Acids in Wine & Cider

November 29, 2010

I have mentioned before that pH is important when making wine and cider because it helps protect the wine from bacteria and it tastes better. A wine or cider low in pH is high in acid due to the pH scale. Different fruits have different types of acids in them that come into play when making wine and cider, and they do not have the same affect on pH.

First and foremost, when reading any wine making book dedicated to grape making wine, remember that there are three acids – tartaric, malic, and lactic. Tartaric acid is an acid specific to grapes, and so anything written about it can be ignored if working with other fruit. In fact, Peter Mitchell told us a story in his class about lab work that came back on cider reporting the tartaric acid, and since this is a grape acid, he made them retest the cider as he thinks they really didn’t do the test. Apples only contain malic acid and lactic acid.

Malic acid is actually named after apples, whose Latin name is Malus domestica. It is the primary acid in apples, but it is also in other foods and credited for giving a sour or tart taste, more so than citric acid. This is what is most commonly used to make sour candy.

Latic acid is a milder acid than malic. It is found naturally in animals, especially when exercising or digestion. In food, it is found in sour milk products and in sourdough bread.  In wine, it gives a kind of buttery creamy taste.

Some other fruits such as citrus and pears contain citric acid. This is also a sour taste, and is sometimes used as a preservative. For instance, some citric acid on avocados, apples, and bananas keep the food from turning brown quickly.

Part of the reason all these acids are so different is that they contain different amounts of the actual acid component in their molecules, the carboxylic acid, COOH. For instance, malic acid contains twice as much COOH in their molecules as latic acid, which is why it is more sour tasting. This in turn has an effect on pH testing.

Carboxylic acid, where R is the rest of the molecule it is attached to.

There is a laboratory method of testing for total acid (AKA – titratable acid) in wine and cider, but the big flaw in the test is that the test cannot tell the difference between the types of acids, so it assumes that it is all the same kind of acid. Mitchell supplied us with these formulas to show us the difference:

  • 1 g/L sulphuric acid = 1.4 g/L malic acid
  • 1 g/L tartaric acid = 0.89 g/L malic acid

Also, because each acid has a different strength, there is no correlation between the total acid and pH of the product, though it can help you get in the general area.


3 Responses to “Acids in Wine & Cider”

  1. […] 30, 2010 Yesterday, I talked about different acids in wines and cider, such as malic acid and lactic acid. It is actually possible, using bacteria, to convert malic acid […]

  2. […] you through the step by step laboratory procedures to determine free sulfites, total sulfites, and titratable acidity, and talks about the formula to convert SG to potential alcohol and chaptilization. Moving on, it […]

  3. […] 5.3%. I decided to go ahead and bump up the sugar to a ripe apple of 1.055, or 7%. It was also a little high in pH, so I had to break out my lab equipment to test what the actual acid content was to add more to […]

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