All fruits contain a certain amount of acid, and grapes are no exception. Grapes differ from other fruits in that they contain less citric acid, while they have a higher tartaric acid content. The most in grapes are "tartaric acid" and "malic acid". Then, as the fruit matures, "acetic acid" gradually increases.
In the process of winemaking, more acids are produced: "lactic acid", "succinic acid", "carbonic acid" and so on. For winemakers, that's not enough! So he may also add some "ascorbic acid" (that is, the familiar vitamin C), a little "sorbic acid" or a little "sulfonic acid".
So many acids mainly serve two effects: the first is to make the wine taste more refreshing, and the second is to prevent some bacterial infections.
One of the essential characteristics that a good bottle of wine must have is "balance". Balance means that the aroma, alcohol, tannins and acidity must form a harmonious whole, one of which must not be overbearing. In general, we can use pH to determine the overall acidity of a wine. pH 7 is roughly equal to the acidity of drinking water, pH 0 to 7 belongs to acid, and pH 7 to 14 belongs to alkali. So what is the pH of a typical wine? The pH of wine is probably between 3 and 4. The pH value of wine will be affected by many factors, such as origin, grape variety, winemaking technology, etc., but in simple terms, the pH value of white wine from cold climate production areas is generally between 3.0 and 3.2, while the pH value of red wine from warm climate production areas is usually between 3.4 and 3.6.
Most fungi cannot survive in highly acidic environments. Secondly, the high acidity contributes to the preservation of sulfur dioxide. Without a little sulfur dioxide to keep it fresh, I'm afraid we won't be able to taste imported wine in China. Because pure natural wines will not be able to survive the various torments of long transportation.
Why is white wine more acidic than red wine? In order to produce red wines, an important process is "maceration", in which the must comes into contact with the skin in order to extract the pigments in the skin. While extracting the pigments, many other ingredients are also absorbed by the wine, one of which is "potassium". Potassium is alkaline, so when dissolved in wine, it will reduce its acidity.
In addition, the pH of the wine also affects the color of the red wine - the color of red wine with high acidity tends to be bright red, while the color of low acidity is more purple.
Finally, acids can be divided into fixed acids and volatile acids. Simply put, fixed acids are found in the mouth such as tartaric acid and malic acid, while volatile acids are those acids that can be smelled, such as acetic acid and lactic acid.
Later, when the guest asks why your wine is so sour, you probably know how to answer.