Otimização da obtenção de gelatina a partir da pele residual de Tilápia do Nilo (Oreochromis Niloticus)

Abstract

Fish production is growing worldwide, and its growth rate is bigger than the population growth rate. The Nile tilapia is the most produced fish species in the world and in Brazil. It is mostly used to food consumption, in the form of fillets. Residues such as skin, head and bones are produced during the processing of fillets, but they have great potential for the production of many materials. The skin is the most suitable for the production of gelatin because it has a large collagen content. Collagen is the major class of proteins existing in both, animals and humans, and has the capacity to produce gelatin by thermal hydrolysis. Acid and base pretreatments are used to produce a better and purer material. The most important properties of gelatin are gel strength, moisture, ash content and viscosity, and the type of pre-treatment influences these properties. To optimize the obtaining process of gelatin from the Nile tilapia (Oreochromis niloticus) residual skin was used the fractional factorial design. The concentration and reaction time of HCl, NaOH and CH3COOH was varied, such as the extraction time and temperature, and the use of resin, to evaluate response factors as gel strength, yield and ash content. The best sample was chosen based on the highest gel strength, better yield, lower ash content and lower total extraction time. The best sample was analyzed by DSC, TGA, FTIR and water activity. Of all the dependent variables, only the concentration of acetic acid and its pre-treatment time were statistically significant for the ash content, having a positive effect. The best gelatin was obtained using the following extraction conditions: without pre-treatment with HCl, 30 minutes of pre-treatment with 0.1 M NaOH, 30 minutes of pre-treatment with Acetic Acid 0.1 M, 1 hour of extraction at 45 ° C and no use of resin. This gelatin showed a gel strength of 705.898 Bloom, 9.84% of moisture and 1.741% of ash content. By TGA analysis, the gelatin was stable up 266,71ºC, suffering degradation after that, and having 2.375% of ash content. The DSC and FTIR results were compared with the literature, showing agreement with the expected results. The Aw value was 0.3388 ± 0.0087 at 26.34 ± 0.36 °C. Therefore, it was possible to determine the best conditions of the variables and their significance in fractional experimental design to obtain the gelatin. The best gelatin obtained showed good properties such as high thermal stability, high purity and low moisture content and can be applied to obtain polymeric bioblends using corn starch.