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A year in the vineyard: June

What really goes into a bottle of wine? Many wines contain more than just the latest grape harvest, says Jonathan Hesford

I have seen a number of articles in the press and on social media about additives in wine and how producers should declare everything that has been used.

While wine is a pretty natural product made just from the fermentation of grapes, there are various things that are added to wines to improve them, alter them or make them more stable.

Many of those additives do not end up in the bottle but are used in the process, usually to remove something else. So let’s look at what might have been added.

First of all we have sulphites. I have written about these in the past. Essentially potassium metabisulphite is dissolved in water to create sulphur dioxide, which when added to wine will make it immune to bacterial spoilage and resistant to oxidation. These are very real risks to wine and why sulphites have been added for hundreds of years.

Winemakers may want to adjust their juice to make it more balanced. This includes adding water to dilute the sugar (and therefore reduce alcohol content). The addition of water is prohibited in France but permitted in the New World. Tartaric acid can be added to make the wines more refreshing and crisp.

Adding sugar (called chaptelisation in French) will increase the alcohol content and weight of the wine, while acidity can be reduced by adding calcium or potassium carbonate. Acid, sugar and de-acidification are all permitted but are controlled by regulations and restricted to those vintages and regions that require it.

Enzymes may be added to extract more colour, reduce protein content or extract more juice during pressing.  To ferment the wine, yeast is usually added alongside nutrients such as di-ammonium phosphate and thiamine. Sometimes malolactic fermentation, to convert malic acid to lactic acid is achieved by adding a laboratory-bred bacteria.

The second set of additives are those which are designed to remove things from the wine. Known as fining agents, they are mainly used for two reasons. The removal of tannins to make wines softer and smoother, ideal for early-drinking, is done by adding a protein, such as gelatine, casein, milk, egg-white or isinglass (made from fish stomach).

The fining agent attaches itself to the tannins and forms a sediment which can be filtered out. On the other hand, wines which have proteins in them (possibly as a result of adding a fining agent) can turn cloudy over time or if subjected to heat. Therefore most commercial wineries will remove protein by adding a fine clay called Bentonite or tannin powder, which again is filtered out.

Another visual problem, particularly in white wines, is the formation of crystals of potassium tartrate, which resemble bits of coarse sand.

To prevent this, wineries may either chill the wine and add some potassium tartrate to seed the precipitation of crystals in the tank before filtering or add mannoproteins to the wine to prevent precipitation at all.

Traditional barrel-aging on lees for several months in cold cellars reduces or removes the need for fining agents, protein stabilisation and tartrate crystal stabilisation.

When faults arise due to mouldy grapes, unclean equipment or poor fermentation they can be removed by the addition of chemicals such as copper sulphate, wood tannin, activated carbon or ascorbic acid. Carbon is also used to make Rosé and white wine look paler.

Many lower-priced red wines are given an oaky aroma and taste by adding oak powder or chips for a certain amount of time. This may be during or after fermentation and replaces the costly and laborious task of ageing the wine in oak barrels.

A lot of popular brands of wine have some sugar added to them before bottling to make them taste more fruity. This could be in the form of grape concentrate or simply glucose.

None of these additives are necessary in an ideal world, although many winemakers would argue that making wine without adding any sulphur dioxide is asking for trouble.

The lower the quality of grapes being used, the more things are needed to adjust the wine. Many of the measures discussed above are taken to create easy-drinking wines that do not risk putting off consumers with visible sediments, crystals or haze and to get the wine onto the shelf in as short a time as possible.

Therefore they are more likely to be used in cheaper, mass-produced wines. Traditional methods, using grapes of uniformly high quality, avoids the need for most additives.

Jonathan Hesford has a Postgraduate Diploma in Viticulture and Oenology from Lincoln University, New Zealand and is the owner, vigneron and winemaker of Domaine Treloar in the Roussillon –  visit

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