Why stuck fermentation happen?

Answer 1

A stuck fermentation is where fermentation has stopped before all the sugar has been consumed. Yeast are organisms, and like most organisms they have an expected lifespan and they have nutritional requirements. You generally add less yeast to a fermentation than is required to complete the task on its own. Before fermentation starts the yeast rapidly reproduces itself so you end up with a much larger yeast colony. If what you are trying to ferment does not contain enough nutrition (i.e. oxygen, nitrogen, vitamins, sterols, UFAs) you will get a small, weak yeast colony that will all be dead before the sugar is completely consumed. Another factor is temperature. Most yeast has a quoted alcohol tolerance, but this is temperature dependant. Although fermentation speeds up as temperature increases, so does yeast mortality, and alcohol tolerance decreases.

Answer 2

There are two main reasons why fermentation stops:

1: Because the glucose has run out i.e. the organism no longer has food to survive on

2: The alcohol concentration has become so high that it becomes toxic for the organism.

Answer 3

Fermentation does not necessarily stop when percentage of alcohol in solution reaches 15%. Fermentation is primarily dependent on two things: the yeast and the food available for the yeast to consume (sugars.) Most beer yeast strains do best up to about 10% alcohol. Any higher than that and they tend to die. Some can survive in solutions higher than 10%, such as those used to make some high alcohol Belgian ales, but fermentation will stop when all of the fermentable sugars have been consumed. Yeasts used to make wine and champagne will have higher alcohol tolerances than beer yeasts (typically,) although Sam Adams has recently cultivated a yeast strain that will survive in solutions upwards of 20% alcohol.

Answer 4

Stuck fermentation can happen due to factors such as nutrient depletion, improper temperature control, pH fluctuations, or the presence of contaminants. The stress on yeast cells can lead to a slowdown or halt in fermentation, resulting in a stuck fermentation process.