Emulsion formation during enzymatic protein hydrolysis and its effect on protein recovery and molecular weight distribution of protein hydrolysates from sardine (Sardina pilchardus) by-products

Recovery of protein is one of the important variables to optimise enzymatic hydrolysis of fish processing by-products. This study investigated the role played by emulsion formation on protein recovery and the molecular weight distribution of the protein hydrolysates at different solids concentration of fish processing by-products with a high oil content. Solids concentration of fish processing by-products was varied between 26 and 50% at constant pH of 7.8, 60 degrees C hydrolysis temperature and 4% enzyme dosage using Alcalase 2.4L. The results showed that emulsion formation, more than inhibition of enzyme activity, at high solids concentration contributed to the reduction in yield of dry solids and protein recovery. Emulsion formation also led to the presence of high molecular weight lipo-protein complexes in the protein hydrolysates, which caused an increase in the average molecular weight of the hydrolysates. The findings show the negative relationship between solids concentration, protein recovery and emulsion formation in enzymatic hydrolysis, and the need for methods that eliminate or reduce emulsion formation at high solids concentration without increasing process complexity or reducing protein recovery.