Alcoholic and Lactic Acid Fermentation in Food – A Primer

fermenting mash used to produce woodford reserve whiskey

Woodford Reserve bourbon mash fermenting

We eat plenty of fermented foods in the U.S. and around the world. Many foods are fermented that you may not even be aware of. Cheese, yogurt, bread, beer, wine, soy sauce, salami, and sauerkraut (recipe here) are just a few common fermented foods. Pickles are often thought to be fermented but more often than not they aren’t. Distilled liquors and coffee utilize fermentation in the production process but the final product is not considered fermented. Foods that are considered fermented however, have a lot of benefits.

These foods preserve well, are flavorful, and even beneficial to our digestive systems. Fermentation as a way of preservation has been around since almost 10,000 B.C.!

There are two types of fermentation that are used to produce most of these delicious foods: alcoholic and lactic acid fermentation.

Lactic acid fermentation (aka lacto-fermentation), is one type of fermentation through which foods like cheese, yogurt, sauerkraut, and these delicious pickled Brussels sprouts are made.


lacto-fermentation converting sugars in to lactic acid

In these foods, lactic acid bacteria (commonly lactobacillus) transform sugars into lactic acid. This buildup of lactic acid can be very apparent in foods like sauerkraut, yogurt, and these tangy fermented jalapeños, for example.

Many times you can use the lactic acid bacteria already present in food for fermentation. All you need then is salt and time. When you use organisms already present in the food for fermentation, it is referred to as wild fermentation. Sauerkraut is often made this way.

The opposite of wild fermentation is cultured fermentation, where an organism (bacteria, yeast, mold) is introduced from an exterior source. This source can be store-bought or taken from a previous batch of the desired fermented food. When taken from a previous batch, it is called backslopping. This is commonly how sourdough bread is made.

There are two types of lacto-fermentation: homolactic and heterolactic.

In homolactic fermentation, glucose (or lactose in dairy foods) is converted solely into lactic acid. Here are the chemical formulas for homolactic fermentation with glucose and lactose:

homolactic fermentation chemical formula

homolactic fermentation chemical formula - lactose

In heterolactic fermentation, ethanol and carbon dioxide are also produced:

heterolactic fermentation chemical formula

To make most lacto-fermented foods, salt is usually required in some amount. The primary purpose of using salt in lacto-fermentation is to add flavor, draw out moisture, and to keep the lactic acid bacteria from multiplying too quickly. Salt can also suppress the growth of some undesirable organisms. So if salt is not added, the final product will probably taste pretty awful. Also, remember that it is important to use the right type of salt.

Another important step of lacto-fermentation is to starve the food of oxygen. Lacto-fermentation is anaerobic, meaning the bacteria don’t need or want oxygen to transform the sugars into lactic acid. Keeping oxygen out of the equation creates a safe-haven for lactic acid bacteria to do their thing without interruption from molds and other undesired organisms.

Alcoholic Fermentation

alcoholic fermentation converting sugars to ethanol and co2

Another common type of fermentation is alcoholic fermentation. Alcoholic and lactic acid fermentation both utilize organisms to transform sugars into other products. Instead of lactobacillus though, the organism often used in alcoholic fermentation is yeast. Yeast is a type of fungi, usually store-bought and added into a recipe. Common foods made through alcoholic fermentation include bread, wine, and beer.

Like lacto-fermentation, the organisms (yeast in this case) consume sugars but instead of producing lactic acid they produce ethanol and carbon dioxide.

alcoholic fermentation chemical formula

Carbon dioxide is what is responsible for making bread rise.

Alcoholic fermentation causing bubbles in bread

Photo by SKopp

It is also responsible for the carbonation in real Champagne.

Alcoholic fermentation causing bubbles in champagne

The ethanol produced is what makes beer, wine and champagne alcoholic.

In alcoholic fermentation, the addition of enough salt as well as oxygen deprivation is not mandatory. In fact, many alcoholic fermented foods require oxygen to achieve a successful fermentation.

Other Fermentations

Not all fermented foods are made by these two methods but they are the most common. Sourdough bread, for example, is made by a combination of both yeast and lacto-fermentation.

Vinegar is produced through acetic fermentation. Acetic acid is a byproduct and is what gives vinegar its super sour taste. Stay tuned to follow my adventures in making vinegar!

From a top level, both alcoholic and lactic acid fermentation use tiny organisms to transform sugar into other products. The difference between the two lies in the products they produce and the organism used to do the work. No matter the type of fermentation, these foods are delicious. They are good for your gut and keep well on the shelf and in the fridge. They are an ancient art form and will probably continue to be for centuries to come.


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2 thoughts on “Alcoholic and Lactic Acid Fermentation in Food – A Primer

  • Suzi

    Thank You. This is a very interesting and informative article. I am trying to use lactic acid bacteria as a culture to ferment pineapples. I don’t want any alcohol in my end product due to religious reasons. I have bought a hydrometer but can’t understand how the original gravity reading can be taken with the fructose and glucose trapped in pineapple pieces. I want to limit the natural alcohol level to 0.5 % Is this possible? Can the addition of plantarum inhibit the yeast from breaking the sugars and so limit the alcohol production? Or do you have an alternative suggestion? I would appreciate your response, as this important for my health. Thank you.

    • Jake - Site Manager

      I don’t think I can be much help – I’m not familiar with hydrometers or plantarum. However, I’d highly recommend joining a fermentation Facebook group and ask your question there. There are a lot of knowledgeable people that could give you an answer.