Production and antioxidant activity of peptides from sturgeon head

The head is a significant, but typically unused, fish by-product. Here, we developed an industrially applicable new method to make head tissue peptides (HTPs) by autoclaving, blending and enzymatic hydrolysis of sturgeon head tissue. Four conditions were tested: head tissue autoclaved in distilled water (DW) and hydrolyzed with papain (DW-P) or papain and bromelain (DW-P + B), or head tissue autoclaved without DW and hydrolyzed with papain (WDW-P) or papain and bromelain (WDW-P + B). Among these conditions, DW-P + B resulted in the highest peptide yield, more peptides of <500 Da, and peptides with the highest antioxidant activity. Next, the same method produced sturgeon skin tissue peptide (STP) and skin collagen peptide (SCP) and the bioactivities were compared. The gross yield of HTP per fish was higher than that of STP and SCP because the sturgeon's head is ∼3 times heavier than its skin. The HTP contained more reactive oxygen species (ROS)-scavenging amino acids (Glx, His, Leu, Lys, Met, Phe, Tyr, Val) and showed significantly higher ABTS• scavenging activity than STP and SCP. The extracellular cell-protection and intracellular anti-ROS activities of HTP on the application of oxidative stress were similar to those of STP and SCP. Moreover, HTP showed high transparency and high safety (a low endotoxin level). All these features suggest that HTP is suitable for percutaneous applications. Extracellular oxidative stress promotes human skin aging; thus, HTP may be a novel, low-cost ingredient for anti-aging cosmetics. The present study will help to exploit zero industrial discards, resulting in blue transformation of by-products.