alcohol unit: (V/V), 7% means that 1 unit of volume's wine contains 7 unit of volume's ethanol. For example, 1 liters of wine contains 7 liters of ethanol.
Generally, it is calculated by capacity, so "Vol" will be added after alcohol concentration to show the difference from weight calculation.
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alcohol content expression and conversion
alcohol content can also be expressed by weight ratio, and weight ratio and volume ratio can be converted to each other.
at present, there are three kinds of alcohol degree expressions in the world:
the first one: Alcohol％ by volume. The standard alcohol content was invented by Gay．Lusaka, a famous French chemist. It refers to how many milliliters of alcohol are contained in every 1 milliliters of liquor at 2℃. This representation is easy to understand, so it is widely used. The standard alcohol content, also known as Guy Lussac alcohol content, is usually expressed as a percentage or the abbreviation GL.
the second type; Degrees of proof VK. British alcohol content is a method of alcohol content calculation created by an Englishman Clark in the 18th century.
the third type: degrees of proof. American alcohol degree is expressed by alcohol purity, and an alcohol purity is equivalent to .5% alcohol content.
The invention of British alcohol degree and American alcohol degree preceded the appearance of standard alcohol degree, and they were both expressed by alcohol purity "proof". However, conversion can be carried out among the three alcohol degrees. Therefore, if you know the British alcohol content and want to calculate its American alcohol content or standard alcohol content, you can work it out as long as you have the following formula:
standard alcohol content x1.75＝ = British alcohol content
standard alcohol content x2 = American alcohol content
British alcohol content x8/7 = American alcohol content
European alcohol content percentage method: Europe and Europe.
American proof method: the United States and Canada are represented by proof. The value of proof is equal to twice the percentage, such as 8proof=4%. [edit this paragraph] determination of alcohol content
1. density bottle method
1. principle
the nonvolatile substances in the sample are removed by distillation, and the density of the sample (alcohol aqueous solution) at 2℃ is measured by density bottle method, and the volume fraction of alcohol content at 2℃ is obtained by looking up the table.
2. Instrument
2.1 All-glass still: 5mL.
2.2 constant temperature water bath: the temperature control accuracy is .1℃.
2.3 density bottle with thermometer: 25mL or 5mL.
3. Preparation of sample solution
Use a dry and clean 1mL volumetric flask, accurately measure 1ml of the sample (liquid temperature is 2℃) into a 5mL distillation flask, rinse the volumetric flask with 5mL of water for three times, merge the washing liquid into the distillation flask, add a few zeolite or glass beads, connect a serpentine cooling tube, use the original volumetric flask for sampling as a receiver (plus ice bath), and open it. Slowly heat and distill (the distillation time after boiling should be controlled within 3min-4 min), collect distillate, when it is close to the scale, take off the volumetric flask, cover it, keep the temperature in a water bath at 2℃ for 3 min, then add water to the scale and mix it evenly for later use.
4. Analytical step polymerization
Wash the density bottle, dry and weigh it repeatedly until the weight is constant (m).
take off the bottle stopper with thermometer, fill the constant-weight density bottle with water that has been boiled and cooled to 15℃, insert the bottle stopper with thermometer (no bubbles are allowed in the bottle), immediately immerse it in a constant-temperature water bath at 2.℃ .1℃, and after the temperature of the contents reaches 2℃ and remains unchanged for 2min, quickly suck off the liquid overflowing from the side tube with filter paper, immediately cover the small cover on the side branch, and take out the density bottle.
pour out the water, first rinse the density bottle with absolute ethanol, then with ether, blow dry (or dry it in an oven), rinse the density bottle repeatedly with sample solution for 3 to 5 times, and then fill it up. Repeat the above operation and weigh (m2).
5. calculation of results
the relative density of sample solution (2℃) is calculated according to the following formula.
where:
—— the relative density of the sample solution (2℃);
m2-mass of density bottle and sample solution, in g;
m —— the mass of the density bottle, in g;
m1—— the mass of density bottle and water, in g.
according to the relative density of the sample, look up the table to get the alcohol content of the sample at 2℃.
the result is expressed to one decimal place.
