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Even strict adherence to the recipe and manufacturing technology does not guarantee that the fermentation process of homemade wine will go according to plan. It happens that after some time the release of bubbles stops and the wort ceases to “show signs of life”. This happens even with experienced winemakers, what can we say about beginners? There is no need to panic, most often the situation can be corrected.
First of all, you need to find out where the mistake was made, and only after that – try to fix it. In this article Shakedown will understand the reasons leading to the cessation of fermentation, and suggest a course of action to solve the problem in each case.
Poor sealing
Quite often, stopping fermentation is just an appearance. Due to the loose fit of the glove / shutter, carbon dioxide bubbles do not come out through special holes, but in places of gaps. Therefore, the wort continues to play, but it seems that the process has stopped.
However, the ingress of air into the vessel in the later stages can lead to sourness of the drink. To prevent spoilage, you should carefully take care of the tightness and do not open the container unnecessarily.
Recommendations:
Check bottle seal/glove for tightness.
To increase reliability, cover the joints with adhesive dough or silicone.
Open the vessel only when necessary (to add sugar, stir, remove foam) for no longer than 15–20 minutes.
Wrong temperature
One of the most common factors preventing fermentation. The optimum temperature for active yeast activity is 15–25 °C, plus/minus a couple of degrees.
It is important to avoid frequent fluctuations in one direction or another.
Low temperature leads to a slowdown in fermentation, high temperature leads to the death of fungi. Overheating is especially dangerous.
Recommendations:
Monitor the temperature and keep it constant. If necessary, move the container to suitable conditions.
When heating the must above 30 °C (even for a short time), add the wine starter or yeast again.
Too little/too much sugar
The optimal indicator of sweetness in wine must is 10-20%. With strong deviations in any direction, fermentation proceeds incorrectly. Sugar is necessary for the nutrition of yeast, but with an excess of it, their activity decreases. The lack and at all leads to a process stop. The same thing happens in a very thick must: the wine stops fermenting.
Recommendations:
Get a hydrometer and measure the level of sugar content. When tasted, the wort should be moderately sweet: not cloying and not sour.
When making dessert wine, you need to add sugar in small portions so as not to stop fermentation.
If the recommended level of sweetness is exceeded, dilute the drink with water, if it decreases, sweeten it.
Too little/too much acidity
The normal acidity of the wort is about 4 pH. Fluctuations of the indicator by 1,5 units in one direction or another are allowed.
Severe deviations from the norm negatively affect the functioning of yeast. If the acidity falls, fermentation is inhibited; if it rises, the risk of the appearance of microorganisms and the development of diseases increases.
Recommendations:
Take pH measurements.
With a strong drop in the indicator, add lemon juice (1-2 fruits per 4 liters of must) or tartaric acid.
At high acidity, dilute the drink with water.
High alcohol content
Excessive levels of alcohol in the wort leads to a decrease in yeast activity. Fungi “fall asleep” or die off with an increase in strength to 12-14%, falling to the bottom of the vessel in the form of sediment. Usually, an increase in the degree is noted after the completion of active fermentation. It can also be due to too much sweetening of the wort. An approximate strength should be calculated even at the stage of adding sugar: about 1-0,5 ml of pure alcohol per 0,6 g.
Recommendations:
The best solution would be to stop the process and move on to the next step – clarification, exposure, etc.
If you want to experiment, you can add alcohol-resistant yeast to the wine and continue observing.
Lack of nitrogenous compounds
Yeast requires a nitrogen supplement to function properly. Usually the necessary trace elements are contained in the juice, but with a strong dilution or sweetening of the drink, their concentration may drop.
The lack of nitrogenous compounds is often observed in homemade wines from forest berries, vegetables, flowers, fermented with wild yeast.
The lack of top dressing may be indicated by a sharp slowdown in the fermentation processes in the must after an active start or dilution with water.
Recommendations:
Buy in a pharmacy and add ammonia to the wine. The amount is calculated depending on the concentration of the substance: a 10% solution is injected in an amount of 0,5 ml / l, a 5% solution is 1 ml / l, etc. If ammonia is used in powder, then 0,25 g / l.
When working with store-bought yeast, nitrogen fertilizer is not added, since it is already contained in them.
The appearance of mold, microorganisms
Due to non-compliance with sterility or the use of spoiled raw materials, the wine may become moldy or sour. Therefore, it is important to carefully select the fruits for making a drink, wash your hands when working and keep the dishes clean.
Recommendation:
Dispose of raw materials and start again, taking into account the experience gained.
inactive yeast
This option is relevant if fermentation was started on natural fungi, and all other indicators are normal. The behavior of wild strains of yeast is unpredictable: they can suddenly stop working without any reason.
Recommendation:
You need to add homemade sourdough or wine yeast to the wort and restart the process. You can simply add fresh unwashed grapes (5-6 pieces per 10 liters of must), after crushing them, or good raisins (50 g per 10 liters). But it is better to buy high-quality yeast, activate it correctly and add it to the drink.
Completion of fermentation
Usually homemade alcohol ferments violently for 2-5 weeks, after which the process gradually stops. However, in some cases (high room temperature, sufficient nutrition, high yeast activity), the process may complete faster.
Some strains of yeast can process all the sugar in 1 week.
The following signs testify to the completion of active fermentation: bubbles ceased to stand out / the glove deflated, the drink brightened, sediment formed at the bottom, there is a slight bitterness in the taste, sourness without obvious sweetness and cloying.
Recommendations:
Taste the wine, evaluate it visually. If vigorous fermentation is over, you can proceed to the next stage: filtration and long exposure.
Take a degree measurement. Normally, young wine has a strength of 10-14%. If you want to strengthen it, you can add alcohol.
Relevance: 27.01.2019
Tags: Wine and vermouth, Wine tips