Effects of Milk Total Solids on the Growth of Starter Cultures and Quality of Yoghurt

In or to evaluation the effects of milk total solids on the growth of starter bacteria during fermentation، pastorizied skim milk concentrated to 4 levels of total solids (14،18،23 and 27%) using a vaccume evaporator. Concentrated milk samples inoculated with a yoghurt starter culture (CH1) and incubated at 43°C for 6 hours. At intervals of 1 hour tow samples removed from the incubator and cultured in BGWA medium. The results showed that increasing milk total solids، increased the lag phase time for both of starter bacteria but increased growth coeficiant. The acidity increased and syneresis decreased with increasing total solids. Increasing total solids to 23% had no significant effect on the flavour scores but increasing of them more than this level decreased the flavour scores significantly. The texture scores increased with increasing of total solids.