The effect of casein hydrolysate formed by trypsin or bifidobacterium animalis subsp. lactis (Bb-12) culture on cholesterol and angiotensin converting enzyme (ACE) inhibition

Abstract

The hypocholesterolemic effect of peptides present in crude casein hydrolysate using trypsin from Bifidobacterium animalis subsp. lactis (Bb-12) culture grown in casein solution or in MRS broth were compared with the control (unhydrolysed crude casein). These samples have shown to reduce cholesterol level in vitro to varying degree between 24-87%. The unhydrolysed crude casein (control) has shown not to have a reducing effect on cholesterol level. The reduction level of cholesterol was found to be dependant on the degree of hydrolysis. Fractions obtained after size exclusion from crude casein hydrolysate formed by trypsin after 48h hydrolysis have shown to reduce cholesterol level to degree vary between 2.7% to 50%. Bb-12 or trypsin crude casein hydrolysates were also found to possess angiotensin-converting enzyme (ACE) inhibitory activity in vitro to a varying degree between 29% and 38%, respectively. Unhydrolysed crude casein showed no real effect on ACE inhibitory activity. Trypsin hydrolysate has slightly more effect on ACE activity than Bb-l2. A relationship was also found between ACE-inhibitory activity and degree of hydrolysis. Fractions of crude casein hydrolysate after 48h hydrolysis with trypsin by size exclusion have shown to have ACE-inhibitory activity varying between 37% and 50%. Several identified ACE-inhibitory peptides from active fractions were found to have Phe, Trp, Tyr, Arg, Lys or Pro at their ultimate C-terminal position, making them a possible candidate for ACE-inhibitory activity. Further analysis on the profiles of casein and whey protein fractions, obtained by fast protein liquid chromatography (FPLC), of skimmed milk and four different commercial types of probiotic health drinks, and casein profile of added Bb-12 culture were investigated to study the possible effect of probiotics on milk proteins. Differences in protein-profile were found between the control and the four commercial probiotic health drinks as well as with added Bb-12 culture. Whey proteins were more resistance to hydrolysis than caseins.