Fermentation is an amazing natural tool that can help make food more digestible, nutritious and flavorful.
In this post we review the basics of fermentation.
Fermentation's Key Ingredients
Without these helpful microorganisms, the basic conversion of carbohydrates into alcohols and acids, which we refer to as fermentation, couldn't take place.
However they've enjoyed an uneasy relationship with us ever since their discovery in the 17th century. Initially linked to illness and disease, the benefits of microbes - especially in the food chain - have only recently begun to be understood and publicized.
Now the emphasis is on incorporating a wider range of fermented foods into our diets to support overall health and nutrition. However many of the traditional tools and techniques used to produce these foods have become less well-known.
Fermentation: Three Different Types
There are three basic forms of fermentation:
Lactic acid fermentation; when yeasts and bacteria convert starches or sugars into lactic acid in foods like sauerkraut, kimchi, pickles, yoghurt and sourdough bread.
Ethyl alcohol fermentation; where the pyruvate molecules in starches or sugars are broken down by yeasts into alcohol and carbon dioxide molecules to produce wine and beer.
- Acetic acid fermentation of starches or sugars from grains or fruit into sour tasting vinegar and condiments. This is the difference, for example, between apple cider vinegar and apple cider.
Each of these kinds of fermentation is down to the work of microbes specialized at converting certain substances into others.
How Does Fermentation Work?
Microbes use carbohydrates (sugars, such as glucose) for energy to fuel their survival. To make use of that energy, organic chemicals like adenosine triphosphate (ATP) deliver it when needed to every part of a cell.
Fermentation is similar to the kind of respiration that takes place when there isn't enough oxygen present, namely anaerobic respiration. However unlike respiration, which uses pyruvic acid, fermentation leads to the production of different organic molecules like lactic acid, which also leads to ATP.
Individual cells and microbes have the ability to switch between these different modes of energy production based on the environmental conditions.
Different Stages of Food Fermentation
Fermentation can have several stages depending on what's being fermented.
Primary fermentation is when microbes rapidly set to work on initial raw ingredients such as fruit, vegetables or dairy.
During this short phase, yeasts or other microbes convert carbohydrates (sugars) into other substances such as alcohols and acids.
Secondary fermentation, a term often referred to in winemaking and brewing circles, refers to a longer stage of fermentation that takes place over several days or weeks.
Secondary fermentation occurs when many yeasts and microbes start to die off and their available food source (the carbohydrates) becomes more scarce.
At this stage, the pH of the ferment may be significantly different from when it started out, which also affects the chemical reactions taking place between the microbes and their environment.
The length and stages of fermentation will vary depending on what's being made. Beer and wine, for example, pass through several different stages of fermentation that behave and look markedly different from each other.
Getting Fermentation Started
While many microbes are naturally present in the air we breathe, fermentation often requires a specific "starter" set of cultures.
Making fermented vegetables, on the other hand, is a more gradual process composed of several phases that don't require as much direct intervention to manage.
Many of the commercially available fermented foods today, including Cultured Coffee, are produced using select microbes whose role in producing healthy fermented foods has been scientifically evaluated.
These microbes can be introduced into food in a number of different ways. Many cultured dairy products, for example, start with dairy grains or specific strains of milk-loving cultures, which are commercially cultivated.
The flavor and textures of products such as yoghurt and cheese can be manipulated by selecting specific starter cultures. The environment in which they're produced can then further refine these qualities.
Similarly many wines and craft beers owe their particular characteristics to the wild or commercially cultivated yeasts used to produce them. These can be added during the brewing process.
The subsequent production and aging process for these products should ideally be controlled to prevent spoilage through external microbial contamination.
Once fermentation begins, controlling the rate of fermentation and end product is all down to the balance of water and sugars, temperature and time.
Fermentation: Protecting Your Food
Exposing your fermenting food to air can not only prevent proper fermentation from taking place but also increase the risk of spoilage and food poisoning.
There are a number of ways to prevent this.
Aside from being a part of many recipes, submerging fermenting food in brine (a salt solution) prevents it from coming into contact with the air. This method works for solid pieces of food like chopped vegetables.
Many home fermenters use containers such as a mason jar with a lid or storage containers where food can be sealed and stored for long periods without air contamination.
Typically this equipment will have a valve or release to vent carbon dioxide released during fermentation unless the end product (wine or kombucha, for example) benefits from carbonation.
Alternatively sealed containers can be opened on a regular basis to manually let trapped carbon dioxide out. This process requires more careful monitoring to prevent food spoilage.
Commercial fermentation requires specialist equipment such as fermentation tanks for brewing beer, for example. Using special equipment enables fermentation to be controlled and standardized at scale.
Microbes typically like to work in a warm, room temperature environment. The exact temperature range will vary based on the types of microbes involved and product that's being fermented.
Changing the temperature can have a big impact on fermentation. Moving a fermenting product to a cooler temperature, for example by placing it in the fridge, will slow down the rate of fermentation or stop it altogether. Heating a ferment too much may kill the microbes doing the fermentation.
Aside from these basics, the rest of the fun is all down to the recipe!