thymol had a high release of the active compound and high antioxidant effectiveness. The spoilage and deterioration of salmon slices were minimized, resulting in a 3–4-day extension of the shelf-life during cold storage.

81Polyhydroxyalkanoate (PHAs) is a biodegradable, intracellular, and biocompatible family of bacterial polyesters, which are produced by bacterial fermentation of sugar and lipids. They have similar mechanical and thermal properties to synthetic polypropylene. The merits of PHA include good tensile strength, printability, flavor and odor, barrier properties, and temperature stability. The application of PHA is limited due to its high cost. Different polymers of PHAs have been produced by different substrates; Poly-3-(hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is produced from starch, vinnase, ethanol stillage, and cheese whey, while Poly-3-(hydroxybutyrate) (PHB) is produced from molasses wastewater and date syrup. Similarly, poly-β-hydroxyvalerate (PHV) is produced from molasses wastewater. PHA is used for industrial applications such as in the pharmaceutical, medical products, cosmetics, agriculture, aerospace, and food packaging industries. During industrial applications, PHAs can be used as raw materials or as blends with other polymers such as PLA, PBS, and PCL. PHA is used as a biodegradable packaging application in bottles, containers, sheets, films, laminates, fibers, and coatings manufacturing. Metabolix (US) produces Metabolix PHA (blend of PHB and poly 3-hydroxyoctanoate) for food packaging and additive application.

82Polyhydroxybutyrate (PHB) is the most abundant PHAs that is a biodegradable lipid-like polymer synthesized by different bacteria that has a rigid structure. It is suitable as a food packaging material since it is renewable, biocompatible, and has low oxygen and water permeability and increased barrier properties. A study by Rech et al. combined PHB with essential oils (cinnamon, melaleuca, and citronella) to form an edible film for food packaging by using the solution casting method. Essential oils increased both the crystallinity degree and the thermal stability of PHB films. Furthermore, by lowering the melting temperature from 155.7 °C to 143.7 °C (melaleuca-cinnamon) and increasing film flexibility by the reduction in the elastic modulus from 1030 MPa to 286 MPa (melaleuca-cinnamon) of the polymer, these oils created a plasticizing effect. Additional studies on PHB incorporated with NPs were performed by PHB-graphene nanoplatelets and PHB-polycaprolactone (PCL)-organo-clays. Manikandan et al. formed a PHB nanocomposite film by incorporating different concentrations of graphene nanoplatelets (0–1.3 wt%) via the solution casting method. The incorporation of graphene nanoplatelets into PHB increased the melting point by 10 °C, thermal stability (by 10 °C), tensile strength by 2 times, and reduced oxygen and water vapor permeability by 3 and 2 times, respectively. Further, there was a four-fold increase in the shelf-life of potato chips and milk products. Correa et al.] incorporated organo-clays (Cloisite® 30 B and 10A) into a matrix of PHB/PCL by melt intercalation, and the nanocomposite films were formed by compression molding. Although organo-clays have antimicrobial activity against Lactiplantibacillus plantarum, their incorporation in the polymer blend did not result in antimicrobial films. However, the nisin-activated PHB-PCL film showed antimicrobial activity against Lactiplantibacillus plantarum by prolonging the shelf-life of sliced ham. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) has higher processability and physical properties than PHB. PHBV also has high flexibility, toughness, and low melting point. Recently, Figueroa-Lopez et al. developed a multilayer PHBV-PHB-eugenol active food packaging material by incorporating different concentrations of eugenol into the PHBV ultra-thin fibers by electrospinning. Then, this PHBV monolayer was interlaid between PHB sheets by annealing at 160 °C for 10 s to form a multilayer active packaging material. This film showed high hydrophobicity of 75.53 and improved mechanical (tensile strength improved from 1252 MPa to 2884 MPa with the addition of 2.5 wt.% of eugenol to PHBV), thermal, barrier, and antimicrobial (against S. aureus and E. coli) properties. Further studies were performed on developing PHBV-PHB–cellulose nanofibrils–lignocellulose nanofibrils containing mono- and multilayer films by using the electrospinning coating technique. The multilayer film with PHBV-PHB–cellulose nanofibrils–lignocellulose nanofibrils reduced oxygen permeance by 35% when compared to the control film, thus having enhanced gas barrier performance.

83Biopolymers are eco-friendly, biodegradable, nontoxic, renewable, and biocompatible alternatives to synthetic packaging materials. These are easily recycled, avoiding the environmental pollution caused by synthetic polymers while addressing the important question of environmental pollution. Thus, it is environmentally friendly and possesses a much lower risk than synthetic products. Biopolymers are naturally occurring in animals, plants, and microorganisms and are thus highly abundant. The extraction process and the synthesis depend on the different biopolymers.

