The effects of α-lactabumin and whey protein concentrate on dry matter recovery, TCA soluble protein levels, and peptide distribution in the rat gastrointestinal tract

The effects of two dietary proteins on dry matter recovery, trichloroacetic acid (TCA) soluble protein concentration, and peptide distribution in gastrointestinal contents were investigated in rats trained to consume, in a single 2-hour daily meal, diets containing α-lactalbumin (α-LA) or whey protein concentrate (WPC) for two weeks. Compared with the WPC diet, the α-LA diet emptied faster from the stomach. Dry matter recovery was higher in the stomach contents of rats fed the WPC diet than in those given the α-LA diet, but dry matter content in the small intestine was comparable. TCA soluble protein levels in the stomach and the small intestinal contents were also significantly (P &lt 0.001) higher in rats fed the WPC diet. The concentration of peptides having molecular weights (MW) ranging from 12 500–30 000 daltons (Da) was higher in the stomach contents of rats fed the WPC diet. Conversely, the level of peptides ranging from 5000–12 500 Da was higher in the stomach contents of rats fed the α-LA diet. For both diets, the small intestinal contents were characterized by high levels of amino acids and small peptides. These results suggest that the hydrolysis and absorption of α-LA is faster than that of WPC.Key words: In vivo protein digestion, peptides absorption, whey protein concentrate, α-lactalbumin, stomach emptying.