Formation and stabilization of diacetyl and acetoin concentration in fully grown cultures ofStreptococcus lactis subsp. diacetylactis

Summary The effects of pH and temperature on diacetyl and acetoin concentration and diacetyl:acetoin ratio evolution of non-growing cells ofStreptococcus lactis subsp. diacetylactis CNRZ 124 were studied. A cooling down to 10°C allowed the cells to retain 6 to 10 times as much diacetyl. A large reduction of acetoin was promoted at pH 7 whereas a twice increase was observed at pH 4,8. As a result of these variations, the ratio diacetyl: acetoine showed an opposite evolution according to the pH.