effects of co2 addition to raw milk on microbial, physiochemical and sensory properties of probiotic set yoghurt

the suitability of milk preserved by refrigeration and co2 addition for the manufacture of plain yoghurt using two commercial strains of lactobacillus delbrueckii ssp. bulgaricus and streptoccocus thermophilus and probiotic yoghurt by lactobacillus acidophilus was evaluated. yoghurts (plain and probiotic) manufactured after milk pasteurization, from fresh and refrigerated co2 treated samples (ph= 6.2), were compared with the corresponding controls (fresh and refrigerated). the multiplication and acidification capacity of the starter were neither affected by the previous refrigeration and co2 addition of raw milk nor by the residual co2 present in the pasteurized milk. co2 addition of raw milk slightly enhanced viscosity and reduced synersis of yoghurts. the taste panel preferred yoghurts made from co2 treated milks to the corresponding controls during cold storage. these results support the suitability of co2-addition in preservation of milk for manufacturing of yoghurts.