6. Precision
The absolute difference between two independent determination results obtained under repetitive conditions should not exceed .5% of the average value.
2. Alcohol meter method
1. Principle
Use a precision alcohol meter to read the indication value of alcohol volume fraction, look up the table for temperature correction, and get the volume fraction of alcohol content at 2℃, which is the alcohol content.
2. instrument
precision alcohol meter: the dividing value is .1%vol
3. Analysis step
Inject the sample liquid (prepared by density bottle method) 5minto a clean and dry measuring cylinder, and let it stand for several minutes. After the bubbles in the wine disappear, put it into a clean and dry alcohol meter, and then gently press it, without touching the cylinder wall. At the same time, insert a thermometer, balance for about 5 minutes, observe horizontally, read the scale indication at the tangent to the meniscus, and record the temperature. According to the measured alcohol meter value and temperature, look up the table and convert it into the alcohol content of the sample at 2℃.
the result should be expressed to one decimal place.
4. Precision
The absolute difference between two independent determination results obtained under repetitive conditions should not exceed .5% of the average value.
III. Major changes between the new standard and the original standard
1. The name of the arbitration method in the new standard is changed from the specific gravity bottle method in the original standard to the density bottle method.
2. The new standard increases the temperature of cooling water, which should be lower than 15℃.
3. The new standard increases the distillation time after boiling, which should be controlled within 3-4 min.
4. The parallel error in the new standard should not exceed .5% of the average value, and the parallel error in the original standard should not exceed .2%(V/V).
IV. Discussion
1. The temperature of the sample before bottling must be lower than 2℃. If it is higher than 2℃, the sample in the bottle will be dissatisfied due to liquid contraction at constant temperature, which will bring errors.
2. When the room temperature is higher than 2℃, water vapor will condense on the outer wall of the density bottle during the weighing process, which will increase the mass, so it is required to weigh very quickly. Therefore, the density bottle can be weighed for the first time, and all the balance weights are added, and then the density bottle can be dried again with silk cloth, put into the balance, and quickly read the balance point scale.
3. The thermometer in the density bottle has a maximum scale of 4℃. When drying, it shall not be put into an oven or dried in other environments higher than 4℃.
4. The alcohol meter should be kept clean, because the oil stain will change the characteristics of the alcohol meter surface's infiltration of alcohol semen, affect the direction of surface tension, and make the reading error.
5. The measuring cylinder used to hold the sample should be placed on a horizontal desktop so that the measuring cylinder is vertical to the desktop. Do not hold the measuring cylinder by hand to avoid the local temperature of the sample rising.
6. Try to avoid stirring when injecting samples to reduce air bubbles. The amount of injected sample should be slightly lower than the mouth of the measuring cylinder after adding alcohol.
7. Before reading, carefully observe the sample, and then read after the bubbles disappear.
8. When reading, you can make your eyes slightly lower than the liquid level, and then slowly raise your head. When the oval liquid level becomes a straight line, you can read the scale at the intersection of this straight line and the alcohol meter. [edit this paragraph] the alcohol content of beer
the degree of beer does not mean the content of ethanol, but the concentration of wort, the raw material for beer production. Take 12-degree beer as an example, the concentration of wort extract before fermentation is 12% (weight ratio). The extract in wort is a mixture of various components, mainly maltose.
The alcohol in beer is converted from maltose, so it can be seen that the alcohol content is lower than 12 degrees. Such as common light-colored beer, the alcohol content is 3.3-3.8%; The alcohol content of dark beer is 4-5%. [edit this paragraph] alcohol content of wine
Generally speaking, the alcohol content of wine is mostly between 8% and 15% (alcohol content is usually% or ), which is mainly determined by the sugar content in grape fruit. Although wine fermentation is a complicated chemical reaction process, the most important chemical change is that sugar is converted into alcohol and carbon dioxide under the action of yeast, that is, fermentation can be simply expressed as: sugar in grapes+yeast → alcohol+carbon dioxide+heat. Therefore, if the sugar content of grapes is high, the alcohol content will be correspondingly high, while if the sugar content of grapes is low, the alcohol content will be low.
