Temperature: The Killer of Yeast

Temperature plays a crucial role in the life and activity of cells. As a baker or someone who loves to make homemade bread, understanding how temperature affects yeast can greatly impact the outcome of your bread-making endeavors.

Yeast, a microorganism, is responsible for the fermentation process in bread-making. It feeds on sugars, converting them into carbon dioxide gas and , which causes the dough to rise. However, extreme temperatures can have detrimental effects on yeast, ultimately killing them and hindering their ability to do their job.

When it comes to cold temperatures, yeast cells tend to slow down their metabolism. This is why it is recommended to store fresh yeast at temperatures between +2°C and +4°C. At temperatures below +10°C, yeast becomes sluggish and their activity decreases significantly. While they may not die completely, their ability to ferment the dough and produce carbon dioxide gas is severely impaired.

On the other hand, hot temperatures can also be detrimental to yeast. If the used to activate the yeast is too hot, around 130 degrees Fahrenheit or above, it can kill the yeast cells. This means that they won't be able to produce any carbon dioxide gas, resulting in dough that fails to rise. It is important to note that using water that is too hot can also cause the yeast to work too quickly, resulting in bread with a sour flavor and less rise.

To determine if yeast is still active and alive, it is important to observe its reaction when rehydrated. When yeast is added to warm water (around 100-110 degrees Fahrenheit) with a small amount of sugar, it should start bubbling or foaming within a few minutes. This reaction indicates that the yeast is still alive and ready to be used.

If the yeast does not show any reaction, it is likely that the yeast is dead or too old to be used effectively. Using expired or partially expired yeast can lead to bread with poor texture and flavor.

Temperature plays a crucial role in the life and activity of yeast cells. Cold temperatures slow down their metabolism, while hot temperatures can kill them. It is important to store yeast at the recommended temperature range and to use water that is at the right temperature when activating yeast. By understanding how temperature affects yeast, you can ensure successful bread-making and delicious homemade loaves.

temp that kills yeast

What Is The Lowest Temperature Yeast Will Work?

The lowest temperature at which yeast will work is generally around +2°C to +4°C. At temperatures below +10°C, the metabolism of yeast slows down significantly. This is why Lesaffre, a leading yeast manufacturer, recommends storing fresh yeast at temperatures between +2°C and +4°C to maintain its quality and effectiveness.

Effects of Cold Temperatures on Yeast:
1. Slowed Metabolism: Yeast cells experience a decrease in metabolic activity when exposed to cold temperatures below +10°C. This slowdown in metabolism can affect the yeast's ability to ferment and produce carbon dioxide, which is essential for leavening dough.

Storage Recommendations for Fresh Yeast:
– Ideal Temperature: The recommended temperature for storing fresh yeast is between +2°C and +4°C. This range helps to maintain the yeast's activity and prolong its shelf life.
– Refrigeration: It is advisable to store yeast bread in a refrigerator to maintain its freshness and keep it within the recommended temperature range.
– Importance of Proper Storage: Storing yeast at temperatures outside the recommended range can impact its performance and result in less effective fermentation.

Benefits of Storing Yeast at Low Temperatures:
– Extended Shelf Life: Storing yeast at low temperatures helps to slow down its metabolism, which can extend its shelf life. This is particularly important for commercial bakers who need to store large quantities of yeast for longer durations.
– Maintaining Quality: By keeping yeast at low temperatures, its quality and effectiveness are preserved. This ensures that the yeast will perform optimally when used in baking applications.

The lowest temperature at which yeast will work is typically around +2°C to +4°C. Cold temperatures below +10°C slow down the yeast's metabolism, impacting its ability to ferment dough. Following Lesaffre's storage recommendations by keeping fresh yeast at the recommended temperature range helps maintain its quality and extend its shelf life.


Temperature plays a crucial role in the survival and effectiveness of yeast. Extreme temperatures can be detrimental to yeast cells, with hot temperatures above 130 degrees Fahrenheit being particularly harmful. At these high temperatures, the yeast cells are killed, rendering them unable to produce carbon dioxide gas and causing the dough to fail to rise.

On the other hand, cold temperatures below +10°C slow down the metabolism of yeast, making them less active. While yeast can survive in cold temperatures, it is generally recommended to store fresh yeast between +2 and +4°C to maintain its quality and viability.

It is important to note that using yeast that is expired or partially expired can also lead to problems in bread making. If the yeast does not show any signs of activity, such as bubbling or foaming, it is likely dead and should be discarded. Slow or moderate reactions are also a sign of yeast that is not at its optimal freshness.

To ensure successful bread making, it is crucial to handle yeast with care and pay attention to the temperature at which it is used. By understanding the effects of temperature on yeast, bakers can create delicious, well-risen breads every time.

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Thomas Ashford

Thomas Ashford is a highly educated brewer with years of experience in the industry. He has a Bachelor Degree in Chemistry and a Master Degree in Brewing Science. He is also BJCP Certified Beer Judge. Tom has worked hard to become one of the most experienced brewers in the industry. He has experience monitoring brewhouse and cellaring operations, coordinating brewhouse projects, and optimizing brewery operations for maximum efficiency. He is also familiar mixology and an experienced sommelier. Tom is an expert organizer of beer festivals, wine tastings, and brewery tours.