Effect of simulated gastric conditions and bile salts on yogurt lactase activity

Lactose from yogurt is normally well digested by lactose deficient people. Intestinal hydrolysis of lactose by yogurt lactase is one of the mechanisms proposed. This mechanism would involve a significant enzymatic activity in yogurt, arrival of active enzyme at the small intestine, further release by bile salts and finally intestinal lactose hydrolysis. Lactase activity has been determined both in commercial products and in yogurt handled under simulating physiological digestion conditions. Results show an important variability between different brands of yogurt. Refrigerated storage did not affect the enzymatic activity. However, the activity was quickly lost at low pH or when the enzyme is exposed to simulated gastric conditions of pH and estimated emptying half-time. Bile salts are less effective than other cellular disruptor to release bacterial enzyme. Then the efficacy of yogurt lactase as an aid to hydrolyze intestinal lactose appears not to be reliable. Enzyme arrival at the small intestine and its later release by bile salts depend on the initial enzymatic activity of the ingested yogurt, gastric conditions and the effectiveness of bile salts. Therefore, mechanisms other than bacterial lactase activity would be relevant to explain the widely observed improvement of lactose digestion following yogurt instead of milk consumption.