In Processing


I’ve often said “There are only two processes to winemaking. Flavours are created in the vineyard and extracted in the winery. The rest is only details”.

Every time someone speaks of a great new winemaking process such as cold maceration or délestage, it’s time to ask yourself “Is this consistent with the style of wine I want to make?” Will this improve my process or handicap it? Will this create a greater risk of something going wrong? Break the process down into its individual elements and consider the effect of each element on flavour development. For example, a prefermentation cold soak selectively extracts water soluble compounds whereas extended post fermentation contact selectively extracts alcohol soluble components. The influence of aeration is affected by the stage at which it occurs. An early aeration can oxidize tannins and diminish their solubility whereas later stage aeration will diminish tannin astringency but may contribute to bitterness.

In some ways there is less flexibility during white grape extraction, so winemaking is more affected by grape flavours. If you wish to suppress flavour extraction, for example when working with over ripe grapes whose cellular structure has begun to break down, then you may resort to a whole cluster press. This occurs when making the typical big alcoholic Chardonnays that are left to hang until the berry begins to become flaccid. If the typical destemming were used, then tannin extraction would be a problem. This style of winemaking typically occurs at an elevated pH and runs the risk of developing bitterness in the presence of higher tannin extraction. Whole cluster pressing is also used when making a sparkling cuvée. The first, gentle press will have very little tannin extraction and is considered to be the premium part of the cuvée. Each subsequent pressing will have higher tannin content and should be kept separate, and perhaps treated with isinglass or gelatin to precipitate the tannins.

 When working with aromatic grape varieties the strategy is completely different. In this case the objective is usually to maximize flavour extraction. There is a hierarchy of aggressiveness that can be used. The most common technique is to simply run the berries through a destemmer and then press. The aggressiveness of pressing and the thoroughness of crushed berries affect the level of extraction. Flavour extraction is also affected by berry pH and sulfite. A more aggressive extraction can be carried out by using cold maceration prior to pressing. A convenient timing for cold maceration is to destem and crush in the afternoon and press the next morning. Again, the amount of air contact and presence of sulfite affect flavour. If tannin extraction is expected to be a problem, then a small amount of gelatin or isinglass can be dispensed into the crushed berries after destemming. An even more aggressive extraction of white berries can be made by adding pectinase during maceration. In this case it is highly recommended that gelatine or isinglass be added during the maceration. Tannins will tie up pectinase and inactivate it.

With aromatic varieties much of the aroma is often present as non volatile terpenes. These compounds can only be detected by the nose after they are converted to the volatile form. Many yeast contain a beta glucosidase that can carry out this reaction, but if you’re wanting more aroma, you can buy the pure enzyme preparation from suppliers.

The way in which you extract berries can also affect the stability of the resultant wine and its eventual sulfite requirement. Pre fermentation oxygen contact causes browning, especially noticeable in white wines. This results in wine that has a lower bound sulfite and is more heat stable without treatment. The down side is that you may also diminish varietal character if your oxidation is too aggressive.

I haven’t touched on the ways in which a vineyard can be manipulated to develop flavours nor have I suggested ways of blending different varieties. I’ve heard it said that if an identical batch of grapes were split among a dozen winemakers, they would still produce a dozen different wines. Even winemakers with the same training eventually develop a preferred pattern that results in recognizable differences. The potential process variations are essentially infinite. Every time the winemaker touches the process he leaves his fingerprint.

 Gary Strachan is an expert consultant and planner for the grape and wine industry. He can be reached at

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