Reliable Roadmap to Become an Expert in Fermentation Biology (And Create a Better Relationship with Alcohol)

Learning fermentation biology allows us to dive deeper into our relationship with alcohol. Why is this important? To not abuse alcohol, we must respect it. To respect it we must understand it.

Understanding the nuts and bolts of fermentation is a step towards respecting one of nature’s greatest gifts.

When I began my undergraduate degree in evolutionary biology I realized how powerful this planet truly is. How powerful nature is, and the effect it has on us and vise versa.

Not only do humans have an enzyme in our gut specifically for breaking down alcohol, alcohol dehydrogenase (ADH), but we have evolved alongside fermentation since the Neolithic Period.

But, before humans and animals have an opportunity to break alcohol down: yeasts, sugars, and bacteria undergo a process called fermentation.

You will learn what fermentation is, the biology behind fermentation, factors affecting fermentation, evolutionary biology of fermentation with humans and animals, and common challenges in fermentation practices.

This post is all about fermentation biology.

The Biology of Fermentation | The Nuts & Bolts

Why does the Biology of Fermentation Matter?

Understanding the process of fermentation, we can connect better to our ferments we make, beers at the store, and even prevent spoilage of our homemade wine and beers.

Fermentation biology can be complex. There are many players involved in the process, though, once we break it down and see what is really important we can create better fermented drinks with respect for the craft.

What is Fermentation in a Biological Context?

So, as we sip our wines and gaze over the horizon we feel the beauty this craft can create. But, what about the nuts and bolts of creation? How does that work?

Fermentation is an anaerobic AND aerobic process. In simple terms, anaerobic means “without oxygen”. Where as aerobic means “with oxygen”.

Some types of fermentation require oxygen (vinegar and some fermented foods) and others do not. During these processes, yeasts and other bacteria convert sugars into alcohol, gasses, and acids.

The main conversion: yeast eat the sugars and the byproducts are alcohol and carbon dioxide. Along with other bacteria, acids, etc.

Hence why home fermentations usually have an airlock. It keeps oxygen out, but allows carbon dioxide to escape.

Each byproduct of this reaction contributes to the flavor and texture of the food or drink being fermented.

Let’s dive into the different yeasts and bacteria involved in this process. All of which give us the flavor profile and mouthfeel of various fermented drinks!

Yeasts Involved in Fermentation

If you are new to fermentation, there are multiple strains of yeast! Actually, there are tons of yeast strains. Each providing different flavors and mouthfeels. So, when fermenting and choosing yeast it can be beneficial to know the varieties.

Brewer’s Yeast (Saccharomyces cerevisiae)

Transforms sugars in alcohol through alcoholic fermentation.
Creates a by product called “esters”. Esters are derived from an acid and produce fruity flavors and can contribute to the overall mouthfeel, most specifically, in beers.

Wine, cider, and lager yeast (Saccharomyces bayanus)

A yeast strain which holds a higher tolerance to cold temperatures.
Creates less fruit esters than S. cerevisiae resulting in a clean, crisper, and more neutral flavor. As seen in most white wines, lagers, and ciders.

Belgian yeast strain (Brettanomyces)

A yeast strain most popular in Belgian style beers.
Produces the “barnyard” flavors in beer.
Considered a “spoilage” yeast in most other fermented drinks due to the funky flavors it provides.

Bacteria Involved in Fermentation

Along with yeasts in fermentation, bacteria also play a huge role. Some bacteria are helpful to produce elegant ferments, others are spoilers and can ruin your hard work.

Lactobacillus bacteria

A bacteria the creates lactic acid.
A key player in lactic acid fermentation for sour beers, kimchi, pickles, and some dairy products like yogurt or kefir.
Creates a low pH environment.
Produces a tart, sour, taste and acts as a natural preservative.
Well documented for it’s potential gut-health benefits.

Pediococcus bacteria

Similar to lactobacillus, used in sour beers, mostly Belgian lambics or Berliner Weisse beers.
Also produces lactic acid but when not managed properly can result in a “stringy” texture.
In some fermented foods, the ropiness of this bacteria is desired.
Can be used in secondary fermentation when a slow, steady acidification is needed. Usually to contribute to the aging process.

