Winemaking Terms Defined: Fermentation Terms

Here are a few terms used by home winemakers to describe the fermentation process:

alcohol by volume (ABV)  the percentage of alcohol in a wine.

Brix  one of the scales on a hydrometer, the one that tells you the percentage (known as degrees) of sugar in juice or wine. Also called Balling scale.

cap  a layer of fruit pulp, skins and seeds that floats to the top during fermentation.

chaptalize  (SHAP-tuh-lize) to add sugar, either to a juice to create more alcohol during fermentation, or to a finished wine to sweeten it.

cold stabilization  to place wine in a cool temperature environment for a period of time, to help it clarify and to let any excess tartaric acid settle out.

fermentation  conversion of sugar to alcohol by yeast.

lees  sediment that falls to the bottom of a container during fermentation. Gross lees contain fruit pulp. Fine lees are mainly dead yeast.

macerate  to soak skins, seeds and pulp in the juice during part of the fermentation to release tannins and other compounds that contribute to flavor or color. Maceration is a common process with red wines and some fruit wines.

malolactic fermentation (MLF)  a second fermentation sometimes used for red wines to soften their taste, during which malic acid gets converted to lactic acid.

must  the wine while it’s in the initial stages of fermentation.

oak  to age wine in an oak barrel or with oak chips submerged in it, to add tannin and various taste notes to the wine.

pH  scale for measuring the strength of an acid. A value below 7 means the substance is acidic; the lower the number, the stronger the acid.

pomace  the skin, seeds and pulp left after juice is removed during pressing.

potential alcohol (PA)  one of the scales on a hydrometer, the one that tells you the estimated percentage of alcohol that could be produced if all the sugar in a juice or wine is fermented.

punch the cap  to push down and submerge the layer of fruit pulp, skins and seeds that floats to the top during fermentation, to aid in flavor extraction and to prevent it from spoiling.

rack  to move the wine from one container to another using a flexible plastic tube and a siphon device. Any sediment at the bottom is not moved with the wine.

residual sugar  any sugar that remains in the wine when fermentation is complete.

sanitize  to sterilize equipment using a sulfite solution. It’s important to sterilize with something that kills unwanted microbes but not wine yeast.

specific gravity (s.g.)  one of the scales on a hydrometer, the one that measures how dense the juice or wine is compared to water.

stuck fermentation  fermentation that has stopped prematurely before the desired amount of alcohol has been achieved.

stabilize  to stop fermentation so the wine can be bottled. This is achieved by filtering to remove the yeast or by adding potassium sorbate to prevent the yeast from reproducing.

titratable acidity (TA)  the amount of acids in a wine. Not to be confused with pH, which is the strength of the acids in a wine.

top up  to add a liquid to wine so it fills the container to the desired level. Water, juice or a finished wine may be used.

transfer  to siphon wine from the primary to the secondary container. Sometimes referred to as the first racking, but differs from racking because yeast (fine lees) may need to be transferred with the wine this time in order to allow complete fermentation.

Some resources were used from winemaking.jackkeller.net.