Pepsin from yellowfin tuna gastric: Physicochemical characterization and its use in the hydrolysis of fish skin collagen with biological activity

Enzymatic hydrolysis is an effective approach for producing bioactive collagen peptides with potential health benefits. This study evaluated the effect of tuna gastric pepsin concentration on the hydrolysis of tuna skin collagen and characterized the physicochemical and bio-functional properties of the resulting hydrolysates. Pepsin was extracted from tuna gastric tissue and applied to acid-soluble collagen at enzymatic activities of 7,000, 14,000, and 21,000 U. The extracted pepsin exhibited a specific activity of 27,438.50 U/mg. Native collagen displayed characteristic β, α1, and α2 chains with molecular weights ranging from 150 to 260 kDa. Enzymatic hydrolysis using pepsin at 14,000 and 21,000 U produced low-molecular-weight peptides (41-3 kDa). The collagen hydrolysate obtained at 21,000 U showed the highest antioxidant activity, with an IC₅₀ value of 167.7 ± 0.47 ppm. In addition, this hydrolysate exhibited notable angiotensin-converting enzyme (ACE) inhibitory activity, achieving 68.63% inhibition at a protein concentration of 0.5 mg/mL. These findings demonstrate the potential of utilizing tuna processing by-products as a sustainable source of bioactive collagen hydrolysates with antioxidant and antihypertensive properties.