Impact of acidification by fumaric acid at vatting on Cabernet-Sauvignon wine during winemaking

Abstract

AIM. Acidity of grape berries is lowered due to climate changes (1), resulting in musts and wines with higher pHs. These higher pHs induce microbiological instability and chemical modifications with damageable consequences on the color and the organoleptic qualities of the wines (2). To acidify musts, OIV authorizes different approaches such as the use of cation exchangers, treatment by electromembrane, microbiological acidification and chemical acidification. Chemical acidification, the most common, refers to the addition of lactic, malic and tartaric acids. Fumaric acid, known for its high acidifying power, its antimicrobial properties (3,4) but also its high availability, could be a good alternative to acidify musts chemically. Therefore, the present study aims at evaluating the impact of fumaric acid addition at vatting on wine quality in comparison with tartaric acid addition.

METHODS. Micro-winemakings were conducted with mature Cabernet Sauvignon grapes. Two treatments were applied at vatting in duplicate: 1.5g/L tartaric acid (TA) and 1.5g/L TA eq. fumaric acid. Three vats were untreated (controls). Oenological (pH, total acidity, tartaric, malic and lactic acids) and color (CIELAB) parameters, phenolic compounds (total polyphenol index, Folin-Ciocalteu, total free anthocyanins and total tannins) and antioxidant capacities (DPPH, CUPRAC, ORAC) were evaluated at vatting, end of alcoholic fermentation (AF) and malolactic fermentation (MLF). A ranking test and sensory profiles were realized on three-months wines after bottling.

RESULTS. Acid addition at vatting induced an immediate decrease of pH, an increase of total acidity and a change of color but at the end of MLF these changes were attenuated and even disappeared. Total phenolic compounds and antioxidant capacities in post-MLF wines were not or slightly affected by acidification. The major difference was observed for malolactic acid production during MLF. Indeed, wines treated with fumaric acid produced 20% more lactic acid than control and TA-acidified wines. 

CONCLUSIONS

Addition of FA at 1.5g/L tartaric acid eq. during vatting induced a 20% increased production of lactic acid in wine which did not allow a pH decrease or an increase of total acidity in resulting wine compared to control wine. To acidify wines, acid fumaric should be added at another step of winemaking. A current study is investigating FA addition at the end of AF and just before bottling.