Reduction of Malic Acid in Grape Wine by Using Natural and Genetically Enhanced Micoorganism

Naturally selected yeast ICV-GRE and 71B, malolactic bacteria Lalvin31, and genetically enhanced yeast ML01 were compared for biodeacidification of malic acid in the production of Vignoles wine. ICV-GRE yeast consumed 18 % of malic acid with no lactic acid production. Lalvin31 promoted wine fermention like ICV-GRE and it converted the residual malic acid to lactic acid and consumed some citric acid. ICV-GRE plus Lalvin31 treatment produced less lactic acid compared with ML01 treatment (because malic acid consumed by the ICV-GRE yeast) and had the lowest titratable acidity. ML01 could effectively convert 5.7 g/L (100 %) malic acid to lactic acid during the first 60 h of fermentation.The 71B yeast consumed 1.9 g/L(33 %)of the malic acid with no lactic acid production.Grape wine produced with ML01 had higher level of total sulfur dioxide (SO2) than grape wine by other treatment. Secondary experiments found that ML01 yeast produced 34.6 mg/L SO2 (three times as much as ICV-GRE and six times as much as 71B).