Difference Between Mold and Yeast

Edited by Diffzy | Updated on: September 15, 2023


Difference Between Mold and Yeast

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Mold and yeast are part of the fungus kingdom. While people may be tempted not to look beyond the fact that they are both a type of fungi, they need to understand that mold and yeast differ in several ways. Knowing the difference could be the key to realizing the extent of damage their growth inflicted. Molds cause the biodegradation of organic materials, which is welcome when it enables the recycling of nutrients. However, they may be a cause for a major headache when it results in food spoilage or damaged property.

Yeasts cause several problems like fruit decay, toe infections, and several infections/diseases (for example, cryptococcosis and candidiasis). However, they are beneficial, too. They play a significant role in the production of alcoholic beverages, as yeast fermentation results in ethanol production. Ethanol is also important in the biofuel industry. Moreover, they are useful in baking, as they act as leavening agents (substances used in dough that cause a foaming process, which results in the softening of the mixture).

Mold Vs. Yeast

Mold is a multicellular (more than one cell) organism, whereas yeast is a unicellular (single cell) organism.

Difference Between Mold And Yeast In Tabular Form

Parameters of ComparisonMoldYeast
HabitatMold can be found in dark and damp areas (like creatures that go bump at night).Yeast can be found in plant saps, soil, fruit skins, and in the stomachs of mammals and insects.
UsesIt is useful in food production processes. For example, Penicillium is used in cheese production (who knew that people would have to thank mold for cheese’s existence?).It is aid in ethanol production – face it, the wines available today taste heavenly as a result of perfecting this process.
ReproductionMolds reproduce through small spores that may be sexual or asexual (equal chance). That is, reproduction may be through meiosis or mitosis.Yeasts mostly reproduce asexually through mitosis and a division process better known as budding.
Energy ProductionIt secretes hydrolytic enzymes (catalysts) that break down biopolymers (large molecules composed of similar smaller molecules) into simpler substances. The hyphae (filamentous structures in fungi) absorb the broken-down simpler units.It converts carbohydrates into alcohol and carbon dioxide during fermentation (an anaerobic process). Yeasts obtain carbon from monosaccharides or disaccharides (saccharides refer to sugar).
AppearanceMolds have a dusty texture and come in multiple colors, such as orange, green, black, etc.Yeasts are white (or colorless) and have a smooth texture.

What Is Mold?

Molds may not necessarily cause severe illnesses when they spread at home; however, they cause people to sneeze, cough, wheeze, and get a headache or a runny nose when touched or inhaled. Furthermore, mold problems are pretty common in many households. The tiny spores of molds get into homes through windows, doors, and vents or hitch a ride by sticking to pets’ furs or people’s clothing and shoes. These spores reproduce when the right moisture level is present and latch onto ceilings, fabrics, wood, carpet, etc.

So, how can people find out if their house has a mold problem? After all, at first glance, people cannot tell mold and stains or dirt apart. Well, for one, mold spreads, whereas dirt or stain will not. However, patience is seldom part of a person’s personality. So, a much more immediate way to figure out whether the spot on one’s wall is mold is to splash a drop of bleach on it. It is mold if its color lightens in a few minutes.

However, mold is not always a problematic agent. Penicillin, an antibiotic, was discovered in a type of mold called Penicillium, and several cholesterol-lowering drugs are derived from molds. The immunosuppressant drug cyclosporine comes from the mold Tolyplocadium inflatum; this drug suppresses the rejection of transplanted organs (whoa, so molds led to the creation of a life-saving drug).

Types Of Mold

Molds may be categorized as allergenic, pathogenic, and toxigenic. Some of the common types of mold under each category are the following:

Allergenic Molds

Though not toxic, these allergenic molds (as the name gives away) cause allergic reactions. Chaetomium is an allergenic mold that initially looks like a fuzzy white growth but darkens over time. It is found in houses affected by flooding or major leaks (People have to deal with molds in addition to the maddening mess? Eeks!). Alternaria forms along the bottom of windows during cold weather. They can induce hay fever and asthma. Ulocladium, Serpula, and Penicillium are other examples of allergenic molds.

