Effects of exopolysaccharide-producing strains of thermophilic lactic acidbacteria on the texture of stirred yoghurt

Rheological and sensory properties of yoghurts prepared from commercially a vailable cultures that had ropy and non-ropy characteristics were compared. Our results from both instrumental and sensory data suggest that it may no t be the amount of polysaccharide that is important to rheological properti es, but the type of exopolysaccharide (EPS)-producing strains and consequen tly the interaction of the polymer with the milk proteins during the fermen tation. Data also suggest that the interaction and co-operative growth that occurs in mixed cultures also influences the yield of EPS production in th e fermentation, as combining two ropy strains does not lead to an increase in total polysaccharide, although the viscosity can be improved. Texture me asurements for viscosity correlated with sensory evaluation of viscosity an d with slipperiness.