29C-7 |
Rheological properties of a novel microbial exopolysaccharide produced from lactose by Bifidobacterium longum BB-79 |
Y. M. Lo1, L. N. SADAR2, and S. Argin2. (1) Dept. of Nutrition & Food Science, Univ. of Maryland, Food Bioprocess Engineering Lab., 3102 Marie Mount Hall, College Park, MD 20742, (2) Department of Nutrition and Food Science/Food Bioprocess Engineering Lab, University of Maryland, 3407 Marie Mount Hall, College Park, MD 20742 There is growing interest in using microbial exopolysaccharide (EPS) produced by acidifying bacteria to directly affect the rheological properties of fermented dairy products. We have found that Bifidobacterium longum BB-79 produced the highest amount of EPS when lactose was used as the primary carbon source in liquid media, both in terms of weight and in glucose equivalents. The total biocompatible nature of the resulting rheologically active EPS plays in favor of its possible extensive use in the food industry. The value of this EPS could be greatly elevated if its rheological properties were characterized. The objective was to evaluate the rheological properties of the EPS produced from lactose by B. longum BB-79. Actively growing B. longum BB-79 was used to produce EPS from lactose under anaerobic conditions. Commercial yogurt starter cultures were employed to study the effects of EPS on yogurt viscosity. The rheological properties of the EPS were evaluated using AR2000 controlled stress rheometer with a peltier plate. The viscosity was then compared to a standard correlation between the viscosity and EPS concentration. The gel strength was measured using a TA.XT2i Texture Analyzer. The EPS was found to behave shear thinning in aqueous solutions. When added to plain yogurt inoculated with commercial starter cultures, this EPS provided a synergistic enhancement in yogurt viscosity. Synergistic effects were also found in gel strength when mixed with curdlan gum. As seen in SEM pictures, this EPS appears capable of providing the third dimensional stretch to the multi-layer network formed by curdlan. The formation of co-polymers with other EPSs should be of interest to the food industry. The value of the bifidobacteria-containing EPS would be increased if the final product could meet most, if not all, of the functionality desired in texture improvement besides its nutritional attributes.
Session 29C, Food Engineering: Rheology and texture
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