Angiotensin-converting enzyme-inhibitory peptides in Manchego cheeses manufactured with different starter cultures

The angiotensin-converting enzyme (ACE)-inhibitory activity of water-soluble extracts from Manchego cheeses, which were manufactured with different starter cultures, was monitored during cheese ripening. On activity basis, the 3000 Da permeate from an 8-months-aged cheese, which was prepared with a defined-strain bacterial inoculum, was selected and fractionated by following several chromatographic steps. A total of 22 peptide fragments were identified in nine fractions by electrospray-ionisation-tandem mass spectrometry. Five of them corresponded to alpha(s2)-CN-fragments, six to beta-CN fragments, and 10 of them were peptides derived from the alpha(s1)-CN sequence. The di-peptide, FP, could be originated from hydrolysis of various casein fractions. The complexity of the collected fractions after three chromatographic steps precluded the assignment of a single peptide responsible of the ACE-inhibitory activity. Fragment (199-204) from ovine beta-CN, which was included in one of the most active fractions, was chemically synthesised and it was found to have an IC50 value of 592 mum. (C) 2002 Elsevier Science Ltd. All rights reserved.