How Wine is Produced

Wine is made from the fermentation of grape juice. But, there is a little more to it than that, otherwise we would all be doing it!

There are six factors that influence the final product in the bottle:

1. Grape variety

   Not all grapes make a drinkable wine. If you made wine from your standard table grapes, you would be sorely disappointed!

   For those who want the technical terms, most wine is made from vines belonging to the species vitis vinifera...however, using this term at dinner parties will only get you blank stares at best.

   There are over 3000 varieties derived from vitis vinifera (yep, some poor sod counted) that are known to produce wine.

   Of course, the important thing is that each grape variety has its own characteristics that influence the final taste.

2. Climactic conditions

   To grow any sort of plant variety, let alone fruit, you need climate conditions that are suitable. In the case of grapes, you need to ensure that the climate will allow the grapes to ripen satisfactorily. Just as you can't grow apples in all parts of the world, so too with grapes. That is why production of wine is limited to certain areas of the world, most notably France, Italy, Spain, Portugal, Germany, South America, North America, South Africa, Australia and New Zealand.

   In general, for grapes the ideal climate includes:

   • Winter - cold enough for the vine to rest, perhaps with enough frost to kill diseases, but not enough to harm the vine. Not too dry, as the soil needs to build some moisture.
   • Spring - Mild and warm with sufficient light rain to feed the vine's growth. During flowering, wind and rain need to be moderate enough to not cause any damage.
   • Summer - Warm and sunny with enough moisture to ripen the fruit.
   • Autumn - An extended, dry season to aid in the ripening and harvest conditions.

   Too much rain can cause rot, too much wind and frost can damage the vines, and too little heat and rain can cause the fruit to not ripen fully.

3. Weather patterns

   Each year, each individual area's climate will have variations of its annual weather patterns - more heat, longer dry spells, higher wind. All of these variations affect the final fruit, and therefore the final product. It is why vintages can vary from year to year for the same wine from the same vineyard.

4. Soil

   In general, the grape vine likes to struggle. It tends to like poorer quality soil that forces it to grow extended root systems to tap into its food. The deeper the root systems, the more nutrients and minerals extracted from the soil. The soil does require excellent drainage to avoid rot issues.

   On a little less scientific note, certain types of wine styles and grapes tend to obtain different qualities of taste and texture from different soil types. High limestone or chalky soils seem to produce excellent chardonnay, for example. This "mystical match" of how individual soils can affect the wine is one of the factors that makes selecting sites for growing vines more of a lottery than it would seem!

5. Viticulture or, growing the grapes

   This is the term used to describe the art of tending to the grapes as they grow. This includes everything from how the vines are pruned, trained, (how the grower encourages the growth of a shape agreeable to attracting favourable sun, rain etc) fertilized, ploughed, sprayed for pests and diseases, protected from wind, irrigated (if allowed by local laws) and harvested. For some styles of wine, the grape grower has to worry about encouraging what would normally be seen as a bad thing, as in the case of the fungus botrytis cinerea. Getting it right produces Noble Rot, shrivelling the grapes and concentrating the sweet juice for sweet dessert wines. Getting it wrong produces grey rot, which just produces bad fruit!

   For harvest, machine picked grapes include a fair bit more stalk, leaf, lizards, birds - basically anything that has gotten in the way of the machine! Hand picked grapes for obvious reasons include a little more proper grape matter and quite often better quality grapes too, as fruit that does not meet quality standards can be discarded by hand pickers.

   In the end though, poor viticulture will produce poor fruit, and poor fruit makes bad wine!

6. Vinification or, making the wine once the grapes are picked!

   White Wine

   • Crush

     The picked grapes are firstly put through a crusher. Grape juice is colourless, so white wine can be made from both "white" and "black" grapes.

   • Press

     The skins from the crusher go through a press to extract further juice. Generally, the more of this pressed wine that is included, the more tannin taste the wine will have from the stalks, skins and pips.

   • Fermentation

     The juice, referred to as must, is then put into a fermentation vessel. The skins and other matter left over in the press are discarded. The chemical reaction when yeast and sugar come into contact with each other then starts to produce alcohol and carbon dioxide. When all the sugar is "consumed" by the yeasts, the wine is left "dry" - in other words, all the sugar from the fruit juice is gone. If the winemaker wants to make a "sweet" wine, they need to either halt the fermentation before all the sugar is consumed, or introduce grape must that has not been through fermentation. This process is called chapitalisation.

   • Racking & Fining

     The juice then goes through the process of racking, which is running the wine off the dead yeasts, known as the lees. It can also be fined, which is done to remove substances within the wine that can cause problems after bottling, such as haziness. Substances such as gelatine, egg white or bentonite are mixed with the wine, gradually settling at the bottom attracting the substances to them where they are removed.

   • Maturation

     The important thing for maturation is that the wine rests for enough time to allow the flavours to develop and integrate. It is also important that the wine does not come into contact with air. Air causes wine to oxidize and spoil. Many styles of wine mature in stainless steel tanks, however many styles of wine mature in oak casks, which impart their own flavours to the wine.

   • Filtration & Preservative

     Prior to bottling, the wines will often go through a chilled filtration to extract further sediment, and will also often have sulphur dioxide levels in the wine adjusted to protect the wine from spoilage due to various kinds of bacteria.

   • Bottling

     The final product is bottled and shipped!

   Red Wine

   The differences when making red wine are:

   • Crush

     Grapes are crushed. Red wine is made from "black" grapes, as the colour comes from the skins.

   • Fermentation

     The entire product from the crusher is then introduced to the fermentation vessel. So, the main difference between white and red wine is that the skins are included in the fermentation, which results in the colour of the wine. Rose wines will be run off the skins and into a further fermentation vessel after only a few hours and thus have extracted less colour. Red wine will stay in contact with the skins longer. Generally speaking, the more full bodied the wine, the longer it has stayed in contact with the skins, often up to two weeks.

   • Press

     What is left is pressed further - the more highly pressed, the higher the colour in the wine, and again the higher the tannin content in the resultant wine. This harder pressing of the wine is referred to as having higher maceration.

   For sparkling wines, the carbon dioxide is trapped in the wine during fermentation and not allowed to escape, creating an effervescence. This can produce either a fully sparkling style of wine, or in smaller amounts simply give the wine a slight spritz, eg many styles of Lambrusco.

   At this the end of the fermentation period, most wine will have at most an alcohol content of about 15%. Liqueur wine will have further spirit added to the must, either during or after fermentation. For Port, for example, the spirit is added during fermentation, whilst with Sherry, it is added after.