Release of angiotensin converting enzyme-inhibitory peptides by simulated gastrointestinal digestion of infant formulas

The angiotensin converting enzyme (ACE)-inhibitory activity of several infant formulas was evaluated. Most of these products showed moderate inhibitory activity, but two exceptions that corresponded to an extensively hydrolysed whey formula and an extensively hydrolysed casein formula were detected. Two products (a non-hydrolysed milk protein-based formula and an extensively hydrolysed whey formula) were subjected to a two-stage in vitro enzymatic procedure, which simulates physiological digestion, in order to study the impact of digestion on ACE-inhibitory activity. The ACE-inhibitory activity of the non-hydrolysed formula increased during simulated gastrointestinal digestion, while no significant change was observed in the activity of the hydrolysed whey formula prior to and after, digestion. The peptides generated from these two products during simulated physiological digestion were sequenced by tandem spectrometry. At the end of the digestion, most peptides found in the nonhydrolysed milk protein-based formula were formed during incubation with the pancreatic extract, but, in the hydrolysed whey formula, many peptides present in the undigested product survived simulated digestion. The potential ACE-inhibitory activity of these peptides is discussed with regard to their amino-acid sequences. (C) 2004 Elsevier Ltd. All rights reserved.