How to make wine - FAQ

Questions and answers

What is chaptalisation?

Simply put, it is adding sugar to the grape juice to increase the potential alcohol of the wine.

It is often used in northern Europe which sometimes stuggles to ripen its grapes in its cooler climes. Another technique, enrichment, can be used to increase the potential alcohol of a wine - this is the addition of rectified concentrated grape must (RCGM).

The addition of sugar or RCGM is falling, perhaps due to climate change.

What is malolactic fermentation?

This is the conversion that turns harsh-tasting malic acid into softer lactic acid.

Lactic bacteria are responsible for the conversion. The bacteria like to operate in a warm cellar and traditionally this meant winemakers had to wait until the spring following the harvset for the malolactic fermentation to occur. However, modern cellars can be heated up to allow the malolactic fermentation to start as soon as possible. In addition, many commercial wines will have lactic bacteria (from a packet) added to the wine as soon as alcoholic fermentation is finished.

Some wine styles are not put through malolactic fermentation as producers want to keep the zingy acidity in varieties such as Riesling and Sauvignon Blanc. To stop the malolactic occurring, winemakers will add sulphur and cool the wines.

Wines high in acid/low pH, which would benefit from malolactic fermentation are ironically the most unliokely to go through malolactic as the bacteria does not like high acid environments.

All red wines go through the malolactic fermentation

What's the difference between Amarone and Recioto della Valpolicella?

They are both made from dried grapes.

However, Amarone is a dry wine while Recioto is a sweet wine.

Both wines must be made from 40-80% Corvina grapes and need to be raisined in special drying lofts or drying rooms (aka appassimento) for several months after they have been picked.

Amarone is a rich, dry wine normally reaching alcohol levels of 15%. Once the grapes have been dried, they are crushed and fermented to dryness (but not before 1 December following the harvest). The fermentation takes a long time as the grapes lose around half of their liquid while they are being dried and are very rich in sugar. The wine is then aged in cask or, increasingly, barrique. The legal minimum alcohol for Amarone is 14% but the majority reach 15% and higher.  They can taste like vintage Port but drier and without any fortification.

Recioto della Valpolicella cannot be crushed until 1 January and is then fermented. It is a sweet, unfortified wine with lots of fresh black fruit and cholocate. It usually reached an alcohol level of 12% with a high residual sugar of 250 grams/litre).

How many grams of sugar do you need to make 1% alcohol

Roughly 17g/l of sugar is needed to produce one degree of alcohol.

So, if a grape is picked at 204g/l of sugar, it will produce a wine that has a potential alcohol of 12% (17 x 12 = 204).

What is fining?

The process of clarifying and stabilizing a wine.

If wines are left long enough, wines will naturally self clarify - and this is the method used for many fine wines. However, winemakers like to hurry along the process by using fining agents including egg white and bentonite. Fining removes 'colloids' which are molecules that include tannins, phenolics and polysaccharides.

If they are not removed, a white wine may appear cloudy and a red wine may be astringent and bitter.

There is an increasing tendency for natural wines that are neither fined nor filtered.

How many kilograms of grapes does it take to make one bottle of wine?

Approximately 1-1.2kg of grapes.

However, this depends on how hard the grapes are pressed. If you are only using the free-run juice which drains off the fruit without pressing, you will obtain less juice. The harder the grapes are pressed, the more juice is obtained. However, a larger quantity of juice obtained generally equates to lower quality with tannins and bitter flavours extracted.

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