Blending pectin and κ-carrageenan converted the liquid yogurt induced by pectin into the solid yogurt

Effects of 0.11 %–0.17 % pectin and the mixture of 0.03 % κ-carrageenan and 0.11 %–0.17 % pectin on texture and microstructure of yogurt were investigated in this work. Rheology analysis demonstrated that adding 0.11 %–0.17 % pectin before fermentation inhibited gelation of yogurt and liquid yogurt was formed. However, when the above κ-carrageenan/pectin mixture was added, yogurt was gelled and solid-like. It was demonstrated by CLSM that milk protein aggregated into separated particles in the liquid yogurt induced by pectin, while milk protein aggregated into a continuous network in the solid yogurt induced by the mixture. Adding 0.11 %–0.17 % pectin into the casein micelle suspension induced aggregation of casein micelles into separated particles, which was the same in the corresponding liquid yogurt samples. Moreover, casein micelles precipitated in the pectin/casein micelle mixtures after storage for 3 h. However, when the above mixture was added into the casein micelle suspension, tightly-connected casein micelle aggregates appeared and the resultant κ-carrageenan/pectin/casein micelle mixtures were stable after storage for 3 h. These results indicated that the pectin-casein micelle interaction played an essential role in formation of the liquid yogurt and κ-carrageenan altered this interaction. Thus, blending κ-carrageenan and pectin converted the liquid yogurt induced by pectin into the solid yogurt.