Examination of finished wine + table of alcohol content in wine

What is the question

In home winemaking, it is important to make sure that the wine really contains as much acid, sugar and alcohol as was expected during the preparation of the must, or whether all the sugar has fermented, etc. д.

You can determine the acidity and sugar content of wine simply by taste, but this method will not work with the amount of alcohol in the drink.

Determining the amount of alcohol in the prepared wine

Strange as it may seem, but to determine the alcohol you need to have alcohol meter.

But there is also a simple way to determine alcohol, although rather crude, but giving an error of no more than 1/2%, which is quite acceptable for home determination. To determine the alcohol in wine by this method, you need to have good accurate scales (with an accuracy of 1 g), gram weights for them and a glass pipette for 10-15 cc. м. cm (but you can do without a pipette).

If there is no pipette

To determine the alcohol in wine, do the following. A deep plate is placed on one of the cups of the scales, and a glass or other vessel of any size is placed on it, and the scales are balanced as accurately as possible with sand, pebbles, meal, etc. п. Then water of room temperature is poured into the vessel so that the vessel is filled to the top, t. е. so that the surface of the water in the vessel is slightly convex and slightly rises above the edges of the vessel.

After that, the water is weighed accurately, and if some of the water spills from the shaking of the scales, it does not matter - it will remain on the plate and will be included in the weight of the water. The exact weight of water is obtained and recorded. After that, the water is poured out, the vessel and the plate are wiped dry, put on the scales and balanced again with sand, if necessary. Then the wine we want to test is poured into the vessel, preheating it to 15° if it is cold.

The wine is poured into the vessel, just as precisely to the top as it was done for water. This wine is weighed accurately, the exact weight of the wine is obtained and recorded. Then all this wine is poured into a saucepan, put on fire and boiled vigorously for 1/2 hour to evaporate all the alcohol from the wine. When this is achieved and there is no more alcohol in the wine, it is cooled to the desired temperature of 15° and poured back into the same vessel that is on the scales. Since part of the wine boiled off, water (also at 15°) is added to replace the boiled part, and first a small amount of water is rinsed from the pan and the vessel on the scales, and then the vessel is refilled with water so that the liquid is again on top of it. Weigh it, get the exact weight of the wine without alcohol, and record it as well.

Let's start the calculations

First of all, the specific gravities of wine and wine without alcohol are determined. To do this, divide the weight of the wine by the weight of the water, and the specific gravity of the wine is obtained; then divide the weight of the wine without alcohol by the weight of the water and obtain the specific gravity of the wine devoid of alcohol. Next, the specific gravity of the wine without alcohol is subtracted from the specific gravity of the wine with alcohol (before boiling) and the difference is again subtracted from one. The result is a figure indicating the specific gravity of a mixture of water and alcohol, taken in the same exact amount as the wine used for the study. This figure is looked up in the table below, and you can find out what alcohol content it corresponds to.

To explain, let's take an example. Let's assume that the vessel with water weighs 1000 g, with wine 998 g, and with wine after removing alcohol - 1014 g. Hence the specific gravity of wine is 998 : 1000 = 0.998; and the specific gravity of wine without alcohol 1014 : 1000 = 1,014. Now subtract the first specific gravity from the second, i.e. е. 1,014 - 0,998 = 0,016. This difference is subtracted from one: 1 - 0,016 = 0,984. According to the table, this figure corresponds to 9.8 weight percent or 12.3 volume percent of alcohol contained in the wine under study.

If you have a pipette, the work is even easier. In this case, it is not weighed, because the weight of water is always known, and the wine is poured into the vessel without worrying about filling it to the top. Given a 25 cm3 pipette, for example, take four 25 cm3 samples, drawing the wine into the pipette until it is exactly at the mark on the tube.

Thus, exactly 100 cm3 of wine is taken and weighed to the nearest gram. Then the wine is deprived of alcohol by boiling, and after cooling, it may happen that there is not enough wine for the third or fourth pipette because it has boiled off. In this case, without pouring the rest of the wine out of the pipette, transfer it to a glass of water and add the amount of liquid that is missing to the line. After taking exactly 100 cc of this wine, weigh it, and then proceed with the calculations, which in this case are much simpler and easier to do, because 100 cc of water weighs exactly 100 g. All other calculations in this case are carried out in exactly the same way as explained above.

Table for determining the alcohol content of wine by the specific gravity of alcohol evaporated during boiling in a mixture with water equal to the volume of wine taken

Update: 11.08.2021

Category: Wine and Vermouth