Hydrolyzed collagen from tuna skin is widely used in cosmetics, pharmaceuticals and food industries. To optimize the conditions for collagen extraction from yellowfin tuna (Thunnus albacares) skin by pepsin enzyme, experiments were designed according to Box-Behnken with the influencing factors being hydrolysis temperature (X1:35 - 45^oC), pH (X2: 1.5 - 2.5), pepsin concentration (X3: 25 - 35 UI/g), Hydrolysis time (X4: 3 - 5hours) for a maximum degree of hydrolysis (DH: Y1 %) and nitrogen recovery efficiency (NR Y2 %). There are 27 experiments in which there were three experiments in the center and each experiment was repeated three times. According to the results, optimum hydrolysis conditions were as follows: X1 = 39.5^oC (Hydrolysis temperature), X2 = 2 (pH), X3 = 32 UI/g (pepsin concentration), X4 = 4.5 hours (Hydrolysis time). The predicted DH and NR under optimal conditions were 13.65% and 64.43%, respectively. Hydrolyzed solution from yellowfin tuna skin was obtained with six fractions, of which 10% peptides have a molecular mass less than 17.24 kDa, 20% (17.24 kDa to 34.93 kDa), 20% (34.93 kDa to 58.40 kDa), 20% (58.40 kDa to 96.25 kDa), 20% (96.25 kDa to 162.55 kDa) and remaining 10% are molecular mass peptides from (162.55 kDa to 500 kDa).

Keywords: Collagen, nitogen recovery efficiency, degree of hydrolysis, yellowfin tuna skin,
enzymatic hydrolysis.