Inhibit malolactic fermentation through the use of fumaric acid

Dr. Serena Belfante – Laboratory Manager

Fumaric acid (FA) is an additive already permitted by Codex Alimentarius, and, as of 08/02/2022, has also been approved by the International Organization of Vine and Wine (OIV) to improve microbiological stability through the inhibition of malolactic fermentation.

Inhibition of MLF turns out to be an extremely topical subject, given the significant climate change and the increase in average temperatures, which result in the production of wines increasingly with high alcohol content and low total acidity, due to the degradation of malic acid naturally present in grapes. This makes it very important to preserve it from the action of malolactic bacteria, especially in wines in which the characteristic freshness imparted by this organic acid is essential.

Additives commonly used to safeguard malic acid, so as to prevent lactic acid bacteria activity, are sulfur dioxide and lysozyme. An interesting alternative, also with a view to reducing SO2 levels, is through fumaric acid.

The purpose of this work was to evaluate how the use of this organic acid, at different dosages (30 g/Hl and 60 g/Hl), could both prevent the development of MLF and stop it once it had started.

It can be observed that, from the same malic acid content, the higher dose of FA was able to preserve the malic acid, as it was able to stop the growth and metabolism of lactic acid bacteria (fig.1); as well as it was able to stop fermentation and not restart it. To confirm the latter mechanism, it is possible to notice the lactic acid value, which remained constant for more than 30 days. In addition, it is also evident how the dose of 30 g/Hl is not sufficient to stop the course of fermentation (fig 2).

From our results it can be concluded how fumaric acid is able to inhibit malolactic fermentation, even once it has started, thus enabling the production of fresh wines, increasingly appreciated by consumers, with microbiological stability and low SO2 requirements.

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