TILAPIA SKIN GELATIN WITH POTENTIAL FUNCTIONAL USE IN FOOD

Tilapia skin, a by-product of fish processing, represents a source of collagen and gelatin with potential application in the food industry. The use of this waste enables sustainable practices and adds value to the production chain. The objectives of this work were to evaluate the protein solubility (PS) of gelatin extracted from tilapia skin and to determine the degree of hydrolysis (GH) after catalysis with the enzyme alkalase® (AL). The skin underwent pre-treatment steps: removal of non-collagenous proteins with 0.8 M NaOH solution (1:7 w/v, 2 h); demineralization with 0.5% HCl (v/v, 1 h); thermal extraction of gelatin (60 °C, 1 h 30 min) and freeze-drying. PS was evaluated by measuring soluble proteins in the supernatant (Biuret method) at different pH values (3, 4, 5, 6, 7, 8, 9 and 12) and total proteins were determined by the Kjeldahl method. Enzymatic hydrolysis with LA occurred at pH 9.0, T= 50° C for 150 minutes. The results indicated that tilapia gelatin had higher SP at acid (pH 3-4) and alkaline (pH 9-12) pH, with a minimum of around 6-7, demonstrating amphoteric behavior characteristic of collagenous proteins. SP relies heavily on the isoelectric point which, for collagen, is around pH 6-7, depending on the donor species and the extraction process. At this point, there is minimal electrostatic repulsion between the molecules, favoring their aggregation and, therefore, lower solubility, as verified in this work. The evaluation of the SP of tilapia gelatin at different pH values is fundamental to determine its technological applicability in liquid and functional foods