Abstract/Summary

Pterygoplichthys disjunctivus locally named as armored catfish ” is a by-catch of tilapia fishing which accounts for up to 80% of total captured fish in the Adolfo Lopez Mateos dam, in Michoacán, México affecting the economy of its surrounding communities. This invasive fish is discarded by the fishermen since native people do not consume it; partly due to its appearance yet is rich in protein. The aim of this study was to produce hydrolysates from armoured catfish using food grade proteases (neutrases HT and PF and alcalase PAL) and investigate process conditions (pH and temperature) that lead to high degree of hydrolysis, antioxidant activity, and Angiotensin I-Converting Enzyme (ACE) Inhibitory activity. No other similar research has been reported on this underutilized fish. The antioxidant activity was measured by three different methods, ABTS, FRAP, ORAC with relevance to food and biological systems in order to obtain a more comprehensive assessment of the activity. In addition, main peptide sequences were identified. All enzymes produced hydrolysates with high antioxidant activity. In particular, the protease HT led to the highest antioxidant activity according to ABTS (174.68 mol Trolox equivalent/g fish) and FRAP (7.59 mg ascorbic acid equivalent/ g fish) methods and almost the same as PAL according to the ORAC method (51.43 mol Trolox equivalent/g fish). Moreover, maximum activities were obtained at mild pH and temperature conditions (7.5; 50 °C). Interestingly, the ORAC values obtained here were higher than others previously reported for fish hydrolysates and similar to those reported for fruits such as, blueberries, apples and oranges. The peptide sequence IEE(E) was present in several peptides in both hydrolysates; this sequence may be partly responsible for the high antioxidant activity particularly for the one based on the iron reducing power. These findings will be relevant to the valorization of other fish/fish muscle discards and could contribute to the production of food supplements and nutraceuticals.