Fermentation – Fact Friday

In order to make grape juice into wine fermentation must occur: During fermentation, grape sugars are converted into alcohol by yeast making the grape juice into wine. This week’s Fact Friday provides some vocabulary terms about the fermentation process.

Primary Fermentation – Alcoholic fermentation process occurs in the ‘primary’ stage. This is an aerobic stage in which air interacts with the wine allowing yeast to multiply up to 100 to 200 times it initial quantity. During the primary stage, large amounts of sugar in the grapes are converted into alcohol. Converted sugars are mainly glucose and fructose.

Secondary Fermentation – Another fermentation occurs during the secondary stage. This is an anaerobic stage in which air locks prevent air from reaching the wine. The secondary stage is a slow process where the taste of a wine becomes smoother due to malic acids converting to lactic acids (MLF).

Carbonic Maceration – Primary fermentation that occurs in the absence of oxygen.   This can occur naturally, with whole berry and whole cluster fermentation, or by surrounding the grapes with CO2.

Inoculate- To kill wild yeast and “add an active, selected culture of yeast or malo-lactic bacteria to a must, juice or unfinished wine”. (http://winemaking.jackkeller.net/glossary.asp)  We never inoculate.

Wild Yeast- The natural yeast readily occurring in our grapes. We only use wild yeast as we believe it provides a superior and healthier wine.

Stuck Fermentation- When yeast has become dormant before the fermentation process is complete in most cases destroying the wine (unless multiple chemicals are added). This has happened once to Donkey and Goat in 2004 during an experiment with inoculation. The stuck fermentation during our inoculation experiment further supported our preference for wild yeast fermentation.   There is another question as to whether stuck means slow or really stuck.   There have been examples of fermentations lasting 30 years.  One person’s stuck is another persons slow.