The label may say Cabernet Sauvignon or Chardonnay but legally the bottle doesn’t have to contain 100% of that variety. Peter F May looks into why there’s often a secret ingredient.

I make a mean dish of chicken in a thick sauce of dissolved onions and tomatoes with butter beans. When my guests ask for the recipe I am glad to tell them, but I don’t mention everything that goes into the pot. Like the generous dash of Tabasco, splash of Worcestershire and slurp of dark soy sauce. These can’t be identified in the finished meal but each adds a little to the taste: brightness from Tabasco, complexity from the Worcestershire and an underlying meaty ‘umami’ from soy.

Winemakers too add secret ingredients. When a winery puts Cabernet Sauvignon or Chardonnay on the label that doesn’t necessarily mean that the contents are 100% the named variety. In the USA there can be up to 25% other varieties that don’t have to be identified. In Europe the limit is 15%. Some places use cheaper varieties to stretch out a more expensive one. Some use another, similar, variety for topping up barrels. You’ve seen wine barrels aging: as time goes by contents evaporate and winemakers take samples to taste. The barrel must be refilled to the top or the increased airspace will cause the wine to go bad.

When the time comes for the barrels to be blended together and the wine to be bottled experts first taste the wines. Sometimes something is lacking. That Chardonnay may be OK, but a little flabby: it is lacking acidity. Another wine may be too acidic, a third may be too alcoholic – or not alcoholic enough, a red wine may be too pale. There are various winemakers’ tricks that can help.

But a more sympathetic way is to blend in a little wine which has the missing attribute. A pale red wine could have some Ruby Cabernet or Alicante Bouschet added, both are varieties with good colour. A flabby wine could be joined by a more acidic one and vice versa.

I know an estate that makes just a handful of wines from Cabernet Sauvignon, Cabernet Franc and Merlot. But they also grow some Ruby Cabernet on land unsuitable for their main varieties. Tasting room staff told me those grapes were sold. But some years later, while in the cellar with the winemaker, he let on that Ruby was used to top-up barrels and deepen colour.

The purpose of the secret ingredients is to make the best possible wine.

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Peter F May is the author of Marilyn Merlot and the Naked Grape: Odd Wines from Around the World which features more than 100 wine labels and the stories behind them, and PINOTAGE: Behind the Legends of South Africa’s Own Wine which tells the story behind the Pinotage wine and grape, also available for the KIndle.

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