The effects of alpha-lactalbumin and whey protein concentrate on alpha-amino acids, calcium and phosphorus levels in blood and gastrointestinal tract of rats.

The effects of two dietary proteins on alpha-amino acids, calcium and phosphorus concentrations in plasma, stomach and intestine were investigated in rats trained to consume, in a single two-hour daily meal, diets containing a-lactalbumin (alpha-la) or whey protein concentrate (WPC) for two weeks. The results indicated that the concentrations of calcium and phosphorus in the gastrointestinal tract and that of a-amino acids in portal vein were not significantly influenced by the nature of diets. The amount of alpha-amino acids in the gastrointestinal tract of rats fed on WPC diet was significantly (p < 0.001) higher than that of alpha-la group. The levels of insoluble calcium and insoluble phosphorus in the small intestine were significantly (p < 0.001) higher in alpha-la group than in WPC group. These results indicated that the kinetics of alpha-amino acids, calcium and phosphorus were differently influenced by the nature of diet ingested, the sampling time and the sites of sample collections.

The effects of alpha-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 alpha-lactalbumin (alpha-LA) or whey protein concentrate (WPC) for two weeks. Compared with the WPC diet, the alpha-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 alpha-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 < 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 alpha-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 alpha-LA is faster than that of WPC.