EFFECT OF FUMARIC ACID ON SPONTANEOUS FERMENTATION IN GRAPE MUST

Abstract

Malolactic fermentation (MLF)¹, the decarboxylation of L-malic acid into L-lactic acid, is performed by lactic acid bacteria (LAB). MLF has a deacidifying effect that may compromise freshness or microbiological stability in wines² and can be inhibited by fumaric acid [E297] (FA). In wine, can be added at a maximum allowable dose of 0.6 g/L³. Its inhibition with FA is being studied as an alternative strategy to minimize added doses of SO₂⁴. In addition, wine yeasts are capable of metabolizing and storing small amounts of FA and during alcoholic fermentation (AF). Our aim was to study the effect of FA addition in natural grape must without SO₂ on alcoholic and malolactic fermentation. AF was performed on Muscat of Alexandria grape must without SO₂ under two different conditions. i) Grape must 1 without FA, pH 3.49 and ii) Grape must 2 with 0.6 g/L of FA, pH 3.39; both had an L-malic acid concentration of 1.44 g/L. AF was developed at 20°C and spontaneously, monitored by must density determination. The evolution of L-malic acid and FA was monitored enzymatically⁵ and plate counts were performed for Saccharomyces, non-Saccharomyces and LAB populations. In both grape musts, no significant differences were observed in the development of AF. In grape must 1 MLF was performed during AF and produced a lactic bite. A progressive decrease in FA was observed in grape must 2 during AF, reaching 0.087 g/L at the end. From the wine obtained from grape must 2, two conditions were prepared i) a wine uncorrected with FA with a concentration of 0.087 g/L and ii) a wine with FA correction to 0.6 g/L. MLF was tried to take place at a temperature of 20°C under two new conditions, i) spontaneous and ii) with inoculation of O. oeni VP41 (Lallemand S.A.). MLF was monitored following the evolution of L-malic acid and LAB populations by plate count. MLF was not performed in all conditions, except for wines without FA correction inoculated with LAB. In conclusion, the addition of FA in must at pH 3.5 without SO₂ with low initial LAB populations may be an effective strategy to prevent MLF during AF in conditions of absence of SO₂. However, FA supplementation in the grape juice will not inhibit the subsequent development of the MFL in the wine, since a large part of this acid is metabolized by the yeasts, being necessary supplementing with FA again to ensure the non-development of malolactic fermentation in the case of high LAB populations.