usually, 17g/l-18g/l of sugar can be converted into 1 alcohol, that is, 1L of grape juice must have 17-18g of sugar to obtain 1 alcohol, which is 17g for white wine, while red wine needs a higher sugar content, that is, 18g, due to fermentation with skins or other losses.
climate, grape varieties, years and other factors in different countries and regions will lead to different sugar content of grapes and even wine alcohol content. For example, wines from California and Australia usually have a higher alcohol content, so we often see that the alcohol content of American wines is 13%, and that of Australian wines is 13.5% or even 14%. Countries with a relatively cold climate, such as Germany, have low sugar content in grapes, so the alcohol content of wine is relatively low. Too high or too low alcohol content will affect the taste of wine: too high will mask the natural aroma of wine, while too low will lead to insufficient taste of wine. In order to change the alcohol content of wine, various technologies are applied to the wine production process. For example, if the sugar content of grapes is too high, the Spinning Cone Column (SCC) can be used to reduce the alcohol content of wine. However, if the sugar content of grapes is too low, the alcohol content of wine can be improved by adding sugar.
About Spinning Cone Column, the introduction found on the Internet:
The technology of "rotating cone column" was first developed in Australia, and now it is popularized and used by Cone Tech Inc in California. The core of "rotating cone column" separation device is SCC separation column, which is a vertical stainless steel cylinder. Under the vacuum condition in the cylinder, inert gas is used to remove the volatility of liquid.
This separation device consists of two groups of inverted cones: one is fixed on the inner wall of the column, and the other is fixed on the central axis that can rotate at high speed. The fixed and rotating cones operate alternately in the main body, and the operation principle can be demonstrated by Figure 2. In operation, the material added from the top flows from the cone fixed on the inner wall of the column to the first rotating cone below due to inertia, and the centrifugal force pushes the material to fall onto another fixed cone. In this way, the final material flows to the bottom of the column. Through a special technology, aromatic gas is formed in vacuum and moves upward along the thin liquid surface to gather volatile elements. The aromatic gas is separated at the top of the column and compressed to contact with the liquid. The "rotating cone column" device can basically separate out substances that are not needed by the brewer in any fermented alcoholic beverage, for example, alcohol can be completely separated.
In practice, 1%% of wine samples can be treated by "rotating cone column" technology to separate their alcohol. The treated alcohol-free products are blended with untreated wine to adjust the satisfactory alcohol content. The alcohol and sugar content of the ideal mixture reach the equilibrium value. Too high or too low alcohol content will affect the taste of wine: too high will mask the natural aroma of wine, while too low will lead to insufficient taste of wine. At present, the technology of "rotating cone column" is widely recognized and recommended by OIV International Grape and Wine Organization in 24. The United States, Chile and Australia have allowed the use of this technology, and the relevant regulations in South Africa are in the process of operation.
The advantages of "rotating cone column" device can be summarized as follows:
● Stainless steel container is clean, sanitary and easy to clean.
● No filtering membrane or other substitutes are needed.
● the natural fragrance of the processed object is not easy to be lost.
can work continuously.
Both transparent and opaque wines can be processed.
in addition, its operating cost is low. In South Africa, the cost is .23 rand per liter (excluding freight). Because only 1% of the wine needs to be processed, the final total production cost is only equivalent to .23 rand per liter. However, due to the high cost of independent investment in building such processing workshops, wineries usually use this technology to process their wines in the form of contract.
Red wine needs more sugar to be converted into alcohol for the following reasons: 1. The fermentation temperature of red wine is higher, which will cause more alcohol to volatilize. Regular spray cycle will also cause alcohol loss.
the key technology of SCC is to reduce the boiling point of liquid by vacuum, which is similar to distillation to some extent, but due to vacuum pressure, substances with different boiling points can be separated at a relatively low temperature. Double cone is actually a way to collect effective substances.