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What is Food Fermentation?

Lately, I have been hearing SO much about food fermentation. Sourdough bread. Kefir. Sauerkraut.

It has me asking what is food fermentation, and why is everyone talking about it? I decided to write an article all about food fermentation so I can answer this question for you and for me.

By the end of this article, I’m pretty sure we’re all going to be fermenting foods in our homes like little domestic scientists. But without further ado, here’s a comprehensive answer to the question: What is food fermentation? 

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What is Food Fermentation (A Quick Rundown)

For a quick definition, food fermentation is the process of converting carbohydrates into alcohol or acid using microorganisms like fungi or bacteria. This fermentation process helps preserve food and changes its taste and texture. Besides being a good way to preserve food, food fermentation is thought to be very good for a person’s health.

Here’s a quick TED-Ed video that explains some of the science involved in fermentation.

What Are the Three Types of Food Fermentation?

There are three main types of food fermentation: alcoholic, lactic acid, and acetic acid.

What is alcoholic fermentation?

Alcoholic fermentation is exactly what you would expect. It’s the fermentation process that turns things like grapes and grains into alcohol. Alcoholic fermentation, also known as ethanol fermentation, converts sugars into alcohol and carbon dioxide.

What is lactic acid fermentation?

Lactic acid fermentation requires no heat and is surprisingly NOT made from milk. So you might be thinking this is milk that has been fermented, but it is in fact things that have been fermented with a bacteria called lactobacillus. Once the bacteria lactobacillus does its thing, it is then turned into lactic acid. Ergo facto, lactic acid fermentation.

The fermentation process with lactic acid does not require heat, but it does require an environment without oxygen. Another word for “without oxygen” is anaerobic, which is a term you may come across as you learn more about fermentation.

Examples of foods fermented by lactic acid are:

  • Sourdough bread
  • Sauerkraut
  • Kimchi
  • Yogurt
  • Cheese
  • Buttermilk
  • Cottage cheese
  • Kefir
  • Miso
  • Natto
  • Tempeh
  • Other vegetables such as carrots, radishes, cucumbers, and green beans can also be fermented

What is acetic acid fermentation?

It took me some time to understand what acetic acid fermentation is. Some people say there are just the two main types, lactic acid, and ethanol fermentation, but other lists also included acetic acid fermentation as a third type. One article even said acetic acid fermentation is a sub-category of ethanol fermentation.

Acetic acid fermentation requires acetic acid bacteria (AAB) and it takes two steps. The first step is creating ethyl alcohol in the absence of oxygen (or anaerobically). The next step is to oxidize or expose the mixture to oxygen, which produces acetic acid.

Examples of foods fermented by acetic acid are:

  • Apple cider vinegar
  • Kombucha
  • Water kefir

Why Do People Ferment Foods?

People typically ferment food for three main reasons:

  • Food preservation
  • Health benefits
  • Flavor/texture changes

How Does Fermentation Preserve Food?

Microorganisms that can make people sick — we’ll call it bad bacteria — can’t survive in foods that have a high acid or alcohol content. As foods ferment, the good bacteria in it survive while flushing out the harmful bacteria.

You may have heard about pH balances that refer to how acidic something is. A pH balance runs on a scale with higher numbers meaning less acidic and lower numbers meaning more acidic. In your garden, you might use a soil test kit to see if your soil is too acicid or too alkaline (opposite of acidic) for the plants you want to grow.

pH levels are also important in canning. Certain things you can such as fruit have a low pH level. That’s why you can run your jellies through a water bath canner as opposed to a pressure canner. The acidic level is already high enough that it kills off unwanted bacteria. On the other hand, if you want to preserve something like fresh vegetables or protein that has a lower pH level, you would need to preserve it in a pressure canner that allows the jars to reach a much higher temperature and kill harmful bacteria. You might also use a pickling method to kill harmful bacteria such as when you pickle peppers in vinegar.

When you use a lactic fermentation process, the good bacteria do all the work for you. It eliminates the bad bacteria while leaving the healthier good bacteria for consumption.

What are the Health Benefits of Fermentation?

