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RESEARCH PRODUCT

Malolactic fermentation in white wines

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Abstract Malolactic fermentation (MLF) is an important process in wine production and involves the bioconversion of malic acid into lactic acid and CO2. However, many other biochemical reactions occur simultaneously, and several other grape must and wine compounds are also modified besides malic acid. Some can improve quality, while others may be detrimental to sensory quality or health. Among them, there are the synthesis of carbonyl compounds, esters, monoterpenes, volatile phenols, acetamide or mousy odor, methanethiol, dimethyl disulfide, methionol, 3-(methylsulfanyl) propionic acid, citrulline, or biogenic amines. The role of MLF in winemaking is triple: reducing the acidity of the wine, stabilizing wine by removing potential nutrients for other microorganisms, and producing aroma and flavor changes. In recent years, there has been a tendency to induce MLF also in white wines. Reasons for this increasing interest are diverse and largely depend on the variety, characteristics of the wine, and intention of the winemaker. For some producers, malic acid contributes to a green taste, which is considered detrimental to the quality; the MLF can fix this problem by converting it into lactic acid: smoother and with a different particular taste. For others, MLF can bring a bioprotection to the wines, avoiding spoilage or decreases in wine quality. Another aspect of the bioprotection of induced MLF in white wines, especially interesting in sparkling ones with a second alcoholic fermentation in bottles, is the prevention of hazing in bottles when a late and undesired MLF is produced, avoiding a big economic loss whenever it happens. Finally, the third reason is the change in organoleptic characteristics that an MLF induces in wine, and whites are no exception. Greater complexity in wine profile is obtained when MLF is conducted in white wines, which can be used to obtain new and different wines with a different personality and unique, pleasant, and distinguishing sensorial characteristics.