In vitro digestion of bovine and caprine milk by human gastric and duodenal enzymes

Abstract

In vitro digestion was performed by human proteolytic enzymes on bovine and caprine individual milks. Two types of caprine milk were investigated: with high and low contents of α S1-casein (CN). In addition the influence of heating of the milk on digestion was examined. The digestion was performed in two steps using human gastric and duodenal juice. Protein and peptide profiles were studied by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and isoelectric focusing (IEF). Caprine milk proteins were digested faster than bovine milk proteins. This was confirmed by the degradation profile obtained for both cows’ and goats’ milk, and was most evident for β-lactoglobulin. Comparing the digestion of milk protein from two groups of goats, high and low in α S1-CN content, respectively, did not show significant differences. Heat treatment of milk had a strong and significant effect on the level of digestion. Raw milk was degraded faster than the heat-treated milk, and the effect of heating was different for bovine and caprine milk.