The physico-chemistry of milk changes when it is homogenized and subjected to various types of pasteurization, altering the way milk is digested.  The effects of homogenization, high temperature short time pasteurization, and ultra-high temperature pasteurization (UHT) were compared in the in vitro digestion of raw whole milk and skim milk.  Milk samples were subjected to simulated gastric digestion for 1 h followed by intestinal digestion for 2 h.  The particle sizes in the native samples were 8.2 �m in whole milk, 4.3-4.5 �m in homogenized milk, 4.7 �m in UHT milk, and 0.5 �m in skim milk, and 0.7 in UHT skim milk.  At the start of digestion, clotting caused the particle sizes to increase to 105-160, 92-122, 30, 195-210, and 97 �m, respectively.   These values decreased to < 15 �m within 1 h.  Particle size analysis and confocal laser scanning microscopy suggest that UHT induced protein conformational changes that caused the clots in these samples to degrade faster.  Electrophoresis showed that proteolysis was enhanced in these samples during digestion.  The zeta potential of homogenized and UHT whole milk decreased at a faster rate than the other milk samples, apparently because the milkfat globule membrane was dislodged; fat and protein aggregation increased as a result.  Homogenization increased the release of free fatty acids during digestion.  Stearic and oleic acids decreased at a faster rate than other fatty acids during digestion in all full-fat samples.  The way milk is processed for consumption affects its chemistry and physical properties, which will affect its digestibility.

Effects of pasteurization and homogenization on milk during in vitro digestion

248th National Meeting (2014)

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