Merlot Wine Case Study

1610 Words 7 Pages
Evaluating the benefits and problems associated with malolactic fermentation of Merlot wines

Emma Bruwer, 16122364, BSc Agric (Viticulture and Oenology), J.H Neethling Building, Victoria Street, Stellenbosch University.

Rudi Scholtz, Thelema Mountain Vineyards, Helshoogte Pass, Stellenbosch.
August 2015

Malolactic fermentation is the conversion of harsh and acidic malic acid to a more desirable form of lactic acid in wine by Lactic acid bacteria, after the completion of alcoholic fermentation. This reaction can take place naturally in wine, proving to be very unpredictable and not always favourable, or by inoculation with bacterial cultures. Malolactic fermentation (MLF) is mostly found in barrel aged red or white wines. For this
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The bacteria are environmentally sensitive and therefore the strain to be used was only determined at harvest with regards to the juice analysis.
For wine with a pH of 3.4, CH 11 was found to be the more suitable bacterium to use.
10 x 225L barrels of each vineyard block were inoculated and 10 barrels were left as the control for spontaneous fermentation.

The wines were analysed during MLF on a weekly basis to monitor the progress as well as track unfavourable compound production. The results are shown in figure 1.

Wine making process
The wine making procedure was followed according to the general practices of Thelema Mountain Vineyards. Whole berry fermentation was used; the bins were tipped into a destemmer where they were sorted to remove any unripe berries. A juice sample was taken from each treatment for analysis. General analysis was completed for pH, TA, Balling and malic acid concentration (analysis performed by Vinlab (Pty) Ltd).
Bisulfite 18, a product developed by Laffort incorporating potassium bisulphate and sulphur dioxide, was added to the grapes at 50 mg/L and the grapes were pumped into 20hL fermentation
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Sulphur dioxide (total and free) analysis was carried out using the Metrohm titration unit (Metrohm Ltd., Switzerland). Malolactic fermentation in the wine was monitored by obtaining the malic- and lactic acid concentrations on a regular basis (at the start of MLF and every seven days thereafter) until its completion (taken as the point when the malic acid concentration is equal to or lower than 0.3 gIL). This was done by Fourier-transform Infrared Spectroscopy (FT-IR) (WineScan FT120, FOSS Analytical, Denmark) as well as determination of the malic acid concentration with an enzymatic assay (Roche, Boehringer Mannheim,

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