Pathogenic Molds

Molds belonging to this category cause illnesses in people with a weak immune system (it does not matter whether they are born with one or if some disease weakened their normally strong immune system.). Some members of the Aspergillus genus are pathogenic molds that can trigger respiratory problems, lung infections, and allergic reactions. They are abundant in water-damaged buildings.

Toxigenic Molds

These molds are lethal and create toxins that can be life-threatening. Stachybotrys or the infamous black mold is toxigenic. This type of mold grows and spread due to too much moisture in the air and is typically found in ventilation systems. Those thinking about dealing with it on their own should immediately banish the thought. Getting rid of this type of mold is a job for professionals. Trichoderma is another example of toxigenic mold.

What Is Yeast?

Yeasts have been around for several million years. However, the most popular species is Saccharomyces cerevisiae. Besides being useful in baking and alcoholic beverage production, this yeast species is helpful in modern cell biology research. The Dutch have been selling S. cerevisiae since 1780 for bread making. Yeasts are also used for producing non-alcoholic beverages such as root beer, kvass, and mauby.

Certain strains of some yeast species, dubbed killer yeast, produce toxic proteins capable of killing susceptible cells of the same or related species. Over the years, people experimented with killer yeasts to control undesirable yeasts. Killer yeasts are used to control spoilage yeasts like Zygosaccharomyces, which grow in the presence of some commonly used food preservatives.

Types Of Yeast

Yeasts are classified based on the purpose for which they are used. Therefore, baker’s yeasts, brewer’s yeasts, and yeasts used for cooking are the various yeast types.

Baker’s Yeasts – Types

Though collectively known as the baker’s yeast, each type has different properties and flavors. The following are the types of baker’s yeast:

Active Dry Yeast

Fleischmann developed active dry yeasts during World War II. They are inert granules that need to be dissolved in warm liquids (water or milk) to become active. Only after activations can they be used as an ingredient. This type of yeast should not be exposed to temperatures above 120 degrees Fahrenheit, as it will start dying. Active dry yeasts are sold in 14 – ounce packets or 4 – ounce jars. Storing them in airtight bags in a freezer helps extend their life. These yeasts are suitable for recipes that require a double rise.

Fresh Yeast

Fresh yeasts are big blocks or small cubes that are also known as cake or compressed yeasts. It has a rubbery, crumbly texture and is extremely perishable. They last for around two weeks when refrigerated. To test these yeasts for potency, they must be dissolved in water along with a pinch of salt. The yeasts should start foaming within 5 – 10 minutes; if not, they are no longer active or fit for use.

Mold may form on the yeast or their container if the yeasts are not refrigerated properly (wrapping them in plastic wraps tightly helps extend their lives). One ounce of fresh yeast is equivalent to four ounces of active dry yeast. It is essential to know the substitution rate when using fresh yeast for a recipe instead of active yeasts. For example, some bakers use fresh yeast for making donuts.

Instant Yeast

Instant yeast is the most reliable and active yeast sold commercially. It does not have to be dissolved in a liquid before use as an ingredient (a godsend to home bakers). However, some people still do it to evenly distribute it in the dough. This type of yeast has the longest shelf-life. It is often labeled ‘bread machine yeast’ or ‘rapid rise yeast’. Instant yeasts must be stored in airtight containers.

Liquid Yeast

Liquid yeasts are a mix of live yeasts, carbohydrates (such as flour), and water. They were popular before the invention of cake or compressed yeasts. To ensure that the yeasts live and replicate, fresh carbohydrates are added periodically.

Brewer’s Yeast – Types

Bajer’s and Brewer’s yeast belong to the same species (S. cerevisiae). However, they belong to different strains. Brewer’s yeast is of two types: top-fermenting and bottom-fermenting yeasts.

