Gelatin films from wastes: A review of production, characterization, and application trends in food preservation and agriculture.

Gelatin is the product resulting from collagen denaturation, which, in addition to conventional sources of extraction, can be recovered from wastes and byproducts rich in collagen widely generated by the industrial activities of poultry and cattle slaughterhouses and the fishing industry. Given the properties of good film-forming ability, nontoxicity, and biocompatibility for the addition of other compounds to obtain composite materials, gelatin is a potential polymer for the production of biodegradable films and, if extracted from waste sources, can contribute to the reduction of environmental pollution and positively impact several of the Sustainable Development Goals from the United Nations Organization. The gelatins extracted from porcine, poultry, and fish skins and untanned bovine hide wastes, or by-products can be used for the production of packaging films or edible coatings, while chromium-tanned leather wastes can be applied with mulching films in agriculture aiming at greater crop yield for food production. Also, the crosslinking of gelatin protein chains and the addition of plasticizers and other additives have shown promising results in improving gelatin films' mechanical, barrier, and solubility properties. In this sense, this paper reviewed gelatin-based films from wastes, covering the main characteristics of gelatin, techniques for film production and characterization, and applications of obtained films for the food field, in addition to considerations about social, environmental, and economic aspects.