Acetobacter bacteria

Converts ethanol alcohol into acetic acid, contributing to the production of vinegars, but can be undesirable in beer or wine.
If oxygen is overly-present, acetobacter can turn alcoholic beverages into vinegar. Mostly an issue with homemade fermented beers and wines.
Can contribute to acidic flavors, or complete spoilage of a ferment.
One can use Camden tablets and Star Sans to rid a ferment of acetobacter before it becomes an issue.

Bifidobacterium and Leuconostoc

Found in some cheeses and fermented vegetables.
Contributes to the texture and flavor in cheese, and some creating diacetyl, which creates a buttery aroma.

How Has Fermentation Evolved with Humans & Other Animals (Evolutionary Biology Perspective)

We can see the elements that play a huge role in fermentation: bacteria and yeast. They are vital for creating fermented drinks with complex flavors and an organically drawn mouthfeel.

Luckily, we won’t run out of these lovely microorganisms, they exist everywhere. Even such, we have evolved with and around them since the dawn of time.

Fermentation in Nature

Humans are not the only species that enjoy fermented beverages, and why should we be. Fermentation is a naturally occurring process.

A great book, Sacred and Herbal Healing Beers, discusses elephants and their relation to fermented palm sap. The elephants knock down these palm trees, then stomp in the middle of the stump to release the juices.

The naturally occurring yeasts and bacteria either on the tree, or from the feet of the elephant, will inoculate the sugary palm sap to start fermentation.

They leave the stump alone for 2 weeks and when they return they enjoy a fermented drink.

Bees experience similar intoxication.

Under certain conditions, the nectar or honey can get fermented in the hive or from a flower that has a high yeast content that ferments quickly.

Our friend, fermentation, interacts with lots of the animal kingdom. Providing ease and euphoric sensations to these creatures. We are no different.

Fermentation in Humans

For humans, we have an enzyme in our digestive system specifically designed for breaking down alcohol, alcohol dehydrogenase (ADH). Which shows our evolved relationship with alcohol.

Not only are there amazing varieties of fermented beverages in the world, we have learned how to coexist with them.

It is no secret that fermented drinks (beer, wine, cocktails) have taken over a large portion of our society. From bars, wineries, brew pubs, and cocktail bars, fermentation plays a large role in the world around us.

But, how did we get here?

A great anthropologist Patrick E McGovern in his book, “Uncorking the Past“, goes on a quest to finding humanities first fermented drinks, and our relationship to them.

Our relationship to fermented drinks, and alcohol, can date back as far as the Neolithic Period (around 10,000 BC).

With the invention of pottery around 6,000 BC, anthropologists were able to track shards of pottery back to this period AND identify the liquids that once filled them.

Through in depth research, the scientists were able to find tartaric acid on the inside of the shards of pottery. Which confirmed the jar was once filled with wine (McGovern p.74).

McGovern goes on to describe the tribal relationships humans had with fermentation. The role of “shamans” and “medicine men” in these early civilizations.

From rice wine in China to sorghum beers in Africa, he lays out our amazing evolved relationship with alcohol.

Read Uncorking the Past to explore the evolution of humanity with fermented drinks.

The Biology of Fermentation | Types of Fermentation

Now, we know the phases of fermentation, the yeasts and bacteria involved, and how we have evolved with these organisms. Let’s dive into the 4 types of fermentation as it relates to biology.

Each type can be practiced at home whether it’s making fermented drinks or food.

1. Lacto-Fermentation

Lactic acid ferments use Lactobacillus bacteria.
Lactic acid fermentation lowers the pH which creates an unfriendly environment for other microorganisms to grow.
Lacto-fermentation is mainly fermenting foods.
Traditional Russian Kvass undergoes lacto-fermentation. The Lactobacillus bacteria present on the bread create lactic acid, hence the sour taste of kvass.

2. Malolactic acid

When I worked in Napa at a winery we practiced malolactic fermentation. After primary fermentation is complete we engage in malolactic acid fermentation.

Adding malolactic acid in secondary fermentation converts harsh malic acid to the softer lactic acid.

Overall, malolactic fermentation lowers the acidity of the wine giving the wine more complex flavor profile and a rounder softer flavor.

