In vivo gastric digestion of milk proteins. Effect of technological treatments

Abstract

To compare the effects of technological treatments of milk on the gastric emptying of proteins and peptides, three diets were studied: raw milk, pasteurized milk, and yoghurt. In the preruminant calf, all effluents leaving the stomach during 12 h were collected and analyzed for N emptying, NPN level, amino acid composition, and characterization of proteins and peptides by SDS-polyacrylamide gel electrophoresis. With raw milk, casein coagulation is almost immediate in the stomach and casein is evacuated in the form of peptides. With pasteurized milk, casein coagulation is slower. Casein is also evacuated in the form of peptides. With yoghurt diet in which casein was gelified by acidification to pH 4 before ingestion, there is no coagulation in the stomach. Casein is evacuated during the whole digestion process in intact and degraded form. For the three diets, a-lactalbumin was degraded when the pH value was under 3.5. /3-Lactoglobulin did not seem to be proteolyzed. Amino acid compositions of the effluents are not so variable in the process of digestion with pasteurized milk as in digestion with raw milk. With yoghurt, amino acid compositions of the effluents are almost identical during the whole digestion process.

Food-derived Bioactive Peptides - Opportunities for Designing Future Foods

“…Digestive enzymes react with structurally altered proteins, as they are various substrates. The influence of technological treatment of milk on gastrointestinal proteolysis has been demonstrated in minipigs [102,103], rats [104] and calves [105][106][107]. In addition, milk fermentation has been found to affect in vitro digestibility with trypsin [96].…”

Whey Protein Antigenicity Reduction by Fungal Proteinases and a Pepsin/Pancreatin Combination

“…P-Lactoglobulin (PLg) is considered the most important allergen because it is the main protein of cow milk which is not present in human milk (Bell and McKenzie, 1964;Taylor, 1986). In addition, it appears to resist enzymatic digestion by pepsin in the stomach (Yvon et al, 1984;Scanff et al, 1990) and may, therefore, pass undigested through the gut epithelial cells into blood circulation. Indeed, by use of anti-bovine PLg antibodies, low concentrations of PLg have been detected in human milk (Mgkinen-Kiljunen and Palosuo, 1992;Lovegrove et al, 1993).…”

Portal absorption of 15N and amino nitrogen in the growing pig after ingestion of labelled milk, yogurt or heat-treated yogurt

“…This result is undoubtedly related to the different intestinal emptying rates between milk, yogurt and heat treated yogurt as has been suggested by several authors [7,8,33,35]. Since the viscosity differences between milk and live yogurt result in a slower gastric emptying rate for yogurt [33], it is understandable that the portal absorption profile of 15 N and AN is for live yogurt (Y0 and Y21) when compared to M and HY. Thus each milk product can be characterised by its specific nutritional behaviour.…”