The fourth lesson explored secondary fermentation. The lecture described in detail the conversion of malic acid to lactic acid. This malolactic conversion is going to affect the pH and TA levels. The lactic acid is less acedic than the malic acid. The secondary fermentation can stabilize the wine and change the flavor.
Some winemakers inoculate with ML strain rather than relying on native ML strain to begin the process. There is some debate on when to begin malolactic fermentation. There are those who argue that primary and secondary fermentations should be separate so that yeast and ML bacteria do not inhibit each other. However some winemakers have done studies on their own and concluded that this in practice is not the case. There are new stains of yeasts that can tolorate a malolatic fermentation going on at the same time. Perhaps when secondary fermentation is started is more of a winemaker’s style.
The flavor of the wine will change after secondary fermentation. Hopefully the wine will become less sour. Usually red wines undergo the malolatic fermentation. White wines depend on the variety and desired end product. Secondary fermentation can produce a buttery component which may be desireable in a Chardonnay, but not wanted in a tropical fruit forward Sauvignon Blanc.
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