Reduction of Malic Acid in Wine Using Natural and Genetically Enhanced Microorganisms

Abstract

Naturally selected yeast ICV-GRE and 71B, malolactic bacteria Lalvin 31, and genetically enhanced yeast ML01 were compared for biodeacidification of malic acid in production of Vignoles wines. ICV-GRE yeast consumed 18% of malic acid with no lactic acid production. Lalvin 31 added to the wine fermented with ICV-GRE converted the remainder of the malic acid to lactic acid and consumed some citric acid. The ICV-GRE + Lalvin 31 treatment produced less lactic acid compared with the ML01 treatment due to malic acid consumption by the ICV-GRE yeast and had the lowest titratable acidity. ML01 was effective at converting 5.7 g/L (100%) malic to lactic acid during the first 60 hr of fermentation. The 71B yeast consumed 1.9 g/L (33%) of the malic acid with no lactic acid production. Wine produced with ML01 had higher levels of total sulfur dioxide (SO₂) than the other treatments. A secondary experiment found that the ML01 yeast produced 34.6 mg/L SO₂, which was three times as much as produced by ML01 yeast could be of ICV-GRE and six times as much as 71B. The amount of lactic acid and SO₂ concern to enologists depending on style of wine desired.