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Understanding the Difference Between Yeast and Mold: A Guide for Homeowners

When you talk about having mold in a person's home you are typically talking about mold as a pervasive, invasive, and ultimately destructive substance.

When you think about yeast, you typically think of something that you use in baking to create bread or in brewing alcoholic beverages.

However, there is some concern among some people about keeping yeast in their homes. This is because yeast and mold are both classified as a fungus. Fortunately, there are strong differences between the two.

Here we will dive into the yeast versus fungus arena and highlight what makes them similar and more importantly what makes them different.


Yeast is a single-cell organism. Its proper name is Saccharomyces cerevisiae. It is eukaryotic and a member of the fungus Kingdom.

Yeast has been around for millions of years, and there are over 1500 species currently recognized.

In order for yeast to develop and thrive, it must have food, moisture, and warmth.

What is Yeast Used For?

Humans typically use yeast in both baking and in the brewing of alcoholic beverages. When you combine yeast with liquid and sugar it causes dough to rise.

This is because the yeast creates carbon dioxide within the dough which causes it to stretch and expand. It also adds a slight flavor.

In regards to brewing alcoholic beverages, yeast can increase the rapidity of fermentation. This is because when there is no oxygen to be found yeast cells turn sugars into carbon dioxide and alcohol. 

Growth Requirements for Yeast

Like mold, yeast requires moisture and a food source in order to thrive. However, it also requires warmth.

Yeast grows best in temperatures between 100 and 110° Fahrenheit. However, yeast can be killed at around 140° Fahrenheit.

How Does Yeast Reproduce?

Yeast reproduces asexually through a process called budding. Budding is a process in which a “mother cell” grows what is called a bud which gets bigger until it is the same size as the mother cell.

This process repeats more and more until the yeast has formed a cluster.


Unlike yeast, mold is a multicellular organism. Wolf is a fungal growth form that typically spreads on decaying organic matter. There are over 100,000 different types of mold in nature. The majority of those are not a threat to humans, but certain types such as black mold are.

Role of Mold in Food Spoilage

Unlike yeast, which has a permanent role in the creation of food and beverages, mold is most associated with its ability to cause food to spoil. Mold decomposes organic matter due to its corrosive nature.

This process is necessary in order to release carbon and other materials back into the environment.

Potential Health Problems Associated with Mold

Unlike yeast, which is used to create different types of food and beverages, mold can be quite harmful if ingested by humans.

If a human were to ingest black mold, it could lead to a number of respiratory problems such as coughing, wheezing, chest pain, headaches, difficulty breathing, and even nausea.

How Does Mold Reproduce?

Molds reproduce through both sexual and asexual reproduction, however, most commonly most reproduce asexually. Molds reproduce by emitting microscopic spores into the air.

The spores need to land in an environment in which there is moisture and nutrients from which the mold can feed. While there are over 100,000 types of mold, none of them are capable of surviving without moisture.

Differences Between Yeast and Mold

Cellular Structure

The primary difference between yeast and mold is that yeast is a unicellular organism. That means it has only one cell. Mold, on the other hand, is a multicellular organism.


Yeast ultimately has a tan-to-gray appearance and can often be powdery. Mold, on the other hand, can be dark, splotchy, and even slimy in both appearance and texture.


The uses for yeast are well known, particularly in the culinary world. Yeast is used as a leavener in baking and is also used in the world of alcoholic beverage brewing.

Mold, on the other hand, typically is not used. A strong exception, however, would be in the world of high-end restaurants. Mold is typically used in the process of dry aging steaks.

Tolerance of Environmental Conditions

Mold and yeast both share a need for moisture and nutrients to thrive. They especially thrive in warmer temperatures.

It needs to be said that neither mold nor yeast is capable of withstanding exceedingly high temperatures. Mold is incapable of withstanding temperatures between 140 and 160 degrees Fahrenheit.

Any temperature in excess of 140° Fahrenheit will also kill the yeast.


The ways in which mold and yeast are similar can be quite interesting. Fortunately, so long as you use yeast correctly, there should not be any problems with using it for your baking.

If you encounter mold in your home, on the other hand, you should endeavor to get rid of it. You should use either cleaning solutions or the help of a mold removal company that will use the proper tools and know-how to get rid of it.


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