White Wine Acidity
One of the reasons a fine white wine is so distinctive is because of its slightly tart or sour taste.
Like a glass of lemonade a fine wine leaves a refreshing taste in the mouth.
This tartness is the result of acidity in the wine.
In fact, all wines including red and white are on the acid side of the pH scale and acidity is one of the five distinguishing characteristics of wine.
The other distinguishing characteristics are:
Tartaric and malic acids (and their derivatives) are two of the key acids found in wines but there are others and the interplay of all these acids has a profound effect on the resulting taste and character of your wine.
The balance of these acids can make all the difference between a superb light-bodied white and a glass of vinegar.
What Does Acidity Taste Like?
Acidity gives wine its lively flavour but too much acidity can make the wine taste very sour.
On the other hand, if the acidity is too low the wine will taste flat and lack that sparkle, that bite that refreshes your palate.
For the winemaker getting the acidity balance right involves working around complex interactions including the fact that the different acids in wine have varying affects on the resulting taste.
For example, Tartaric acid increases the tartness of wine as well as adding colour and stability to the wine.
Malic acid and citric acid have an even stronger effect on the acidity of a wine.
But too much malic acid in the wine can leave a harsh taste and winemakers will sometimes alter the malic acid content to avoid this problem.
Citric acid may add a subtle fruit taste to the wine that can be really beneficial.
Then there’s that horrible vinegary taste in a really cheap and nasty white wine. This is caused by the presence of too much acetic acid.
Acetic acid is the result of too much of the wrong kind of fermentation.
Our perceptions of wine acidity can also altered by context. For example, the acidity of a white wine high in acidity will not be so obvious when it also has some sweetness.
Our perceptions of the taste of a wine are also altered by the flavours of accompanying food.
This interplay between the flavours in the wine and accompanying food is also what makes for such an interesting journey of exploration when we enjoy a fine wine and dining experience.
What Causes Acidity?
Acids occur naturally in grapes but the acid levels vary across different grape varieties and in different growing regions.
Acid levels are at their highest in unripe grapes and gradually drop as the grapes ripen because the acids are used in the respiration process by the plants.
This is why the timing of the harvest plays such a key role in the final taste of a wine.
Acidity levels, especially of tartaric and malic acid, are generally higher (and sugar levels are lower) in cooler regions than in hotter climates and these factors also play a part in determining the final taste of any wine.
However, a wine maker is also able to artificially remedy certain deficiencies in the normally occurring acidity levels — see below.
Acidity: Red Verses White
White wines generally have a higher acidity level than reds.
A dry white wine will display an acidity level (TA) of around 65% to 75% and a sweet white wine acidity level could be as high as 85%.
On the other hand, a dry red wine will have an acidity level in the range of 60% to 70% and a sweet red wine will range somewhere between 65% and 80%.
White wines tend to have higher concentrations of malic acid than red wines and it’s the malic acid in particular that gives white wine its characteristic sharpness.
Sometimes a winemaker will encourage a fermentation process that will convert the malic acid to the milder tasting lactic acid.
This might be the case if the growing season has been too cold for the grapes to produce sufficient natural sugars to offset the acidity.
In red wines this process tends to happen naturally but in white wines the winemaker may need to initiate the process artificially.
What's The Difference Between Acidity and pH?
When we talk about acidity in wine we need to distinguish between acidity and pH levels.
The pH scale measures the strength or intensity of the active acid content in a substance. For example, milk has a higher pH (weaker acid content) than white wine.
On the pH scale, 7 = neutral, 8 – 14 = alkali, and 1- 6 = acid so a wine with a high pH has a low acidity level and visa versa.
If the pH is too low it can prevent the activity of essential microorganisms but if it is too high the microorganism culture can become unstable and unmanageable.
A very low acid red wine will probably have a pH of around 4 whereas a white wine will have a pH of around 3.
However, wine acidity (Total acidity — TA) refers to the sum or concentration of the acids that are present and how they affect the taste.
For example some white wines will have the same pH levels as vinegar but clearly do not taste the same (unless you are making your way through a really cheap white wine).
Can Acid Levels Be Altered?
Acid and sugar levels in grapes are two variables that many wine growing associations around the world permit winemakers to alter.
Remember, cold climates produce grapes with high acid/low sugar content and warm climates lead to grapes with low acid/high sugar levels.
Winemaker interventions may include:
- Adding tartaric, malic, and citric acids
- Adding sugar
- Reducing the levels of malic acid through malolactic fermentation
If the fermentation process converts lots of the malic acid to lactic acid the acidity levels will be lowered and the resulting wine will not be so tart.
Lactic acid is the acid found in milk and winemakers may artificially encourage this naturally occurring fermentation process known as malolactic fermentation (MLF).
Thus a Chardonnay from a cold climate may need to undergo MLF to lower the sourness while still retaining the essential character of a Chardonnay.
Who would have thought that so much went into that bottle of wine in your hands?
Having some understanding of the marvellous complexities of fine wines only adds to the pleasure of enjoying a glass of your favourite wine.
Knowing what it is about your favourite wine that you like so much will help understand that it’s very important to give careful consideration for your wine storage racks, the environment and also, how to explore other wines.
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