Abstract:

Five enzyme preparations were solely used to hydrolyze channel catfish (Ictalurus punctatus) skin gelatin and pepsin and trypsin were screened for further studies in view of higher hydroxyl free radical scavenging activity of the hydrolysates. Optimization of the conditions for trypsin hydrolysis was carried out using orthogonal array design L9(34) and the optimal hydrolysis conditions were determined as follows: temperature 40 ℃; pH 7.5; enzyme/substrate ratio (E/S) 3.5%; substrate concentration 2.5 g/100mL; and hydrolysis duration 3 h. In addition, pepsin and trypsin were used together for the two-step hydrolysis of channel catfish gelatin in different orders of addition or one-step hydrolysis, namely adding the two enzymes simultaneously. Initial trypsin hydrolysis for 3 h followed by another 3 h of pepsin hydrolysis resulted in the generation of peptides with the highest hydroxyl free radical scavenging rate, up to 47.38%.

Key words: channel catfish (Ictalurus punctatus), enzymatic hydrolysis, bioactive peptides, hydroxyl free radical