Ale Yeasts

Ale yeasts are top-fermenting yeasts necessary for brewing ale, stout, porter, and beer. Ale brewing is a process that has been around since ancient Egyptian times. The ideal temperature for fermenting ale yeasts is 20 degree Celsius, and the resulting beer tastes the best. If people let them ferment longer, the taste may not be what they expected (in short, they may have the urge to spit it out, which is embarrassing).

Lager Yeasts

Lager yeasts are bottom-fermenting yeasts crucial for brewing American malt liquors and pilsners. The ideal temperature for fermenting lager yeasts is 10 – 13 degree Celsius. Beers brewed using lager yeasts have a longer shelf-life, making worldwide distribution possible.

Belgian Yeasts

Belgian beers can be brewed using lager yeasts; however, the original beer’s unique taste cannot be replicated. Belgians make their beers using various yeast strains. Since each beer type is brewed using a mix of different strains, it is difficult to determine which yeast strain was used. Therefore, people who try to brew Belgian beers at home have to try and brew a beer with a close resemblance to the Belgian ones through trial and error (looks like it’s time to practice experimenting!).

Wheat Beer Yeast

Traditional European wheat beers are brewed using wild strains of yeast, which gives them a pleasant taste. These wild strains do not flocculate (the clumping of fine particles) well and so are left unfiltered; this causes the cloudiness that traditional wheat beers have.

Types Of Yeasts Used For Cooking/Food And Nutritional Supplements

Nutritional yeasts and yeast extracts are used to flavor food and do not need to be cooked. Though yeast extract is a type of nutritional yeast, the significantly different purpose for which it is used sets it apart from nutritional yeast.

Nutritional Yeasts

These yeasts star prominently in vegan recipes (see? Vegan food is not so bad.). Nutritional yeasts are not active and are sold in granule, flake, or (yellow) powder form. They have a nutty, cheesy flavor that makes them ideal for use as toppings or seasonings.

Yeast Extracts

Yeast extracts are sold as pastes and have an umami flavor; they are becoming increasingly popular. Marmite and Vegemite are some of the popular brands selling yeast extracts.

Main Difference Between Mold And Yeast (In Points)

  • Molds can be found in multiple shapes, whereas yeasts are oval.
  • Yeasts have false hyphae, which helps to differentiate them from molds. However, some fungal species are capable of taking both forms; they are known as dimorphic fungi (nothing is ever simple, is it?).
  • Around 1000 mold species are known, whereas 1500 yeast species have been discovered. That is, yeasts constitute 1% of all fungal species.
  • Yeasts adapt to aerobic and anaerobic conditions and grow. On the other hand, molds require aerobic conditions to thrive.
  • Molds cause allergic reactions and may lead to respiratory problems. Yeasts are only a serious threat to people with compromised immune systems.


Mold and yeast may be detrimental or beneficial depending on the species and strain. Imagining a world without fluffy cakes and breads is impossible and people must thank yeasts for their availability. Furthermore, yeasts are important for the production of alcoholic and non-alcoholic beverages. So, they may be forgiven for the infections some of their species cause. Mold may be a nuisance at home, but it contributes significantly to food production. People are able to enjoy food products such as cheese, soybean paste, and certain sausages only because of the existence of molds.


  • https://microbiologyinfo.com/difference-between-mold-and-yeast/
  • https://en.wikipedia.org/wiki/Mold
  • https://en.wikipedia.org/wiki/Yeast
  • https://www.healthline.com/health/mold-in-house#prevention
  • https://en.wikipedia.org/wiki/Killer_yeast
  • https://www.delish.com/kitchen-tools/a31956082/what-is-yeast/
  • https://www.thespruceeats.com/yeast-varieties-1328651
  • https://renegadebrewing.com/beer-yeast/
  • https://www.familyhandyman.com/list/common-types-of-mold-in-the-home/


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"Difference Between Mold and Yeast." Diffzy.com, 2024. Fri. 14 Jun. 2024. <https://www.diffzy.com/article/difference-between-mold-and-yeast>.

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