Rheological properties of fermented milk produced by a single exopolysaccharide producing Streptococcus thermophilus strain in the presence of added calcium and sucrose

摘要

The effect of calcium supplementation, presence of exopolysaccharides (EPS) and sucrose on the texture of low-fat fermented milk was examined. Reconstituted skim milk (14%) was acidified by 2% glucono-t-lactone (GDL) or a single strain, EPS-producing Streptococcus thermophilus, and incubated at 42pC. The levels of calcium and sucrose addition ranged from 0 to 9 m m and 0 to 45 m m respectively. Compared with acidified milk (GDL), fermented milk containing EPS showed different rheological properties in the presence of added calcium and sucrose. Calcium addition reduced gel characteristics: G', K, and the second maximum of derivative of shear rate-shear stress; while sucrose addition also increased them but subsequently reduced syneresis. Added calcium or sucrose increased gel hysteresis and reduced apparent yield stress.