Abstract :
Protein degradation of caprinewhey byhumanproteolytic enzymeswas studiedwith regard
to antibacterial effect on Listeria monocytogenes. The digestionwas performed by a two-step
degradation-assay, using human gastric juice (HGJ) at pH 2.5, and human duodenal juice
(HDJ) at pH 8. Protein profileswere studied by SDS-PAGE after each step and compared with
degradation performed by commercial enzymes. Both types of enzymes, both human and
commercial, left most of -LG intact. However, proteins like serum albumin, laktoferrin
and immunoglobulins were rapidly degraded. Only minor parts of -lactalbumin ( -LA)
was degraded by human enzymes, while treatment with commercial enzymes gave full
degradation of -LA. The two types of enzymes resulted in different peptide profiles, where
the commercial enzymes degraded whey into smaller peptides much more efficiently.
The protein digests produced by HGJ and HDJ were screened for antibacterial effects
against L. monocytogenes, a food born bacteria responsible for fatal and sometimes deadly
infections. Cells of L. monocytogeneswere strongly inhibited by caprine whey obtained after
reaction with both HGJ and HDJ. Undigested caprine whey and the products from the first
step of digestion with HGJ demonstrated no significant effect. This indicates that during
digestion the antibacterial effect of caprine whey hydrolysates are most effective in the
duodenum. This gives a promising opportunity to inhibit listeriosis in humans, and results
are also useful for development of dietary supplement, nutraceuticals and functional foods.
© 2008 Elsevier B.V. All rights reserved
