FORMATION AND DEGRADATION OF DIACETYL IN WINE DURING ALCOHOLIC FERMENTATION TH SACCHAROMYCES-CEREVISIAE STRAIN EC11 AND MALOLACTIC FERMENTATION WITH LEUCONOSTOC-OENOS STRAIN MCW

Diacetyl accumulates in wine during alcoholic and malolactic fermentat ion (MLF). In an effort to understand the factors influencing the fina l diacetyl content of wine, we followed the changes in diacetyl concen tration in Cabernet Sauvignon and Pinot noir wines throughout alcoholi c fermentation with the widely used wine yeast Saccharomyces cerevisia e strain EC1118, during MLF with Leuconostoc oenos strain MCW, and dur ing storage. The effect of presence of yeast on the evolution of diace tyl concentration during MLF was investigated using the following trea tments: (1) wine; (2) wine plus 60 mg/L sulfur dioxide; (3) sterile fi ltered wine; (4) wine plus Leuc. oenos strain MCW; and (5) sterile fil tered wine plus Leuc. oenos strain MCW. Diacetyl concentrations increa sed linearly during alcoholic fermentation and then declined. No reduc tion in diacetyl concentration occurred after sterile filtration of wi ne or addition of 60 mg/L SO2 to Pinot noir wine. An increase in diace tyl concentrations was observed two days after inoculation with malola ctic cultures. Presence of S. cerevisiae EC1118 in wines inoculated wi th Leuc. oenos strain MCW resulted in lower diacetyl concentration thr oughout the course of MLF. Final concentration of diacetyl in MLF wine s was brought to a concentration below sensory threshold about 20 days after completion of malolactic fermentation, both in the presence and absence of S. cerevisiae. Utilization of diacetyl by Leuc, oenos stra in MCW, as well as other strains, was demonstrated.