Abstract: What are the precautions for making home-brew wine? Home-brew wine is said to contain methanol. So, where does methanol come from in homemade wine? How to remove methanol from home-brewed wine? In addition, how long is the shelf life of home-brewed wine? Precautions for home-brew wine: How to remove methanol from home-brew wine? Shelf life of home-brew wine

Precautions for home-brew wine

1. Prevent explosions

We all know, During the fermentation of grape juice, a large amount of carbon dioxide will be produced. If the fermentation is carried out in a closed container, the carbon dioxide will basically be compressed in the fermentation container. At this time, the pressure on the fermentation tank will gradually increase. If there is no The carbon dioxide in the fermentation tank must be removed in time. Eventually, when the fermentation tank cannot withstand the huge internal pressure, it will explode, and casualties may even occur. Therefore, be careful not to seal the fermentation tank during grape juice fermentation. In addition, if a large amount of grape juice is fermented at the same time, attention should be paid to the ventilation conditions of the fermentation site. It is not suitable to live in the fermentation site to avoid carbon dioxide suffocation and death.

2. Prevent the damage of auxiliary materials

Modern wineries will add sulfur dioxide as an antioxidant to wine when making wine. However, if it is a small-batch wine brewed at home, it does not need to be added. Potassium bisulfite is added because some people are allergic to sulfur dioxide. In addition, potassium metabisulfite is corrosive and can cause serious damage to skin and eyes. You should pay attention to safety when using it and do not come into direct contact with potassium metabisulfite. In addition, potassium metabisulfite should be placed in a safe place to prevent children from accidentally eating it. .

3. Prevent mold infection

To prevent mold infection, we should first start with the disinfection of fermentation equipment. All utensils that come into direct contact with grape juice should be disinfected, rinsed with high-quality alcohol, and ensured to be dry, water-free, and oil-free before use. No matter what stage of fermentation, do not touch the grape juice directly with your hands to avoid introducing mold into the wine.

When brewing wine, wineries will perform sealed sterilization and sterilization. Home-made wine cannot solve the problem of sealing and sterilization. Many self-brewed wines often have problems such as excessive E. coli and even the carcinogen yellow. Aspergillus. To avoid these situations, the grapes should be fully air-dried after cleaning them, and water should not be added to the fermentation tank during the brewing process, otherwise mold will be introduced. The fermentation place should be in a cool, ventilated and dry place, avoid direct light, and be properly covered with black plastic bags. If you find white hair or other foreign matter in the container during the process of brewing, please do not drink the wine in the container to avoid affecting your health. If the wine has a mellow taste and clear color, you can drink it in moderation, but not in excess.

After taking the above three precautions, there is actually one last point that should be noted. First-brew wine contains a lot of impurities and should be filtered. If there is no way to completely filter the impurities in the wine, you can After letting it sit for a period of time, the wine is barreled using a siphon method to remove impurities from the wine. What we filter is only visible impurities, but there are other invisible impurities in wine that cannot be filtered out, such as methanol and fusel oil. The pectin in the grape skin will decompose methanol under the action of pectinase or heat energy, and the protein in the grape will be hydrolyzed into amino acids, and then fusel oil will be generated through the catalysis of enzymes. Due to process problems, methanol and fusel oils in home-brewed wine cannot be removed, so for any home-brewed wine, you should drink it in moderation.

Where does the methanol for self-brewing come from?

Winemaking professionals explained to reporters that methanol is not obtained by fermenting grape juice. Methanol actually comes from the plant tissue itself. For grape fruits, their cell walls contain a large amount of pectin, which is cross-linked with molecules such as cellulose, hemicellulose, and lignin to form the supporting structure of cell tissue. Pectin is essentially a galacturonan, and its side chains can be esterified. In the presence of pectinase, esterified pectin can produce methanol. The production of methanol is mainly related to the skin and seed parts of grapes, so the content of methanol in red wine fermented with skins will be higher.

It is understood that the methanol content in industrially produced wine is about 60-150 mg/L. According to the standards of the International Organization of Vine and Wine (OIV) (Oeno19/2004, the maximum detection limit for different substances in wine The upper limits of methanol content in red wine and white/rosé wine are 400 mg/L and 250 mg/L respectively. Wines with methanol content lower than this standard can be considered safe.

A food teacher from a university said that if the correct method is used to brew the wine, the methanol content decomposed in the wine is not enough to harm health. In addition to producing too much methanol, bacteria can grow." He believes that the content of methanol decomposed has a certain relationship with brewing time, temperature and raw materials. He recommends using glass vessels or oak barrels to hold wine. “Never use plastic bottles, stainless steel, aluminum vessels and other containers to avoid chemical reactions.”

