REASSESSMENT OF THE INFLUENCE OF MALOLACTIC FERMENTATION ON THE CONCENTRATION OF DIACETYL IN WINES

Diacetyl, a flavor compound having a distinct buttery character, accum ulates during alcoholic and malolactic fermentation (MLF) of wine. In an effort to investigate the occurrence of this compound in US Chardon nay wines, 41 wines from 36 wineries were analyzed for their diacetyl content. Malic and lactic acid concentrations were used as an indicati on of the occurrence of malolactic fermentation. Concentrations of dia cetyl in these wines varied from 0.005 mg/L to 1.7 mg/L. Diacetyl conc entrations higher than aroma threshold were measured in 68% of the win es. Significantly higher diacetyl concentration (p < 0.02) were measur ed in malolactic wines. Concentrations both higher and lower than indi vidual sensory thresholds were, however, measured in wines that had un dergone and not undergone malolactic fermentation. These results sugge st that, depending on the tasters diverse ability to perceive the flav orant and on the winemaking practices, diacetyl may contribute to the flavor of Chardonnay wine irrespective of the occurrence of malolactic fermentation.