Many people like fermented foods because of the health benefits they can get from eating them. The top health benefits that people claim comes from fermented foods are:

  • Probiotic effect
  • Promotes gut health
  • Might help regulate blood sugar
  • Could help reduce the risk of obesity
  • Fermented foods are easy to digest
  • High levels of nutrients are found in fermented foods
  • Might increase immune health

Fermented foods and gut health

Gut health is one of the top reasons people promote fermented foods. According to Harvard Health,

“…one of the biggest benefits of fermented foods comes from probiotics. Recent research suggests that the type of gut bacteria in the bodies of Americans is changing. One possible reason is that the microbiomes in our bodies are not regularly replenished the way they were in past generations. That’s because of changes in the American diet — particularly the rise in processed foods — and because of better hygiene, which cuts down on the number of microbes people are exposed to naturally through dirt and other contaminants…In addition, antibiotics are used widely and can kill off beneficial organisms along with the bad ones.”

Probiotics introduce the good bacteria that your body uses to break down foods for digestion. Without good bacteria in your body, you can start to have different health problems.

Healthline reports, “Many facets of modern life such as high stress levels, too little sleep, eating processed and high-sugar foods, and taking antibiotics can all damage our gut microbiome. This in turn may affect other aspects of our health, such as the brain, heart, immune system, skin, weight, hormone levels, ability to absorb nutrients, and even the development of cancer.”

In addition to the good gut health bacteria, fermented foods are also easy to digest. Fermenting foods acts as a first level of digestion or a pre-digestion before it enters your body. For example, if you eat cabbage raw you will have a harder time digesting it than you will digesting sauerkraut.

Fermented Foods are High in Nutrients

This is crazy, but the fermentation process of food actually increases the nutritional value.

Fermentation Revolution, a website dedicated to all things related to fermentation, writes, “Contrary to canned vegetables, fermented vegetables retain all their nutrients and vitamins. Their nutritional value can even increase! In fact, during fermentation, microorganisms generate various nutrients such as vitamin C, B group vitamins (including the famous B12), and vitamin K.”

Just to be clear, these increased nutrients and gut health improvement happen with lactic acid fermentation, not ethanol fermentation. There’s an ongoing debate about the health or non-health benefits of alcohol, but that’s not really the focus of this article.

Acetic fermentation is also associated with health benefits and is primarily studied in the consumption of vinegar.

What Do Fermented Foods Taste Like?

Besides preserving foods and providing health benefits, people like fermented foods because of their unique taste and texture. Words that people might use to describe fermented foods are “tangy” “sour” “salty” or “savory.” Of course, the exact taste of fermented foods will vary based on what the food is and how it was fermented.

For instance, kefir is described by one source as, “slightly fizzy, viscous consistency; a distinct sour smell; and a tart, creamy taste similar to liquid yogurt or buttermilk.”

Another website describes kombucha as tasting “…effervescent, tart, and slightly sweet. Depending on the added flavors, it can even taste fruity, floral, spicy, or herbaceous. It has a flavor profile similar to sparkling apple cider but with a more pronounced sour taste. After the tea is fermented, the finished drink actually doesn’t taste like brewed tea anymore.”

I’ve never had kefir OR kombucha, but I have had sourdough bread before. I would describe it as tasting very similar to yeast bread, but with a tangy-sour taste mixed in.

Who Discovered Fermentation?

Cultures around the world have been fermenting foods since ancient times. Not totally surprisingly, some of the earliest forms of fermentation have been used to make alcohol. However, non-alcoholic fermentation has also been around for a very long time. The Rockerfeller University claims that cultures in the Middle East have been pickling cucumbers since 2000 BC, and the fermentation of vegetables has been common in China since 300 BC.

Although people have been using this process for many years, a French chemist and microbiologist by the name of Louis Pasteur is believed to have been the first person to fully understand the science behind fermentation. He was asked to help a local distillery solve some problems with their alcohol process, and during this time he discovered that fermentation is caused by living organisms.

During his research into fermentation, Pasteur also discovered the process of heating things up in order to prevent contamination. Today we know this as “pasteurization.” In his time they used this method to destroy harmful bacteria in wine, but today it’s used in other drinks such as fruit juices and milk.

