The type of yeast we choose to use, the concentration of wort to be fermented, whether it is commercial beer brewing or home brewing, and the alcohol concentration we expect to eventually reach all affect the beer fermentation process.Brewing properties
Is it home-brewed beer or craft beer brewed for commercial use using professional equipment?Why is this important?It is only because the small batches and flexibility of home brewing determine that the brewer is free to make certain changes, additions, and operations to the fermentation process (especially adding sugar to increase alcohol production).And the fermentation of professional equipment cannot be easily adjusted.
Remember that sugar is the source of alcohol.No sugar, no fermentation, no alcohol.So obviously, the more sugar, the better, right?To some extent, this is correct.But two aspects of the yeast selected for use play an important role here-sugar tolerance and alcohol tolerance.Alcohol tolerance is the percentage of ABV that yeast dies due to the presence of excessive alcohol, and sugar tolerance is the percentage of brix that yeast dies due to excessive sugar content.The high concentration of sugar acts as a desiccant and “draws water” from the yeast cells, in the process, the yeast cells dehydrate and die.
Therefore, the best way to adjust the sugar content of wort during beer brewing is to increase the initial wort concentration (OG) instead of adding sugar to the wort.
As mentioned in the previous step, two aspects of yeast will affect the fermentation process from the beginning-alcohol tolerance and sugar tolerance.For brewing beer with low alcohol content, if there is only enough sugar in the wort to produce beer with 9% ABV, there is no need to use yeast with an alcohol resistance of 18% ABV.However, when brewing beer or spirits with high alcohol content, the use of yeast with low alcohol resistance will affect the activity of yeast during fermentation, resulting in fermentation failure or insufficient.
The pH value of wort
Like sugar tolerance and alcohol tolerance, each yeast has a pH environment that optimizes its effectiveness, although this is usually related to raw materials.The pH value of the wort of beer before fermentation is usually 5.2-5.6, and as the fermentation process progresses, the pH continues to decrease.Therefore, check the pH value of the cold wort before the fermentation begins to ensure that it does not affect the fermentation process.
Is there enough oxygen in the fermentation tank?
Yeast produces energy through its own metabolism through aerobic and anaerobic stages in the fermentation process.In an aerobic environment, yeast breathes and reproduces.This allows us to use a relatively small amount of yeast in large quantities.Therefore, for beer with insufficient oxygen content, the wort oxygenation process needs to be carried out before the fermentation process.However, the fermentation of the vast majority of beer is isolated from the air, that is, in a closed fermentation tank.Because this allows the yeast to ferment forcibly after all the oxygen in the tank is consumed and create a carbon dioxide-rich environment.
Generally speaking, Al beer (18°C-22°C) is almost always fermented at a higher temperature than Lager beer (7°C-16°C).
In a sense, heat is a catalyst that makes the particles in beer more active and move faster.The higher the temperature of the beer, the faster the yeast consumes sugar and converts it into alcohol and CO2.But high temperature can also cause many problems：
·Miscellaneous alcohol: Warm temperatures can cause yeast to produce more miscellaneous alcohol, which is a particularly strong alcohol that may show a burning sensation when you taste beer.It is often compared to cheap wine, which overwhelms the taste of the key ingredients of beer.
·Acetaldehyde: Warm yeast can also promote the production of additional acetaldehyde.This naturally occurring compound exists in trace amounts as part of normal fermentation, but too much can cause the taste of green apples to appear in beer.
In the planning and progress of beer fermentation, following the above steps for inspection will reduce the possibility of fermentation problems, as well as obtain better alcohol production and better flavor characteristics.