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Neste estudo, foi avaliada a extração de gelatina a partir de cabeças de carpa comum (Cyprinus carpio) provenientes da industrialização. Para tanto, foram estudados os efeitos da concentração alcalina, o tempo de tratamento e troca de solução alcalina na etapa de tratamento das cabeças de carpa. Foi utilizado um delineamento experimental em estrutura fatorial completa com três fatores em dois níveis de variação. Os fatores de estudo foram concentração de solução de NaOH (3-4mol L-1), tempo de tratamento (45-105min) e troca de solução alcalina no tratamento, tendo como respostas rendimento em gelatina e força do gel. A condição mais adequada para se obter gelatina com bom rendimento (1,98%) e força do gel (240,3g) foi utilizando solução alcalina 3mol L-1, tratamento de 105min e com troca de solução de NaOH.

This work evaluated the effects of pH (3, 4 and 5) and addition of glycerol (10, 20 and 30%, w/w) in films of gelatin extracted from croaker skins, and afterward modified by chitosan. The gelatin films were produced by casting technique. The chitosan additions (10, 20 and 30% w/w) in relation to the gelatin films were analyzed. Films were characterized as tensile strength (TS), elongation, water vapor permeability (WVP) and optical properties (color, color variation and opacity). Gelatins were characterized for gel strength (221 g) and viscosity (3.7 cP), and chitosan was obtained from shells of shrimp and characterized (150 kDa and deacetylation degree of 85%). The gelatin film with 10% (w/w) glycerol and pH 4 showed the best TS value and suitable WVP value. The amount of chitosan of 10% (w/w) added to the gelatin film on the best conditions produced the modified films with the best properties of TS and WVP. PRACTICAL APPLICATIONSSeveral types of biopolymeric films have been developed, combining proteins and polysaccharides, and among these, gelatin and chitosan take on homogeneous form because of miscibility between the two biopolymers. Improvements in the connection crossed in gelatin mixture with chitosan are attributed to the formation of polielectrolic compounds, among the groups of amino of the chitosan and of the groups of lateral chains charged negatively of the gelatin through electrostatic interaction. The study of the mechanical properties of the biodegradable films is a subject of great importance, because of its influence on the acting of the product and the consumer's acceptance. In this context, the intensification need is observed in the studies about the gelatin extraction starting from fish skins and its application in the production of pure and modified films with chitosan and plasticizer.

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