Properties of yogurts made using three strains of Lactobacillus delbrueckii ssp. bulgaricus that produce exopolysaccharide or made with a nonproducing strain, with and without addition of commercial stabilizer blends, were compared. A simple test, developed to measure the extensibility of yogurts, was able to discriminate yogurt made with exopolysaccharide-producing strains from yogurt made with the nonproducing strain and to discriminate among yogurts made with different exopolysaccharide-producing strains. The force required to penetrate the surface of yogurt made with exopolysaccharide-producing strains was less than that needed for yogurts made with the nonproducing strain. Yogurt made with exopolysaccharide- producing strains exhibited less shear thinning than products made with the nonproducing strain. Storage and loss moduli decreased monotonically as strain exceeded 5% for yogurts made using the nonproducing strain. Both moduli decreased monotonically between 5 and 10% strain for yogurt made with the exopolysaccharide-producing strains but exhibited an inflection in the slope between 10 and 100% strain. These data are consistent with a mechanism for shear-induced structural degradation of yogurt made using exopolysaccharide-producing strains in which polymer associated with the casein network prevents disruption of portions of the network.
All Science Journal Classification (ASJC) codes
- Food Science
- Animal Science and Zoology