There are several factors that can kill yeast in alcohol, but the primary one is the alcohol itself. Yeast cells have a threshold for alcohol tolerance, and once the alcohol levels reach a certain point, the yeast cells will die off.
Different strains of yeast have different alcohol tolerance levels, but generally, they can survive in alcohol concentrations of up to 16-18 percent. Beyond this point, the alcohol becomes toxic to the yeast cells and inhibits their ability to function properly. As a result, the yeast cells will eventually die.
Alcohol kills yeast cells by affecting their cellular functions. The alcohol molecules disrupt the cell membranes and denature enzymes within the cells, leading to their death. The higher the alcohol concentration, the more severe the damage to the yeast cells.
In brewing and winemaking, there are instances where the desired alcohol content exceeds the alcohol tolerance of the yeast strain being used. In such cases, additional measures need to be taken to stop fermentation and raise the alcohol level. One common method is the addition of a high-proof spirit, such as vodka or grain alcohol, to the fermenting mixture.
The high alcohol content of the spirit is enough to kill off the yeast cells and halt fermentation. By introducing a spirit with an alcohol level beyond what the yeast can survive in, the fermentation process is effectively stopped.
It’s important to note that the addition of a spirit not only raises the alcohol level but also adds flavor and character to the final product. This technique is often used in the production of fortified wines, such as Port or Sherry, where a distilled spirit is added to increase the overall alcohol content.
In my personal experience as a homebrewer, I have encountered situations where I wanted to achieve a higher alcohol content than what the yeast strain I was using could tolerate. In those cases, I have opted to add a high-proof spirit to the fermenting beer to reach my desired alcohol level.
By carefully calculating the amount of spirit to add, I was able to effectively stop fermentation and achieve the desired alcohol content. It’s important to note that this technique should be used with caution, as adding too much spirit can result in an overpowering alcohol flavor and potentially affect the balance of the final product.
High alcohol levels kill yeast cells, and the addition of a spirit with a higher alcohol content than the yeast can tolerate effectively stops fermentation. This technique is commonly used in brewing and winemaking to achieve desired alcohol levels beyond the natural tolerance of the yeast strain being used.