| Volatile sulfur compounds has been assumed to arise from the metabolism of methionine and cysteine. However, the methionine concentration in cheese rises above the amount found in casein during aging, suggesting that alternative sulfur sources are present in milk. Hence we hypothesized: lactococci may acquire inorganic sulfur from milk, in addition to methionine and cysteine, to generate volatile sulfur compounds during cheese ripening.; A turbidimetric method to determine total sulfate content in milk was developed, showing an average sulfate content as 49mg/L ± 2.0mg/L.; Decrease in pH induced sulfate transport by lactococci and maximum transport occurred during exponential cellular growth-phase.; Incorporation of radio-labeled sulfur from sulfate was not detected in proteins on two-dimensional gels. Detectable volatile sulfur compounds were found in ML3 head-space. Radio-labeled volatile sulfur was detected in the head-space of all the three strains with scintillation counting. This study defined that lactococci can fix inorganic sulfur into volatile sulfur compounds. |
