181. Induced O/R potentials, rates of growth and the volatile acid production of lactic acid bacteria in milk

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Abstract
The abilities of type cultures of lactic acid bacteria to reduce five O/R indicators in plain milk and yeast dextrose milk have been described and the factors influencing their behaviour in this respect discussed. Methylene blue, litmus and safranine appear to be of some diagnostic value for the differentiation of types. There is a marked correlation between rapidity of growth in milk, ability to reduce O/R dyes and the proportion of by-products. This relationship holds not only for the different groups and types, but also for variations in behaviour observed in species kept under laboratory observation. It is suggested that rate of growth is fundamentally related to the amount of by-products and hence presumably to flavour-producing substances such as diacety and acetic acid. Thus in cheese-ripening enforced slowness of growth may be as important as the presence of specific types.