Occurrence of β-casomorphins 5 and 7 in commercial dairy products and in their digests following in vitro simulated gastro-intestinal digestion

The occurrence of beta-casomorphin-5 (BCM5) and beta-casomorphin-7 (BCM7) was investigated in commercial dairy products and in their digests, following in vitro simulated gastro-intestinal digestion (SGID), by means of HPLC-MS. The analysed dairy products were as follows: 10 cheeses (Gorgonzola, Caprino, Brie, Taleggio, Gouda, Fontina, Cheddar and Grana Padano 10-, 15- or 25-m ripened); 4 samples of drinking milk (unprocessed, pasteurised, UHT and in bottle-sterilised); 2 yoghurts and 4 fermented milks containing probiotics: 7 infant formulas: and 4 dried milk-derivatives (skim milk powder, calcium caseinate and milk protein concentrates). beta-Casomorphin-5 was not detected in dairy products, either prior to or after SGID. beta-Casomorphin-7 was detected only in cheeses with the exception of Taleggio, Caprino and Grana Padano samples. Peptide amount was in the range 0.01-0.15 mg kg(-1) the highest level being recovered in Brie sample. Following SGID, BCM7 formed in all dairy samples or increased up to 21.77 mg kg(-1) in digests of cheeses. The peptide level ranged from 0.29 to 1.23 mg kg(-1) in fermented milks and from 3.46 to 22.18 mg kg(-1) in dried milk-derivatives. Digests of commercial infant formulas contained BCM7 at concentrations of 0.04-0.21 mg l(-1). For the first time, this work reports quantitative values for BCM5 and BCM7 in a range of dairy products providing evidence that, during processing, only proteolytic systems involved in manufacturing and ripening of cheese can potentially hydrolyse beta-CN to BCM7. Nevertheless, formation or further release of BCM7 is mainly promoted by the action of gastrointestinal proteinases during in vitro digestion irrespective of the type of dairy product. (C) 2009 Elsevier Ltd. All rights reserved.