Effect of hydrochloric acid concentration using acid hydrolysis on the extraction of useful ingredients from residue of dried bonito

Abstract

　The residue of dried bonito after extraction with hot water is a low-value product which is usually used as livestock feed. In order to utilize the residue for high-value added products such as food ingredients, the optimal conditions of acid hydrolysis were investigated. Residue of dried bonito was prepared by extracting shaved dried bonito with hot water. The acid hydrolysates were prepared by hydrolyzing the residue with six concentrations of hydrochloric acid, then removing the hydrochloric acid by repeating vacuum concentration and adding distilled water. The recovery rate of the crude protein from the residue and the amounts of 18 kinds of amino acids in the acid hydrolysates were maximum with 4.0 mol/L and 6.0 mol/L hydrochloric acid. The molecular weight 180-500 content and DPPH radical scavenging activity were maximum with 4.0 mol/L hydrochloric acid. The amount of peptides and anti-mutagenicity were not significantly different among the 1.0 mol/L to 6.0 mol/L treatments. These results suggest that the 4.0 mol/L sample is expected to contain low molecular weight peptides as functional ingredients and could be used as a high-value added food ingredient.