18D-7 |
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W.-L. WENG, Dept. of Food Science, Nutrition & Health Promotion, Mississippi State Univ., 157 Herzer Bldg., Mailstop 9805, Mississippi State, MS 39762-9805 and Y.-S. Chen. Lactose in yogurt was found to be easier to digest than lactose in milk. It is believed that β-galactosidase (β-gal) might contribute to the hydrolysis and usage of lactose. However, the exact role of β-gal toward relieving lactose-intolerance syndrome remains unknown. The objective of this research is therefore to investigate the changes of β-gal activity in yogurt through a simulated gastrointestinal system. Samples of commercial yogurts containing Lactobacillus acidophilus, Lb. bulgaricus, Bifidobacterium longum, and Streptococcus thermophilus were obtained from local stores. Viable cell counts were determined on MRS and LM17 plates, and β-gal activity was measured by a spectrophotomeric method using o-nitrophenyl-β-D-galactopyranoside as substrate. After 3 hour incubation in the simulated stomach, β-gal activity was found to be decreased significantly, whereas successive intestinal condition promotes the increase in β-gal activity. Viable lactic acid bacteria counts were eliminated about 6-log during 3 hour incubation in the gastric compartment followed by increasing to 106-107CFU/ml in the intestinal compartment after 9 hours. These results suggest that both β-gal activity and cell viability were affected by the low pH in the gastric compartment. After 9 hours in the small intestine, viable cells was increased might result in the neutral pH in the small intestine, thereby increasing β-gal activity.
Session 18D, Food Microbiology: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |