Influence of Starter Culture Diversity and Using Wheat Fiber on Yoghurt Characteristics
Project no. 1007 · Status: Kapanmış · 2016
Summary
In the study, the chemical, microbiological, textural and sensory characteristics of wheat fiber-added (0.75% and 1.5%) yoghurts produced by a regular or exopolysaccharide-producing starter culture were investigated during the 28 days of storage. Hardness values did not differ among samples except the values determined at the samples produced by exopolysaccharide-producing starter culture in the middle of the storage. An increasing trend was also determined in hardness of yoghurts during the storage (p<0.05). The viscosity in yoghurts produced with regular starter culture and 1.5% wheat fiber was higher than those found in other yoghurts (p<0.05). In the beginning of the storage, the addition of wheat fiber decreased the syneresis rate of samples produced by both yoghurt culture. However, syneresis was more affected by the culture diversity at the end of storage and the rate of syneresis increased in the samples produced with exopolysaccharide-producing starter culture (p<0.05). The count of S. thermophilus increased in all yoghurts by addition of 0.75% wheat fiber at the first day, while culture diversity had a more effect on the S. thermophilus counts during storage. The counts of S. thermophilus were very high in yoghurts produced by the regular starter culture (over 9 log cfu/g) when compared to ones with exopolysaccharide-producing starter culture (over 7 log cfu/g) throughout the storage. On the other hand, the improving effect of wheat fiber addition at a ratio of 0.75% on the counts of L. bulgaricus was obtained only in the samples produced by regular starter culture throughout the storage. In contrast to enumerations of S. thermophilus, the counts of L. bulgaricus in yoghurts produced with exopolysaccharide-producing starter culture were found as significantly higher (approx. 2 log cfu) in comparison to the samples with regular starter culture (p<0.05). A significant difference was not reported among samples with regard to sensory properties.