Effects of esterified rice flour with citric acid on physicochemical and rheological properties of yogurt

This study examined the effects of replacing the different concentrations (0, 0.1, and 0.2%, w/v) of esterified rice flour with citric acid (ERCA) on the physicochemical and rheological properties of yogurt stored at 4℃ for 15 days. Incorporating ERCA (0.2%, w/v) into yogurt decreased the syneresis values and increased the lactic acid bacteria counts. In steady shear rheological analysis, the values of the consistency index (K), apparent viscosity (ηa,100), and yield stress (σoc) for the yogurt samples containing ERCA were greater than those for normal yogurt. The flow behavior indices (n) of all yogurt samples ranged from 0.22 to 0.39, indicating that all yogurt samples behaved like a shear-thinning fluid. The frequency sweep test showed that the storage modulus (G′) and loss modulus (G″) of all samples increased with increasing frequency and concentration of ERCA. For all samples, the G′ values were higher than the G″ values, indicating that yogurt had elastic properties rather than viscous properties. During heating and cooling, the G′ and G″ values for the yogurt samples containing ERCA were greater than those of the normal yogurt and increased with increasing ERCA concentration. These results indicate that the replacement of ERCA could improve the lactic acid bacteria counts, steady shear rheological properties, and dynamic shear rheological properties of yogurt.