Comparative analysis of milk casein hydrolysates from cow, water buffalo, goat and sheep: effects of flavourzyme and neutrase on formation of bioactive peptides

The casein hydrolysates of cow (CwC), water buffalo (WBuC), goat (GoC), and sheep (ShC) were obtained using neutrase (CwCN, BuCN, GoCN, and ShCN) and flavourzyme (CwCF, BuCF, GoCF, and ShCF). Untreated caseins and their respective enzyme (flavourzyme and neutrase) treated hydrolysates were compared in terms of selected bioactivities, free amino acids, and molecular weight distributions, etc. The enzymes displayed varied activities for 4 casein types. Flavourzyme was more aggressive than neutrase in the formation of peptides and free amino acids. The highest and the lowest degree of hydrolysis were determined for GoCF (166.8 mg tryptone /g casein) and ShCN (37.4 mg tryptone /g casein), respectively. Both enzymes significantly reduced the molecular weights of peptides in hydrolysates. The higher amounts of free amino acids were determined in flavourzyme treated caseins compared to neutrase treated ones; the highest was in ShCF (92.89 mg amino acid/g casein). The polypeptide ratio in ShC was 78.3%, but after treatment with flavourzyme and neutrase, the polypeptide ratio in hydrolysates were diminished to 23.5 and 25.3%, respectively, for ShCF and ShCN. The highest proportion of peptides in hydrolysates were oligopeptides (between 0.5 and 2.5 kDa), ranging from 67 to 76.7% for 8 enzyme treated caseins. FTIR spectra indicated modifications in caseins in amide I and II bands. Compared to their respective enzyme treated hydrolysates, the untreated caseins (CoC, WBuC, GoC, and ShC) displayed higher lipase inhibition activities (GoC having the highest inhibition, 66.34%). In the case of alpha-amylase inhibition, flavourzyme generated higher results for WBuCF (91.09%) and CwCF (86.96%) than their neutrase treated analogs. On the other hand, neutrase generated higher results for GoCN (67.3%) and ShCN (55.77%) than their flavourzyme treated analogs. Regarding ACE inhibition activity, GoCN and WBuCF displayed the highest results as 93.3% and 80.32%, respectively. The study demonstrated the promising potential of casein hydrolysates from different sources for the formulation of functional foods to combat chronic diseases including hyperglycemia, dyslipidemia, obesity, and hypertension.