Published online by Cambridge University Press: 01 June 2009
The effect of ripening cow'milk cream (40% fat) with 4 strains of lactic acid bacteria on the quality of ghee, an Indian product resembling clarified butterfat, was studied by measuring changes in titratable acidity, pH, volatile acids and diacetyl content due to Streptococcus lactis, Str. lactis subsp. diacetylactis (Str. diacetylactis), Str. thermophilus and Lactobacillus bulgaricus in cream prior to conversion into ghee. L. bulgaricus produced the maximum titratable acidity (1·25% lactic acid) followed by Str. diacetylactis (0·80 % lactic acid) after 72 h. Str. diacetylactis produced the highest level of diacetyl (28 ppm), after 48 h. L. bulgaricus produced no detectable diacetyl. Both of these strains produced the maximum amount of volatile acids (2·2–3·5 ml), after 72 h. The flavour and keeping quality of ghee were improved by Str. diacetylactis and Str. lactis whilst Str. thermophilus and L. bulgaricus had no effect.