Functional modification of gelatin-based biodegradable composite films: a review

As one of the raw materials of biodegradable food packaging, gelatin is an environmentally friendly substitute for traditional plastic packaging. In this review both sources and extraction methods of gelatin are introduced, together with recent modification methods and applications of using plant sources instead of synthetic substances to endow gelatin film with functionality. Gelatin is extracted from mammals, marine organisms, and poultry. Different extraction methods (acid, alkali, enzyme treatment) can affect the molecular weight and amino acid composition of gelatin, thus affecting the molecular structure, physical properties, chemical and functional properties of gelatin. Gelatin serves as a good substrate, but its disadvantage is that it is very brittle. However, the addition of plasticizers can improve the flexibility of the film by reducing chain interactions during the dehydration process. Compared with other plasticizers, glycerol and sorbitol have better effects on adjusting the mechanical properties of gelatin films. Gelatin is combined with active substances such as essential oils, plant extracts, and nanoparticles to prepare gelatin based composite films with good mechanical properties and antibacterial and antioxidant properties. Gelatin-based composite films can effectively inhibit the growth and reproduction of microorganisms and lipid oxidation in food. Applying it to food packaging can improve the quality of fresh food and extend its shelf life.