Autolysis of rainbow trout (Oncorhynchus mykiss) by-products: Enzymatic activities, lipid and protein oxidation, and antioxidant activity of protein hydrolysates

Autolysis (at fixed temperatures (40, 50, 60 degrees C) or gradually increasing temperatures (40-60 degrees C) with different times) was used to produce protein hydrolysates from rainbow trout processing by-products. Total proteolytic and trypsin activities with fixed temperatures was higher than gradually increasing temperatures, decreased with increasing autolysis time and temperature with fixed temperatures (P <= 0.05). TCA-soluble peptides decreased with increasing autolysis times from 1 to 3 h (P <= 0.05). Autolysis increased peroxide value and thiobarbituric acid-reactive substances in both lipids and hydrolysates, particularly with gradually increasing temperatures (P <= 0.05) and was associated with oxidation of polyunsaturated fatty acids. Sulfhydryl groups decreased, while protein carbonyls and solubility were increased with fixed temperatures at higher temperatures (50 and 60 degrees C) or with gradually increasing temperatures at longer autolysis time (P <= 0.05). Free radical scavenging activity and the metal chelating ability of hydrolysates were governed by autolysis times and temperatures. Results of size exclusion chromatography-high performance liquid chromatography indicated that autolysis for 1 h at lower temperature (40 degrees C) was sufficient to produce autolysates rich in small peptides from rainbow trout by-products. Autolytic hydrolysis might be useful for production of such protein hydrolysates.

Automated summary

Autolysis was used to produce protein hydrolysates from rainbow trout processing by-products. Higher proteolytic and trypsin activities were observed at fixed temperatures compared to gradually increasing temperatures. Autolysis time and temperature were found to affect the quality of the hydrolysates produced.