Quality of plain yoghurt made from refrigerated and CO2-treated milk

The suitability of milk preserved by refrigeration and CO2 addition for the manufacture of plain yoghurt was evaluated using two commercial strains of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus. Yoghurts manufactured, after milk pasteurisation, from refrigerated CO-treated samples (pH 6,15) were compared with two different controls made from pasteurised milk, either fresh or refrigerated. The multiplication and acidification capacity of the starter as well as the evolution of organic acids were not affected by the previous refrigeration and CO-treatment of raw milk nor by the residual CO2 present in pasteurised milk. However, refrigeration enhanced the production of ethanol and diacetyl. No differences on sensory properties were detected through the cold storage between yoghurts made from CO2-treated milk and those made from refrigerated control milk. It was concluded that refrigerated milk acidified with CO2 could be satisfactorily used in the manufacture of yoghurt. (C) 2002 Elsevier Science Ltd. All rights reserved.