Today racked our 20 gallons of wine. Racking involves siphoning the wine from the sediment. It is essential to the clarification of the wine and helps inhibit the production of unwanted off-flavors. Chromatography shows that our malolactic acid fermentation is complete and we have no more lactic acid in the wine. We added american oak chips to the wine and now we wait.
I tested the Brix with a specific gravity tester and it was 0. Towards the end of fermentation there is a fairly sizeable group of healthy, active yeast cells floating throughout the must that are running out of food (sugar). Once all of the sugars have been consumed, this active, now-starving group of yeast will start a process that can only be described as cannibalization.
The active yeast will instinctively start producing an enzyme that will break-down the dead yeast cells that lay on the bottom. This is done so that dead yeast’s nutrients can be released and utilized by the still-active yeast. This break-down process is known as “autolysis” and its effects can eventually ruin a wine. If given enough time–weeks, not days–this process can produce off-flavors in a wine that range from bitter, to rubber, to even metallic.
Next step should be another racking in about 4 months. Eric suggests adding about 4 grams of Potassium Metabisulfite to the wine to keep it clean.
Meng,
Your wine has finished malo-lactic fermentation. I recommend that you add 3.75 grams of potassium metabisulfite to your 20 gallons of wine. Let me know if you have any questions. Thanks!
-Erik Golobic
Fermentation Solutions
(408) 871-1400
Time to Prune the vines soon also. Much to learn
