Since the Neolithic era, humans have been fermenting food. But the science of fermentation was unknown until Louis Pasteur, a French microbiologist, discovered that living organisms caused the fermentation process. This process not only enhances the taste of foods like sourdough bread, cheese, and wine but also contributes to the survival of our species.
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What is fermentation?
Fermentation refers to a metabolic process where microorganisms induce favorable changes in food and beverages, enhancing flavor, preserving them, and offering health benefits, among other improvements.
Originating from the Latin verb “fervere,” meaning “to boil,” the term “ferment” is somewhat ironic, as fermentation can occur without any heat.
How does fermentation work?
If you want to become an alchemist, you must understand the science behind fermentation and the chemical transformations occurring to your food.
- Microorganisms use carbohydrates like glucose for energy, fuel, and their survival.
- Microbes produce adenosine triphosphate (ATP) via respiration. Aerobic respiration, which depends on oxygen, starts glycolysis (the process of converting glucose into pyruvic acid). Oxygen must be present for aerobic respiration to occur.
- Fermentation is most like anaerobic respiration (occurring with low oxygen). Under these conditions, different organic molecules are formed like lactic acid, which also leads to ATP formation.
- Cells and microbes can adapt to environmental changes by switching between aerobic respiration and fermentation for energy production.
- While fermentation is a common anaerobic energy source, some organisms use sulfate in their electron transport chain as an alternative electron acceptor.
What’s going on during the fermentation process?
The fermentation process is due to a lack of oxygen (anaerobic conditions) along with the presence of beneficial microorganisms (bacteria, molds, yeasts). However some yeast cells, such as Saccharomyces cerevisiae, prefer fermentation over aerobic respiration even in the presence of oxygen when there’s an abundance of sugar.
- Beneficial microbes during fermentation convert sugars and starches into alcohols and acids, enhancing the nutritional value of food and extending its shelf life.
- Fermented foods are a source of essential digestive enzymes, which humans have a limited enzyme supply that reduces with age.
- Fermentation assists in pre-digestion, with microbes breaking down food components like sugars and starches before consumption.
What are the benefits of fermentation?
Fermented foods add beneficial microorganisms to your gut. They are rich in probiotics, helping you to maintain a healthy gut which can extract important nutrients from food.
- Probiotics support the immune system by enabling the gut to produce substances with antibiotic, anti-tumor, anti-viral, and antifungal properties. Additionally, the acidic environment created by fermented foods is unfavorable for pathogens.
- Fermentation neutralizes anti-nutrients such as phytic acid found in grains, nuts, seeds, and legumes, which can lead to mineral deficiencies. By neutralizing phytates, fermentation also enhances the digestibility of starches, proteins, and fats.
- Fermentation enhances absorption of vitamins and minerals in food, particularly increasing B and C vitamins, folic acid, riboflavin, niacin, thiamin, and biotin. Probiotics, enzymes, and lactic acid in fermented foods aid in absorbing these nutrients into the body.
What are the 3 types of fermentation?
Specialized microbes capable of transforming certain substances are used in various food and beverage fermentations. Here are three key types:
- Lactic Acid Fermentation: This involves yeast strains and bacteria converting starches or sugars into lactic acid without heat. In these anaerobic reactions, pyruvic acid uses NADH to form lactic acid and NAD+. This process also occurs in human muscle cells during intense activity, leading to sore muscles. Lactic acid bacteria are essential for producing and preserving cost-effective, nutritious foods, crucial for feeding impoverished populations. Products include sauerkraut, pickles, kimchi, yogurt, and sourdough bread.
- Ethanol/Alcohol Fermentation: Yeasts convert pyruvate molecules, the result of glucose metabolism in glycolysis, into alcohol and carbon dioxide. This process is used to make alcoholic beverages like wine and beer.
- Acetic Acid Fermentation: Starches and sugars from grains and fruit are fermented into sour-tasting vinegar and condiments. Examples include apple cider vinegar, wine vinegar, and kombucha.
What are the key stages of the fermentation process?
The fermentation process varies based on the ingredients and can occur in multiple stages:
- Primary Fermentation: This initial, rapid phase involves microbes working on raw ingredients like fruit, vegetables, or dairy. These microbes, either inherent or added through a surrounding liquid like brine, inhibit putrefying bacteria. They convert carbohydrates into alcohols and acids.
- Secondary Fermentation: This longer phase, lasting days or weeks, sees a rise in alcohol levels as yeasts and microbes deplete their food source (carbohydrates). Common in winemaking and brewing, this stage sees significant pH changes, affecting the chemical interactions between microbes and their environment. Once alcohol reaches 12–15%, it kills the yeast, stopping fermentation. Distillation is then used to increase alcohol concentration by removing water.
7 Tips for Starting Fermentation
Want to try fermentation? Here are six tips for successful fermentation, whether you’re pickling vegetables or brewing beer:
- Start with Cultures: Obtain a “starter” set of cultures, like whey from yogurt, a SCOBY for kombucha, or liquid from a previous ferment. These starters are rich in beneficial microorganisms that accelerate the fermentation process.
- Maintain Clean Equipment: Ensure all kitchen tools and surfaces are clean and sterilized to avoid contamination by harmful bacteria.
- Limit Air Exposure: Prevent air contact with your ferment to avoid spoilage and food poisoning.
- Use Brine for Solids: For solid foods like vegetables, submerge them in a salt solution (brine) to prevent air contact. Adjusting the pH with vinegar can control the oxygen level in the ferment.
- Proper Storage: Store your ferment in a sealable container, like a mason jar, to prevent air exposure. Containers with a valve to vent carbon dioxide are ideal. For ferments like kombucha or wine that benefit from carbonation, you can skip venting.
- Control Fermentation Temperature: The temperature influences fermentation outcomes. Microbes generally thrive in warm or room temperatures, but the ideal conditions vary based on the microbes and ferment type. Cooler environments slow down or stop fermentation, while excessive heat can kill the microbes.
- Monitor Fermentation Progress: Regularly check your ferment for signs of progress and any potential issues. Look for changes in color, smell, and texture, which can indicate successful fermentation or potential spoilage.