84They have great film-forming ability and different strengths specific to each biopolymer as discussed above. Biopolymers can create high-performance packaging materials together with other biopolymers or reinforcement agents, and they are lightweight. Biopolymers work as matrices to incorporate nanofillers, natural compounds, antimicrobial agents, antioxidants, vitamins, minerals, and nutrients to make them more suitable active packaging materials.

85Even though biopolymers are environmentally friendly, their main weaknesses are low mechanical and barrier properties, rapid degradation rate, high hydrophilic capacity, and high sensitivity to moisture. In addition to the poor material performance, they also have weak mechanical and chemical structures, making many of the biopolymers not suitable for food packaging directly. Further, when compared to synthetic polymers, they are difficult to process and relatively expensive. Most of the biopolymers are naturally hydrophilic and deteriorate when exposed to moisture. The above-mentioned characteristics of the biopolymers make them unsuitable as packaging materials since it makes them unsuitable to maintain the shelf-life and quality of food products.

86There are a wide variety of opportunities for using biopolymers in food packaging, including active and smart food packaging materials. Biopolymers are the base compound for most of the packaging material combinations along with nanomaterials or other active compounds. The addition of the reinforcement agents into the biopolymer matrix results in the improvement of essential properties needed in packaging material, such as barrier, mechanical, thermal, antioxidant, and antimicrobial properties. Most of the food packaging materials developed are still in the research stage, and there is an opportunity for the upscale and global production of these materials to use as an alternative to synthetic polymers. Biopolymers and bioplastic industrial production possess the opportunity to reduce global environmental pollution and aid the circular economy as mentioned by the European Union.

87While environmental concerns regarding plastic packaging are well-documented, the assessment of biopolymers’ environmental impact is more nuanced. Biopolymers have the potential to be more environmentally friendly, but their specific advantages and disadvantages hinge on a number of variables, such as their origin, production processes, waste management systems, and end-of-life considerations. To make informed decisions about a material’s environmental impact, it is essential to conduct a thorough analysis of the material’s life cycle. Most of the biopolymers in their pure form do not deliver a threat to society or the environment. However, these biopolymers are combined with nanofillers or other active agents to improve the qualities of the packaging materials. These agents pose a threat of migration into a food product and gradually migrate into the human body. This may cause a threat to human health if the agent is cytotoxic. Further, during the biodegradation process, the active agents are migrated into soil/water, which may affect environmental conditions, leading to pollution. The migration of chemical compounds is not unique to biopolymers; it can also occur with other packaging materials. It is essential to assess and manage the potential migration of compounds from any packaging material, including biopolymers, to ensure food safety and regulatory compliance. Ongoing research and development is aimed at enhancing the safety and efficacy of biopolymers for food packaging applications. This includes the development of novel materials, the optimization of processing techniques, and extensive testing to ensure their suitability for food contact and to minimize the migration of potentially hazardous substances. In addition, the microorganisms used to produce biopolymers may be hazardous and may result in environmental pollution.

88Over the years, synthetic packaging materials have been the primary source of food packaging. However, the use of synthetic polymers presents challenges and limitations, mainly due to environmental pollution issues caused by plastics. Consequently, the trend of using biopolymers in food packaging has significantly increased in recent years. Biopolymers/bioplastics such as thermoplastic starch, PLA, cellulose, and PBAT are already used in industrial production for food packaging applications. Their characteristics, such as biodegradability, eco-friendliness, renewability, nontoxicity, and lightweight properties, make them suitable for food packaging applications. However, the applications of biopolymers in their pure form are limited due to their low mechanical, barrier, and thermal properties. Furthermore, they are less cost-effective compared to synthetic polymers. The negative characteristics of biopolymers can be overcome by adding reinforcement agents such as nanofillers and active agents. These reinforcing agents enhance the properties of the packaging materials, making them suitable for active and intelligent packaging materials by extending their shelf-life and enhancing the quality of packaged food products. In recent years, researchers have focused on conducting studies on the combinations of biopolymers, reinforcement agents, and their applications. However, there are limited studies carried out using some biopolymers; for instance, the natural UV barrier property of lignin has been studied in limited research. Moreover, when compared to starch-based biopolymers, studies on protein biopolymers and some aliphatic biopolymers (PBS, PCL) are limited. The food packaging applications of the produced biopolymers have only become an interest to scientists in recent years, and there is still considerable room for improvement in research. Furthermore, only a few studies have been performed to evaluate the cytotoxicity effect of the produced packaging material and the biodegradation ability of the materials. These two aspects of the study are crucial to avoid global issues in the future. Additional studies are warranted to bring biopolymer-based food packaging to a global level and use it as an alternative to plastic packaging.