Comparison of the Rates of in Vitro Proteolysis in Human Milk, Cow's Milk, and Cow's Milk Preparations by Human Gastric and Duodenal Juices

Summary In in vitro conditions under which nearly complete proteolytic digestion (as measured by decrease in nitrogen precipitable by trichloroacetic acid) occurred through the action of unpurified human digestive secretions, it was found: 1. The rates of in vitro proteolysis of human milk during both peptic and tryptic digestion (after initial peptic digestion) are slower than those of raw cow's milk or sterilized and spray-dried milk products. 2. The rates of in vitro proteolysis during both peptic and tryptic digestion (after initial peptic digestion) are essentially the same in pasteurized and un-heated cow's milk as in heat-sterilized and spray-dried milk products.