Studies on the Malic Acid Fermentation of California Table Wines I. An Introduction to the Problem

¹ University of California, Davis
² Beaulieu Vineyards, Rutherford, California

There is a marked similarity between the secondary, bacterial malic acid fermentation of wines throughout the world and the one which occurs in California table wines, particularly the red wines, regardless of the district of production or storage within the State. This fermentation, which is characterized by decomposition of malic acid to lactic acid and carbon dioxide as major end-products, causes a decrease in total acidity, none to a negligible increase in volatile acidity, sometimes the appearance of an undersirable turbidity, and beneficial or detrimental alterations in the flavor and aroma of the wines thus infected. A number of different lactic acid bacteria are involved in this deacidification process.

It is speculated that the difference between a satisfactory and undesirable malic deacidification involves the ability of the different lactic acid bacteria involved to produce acetoin and diacetyl from this substrate.

Deacidification of California table wines frequently is undesirable. On the other hand, prevention of the malic fermentation requires an undesirable quantity of sulfur dioxide to keep the wine stable—a practice which adversely affects the organoleptic properties of any wine. Therefore, the problem is to determine whether by selection of bacteria a malic acid deacidification can be controlled so that off-flavors and odors will not develop.

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