WINE 101 | HOW WINE IS MADE - THE BASICS

The conversion of grape juice into wine is arrived at through the action of a single celled plant commonly referred to as yeast. Yeast is a thallophyte making it one of the lowest members of the vegetable kingdom along with algae, lichens and fungi. Saccharomyces is the scientific term used for yeast and it translates into ‘sugar fungus' .

Many different types of yeast strains are used in commercial winemaking almost all of which are now commercially cultivated and sold. Yeast then, is the catalyst in this conversion process. In order for yeast to grow and reproduce it needs a food source.

The fructose present in grape juice is yeast's main food source. Through a complicated biochemical process known as glycolosis, yeast will in an oxygen starved environment go on to convert fructose into three main by-products using a method universally known as fermentation .

The three main by-products are: alcohol, carbon dioxide and heat. This conversion or fermentation of grape juice into wine usually takes no more than a week, although in the case of some wines, it may take several. Many factors will affect the length of time required to complete an alcoholic fermentation including the yeast strain used and the temperature it is made to work at.

The family of grape plants responsible for almost all of the world's winemaking is known as Vitis Vinifera. Vitis vinifera grapes are known as the ‘noble' grapes in winemaking due to their high levels of naturally occurring sugars, acids and extracts. This makes them ideal for quality winemaking.

The basic steps in white winemaking are as follows:

1. De-stemming and crushing. After being de-stemmed (almost always mechanically), the berries are crushed by either manual or more often than not mechanical means so as to release their juice.
2. The combination of juice, skins, pips and pulp is then pressed using either a traditional basket or modern pneumatic bladder press so as to further release the liquid portion of the must or freshly prepared grape juice. The juice released upon the application of light pressure is referred to as ‘free run' juice. The juice released upon application of additional pressure is referred to as ‘press' juice and is usually of lesser quality. In some instances the two may be combined in order to produce a balanced end result. The must is then clarified (so as to free it of skins and excess pulp) using filtration and/or centrifugation prior to it being pumped into a fermentation tank. (It should be noted that skins are occasionally left in the must at some stage in order to enable some degree of extraction of color.)
3. Once ready, the must is pumped into the fermentation vessel(s), (either stainless steel or glass lined concrete tanks or oak barrels) where it is inocculated with the appropriate strain of yeast. The fermentation temperature is usually controlled and kept cool.
4. After a period of time, the newly fermented wine is usually racked or transferred from the fermentor into another vessel(s) so as to separate it from its lees (spent grape solids, dead yeast cells, etc.) at the bottom of the fermentor. As the wine travels from one vessel to another it is sometimes run through a centrifuge or filtration system so as to aid its clarification. Wines are also made clear through the use of fining agents such as egg whites or a fine clay known as bentonite.
5. Clarified wine will then be left to age either in stainless steel, concrete tanks and/or oak barrels prior to it being filtered and bottled. The aging period will vary depending on the style of white wine being produced. Some wines are left to age further in bottles prior to their being released.

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The basic steps in red winemaking are as follows:

1. De-stemming and crushing. After being de-stemmed (almost always mechanically), the berries are crushed by either manual or more often than not mechanical means so as to release their juice.
2. The combination of juice and skins is then pumped into a holding tank where it is left to macerate for several days at a cool temperature. Since most ‘red' grapes have white juice, this maceration period with the grape skins is critical as it is from the grape skins that red wines obtain their color.
3. Once the cold maceration is completed, the juice along with the skins is then pumped into a roto-fermentor or stationary fermentor where it is inocculated with the appropriate strain of yeast. Red wine is usually fermented at warmer temperatures than white, usually around 28C. Warmer fermentation temperatures allow for further extraction of color and tannin.
4. When fermentation of the must into wine is complete, the new wine is ‘pressed' using either a basket or pneumatic bladder press so as to extract the wine from the remaining skins and grape pulp. Gentle application of pressure releases what is referred to as ‘free run' wine, additional application of pressure releases ‘press' wine. The two wines may be combined in order to produce a balanced end result. These new wines are then pumped over into aging tanks where they will be allowed time to settle.
5. As wine settles in aging tanks it will over the course of several weeks go on to throw a layer of sediment. Eventually, the wine must be racked off of its sediment and pumped over into a clean aging vessel (either of stainless steel, glass lined concrete or oak). As the wine goes from vessel to vessel it is fined or clarified using a number of methods including filtration, centrifugation, bentonite or egg white fining.
6. After spending the necessary period of time in its aging vessel (or combination thereof), the wine is put through light filtration (or not) prior to being bottled. Some wines will undergo additional bottle aging prior to their being released.

Rose or blush wines:

These wines are produced from ‘red' grapes just as are red wines. The difference is that they are vinified in much the same way as whites albeit with limited skin contact with the juice just prior to fermentation. This limited skin contact is what accounts for their pink hues.

It is important to note that these are basic winemaking steps and that there are sometimes variations in what actually occurrs during the vinification process. Factors accounting for these variations are numerous and include such things as the particular winemaking philosophy of a given winemaker, local differences in climate, soil, grape varieties and clonal selections in addition to the specific types of winemaking equipment being used.

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