Abstract:

This study investigated the preparation of protein hydrolysates from dark muscle from yellowfin tuna as an edible
fish by-product with trypsin. By using orthogonal array design, the optimal enzymatic hydrolysis conditions were determined
as 2 400 U/g, 8.0, 55 ℃, and 6 h for enzyme dosage, initial pH, temperature, and hydrolysis time, respectively, resulting in a
degree of hydrolysis (DH) of (19.89±0.10)% and a nitrogen recovery of (64.88±0.72)%. The molecular weight distribution
of the hydrolysate as determined by high performance liquid chromatography (HPLC) suggested that significant degradation
of macromolecular proteins produced the hydrolysate mostly consisting of oligopeptides below 3 kD with molecules less
than 1 kD accounting for the majority (79.23%) of the total oligopeptides. The hydrolysate contained all the common amino
acids and was rich in eight essential amino acids (accounting for 42.38% of the total amino acids), and thus could be used as
a nutritional supplement.

Key words: trypsin, yellowfin tuna dark muscle, orthogonal array design, molecular weight distribution, nutritional evaluation