As shown in Figure 1 there was an increasing
trend in viscosity of yogurts with time. All the rice
incorporated yogurts exhibited higher (p< 0.05)
viscosity values throughout the storage period.
High total solid contents in rice yogurts could be
suggested as a reason for increased viscosity in rice
yogurts in the present study. According to Tamime
and Robinson (1999), increasing total solid content
in yogurt could result higher consistency and
viscosity values. In the present study total solids in
rice yogurts were within the range of 22.45±4.63 -
24.28±0.31% while total solid content in plain yogurt
was 16.58±2.99% (Table 1). Other than the total
solid content, some researchers claim that viscosity
and texture of yogurt is positively affected by the
microbial exopolysaccharide produced by lactic acid
bacteria in yogurt since exopolysaccharides may act
as texturizers and stabilizers (Duboc and Mollet,
2001). Therefore, exopolysaccharides may increase
the viscosity of the final product as well as the
rigidity of the casein network by binding hydration
water and interacting with other milk constituents
such as proteins and micelles. Thus, higher viability
of B. animalis subsp. lactis BB-12 in rice yogurts
compared to plain yogurt in the present study (Figure
2) might have been responsible for the increasing
viscosity values in rice yogurts through production of
exopolysaccharides. Retrogradation process of rice