What Temperature Kills Yeast? The Effects of Heat on Yeast and How to Avoid Them

Temperature RangeEffect on YeastEffect on Bread
Above 140°F (60°C)Yeast dies offDough does not rise properly
105°F to 115°F (40°C to 46°C)Optimal temperature range for yeast activationIdeal for dough rising
75°F to 85°F (24°C to 29°C)Optimal temperature range for yeast activationIdeal for dough rising
Below 40°F (4°C)Yeast does not activateDough does not rise properly

This table provides a quick and easy reference for understanding the effects of temperature on yeast activation and bread baking. By keeping the temperature of your dough within the optimal temperature range, you can ensure that your bread turns out perfectly every time.

Yeast is a type of fungus that plays a critical role in many baking and fermentation processes. It is responsible for leavening bread dough, producing alcohol in beer and wine, and creating a variety of other foods and beverages. However, yeast is a delicate organism that is easily affected by environmental factors, including temperature. In this article, we will discuss what temperature is too hot for yeast and the consequences of exposing yeast to high temperatures.

Yeast is most active and productive at temperatures between 68°F and 86°F (20°C and 30°C). At these temperatures, yeast cells are able to consume sugars and produce carbon dioxide and alcohol, which are essential for the leavening and fermentation processes. However, if the temperature rises above 86°F (30°C), yeast cells begin to die and the fermentation process slows or stops altogether.

In general, temperatures above 100°F (38°C) are considered too hot for yeast and can kill the yeast cells. This is because high temperatures can cause the proteins in the yeast cells to denature, or break down, which disrupts the cell’s ability to function properly. In addition, high temperatures can cause the cell membranes to break down, leading to the release of cell contents and ultimately cell death.

The consequences of exposing yeast to high temperatures can vary depending on the severity of the heat exposure. Here are some of the possible outcomes:

  1. Slow or incomplete fermentation: Exposing yeast to temperatures that are too hot can result in slow or incomplete fermentation. This means that the yeast cells are not able to produce enough carbon dioxide and alcohol to properly leaven or ferment the dough or beverage.
  2. Off-flavors: When yeast is exposed to high temperatures, it can produce off-flavors in the finished product. This is because the high temperatures can cause the yeast cells to release enzymes that can break down amino acids and produce undesirable flavors and aromas.
  3. Reduced shelf life: Exposing yeast to high temperatures during storage can result in reduced shelf life. This is because the heat can damage the yeast cells, making them less effective at leavening or fermenting the dough or beverage.
  4. Contamination: When yeast is exposed to high temperatures, it can create a favorable environment for other microorganisms to grow and contaminate the dough or beverage. This can lead to spoilage and potentially harmful pathogens.
  5. To ensure that yeast is not exposed to high temperatures, it is important to control the temperature during the fermentation process. This can be done by using a thermometer to monitor the temperature of the dough or beverage and adjusting the temperature as needed. For example, if the temperature is too high, the dough or beverage can be moved to a cooler location or placed in a temperature-controlled environment.

When using yeast in baking or brewing, it’s important to pay close attention to the temperature of the ingredients and the environment. If the dough or wort is too hot, it can kill the yeast or slow fermentation. If the temperature is too cold, the yeast will become inactive and the fermentation process will not begin. To make sure the temperature is within the optimal range, it’s a good idea to use a thermometer to measure the temperature of the ingredients and the environment.

Yeast Types and Temperature Ranges

There are many types of yeast, but the most common types used in baking and brewing are:

  1. Saccharomyces cerevisiae: Commonly used in baking, brewing, and winemaking. Also known as baker’s, brewer’s, or ale yeast.
  2. Saccharomyces pastorianus: Used primarily in brewing lager beer. Also known as lager yeast.

Each type of yeast has a specific temperature range within which it can thrive and perform its metabolic functions. Here are the general temperature ranges for these common yeasts:

  • Saccharomyces cerevisiae: 59-86°F (15-30°C)
  • Saccharomyces pastorianus: 46-59°F (8-15°C)

What Temperature is Too Hot for Yeast?

When yeast is exposed to temperatures above its optimal range, it can become stressed and its performance may suffer. Here’s what happens at different temperatures:

  • Above 120°F (49°C): Yeast cells begin to die off rapidly. When yeast reaches this temperature, it is considered too hot and the yeast will no longer be able to perform its metabolic functions. This can result in dough that does not rise or fermented beverages with undesirable flavors.
  • 104-120°F (40-49°C): Yeast growth and activity are significantly reduced. While some yeast strains may tolerate these temperatures, it is generally not ideal for fermentation or dough rising, and may result in a slower process or incomplete fermentation.
  • 86-104°F (30-40°C): Some yeast strains will continue to function at these temperatures, but their activity may be reduced. This temperature range is typically too hot for optimal yeast performance and can result in uneven fermentation or dough rising.