Nutrition experts remind you that you can drink less home-brewed wine, but it is not suitable to drink a lot. Once the human body accidentally ingests excessive amounts of methanol, it will cause poisoning symptoms such as headaches and eye discomfort. Citizens must not think that this is a simple reaction to drunkenness. If such symptoms occur, citizens should seek medical examination promptly.

Survey: “Homebrewers” ??lack quality and safety awareness

Experts say that many “homebrewers” ??rely on experience and don’t care too much about the post-picking processing. How to control. A sample survey showed that more than 90% of the "home-brewed" people have no awareness of safety throughout the entire process. They do not know that wine-making is actually a complex process. If there is a problem in any link, the "home-brewed" wine is likely to be unsafe. Hidden danger.

How to monitor sugar, how to detect alcohol indicators, how to select raw materials for the fermentation process, etc. These are all blind spots for "self-brewing people". In particular, homebrewers tend to only focus on the freshness of picking, and do not know how to deeply sterilize brewing equipment beforehand. Brewing requires special yeast, how to control the temperature during alcohol fermentation, and the brewing process should be fully enclosed and sterilized.

However, some senior "home-brewers" insisted: "Many people are worried that the methanol content of home-brew wine will exceed the standard. In fact, there is no need to worry. As long as you pay attention to hygiene during the fermentation process, do not be infected with miscellaneous bacteria, and the fermentation temperature Between 28 and 33 degrees, do not touch iron or copper tools, and avoid direct sunlight. The fermented wine will not contain any harmful substances, so you can drink it with confidence. ”

Professor’s Tips to Reduce Methanol

How to reduce the production of methanol? Professor Yuan gave readers some tips.

First, add some yeast with high purity.

Wine is produced through natural fermentation. Therefore, too many bacteria and microorganisms in the air or containers may produce more methanol and fusel oil. Adding yeast can prevent the growth of spoilage bacteria. Thereby, the methanol content is reduced.

Second, choose fresh and uncorrupted grapes. Grape selection may lead to poisoning.

Because the grapes were sprayed with pesticides during their growth. Therefore, when making wine, you must wash the grapes thoroughly. Also, choose fresh grapes. Some people deliberately do not wash their skin clean, saying that it is to prevent microbial fermentation of the epidermis. This approach is not advisable.

Third, the container must be clean. It is best to choose glass, ceramic and other containers.

The choice of container is crucial. The entire home-brewing process requires the use of many containers. Among them, the most important one is the fermenter. It is safest and most reliable to ferment in glass, ceramic and other containers. Readers, please remember not to use stainless steel or iron containers as fermentation containers. Otherwise, poison may be brewed.

Fourth, hygiene and cleanliness must be ensured. Fermentation time usually takes 7 days.

During this process, if the grapes are infected by bacteria, it is very likely that the grapes will rot. Or, if the fermenter is not cleaned and the container is not clean when stirring, it will lead to bacterial infection. At this time, readers must pay special attention. During the brewing process, be sure to ensure container and hand hygiene. "Water-free and oil-free" is the best effect.

Fifth, control the temperature.

If the temperature is too high, it will cause enzyme mutations and other factors, and it will also produce toxic substances.

Sixth, it is not easy to drink excessively.

When drinking home-brew wine, be sure not to overdose. Especially the newly brewed wine, you should try to drink it. If you feel unwell, you should go to the hospital in time.

The shelf life of homemade wine

Although homemade wine has no shelf life, it has the best drinking period. Different wines have different best drinking periods. For example, white wine and rosé wine have a best drinking period of 1 to 3 years.

Red wine should be made after 3 years, but it is not that the older the better. The main reason is that unlike white wine or other distilled spirits such as gin, homemade wine does not seal well, so it is not easy to drink for a long time. It is generally best to drink it within three years. Leaving it for a long time will not only affect the taste, but also be harmful to the body.

How to preserve homemade wine

1. The utensils for preserving homemade wine are usually wooden barrels, Coke bottles, glass jars, etc., but no matter which one is chosen for easy storage, it must be done to good sealing.

2. The best storage environment for homemade wine is 12-15 degrees Celsius, and it must be stored in a dark environment, such as an incubator or basement.

3. The storage time of homemade wine. Generally speaking, how long the homemade wine can be stored should be determined by the quality of the wine itself. However, since it is a wine brewed by an individual at home, the wine grapes, The tools, techniques, and other aspects are not professional enough, so the final wine is often mixed with more magazines and easily deteriorates. Therefore, it is recommended that the storage time of self-made wine should not exceed 2 years. Of course, we do not rule out that we can make wine. Make good wine that can withstand aging.