During his discoveries in food, Pasteur realized that living organisms were also responsible for making people sick, and laid a foundation for developing vaccines.

Does Fermentation Require Oxygen?

This is a commonly asked question and the answer isn’t simple. In most cases, fermentation happens in an anaerobic atmosphere. As we learned earlier, this means without oxygen. As an example, you might place some vegetables in salt brine and seal them to make fermented vegetables. In a sealed jar, the fermentation process is without oxygen. That’s how MOST fermentation takes place. Ethanol fermentation is also made without oxygen. So no, fermentation does not require oxygen.

However, when we’re talking about something like vinegar or kombucha, the fermented foods go through two stages. The first stage is without oxygen and the second stage is with oxygen. Instead of anaerobic, the second stage is aerobic. This is the acetic style of fermentation we talked about earlier.

What is the Difference Between Pickling and Fermentation?

Pickled foods have a distinct taste that comes from the pickling process. Cucumbers taste very different after they’ve soaked up a vinegar brine than they do fresh off the vine. Pickling changes the taste and texture of foods like fermentation, but it’s actually a very different process.

Pickled foods are soaked in an acidic liquid. Fermented foods are not soaked in an acidic liquid, but the liquid becomes acidic through the fermentation process.

Another major difference between the two is pickling happens under heat which kills good and bad microorganisms. Fermentation requires microorganisms to work, but destroys other types of bacteria as it turns into acid. Fermentation does not require heat.

Vinegar which is the product of fermentation does not ferment other foods by proxy. Putting cucumber spears in vinegar doesn’t ferment it, it pickles it.

You can ferment cucumbers through a lactic fermentation process, but it will have a different flavor than pickled cucumbers.

The Disadvantages of Fermenting Foods

There are a lot of advantages about fermented foods, such as health benefits and the ability to preserve food without expensive equipment or an energy source (heat). But there are some potential disadvantages to fermenting food as well. Here are a few things that could go into the cons list for food fermentation.

  • It’s hard to do on an industrial scale. Food fermentation is a slow process and can become contaminated if not carefully monitored.
  • Food contamination or foodborne illness is a problem with fermentation if it is not done correctly.
  • Some people may feel bloated or gassy after consuming fermented foods especially when they first begin consuming them.
  • Some people with a compromised immune system may need to be careful with fermented foods. If you’re concerned about this, consult your doctor.

How to Ferment Foods

I’ve never fermented foods before (although I would like to try!) so I’m not going to teach you how to do it. I will include a few videos that I found helpful in showing how to ferment foods safely.

This video is great for teaching how to make fermented vegetables:

A friend of mine from Leavenly (a sourdough website) also has a great video about how to bake sourdough bread which is geared towards beginners and busy moms.

I like this video to show how to make Milk Kefir

And Brad from Bon Appetit can show you how to make Kombucha

What You Need to Ferment Vegetables

What You Need to Make Sourdough Bread

What You Need to Make Kefir

What You Need to Make Kombucha

The moral of the story is if you want to make fermented foods, you should get a kitchen scale.

How Often Should You Eat Fermented Foods?

How often should you eat or drink fermented foods? My gut answer is “as much or as little as you want.” Ha! But I’m sure that’s probably not the answer you’re looking for.

If you’re new to eating fermented foods, it’s best to start a little at a time. It’s good to see how your body reacts to it. It could make you feel gassy, bloated, or make your stomach ache, especially if it’s a new thing for you.

The general consensus seems to be that a few fermented foods on a regular basis will do more for you than a lot of fermented foods every once in a while. You can try to incorporate fermented foods slowly into your regular diet, but you don’t need to eat tons of it to get the healthy food benefits.

What Else Do You Want to Know About Fermented Foods?

I tried to give a nice round analysis of what food fermentation is as well as the advantages and disadvantages. What else would you like to know about food fermentation? Is it something that’s brand new to you or is it something you’ve been making and eating for a long time?

I would LOVE to hear from you in the comments below! I hope you enjoyed this deep look info food fermentation and even learned a thing or two. I know I did!

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