Films based on chitosan have good permeability to gases (CO2 and O2) and acceptable mechanical properties; however, these materials are not good barrier against water vapor. The properties of chitosan films are impacted by the chitosan morphology and molecular weight, as well as by the N-acetylation degree, solvent type used to manufacture films, among others [54, 57, 58]. Similarly, edible coatings based on chitosan have been applied on fresh fruit and vegetables, as well as on minimally processed, decreasing the respiration rate and delaying the senescence of these products. In addition, coatings based on chitosan can be used to reduce the moisture loss and maintain the overall quality of food products [59]. Therefore, several researchers have used this macromolecule to improve the physical and mechanical properties of films and coatings, including blends with another polymers and nanoparticles. In Table 2.3, recent studies about chitosan films and coating applied in food products are listed.
2.2.4 Collagen and Gelatin
Gelatin and its precursor collagen are biopolymers obtained from protein animal sources. Collagen is considered the most abundant protein of animal kingdom, composed of around 25–35% of total proteins of the animal body and is mostly found in the tissues as bones, cartilage, ligaments, tendons, skins, blood vessels, intervertebral discs, guts, and corneas [70]. Collagen is mainly extracted from bovine, porcine, and fish [71], while gelatin is obtained after partial hydrolysis of the collagen. Gelatin is characterized by its versatility, high digestibility, and gels melting at human body temperature. Both biopolymers show interesting physicochemical and structural properties, especially for food industries [71].
Table 2.2 Films and coatings based on cellulose and derivatives for food packaging applications.
| Components | Production approach | Main results | References |
|---|---|---|---|
| WPIa)/CNFb) | Casting | Improvement of structural properties of WPIa)-based films using CNFb)for food packaging applications | [32] |
| Tara gum/CNCc)/grape skin extract | Casting | Colorimetric pH-sensing films with positive activation test for milk spoilage | [38] |
| HPMCd)/beeswax | Dip coating | Coatings with antifungal activity against A. alternata on cherry tomato fruit | [39] |
| CMCe)/sodium montmorillonite/TiO2 | Casting | Biodegradable nanocomposite films with improved mechanical and light barrier properties | [40] |
| PLAf)/rosin modified CNFb)/chitosan | Casting | Films with antimicrobial activity against E. coli and B. subtilis | [41] |
| Gelatin/CNFb)/chitosan Starch/CNFb)/chitosan | Casting | Films with better structural properties and antimicrobial activity | [42] |
| Chitosan/gelatin/MCg)/tannic acid | Casting | Films with antimicrobial activity against E. coli and S. aureus | [43] |
| Cellulose derived from corncob | Thermo-pressing molding | Biodegradable and sustainable films applied in breads | [44] |
| CMCe)/okra mucilage/ZnO | Casting | Films with antimicrobial activity against E. coli and S. aureus | [45] |
| κ-Carrageenan/HPMCd)/Prunus maackii juice | Casting | Biodegradable pH-sensitive and antioxidant films for oil and lard packaging application and label for testing pork freshness | [46] |
| Gelatin/CMCe)/chitin nanofibers/Trachyspermum ammi (ajowan) essential oil | Casting | Films with improved mechanical and barrier properties and antimicrobial activity against E. coli and S. aureus | [47] |
| ECh)/azo indicators (methyl orange; methyl red) | Casting | Biodegradable material with pH-sensitive properties for food packaging applications | [48] |
| HECi)/ZnO | Casting | Films with antimicrobial activity against E. coli and S. aureus | [49] |
| HPMCb)/liposome/CNFb) | Dip coating | Hydrophobic coatings used for hydration of fat food surfaces (slices of almonds and chocolate) |
|