Tips for Managing Yeast Temperature

To ensure your yeast performs optimally, follow these tips:

  1. Check the yeast’s optimal temperature range: Before using a specific yeast strain, consult the manufacturer’s guidelines to determine the ideal temperature range for your yeast.
  2. Proof your yeast: To test the viability of your yeast, dissolve it in a small amount of warm water (ideally 95-110°F or 35-43°C) with a pinch of sugar. Within 5-10 minutes, the yeast should start to bubble and foam, indicating that it is alive and active. If the yeast does not foam or bubble, it may be dead or too old to be effective.
  3. Control the temperature of your ingredients: Use room temperature or slightly warm water when mixing your dough or preparing your fermentation starter. Avoid using hot water, as it can kill the yeast.
  4. Ferment and proof in a controlled environment: When fermenting or proofing your dough, try to maintain a consistent temperature within the yeast’s optimal range. This may require using a temperature-controlled fermentation chamber, a proofing box, or simply placing your dough in a warm, draft-free location in your home.

Different Types of Yeast and Their Uses

Yeast is a versatile ingredient used in a variety of baking and fermentation processes. Here’s a useful table that outlines the different types of yeast and their uses:

Type of YeastDescriptionBest Used For
Active Dry YeastDehydrated granules of yeast that must be rehydrated before useBread, pizza dough, and other yeast-leavened baked goods
Instant YeastSimilar to active dry yeast but formulated to dissolve more quicklyBread, pizza dough, and other yeast-leavened baked goods
Fresh YeastA wet, perishable yeast that must be refrigerated and used within a week or twoBread, pizza dough, and other yeast-leavened baked goods
Sourdough StarterA mixture of flour and water that has been fermented with wild yeast and bacteriaSourdough bread and other sourdough-based baked goods
Brewer’s YeastA byproduct of the beer-making process that can be used as a nutritional supplementNutritional supplements, animal feed
Nutritional YeastA deactivated yeast that has a cheesy, nutty flavor and is rich in vitamins and mineralsVegan cheese substitutes, seasoning for popcorn and other snacks

Each type of yeast has its own unique characteristics and uses. Active dry yeast and instant yeast are the most commonly used types of yeast in baking and are ideal for yeast-raised bread and pizza dough. Fresh yeast can also be used in these recipes, but is more perishable and less widely available. Sourdough starter, on the other hand, is a natural and traditional way to leaven bread and creates a distinctive tangy flavor that is popular in sourdough bread.

Brewer’s yeast is a by-product of the beer-making process and is often used as a dietary supplement for its high protein and B vitamin content. It is also used in animal feed. Nutritional yeast is a deactivated yeast that is rich in vitamins and minerals, especially B vitamins. It is often used as a vegan cheese substitute and as a flavoring for popcorn and other snacks.

When using yeast in recipes, it’s important to follow the recipe closely and use the type of yeast specified. Using the wrong type of yeast can lead to less than optimal results. It’s also important to store yeast properly to ensure its freshness and effectiveness. Active dry yeast, instant yeast, and sourdough starter should be stored in a cool, dry place, while fresh yeast should be refrigerated and used within one to two weeks. Nutritional yeast should be stored in an airtight container in a cool, dry place.


In conclusion, yeast is a delicate organism that requires specific conditions to thrive, and temperature is one of the most important factors affecting yeast activity. In general, temperatures above 100°F (38°C) are too hot for yeast, and at these temperatures the yeast will begin to die and the fermentation process will slow or stop. It’s important to store yeast in a cool, dry place and to pay close attention to temperature when using yeast in baking or brewing. By keeping the temperature within the optimal range, you can ensure that your yeast stays healthy and active, and that your baked goods and beer turn out delicious every time.


What temperature is too hot for yeast?

140° F
130° F—140° F (55° C–60° C) Yeast cells die (thermal death point).

Is 100 degrees to hot for yeast?

Water at 79°F are considered the optimum temperature for achieving yeast multiplication. Water at 81° to 100°F is the optimum temperature range for the fermentation process. Water at 95°F is the fermentation temperature that yields the best result. Water at 140°F or higher is the kill zone for yeast.

Is 110 too hot for yeast?

For active dry yeast, the water temperature should be between 105 and 110 degrees for proofing. While 95 degrees is the best temperature for yeast to multiply, that’s not quite warm enough for proofing active dry yeast. It needs the extra warmth to dissolve and become active.

Is 30 degrees too hot for yeast?

Optimal yeast growth happens at around 37 degrees Celsius (98.6 degrees Fahrenheit), but dough will rise at any room temperature. As the temp rises, the yeast becomes more active, which is why you’ll sometimes see recipes call over overnight rests in the fridge, where activity slows or stops.

What is the best temperature for yeast to grow?

between 90˚F-95˚F

Maintaining an ideal temperature range during the fermentation process is a difficult task that all ethanol plant operators face, especially in the hotter months (Figure 2). The optimum temperature range for yeast fermentation is between 90˚F-95˚F (32˚C-35˚C). Every degree above this range depresses fermentation.

What do I do if my yeast doesn’t foam?

That foam means the yeast is alive. You can now proceed to combine the yeast mixture with the flour and other dry ingredients in your recipe. If there is no foam, the yeast is dead and you should start over with a new packet of yeast.

How do I know if my water is hot enough for yeast?

Water should be between 100 and 110 degrees. If you don’t have a thermometer, use your wrist to test the water temperature. If it feels very warm on your wrist, it’s ready. Sprinkle the yeast and sugar on top of the water and stir.

How do you tell if you killed your yeast?

After 10 minutes, the yeast should be foamy and bubbly and expanding. It should have expanded to fill over half of the cup/jar and have a distinct yeasty smell. This is yeast that is alive and well. If the yeast doesn’t bubble, foam or react – it is dead.