Effect of sodium alginate on the yogurt stability was dependent on the thickening effect and interaction between casein micelles and sodium alginate

The effect of sodium alginate (SA) on the yogurt stability and the related mechanisms were investigated. It was found that low-concentration SA (<= 0.2 %) increased the yogurt stability, while high-concentration SA (>= 0.3 %) decreased the yogurt stability. Sodium alginate increased the viscosity and viscoelasticity of yogurt and this effect was positively correlated with its concentration, suggesting that SA worked as the thickening agent in yogurt. However, addition of >= 0.3 % SA damaged the yogurt gel. These results suggested that interaction be-tween milk protein and SA might play an important role in the yogurt stability besides the thickening effect. Addition of <= 0.2 % SA did not change the particle size of casein micelles. However, addition of >= 0.3 % SA induced aggregation of casein micelles and increased the size. And the aggregated casein micelles precipitated after 3 h storage. Isothermal titration calorimetry analysis showed that casein micelles and SA were thermo-dynamically incompatible. These results suggested that the interaction between casein micelles and SA induced aggregation and precipitation of casein micelles, which was critical in the destabilization of yogurt. In conclu-sion, the effect of SA on the yogurt stability was dependent on the thickening effect and the interaction between casein micelles and SA.

Automated summary

The effect of sodium alginate (SA) on yogurt stability and the mechanisms involved were investigated. Low-concentration SA (<= 0.2%) was found to increase yogurt stability, while high-concentration SA (>= 0.3%) decreased stability. SA increased yogurt viscosity and viscoelasticity, acting as a thickening agent, but adding >= 0.3% SA damaged the yogurt gel.