Investigation of the quality parameters of hydrolysates obtained from fish by‐products using response surface methodology

Abstract

Fish protein hydrolysates (FPH), which comprise a combination of small protein or peptide and free amino acids, may be suitable for use in a variety of applications. For this purpose, the hydrolysis process was carried out for the by-products of trout, whiting, and anchovy with alkaline protease, protamex, and flavourzyme, and the quality of the protein hydrolysate generated under optimized conditions was determined by proximate compositions, amino acid contents, heavy metal, and trace element levels and peptide molecular weight sizes. The time, temperature, and enzyme proportions were determined according to the hydrolysis degree (DH%) under optimum conditions identified by response surface methodology (RSM). The crude protein, lipid, and ash contents of trout, whiting, and anchovy by-products hydrolysates ranged from 77.03% to 88.54%, 3.28% to 6.12%, and 8.18% to 16.8% for dry matter, respectively. Considering the total amino acid contents, the highest number of amino acids was aspartic and glutamic acid in all fish and enzyme groups. In terms of essential amino acids, the highest concentrations of cystine, histidine, lysine, and methionine were found in anchovy by-product hydrolysates produced using the flavourzyme. Using FAO/WHO reference protein as a base, lysine was found to have the highest chemical score for trout by-products hydrolysates using protamex (85.14%), whiting by-products hydrolysates using alkaline protease (83.66%), and anchovies by-products hydrolysates using flavourzyme (88.45%). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed that the electrophoresis pattern of the hydrolysates of trout, whiting, and anchovy by-products optimized with the RSM using alkaline protease, protamex, and flavourzyme enzymes showed variations depending on the enzyme type and fish by-products. Practical applications The enzymatic hydrolysis of proteins, which produces protein hydrolysates that are composed of free amino acids and short-chain peptides, has proven to be one of the most successful methods for recovering value-added proteins from fish by-products while maintaining their nutritional value. Because of the amino acid composition of these free amino acids and short-chain peptides of hydrolysate, they have several benefits as nutraceuticals or functional foods. As shown in this work, hydrolysates of fish by-products (trout, whiting, and anchovy) improved using the RSM applying alkaline protease, protamex, and flavourzyme enzymes demonstrated that it is an excellent source of important amino acids, particularly lysine and short-chain peptides. Consequently, recent research findings suggest that hydrolysates of trout, whiting, and anchovy by-products may be utilized as bioactive components in a variety of nutritional, pharmacological, cosmetic, and nutraceutical applications.