AIMS: To study arginine degradation and carcinogenic ethyl carbamate precursor citrulline formation during and after malolactic fermentation (MLF). METHODS AND RESULTS: MLF was induced in white wine with two commercial Oenococcus oeni strains under different winemaking conditions regarding the type of alcoholic fermentation (spontaneous, induced) and the lees management (racked, on lees). Arginine degradation and citrulline formation did not occur during malic acid degradation in any treatment. In five of the six treatments in which arginine degradation took place, it occurred 3 weeks after malic acid depletion and significant amounts of citrulline were formed. Presence of yeast lees in wines led to increased citrulline formation. CONCLUSIONS: This study suggests that arginine metabolism is inhibited in oenococci at low pH values (< 3.5) and that in the postalcoholic fermentation phase, citrulline formation from arginine degradation can be avoided if MLF is induced by pure cultures of O. oeni with inhibition of the bacterial biomass after malic acid depletion. Residual yeast lees in the wine have been identified as a significant risk factor for increased citrulline formation. SIGNIFICANCE AND IMPACT OF THE STUDY: Conclusions drawn from this study allow reducing the risk of carcinogenic ethyl carbamate formation from citrulline excretion by wine lactic acid bacteria.
AIMS: To study arginine degradation and carcinogenicethyl carbamate precursor citrulline formation during and after malolactic fermentation (MLF). METHODS AND RESULTS: MLF was induced in white wine with two commercial Oenococcus oeni strains under different winemaking conditions regarding the type of alcoholic fermentation (spontaneous, induced) and the lees management (racked, on lees). Arginine degradation and citrulline formation did not occur during malic acid degradation in any treatment. In five of the six treatments in which arginine degradation took place, it occurred 3 weeks after malic acid depletion and significant amounts of citrulline were formed. Presence of yeast lees in wines led to increased citrulline formation. CONCLUSIONS: This study suggests that arginine metabolism is inhibited in oenococci at low pH values (< 3.5) and that in the postalcoholic fermentation phase, citrulline formation from arginine degradation can be avoided if MLF is induced by pure cultures of O. oeni with inhibition of the bacterial biomass after malic acid depletion. Residual yeast lees in the wine have been identified as a significant risk factor for increased citrulline formation. SIGNIFICANCE AND IMPACT OF THE STUDY: Conclusions drawn from this study allow reducing the risk of carcinogenicethyl carbamate formation from citrulline excretion by wine lactic acid bacteria.