Published online by Cambridge University Press: 01 June 2009
Unlike that of other lactic acid bacteria, the growth of Leuconostoc spp. in milk is poor and the resulting acidification cannot be used to distinguish different strains. An acidification test based on the use of high initial numbers (109 cfu/ml) has been developed and proved to be an efficient tool for discriminating between 110 Leuconostoc strains isolated from French raw milk cheeses. The pH values after 24 h ranged from 6.55 to 4.05 and distinguished four acidification groups. All 34% of the strains that acidified milk to at least pH 5.1, coagulating it and should be considered as Lac+. The differences in rates and degrees of acidification could not be related to the proteolytic activity which was, from all 27 representative strains tested, similar to that of Lactococcus lactis Prt– variants.