In vitro digestibility of bioactive peptides derived from bovine β-lactoglobulin

The in vitro digestibility of three bioactive peptides from ββ-lactoglobulin (ββ-Lg) containing theoretical cleavage sites for pepsin and chymotrypsin was studied. When incubated with pepsin, ββ-Lg f142–148 remained intact whereas β  -Lg f15–20 and f102–105 were weakly hydrolysed (<31%). With chymotrypsin, only ββ-Lg f142–148 was strongly hydrolysed (99.8%). Longer peptides (ββ-Lg f9–20, f92–105, and f139–148) containing the bioactive sequences were treated under the same conditions. All of these sequences were extensively degraded by both enzymes. The degree of hydrolysis was influenced by both the length of the peptide chain and the nature of the peptide. Furthermore, higher degrees of hydrolysis of a ββ-Lg f102–105/f92–105 mixture were obtained with both enzymes than with each peptide treated separately. These results support the view that in vivo studies are essential to validate the physiological effects of bioactive peptides and that long-chain bioactive peptides require protection from gastrointestinal enzymes when orally administered.