THERMAL MODIFICATION OF UF-WHEY PROTEIN . 2. INFLUENCE OF THE NUTRITIVE PROPERTIES

The effects of thermal treatments (90-degrees-C for 1 0 min) were exam ined on ultrafiltered whey proteins under acid, neutral or alkaline co nditions in relation to their nutritional properties. Therefore enzymi c availability in vitro was investigated using physiological relevant proteinases and subsequent investigation of proteolysates by gelchroma tography on Sephadex G-25. The nutritive value was determined by a two -step-digestion using pepsin and trypsin/pancreatin. The resulting pro teolytic patterns were compared with those obtained by digestion of un treated whey protein. It is shown that subtle modifications are not or scarcely detectable under physiological relevant conditions. Further investigations relating enzymic availability of whey protein fractions by pepsin or trypsin made clear that the pepsin resistance of beta-la ctoglobulin can be broken by thermal modification under alkaline condi tions.