Hydrolysis of ovine, caprine and bovine whey proteins by trypsin and pepsin

Abstract

Direct hydrolysis of whey leads to peptides that possess higher digestibility and better functional properties, so these may be incorporated in food formulae to improve their performance. Incubation of pure bovine α-La and β-Lg, as well as of caprine, bovine and ovine wheys with trypsin and pepsin led to the production of various hydrolysates, which absorb at 280 nm and are characterized by molecular weights ranging from ca. 8000 Da to less than 500 Da. Bovine α-La was slowly hydrolysed by trypsin but rapidly by pepsin, in either pure form or in whole whey. Bovine β-Lg was more rapidly broken down by trypsin, and less rapidly by pepsin than α-La, and a similar performance was observed when β-Lg was tested on whole whey. In most whey digests, a peak corresponding to a molecular weight between 3000 and 4000 Da was observed by gel permeation chromatography. It was detected mainly in ovine and caprine wheys, and grew slowly with incubation time in bovine whey but fast in wheys from small ruminants. Incubation of the fraction corresponding to the unknown peak with pepsin did not produce any effect detectable by chromatography, yet incubation with trypsin led to a decrease in the area of such peak and a concomitant rise of the areas accounted for by low molecular weight peptides.