Many people are under the impression that wine is simply the juice of grapes that has been fermented. They often do not realize that most wine undergoes chemical analysis as well as a variety of tests in order to pour out of the bottle the way the winemaker intended. During the winemaking process, a wine may have had a number of additives put into it. Although this does not cover every one of them, we’ll take a look at some of the more common ones:

Yeast

Yeast of course is what actually does the work of turning juice into wine. There are many different yeast strains, and often a winemaker will choose the particular strain for the qualities it will create in the finished product. Yeast selection may also be determined by the environment the wine is being made in. Some yeast strains tolerate different temperatures.

Yeast Nutrient

Often, a juice may not have all of the necessary nutrients to ensure good yeast reproduction, so a nutrient consisting of some vitamins and minerals may be added to ensure healthy yeast.

Pectic Enzyme

Almost all fruit contains some amount of pectin, which if not treated could cause a haze in wine. Pectic enzyme breaks down pectin and can help to extract flavor and juice from the fruit.

Potassium Metabisulfite (K-Meta)

Some people believe that sulfite in wine causes headaches, however sulfites are a common food preservative, and it is likely that it has been added at one or more stages of the wine making process. When the grapes are first picked, sulfite may have been sprinkled over the grapes to inhibit wild yeast and bacterial growth. It is often used in juices before they have been inoculated with yeast, and are almost always added when the fermentation has completed.

As well as inhibiting bacteria growth, sulfite helps protect against oxidation.

Sodium Metabisulfite

Although not as common today, sodium metabisulfite can be used in the same method as potassium metabisulfite. It is more commonly available in the form of “Campden Tablets.” However, due to health concerns of those on sodium restricted diets and the fact that K-Meta is slightly more effective, this form of sulfite is used much less as an additive but is still used to make sanitizing solutions.

Potassium Sorbate

Potassium sorbate is often used in conjunction with K-Meta to stabilize wine. It inhibits yeast from reproducing, thereby preventing any yeast cells that remain after fermentation to begin a new fermentation using residual sugar or sugar added to sweeten.

Clarifying (Fining) Additives

When wine is first made, it is very cloudy with yeast and other particles in suspension. Beginning home winemakers are often quite surprised and shocked at the appearance of wine when it first begins to ferment.

Often, these particles won’t quickly drop out of the wine as sediment, so clarifying additives are used to speed or help the clarification process. Particles in suspension have either a negative or positive charge, therefore clarifying agents have an opposite charge in order to attract the particles and help them along on their way to the bottom of the wine vessel to become sediment.

Common clarifying additives include:

Bentonite – a clay made of volcanic ash. Negatively charged and attracts positive charged matter. Isinglass – made from the air bladder of some fish, most notably sturgeon, cod and cichlids. It is a fairly benign clarifier as it does not strip flavors and colors as much as others might. Positively charged and attracts negative charged particles. Kieselsol – a negatively charged silica gel and used in both white and red wines. Very common in wine kits. Chitosan – often used in conjunction with kieselsol, cheitosan is positively charged. Made from the exoskeleton of crustaceans like crabs and shrimp. (Those who have a shellfish allergy need not be worried – allergies are due to proteins in the shellfish organism – not the exoskeleton). Casein – a derivative of milk and is used to reduce tannins in some wines. Gelatin – not recommended for white wines, but sometimes used in reds to reduce tannin.

Remember that fining agents are added to clarify wines. Therefore, there is very little trace, if any, left in the wine after they have done their job.

Bacteria

In some wines, the presence of malic acid is not desirable, therefore the winemaker may add lactic acid bacteria in order to have the wine undergo a malolactic fermentation. This causes the malic acid to become lactic acid, providing a smoother “mouthfeel.”

Sugar

While some sweet wines have been fermented with yeast that cannot tolerate higher alcohol percent which means the fermentation will stop with some residual sugar left over, other wines are fermented completely and then later sweetened with some type of sugar.

Now you know some of the more common additives used in the wine making process. This is not meant to be a comprehensive guide to every additive that is used, but a description of the more common ones to ensure the bottle of wine you open is clear, good to look at and full of the aromas and tastes that the winemaker intended.