TECHNOLOGICAL AND BIOACTIVE PROPERTIES OF COLLAGEN EXTRACTS OBTAINED FROM BULLFROG SKIN (Lithobathes catesbeianus)

Frog farming occupies a prominent position worldwide for Brazil, and one of the consequences inherent to the processing of frog meat is the generation of by-products, with components of high biological value in their composition. In recent years, some studies have highlighted the use of these by-products. Bullfrog skin is a potential source of collagen, whose structure and properties are like collagen obtained from fish and mammals. Currently, there is great interest in collagen extraction processes and their generated peptides since the application of this protein promotes the replacement of synthetic substances in industrial processes. Thus, the objective of this study was to carry out the process of extracting collagen from the skin of a bullfrog (Lithobates catesbeianus) and to determine the conditions for the best yield and the antioxidant properties. For collagen extraction, a 2x3 factorial design was carried out with two enzymes, pepsin and Brauzyn®, at a concentration of 0.2%, in three hydrolysis times (12, 24 and 36 hours), resulting in treatments CP12, CP24, CP36, CB12, CB24 and CB36. It was observed that the type of enzyme, the time of hydrolysis, as well as the interaction between these factors significantly affected the parameters of yield, collagen content and degree of hydrolysis (p <0.05). Treatments with the highest yield were those hydrolyzed for 12 h with enzymes pepsin and Brauzyn® (CP12 and CB12), with values of 70.46 and 64.57%, respectively. The extracts CP12 and CB12 were submitted to infrared analysis (FTIR), absorption capacity in water at 60ºC, absorption capacity in oil, emulsifying activity, solubility at 70°C, antioxidant activity and electrophoretic profile in polyacrylamide gel (SDS-PAGE). The FTIR analysis indicated that the collagen concentrates maintained their helical structures, while for the technological parameters there was a significant difference (p<0.05) only for the water absorption capacity and solubility of the concentrates. The CB12 treatment exhibited a higher water absorption capacity (9.0 g/100 g) than the CP12 (6.0 g/100 g). In the electrophoretic profile, it was verified that the bands had a molecular weight close to 150 kDa, with a typical bands distribution of type I collagen. For the oil absorption capacity, emulsifying activity and antioxidant activity by DPPH method, there was no significant difference between treatments. The solubility at 70ºC was higher in the CP12 treatment (4.39%). Regarding the antioxidant capacity, among the researched methodologies only ABTS•+ method had a significant difference (p<0.05) and CP12 presented the highest antioxidant potential (2.95 µmol ETg-1) in the scavenging of free radicals. Despite the differences between the protein concentrates obtained, both presented themselves as a potential functional and bioactive ingredient in the food industry. However, the treatment with hydrolyzed pepsin for 12 hours (CP12), due to its greater solubility and antioxidant activity, can be considered suitable for the development of meat products and stabilization of food emulsions, in addition to being able to minimize its oxidative effects.