3. Ethanol, or alcoholic fermentation

Uses either wild yeast, or commercial yeast, to convert sugars into alcohol
The process of beer, wine, cider, mead.
Ethanol fermentation utilizes various kinds of yeasts and bacteria.

4. Acidic Acid Fermentation

The acetobar bacteria creates acetic acid turning the ferment into vinegar.
If not careful, homemade wine can turn into vinegar due to the contamination of acetobar bacteria.

Fermentation Process

The Phases of Fermentation

Adaptation. Adaptation is the lag phase when the yeast cells begin to blend into their environment. No yeast activity is seen yet in the fermenter; it is a relatively short period (12-48 hours).
High growth phase. The yeast have acclimated to their environment and now they begin their ultimate job: eat and reproduce. Eat the sugars and make more yeast cells!!
Maturation / Conditioning. Once most of the sugars are eaten, the yeast cells essentially go into hibernation and the beer begins to “condition”. This is when the flavor profile begins to develop.

Factors that Affect Fermentation

Fermentation, as we can see, has so many elements and players that contribute to the finished product: beer, mead, wine, or fermented foods.

When we are creating our homemade beverages, it is important to keep these factors in mind: temperature, pH, oxygen levels, and nutrients for a successful ferment.

Each of these factors can alter the taste, mouthfeel, acidity, etc of any fermented drink. So, let’s see how each factor reacts to the yeasts and bacteria we learned above.

1. Temperature

Generally, fermentation speeds up with higher temperatures.
Fermenting at higher temperatures create higher levels of fruity esters or spicy and medicinal flavors.
The lower the temperature the slower your ferment will move. For example, a lager is fermented in the cold for months.
Yeast: Usually an optimal temperature is 65-75F.
Bacteria: Lactic acid in food fermentation enjoy 78-86F.

2. pH

Yeasts and bacteria have different pH levels in which they thrive.
Enzymes in fermentation are pH sensitive.
For beer making, the desired pH is between 5.2 and 5.5
For wine making, the desired pH is between 3.3 and 3.6
Undesirable pH can lead to off flavors and contribute to the growth of unwanted bacteria and other microorganisms.

3. Oxygen levels

Anaerobic fermentation creates alcoholic beverages and lactic acid ferments (yogurt).
Too much oxygen during anaerobic fermentation and you get spoilage, off flavors, or acetic acid build up.
Aerobic fermentation produces vinegar.
Oxygen reacts to acetobacter in fruits to create acetic acid which results in the production of vinegar.

4. Nutrients

We can add yeast nutrients into our ferments to support fermentation.
Too much or too little can inhibit the growth of essential microorganisms
Helps fermentations from getting “stuck” which usually is from a lack of nitrogen and nutrients.
Usually in the form of a yeast nutrient.

Common Challenges in Fermentation Practices

As you can see the variety of yeasts, bacteria, interacting with oxygen, the temperature in the environment, and the nutrients available all create the fermentation process.

However, the complex biology of fermentation allows for mistakes and issues to arise.

The common challenges when practicing fermentation are:

Contamination
Consistency
Regulation (mainly for industrial sized breweries, wineries, distilleries)

For example, acetobacter can easily contaminate a fruit wine if you do sanitize your equipment thoroughly. That will turn your amazing fruit wine into vinegar…

Now, the biggest challenge I find in fermentation: consistency.

I mostly work with wild ferments. When working with wild yeast it is challenging to know the exact fermentation biology that occurs in a ferment.

If you do not have a stable temperature to house your ferments you, also, will experience challenges in consistency.

Best Ways to Practice Fermentation at Home

As we see, fermentation biology is a complex array of different microorganisms all working together. Then, once we consume the fermented drinks or foods, our human biology continues to interact with fermentation.

Best ways to practice fermentation:

Beer making at home
Wine making at home
Fermented foods
Sourdough

We have evolved next to these microorganisms since the dawn of time. Fermentation is a sacred and beautiful natural process. Once we learn and understand the importance of this process in nature we can begin to heal our relationship with it.

To respect is to understand. Respecting this natural process allows it to be in our lives in a sacred manner, without abusive actions.

Fermentation biology is the start of a beautiful practice, whether that be cider, wine, mead, beer, or fermented foods.

May this information suit you and bleed into your relationship with alcohol and fermented drinks so we can live in harmony with nature’s greatest gift.