Effect of poly-γ-glutamic acid on the stability of set yoghurts.

The effects of poly-γ-glutamic acid (γ-PGA) on the stability of yogurt were studied in terms of texture, rheology, particle size, and microstructure. The effects of γ-PGA on the pH and water holding capacity (WHC) of yogurt during refrigeration were also studied. The tan δ value of the yogurt with 0.04% (w/w) γ-PGA was significantly lower than that of control. The addition of γ-PGA decreased the particle size. The yogurt with 0.02% (w/w) γ-PGA had denser network structure with less porosity, and cross-linking between complexes occurred with greater frequency. The pH of the yogurt supplemented with 0.02% and 0.04% γ-PGA was significantly higher. WHC increased with the amount of γ-PGA. The addition of γ-PGA to yogurt strengthened the antishear ability, inhibited the postacidification phenomenon, and improved stability during refrigeration.