2.1. Preparation of fish protein hydrolysate Fish protein hydrolysate was prepared from by-products of Pollock(Theragra chalcogramma) processing as described in our previous studies. The hydrolysate was filtered through Pellicon 2 Ultrafiltration Modules PLAC with a filter
of 1000 Da to obtain the small molecular weight compounds. The permeate after ultrafiltration was concentrated, freeze dried and stored at −20 °C prior to use. The molecular weights of the hydrolysate were analyzed by HPLC size exclusion chromatography using a TSK G2000 column, according to Boza et al. (1994). The peptide molecular weight distribution of the fish protein hydrolysate was presented in