Winemaker Intervention
Degree of winemaker intervention can determine how clearly the terroir will (or will not) be expressed.

The Principal Constituents of Grapes
Sugars: The main sugars are glucose and fructose. These obviously build during the growing season.

Acids: The most prominent acid in fully ripe grapes is tartaric acid. Malic acid is also present and will be higher in unripe grapes. Acidity drops during the later stages of the ripening process.

Minerals: There are many minerals but potassium is the most prominent.

Polyphenols: Tannins and bitter compounds found in the skins, seeds and stalks.

Anthocyanins: Give colour to the fruit.

Flavouring components: The basic aroma of grape juice is due to flavour compounds contained in the cells situated on the inner surface of the skins. These are leached out during the maceration process.

Fermentation
Sugar + Yeast = Alcohol + Carbon Dioxide
Must weight (measured in Brix, Baumé or Oechsle with a refractometer)
17 grams/litre of sugar = 1% alcohol by volume

Pressing
Gentleness is very important

Various presses:
Traditional (vertical) – Vaslin (horizontal) – Pneumatic

Treatments
Chaptalisation
Chaptalisation is the addition of sugar to the must prior to or during fermentation. It has nothing to do with sweetening the resultant wine, its all about the potential alcohol level. It is sometimes used as a vinification technique to promote certain characteristics but is banned in many countries. Chaptalisation is strictly controlled where it is permitted.

Sulfur
The use of sulfur dioxide in its various forms is an integral part of grape-growing and winemaking today. The quantity used and the time at which it is used is very important.

Positives:
In the vineyard, many sulfur based sprays used to combat mold and mildew e.g. Bordeaux mixture (Bouillie Bordelaise in French is a mixture of lime, copper sulfate and water). Sulfur is also used to prevent fermentation of grapes during shipping and storage.

In the winery, it protects juice and wine from oxidation… 1 molecule of sulfur will combine with 2 molecules of oxygen to form SO2 (sulfur dioxide). Sulfur is also used for its antibacterial properties and will prevent spoilage due to acetobacters.

(Acetobacters: Genus within the family of Acetic Acid Bacteria (AAB) capable of spoiling wine by converting it ultimately into vinegar. They are found on all grapes but especially rot-affected grapes.)

Sulphur is also used as an antioxidant where it inhibits the negative effects of oxygen at many stages of the production. And finally, it is used as an antiseptic and is considered essential in maintaining hygienic winery equipment.

Negatives:
Hydrogen sulphide (H2S) forms when sulfur reacts with yeasts during fermentation, it smells like rotten egg gas. If H2S is left untreated it will react with other chemicals (most notably ethyl alcohol) to form these potent chemical compounds which are called mercaptans. It can smell like burnt rubber, rotten game or rancid garlic. The resulting flavour of the wine will generally be bitter and astringent.

Yeast Selection
Yeasts can be divided in 2 categories: Natural (or wild), which are found on the grapes, and cultured, which are developed in laboratories to attain specific characteristics. Saccharomyces cerevisae is the name of the yeast most widely used for wine and beer making. Wild yeasts operate in aerobic conditions while wine yeasts operate in anaerobic conditions.

Acidification
Acidification is the addition of acid and is pretty much standard practice in the New World. It is best done prior to or during fermentation. Tartaric acid is most commonly added.

Deacidification
Deacidification is achieved by adding calcium carbonate. Malolactic fermentation is another way of lowering acidity.

Making sweet wine
There are several methods that can be used. One can let fermentation stop naturally or can also filter the wine through a membrane filter. Alcohol can also be added or a heavy dose of sulfur to create SO2.
Sussreserve is concentrated must that is added, mostly used in production of cheap wines.

Malolactic fermentation
MLF is when lactic bacteria converts malic acid to lactic acid, it softens the acidity. It can either be encouraged or inhibited. Most red wines go through MLF. As for white wines, it depends on the style the winemaker wants to achieve.

Carbonic maceration
Carbonic maceration is also called whole berry fermentation. It is done in a vessel that has had all the oxygen removed. The natural transpiration of the grape is halted and the grape essentially begins to die. Intracellular fermentation takes place. This is where the grape’s own enzymes start to attack the structure of the grape. This carries on for 5 to 15 days at a temperature of 35°C and produces aromatic substances and about 2 – 3% alcohol. Regular fermentation takes place afterwards. The purpose of this is to produce light-bodied, brightly colored, fruity red wines for early consumption. This technique is used most famously but by no mean exclusively in Beaujolais.

Maturation
When oak is used to mature wine, there are several factors taken into account:
-The tighter the grain the better
-The size of the barrel
-The type of oak
-The amount of toasting
-Legislation governing maturation

Regional oak varieties
Quercus alba
Fast growing wide grained white American oak that has more pungent aromatics. The barrel-making techniques contribute to the “coconut” character. The sawn staves release more aromatic substances especially vanillin.

Quercus robur and Quercus sessilis
Tighter grained European brown oaks give more, but finer tannins. Staves are split.
Troncais, Allier, Vosges and Nevers are the most well known of the French forests and are all from the Quercus sessilis family. These are forest oaks as opposed to solitary trees that grow straighter trunks and have branches that start higher. It is also four times richer in aromatic compounds.

Stabilization
Operations undertaken to ensure that the wine will not form hazes, clouds or unwanted deposits once bottled. Everyday wines are more stabilized than fine wines.

Physical and chemical stability
Cold stabilization will reduce the concentration of tartrates
Casse: Wine fault involving spoilage either by an excess of copper, iron or protein precipitation.

Microbiological stability
Yeasts and bacteria can sometimes cause undesirable reactions in wine such as a second fermentation if residual sugar level is too high. Acetobacters, which turn wine into vinegar, can also form. SO2 is the cure.

Fining
Fining is done to remove suspended matter. Different substances are used to coagulate with the suspended matter and precipitate the fining. Most widely used substances are:
Egg white, bentonite, isinglass, which is obtained from the bladders of fresh water fish and ox blood.

Filtration
If the winemaker decides to filter the wine, there are four basic types that can be used:
-Earth filtration
-Pad (sheet) filtration
-Membrane filtration
-Cross-flow filtration

Bottling
White wines are bottled earlier than reds. There are 3 types of bottling:
-Hand bottling
-Cold sterile bottling
-Hot bottling

Most common wine faults
-Corkiness: Wine displays a musty taint i.e. smells like an old wet basement (Trichloranisol TCA)

-Oxidation: Excessive exposure to oxygen

-H2S: Hydrogen sulphide (see Sulfur above)

-Mercaptans: Result of untreated H2S

-Brettanomyces: Sometimes called Brett, usually considered a spoilage yeast strain since it can produce off-flavours in the wine.

-Volatile Acidity (VA): Ethyl acetate (Smells like glue or nail polish)

White wine making steps
-Harvest
-Crusher/Destemmer
-Prefermentation maceration in stainless steel tank for some aromatic wines (optional)
-Pressing
-Fermentation (Stainless steel tank or wooden barrels)
-Malolactic fermentation (optional)
-Maturation
-Racking
-Fining
-Cold stabilization
-Filtering
-Bottling

Red wine making steps
-Harvest
-Crusher/Destemmer
-Maceration and fermentation in stainless steel tank or wooden vats (This is where the “remontage” or “pigeage” takes place)
-Free run wine goes to barrels for aging (optional)
-Remaining must is pressed for press wine (optional)
-Malolactic fermentation (Stainless steel tank or wooden barrels – optional)
-Maturation
-Racking
-Fining
-Stabilization
-Filtering (optional)
-Bottling