Effects of temperature and pH on angiotensin-I-converting enzyme inhibitory activity and physicochemical properties of bovine casein peptide in aqueous Maillard reaction system

The purpose of this study was to evaluate the impact of temperature and pH on aginotensin-l-converting enzyme (ACE) inhibitory activity, free amino group, browning intensity, fluorescence intensity and molecular weight distribution of galactose-bovine casein peptide (BCP) Maillard reaction products (MRPs). With increased heating temperature and pH, browning intensity of Galactose-BCP MRPs increased, while free amino groups of Galactose-BCP MRPs decreased. The fluorescence intensity of Galactose-BCP MRPs reached its maximum value at 100 degrees C and thereafter gradually decreased, while fluorescence intensity of Galactose-BCP MRPs showed the maximum value at pH 10.0 and thereafter gradually decreased. Size exclusion chromatography of Galactose-BCP MRPs indicated molecular rearrangements and production of new smaller molecules as a function of the heating temperature and pH. Galactose-BCP MRPs had the lowest angiotensin-I-converting enzyme (ACE) inhibitory activity at 120 degrees C. BCP lost 29.13% ACE inhibitory activity at pH 12.0 by Maillard reaction with galactose. High temperature and alkaline condition of Maillard reaction lead to the loss of ACE inhibitory activities and changes of characteristics of bovine casein peptides. (C) 2014 Elsevier Ltd. All rights reserved.