Malic Acid in Wine: Origin, Function and Metabolism during Vinification

Abstract

The production of quality wines requires a judicious balance between the sugar, acid and flavour components of wine. L-Malic and tartaric acids are the most prominent organic acids in wine and play a crucial role in the winemaking process, including the organoleptic quality and the physical, biochemical and microbial stability of wine. Deacidification of grape must and wine is often required for the production of well-balanced wines. Malolactic fermentation induced by the addition of malolactic starter cultures, regarded as the preferred method for naturally reducing wine acidity, efficiently decreases the acidic taste of wine, improves the microbial stability and modifies to some extent the organoleptic character of wine. However, the recurrent phenomenon of delayed or sluggish malolactic fermentation often causes interruption of cellar operations, while the malolactic fermentation is not always compatible with certain styles of wine. Commercial wine yeast strains of Saccharomyces are generally unable to degrade L-malic acid effectively in grape must during alcoholic fermentation, with relatively minor modifications in total acidity during vinification. Functional expression of the malolactic pathway genes, i.e. the malate transporter (mae1) of Schizosaccharomyces pombe and the malolactic enzyme (mleA) from Oenococcus oeni in wine yeasts, has paved the way for the construction of malate-degrading strains of Saccharomyces for commercial winemaking.

The Biochemistry of Malic Acid Metabolism by Wine Yeasts – A Review

“…Biological deacidification of wine with malolactic fermentation has been the method of choice for most winemakers as it is perceived to be a natural or spontaneous process (reviewed in Volschenk et al, 2006). However, due to inherent problems associated with malolactic fermentation, alternative biological methods for the deacidification of wine have been investigated, including the heterologous co-expression of the S. pombe malate transporter (mae1) and malic enzyme (mae2) genes, as well as mae1 together with the Oenococcus oeni malolactic gene (mleA) gene.…”

“…The different chemical and biological factors that contribute to the presence, role and degradation of L-malate during wine fermentation have been discussed in detail by Volschenk et al (2006). The traditional method to deacidify wine involves the conversion of Lmalic acid to L-lactic acid and CO2 during malolactic fermentation by strains of Oenococcus oeni.…”

Malolactic Fermentation: The ABC’s of MLF

“…The major species of LAB present at this stage include Lactobacillus plantarum, Lactobacillus casei, Leuconostoc mesenteroides, and P. damnosus, as well as O. oeni to a lesser extent Lonvaud-Funel et al, 1991;Boulton et al, 1996;Powell et al, 2006). Most of these LAB species generally do not multiply and decline towards the end of AF, with the exception of O. oeni Lonvaud-Funel et al, 1991;Van Vuuren & Dicks, 1993;Fugelsang & Edwards, 1997;Volschenk et al, 2006). The decrease could be attributed to increased ethanol concentrations, high SO 2 concentrations, low pH, low temperatures, the nutritional status and competitive interactions with the yeast culture (Fugelsang & Edwards, 1997;Volschenk et al, 2006).…”

Determining the Impact of Industrial Wine Yeast Strains on Organic Acid Production Under White and Red Wine-like Fermentation Conditions

“…However, yeast releases a number of additional organic acids, resulting in changes in the final taste and an overall acidification of the wine (Volschenk et al, 2006). The three most prominent acids produced by yeast during fermentation are succinic, acetic and pyruvic acid, while the release of small amounts of fumaric and malic acid has also been reported.…”