Effects of the addition of fumaric acid on the spontaneous alcoholic fermentation of white grape must.

Consumer demand is driving the production of wines without added sulfur dioxide or yeast inoculation. However, this approach can lead to organoleptic defects or health risks due to unwanted microbial activity during alcoholic fermentation (AF). Lactic acid bacteria (LAB), responsible for malolactic fermentation (MLF), may also affect wine quality. Fumaric acid (FUM) inhibits LAB growth and could serve as an alternative to SO₂ in controlling MLF. The objective of this work was to study the effects of adding FUM (0.6 g/L) to natural white grape must without SO2 on the growth of LAB during spontaneous AF and after it. The results showed that during AF, in the absence of FUM, LAB can grow and achieve both MLF and sugar consumption. The ability to prevent MLF after AF was evaluated without and with ageing on lees for 60 days. Without ageing, FUM up to 0.6 g/L effectively inhibited LAB growth and prevented MLF, whereas the residual FUM after AF (0.1 g/L) was insufficient when Oenococcus oeni was inoculated. Ageing on lees promoted MLF, and did not reverse the inhibitory effect of FUM. The residual FUM may not be sufficient for complete MLF inhibition after AF. Therefore, it may be advisable to correct the dose of FUM to 0.6 g/L to ensure its complete inhibition.