Impact of winemaking practices on arginine and citrulline metabolism during and after malolactic fermentation

Abstract

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.

Malolactic Fermentation: The ABC’s of MLF

“…Inhibition of the LAB population immediately after the completion of MLF could avoid the formation of citrulline from arginine and concomitant EC formation (Terrade & Mira de Orduña, 2006).…”

The essential amino acids requirements for Oenococcus Oeni growth and organic acids metabolism

“…There is a hypothesis that O. oeni cannot synthesize cysteine and glutamic acids put forward by Vasserot et al (2001), and linked to a fully inoperative citric acid cycle. Besides, some other amino acids were proved to be essential acids for O. oeni when omitted from media, such as asparagine and isoleucine (Saguir and Manca de Nadra 1997;Terrade and Orduňa, 2006). However, in our study, O. oeni SD-2a is not sensitive to isoleucine but indeed has 28% growth rate reduction in media without asparagines (Table 2).…”

Arginine and citrulline do not stimulate growth of twoOenococcus oenistrains in wine

“…It has been suggested to carry out MLF with pure O. oeni strains and to inactivate the biomass after malic acid depletion in order to prevent other metabolic transformations that could lead to wine quality degradation (Terrade & Mira de Orduña, 2006). However, this technique may only be beneficial if, at the same time, the activity of other wine LAB with different substrate utilization pattern, such as L. buchneri CUC-3, is prevented effectively over time.…”