1、How long does the fermentation period usually take?
Approximately 9 days. The first step is to ferment the glucose into alcohol. There are visible bubbles. The number of bubbles goes from small to large, then from large to small, which takes about a week. The second step is the fermentation of malic acid into lactic acid for red wine. The bubbles are small, uniform and clean. It also goes through a decreasing process, about half a month.
2. When are the red wine lees separated from the white wine?
About 5 days after the start of fermentation, the skins should be separated from the residue (obviously bubbling). Discard the filtered leather residue and keep the liquid. For the first filtering (separation of the leather residue), use a clean cloth or stocking (every drop is hard, do not forget to squeeze out the residual liquid from the leather residue).
3、Do I need to crush the grapes before putting them into jars (bottles)?
It is a must. The contact between the grape juice and the skins helps the natural yeast on the skins to multiply and start fermentation quickly. For red wines, the crushing level can be squeezed to avoid mashing into a paste, which will bring trouble to the subsequent filtering. White wines require juice fermentation. Of course, pressing is to squeeze the last drop of juice.
4、What is the ideal temperature for fermentation?
The temperature is 25-30 degrees for red wines and 18-20 degrees for white wines.
5、What is the proper amount of wine in the container?
In the early stages of alcohol fermentation, a lot of gas will be produced and the grape skins will float on top of the wine in layers. During the insurance period, about 30% space should be left in the container to avoid the overflow of the precious liquid. Fermentation begins (small amount of bubbles) – strong (large amount of gas escapes) – weak (bubbles decrease) – static (fermentation is complete).
This stage lasts about a week. For red wines, the later malolactic fermentation (unnecessary) will reduce the acidity of the wine, making it softer and more flavorful. When the temperature is right (above 20°C), malolactic fermentation starts naturally in the alcoholic wine (in many cases, malolactic fermentation does not start properly).
At this point, the leather residue has been filtered out and the bubbles are fine and clean, not as strong as in alcoholic fermentation. Only 10% of the space above the container should be left. Try to avoid the drying of the wine in the air and to discharge the gas from the container.
If conditions allow, a simple one-way valve can be used to control the gas, but it cannot enter or exit. This stage takes about half a month. If the fermentation of the apple milk has not started that year, the bottles can be kept sealed.
The wine will precipitate tartaric acid salts (particle size, crystals) at low winter temperatures, reducing the acidity of the wine. The following year, when the temperature is suitable, the precipitation is removed by siphoning and the apple milk is expected to start fermenting naturally. Temperature is usually the determining factor for malolactic-lactic fermentation in wine.
6. What are the principles of sugar addition?
The need for sugar and the amount of sugar to be added are calculated based on the final alcohol content and sugar content of the raw grapes. Generally speaking, 17 grams of sugar per liter will produce 1 degree of alcohol. The maximum alcohol content that can be achieved through natural winemaking is 15°C. Low sugar content in grape juice – low alcohol content, difficult to preserve. Too much sugar – incomplete fermentation, resulting in sweet wines.
7. How long should I add sugar?
How many times should I add sugar? If the grapes are not very ripe and the sugar content is low, the future wine will not reach 12 degrees alcohol, which will affect the taste and preservation of the wine. At this point, you can consider adding sugar.
Every 17 grams of sugar per liter will produce 1 degree of wine. Generally speaking, you can add 34 grams of sugar per liter of grape juice to increase the wine by 2 degrees. If the grapes are too unripe, you may consider adding 68 grams of sugar per liter to produce 4 degrees of alcohol. For example, Germany is too cold and glucose levels are low, so you can only drink 7 degrees of wine.
The law allows the addition of 68 grams to 11 degrees, while Bordeaux in France can only add 34 grams to 12 degrees, which must be approved by the state. Sugar should be added two to three days after fermentation begins. This is when fermentation is at its peak, when the yeast content in the wine is at its maximum, and when the yeast is very vigorous.
At this time, the addition of sugar is beneficial to the thoroughness of the fermentation, leaving no residual sugar and ensuring the stability of the wine. The residual sugar will be broken down by lactic acid bacteria, causing irritation and bitterness. Add sugar twice, 1-2 days apart.
This is for red wines. White wines can retain residual sugar up to 8 grams half dry. However, malolactic fermentation should be avoided in white wines. Immediately after the alcoholic fermentation (5-6 days), the legs should be separated, the containers filled and the temperature reduced to 17°C. If possible, additional SO2 should be added to close the containers. The term “malolactic fermentation” refers to red wines. It is the transformation of the acid and does not produce alcohol.
Should we add all sugars to the fermentation process? Is it better to add honey or icing sugar?
It is better to add sugar in several stages. Too much sugar can affect the yeast reproduction because the rock sugar particles are too large to melt. In fact, icing sugar is not as effective as white sugar. Honey is certainly fine, but it contains high water content and other microorganisms.
9. Should the fermentation process be sealed? Do I need to ventilate the grapes after putting them into the jars?
No. Do not seal them. It should be slightly ventilated. Fermentation requires oxygen and emits a lot of carbon dioxide. There is a risk of explosion if sealed too tightly. Because fermentation is not a simple equation, there are many equations. Yeast self-propagation requires trace amounts of oxygen, and the combination of pigments and tannins into a stable color requires the participation of oxygen, otherwise the color will deteriorate, which is the reason for opening and pouring the cans in the large-scale industrial production process.
In addition, the ventilation of the decanters removes the odor of reduced hydrogen sulfide from the wine. Yeast fermentation produces SO2 on its own, and if oxygen is not supplied, the odor is reduced. This is a summary of the process of combining theory and practice.
10. Do you want to stir during the first fermentation?
Usually, the floating skins are pressed into the white wine 2-3 times a day, which helps to macerate the tannins, pigments and other phenolic substances on the skins.
