A happy accident of fermentation may have enticed the last hunter-gatherers of the Stone Age to abandon foraging for farming, thus sowing the seeds of civilization. The Natufians, a semi-sedentary culture, lived in the Levant during the Epipaleolithic Period 14,000 years ago. Charred flatbread remains dating 4,000 years before the birth of agriculture were recently found at their site in Jordan’s Back Desert. It was made from tubers, wild einkorn, and barley that were pounded to make a gruel-like food that could be cooked on hot stones. Doubtless, the perishable gruel fermented from airborne yeasts and bacteria in search of a meal of their own.

Patrick E. McGovern, Ph.D., a pioneer of the emerging field of molecular archaeology, believes thirst — not hunger — inspired grain domestication, with fermentation playing a starring role.

The fermented gruel provided a nourishing drink with a possible side benefit. During fermentation, a biological process produces ethanol, which increases serotonin and dopamine activity in the brain’s “reward center.” Life was challenging in the Stone Age. The neurotransmitter systems may have lessened anxiety and created a sense of pleasure, making the world a groovy place. These Stone Age inhabitants just may have been enjoying the world’s first beer.

The natural metabolic process of fermentation transforms raw ingredients into something delicious with the help of fungi, bacteria, and mold — microorganisms (microbes) that most people try to banish from their kitchens. Each food’s unique flavor profile depends on the raw materials used, the species of microbes, the climate, and the location where they are produced.

Fermentation preserves perishable ingredients in a natural way. Deterioration slows or stops through the hard work of beneficial microbes. Plus, fermented foods have many health-promoting attributes, including increased bioavailability of nutrients and improved digestive health, especially when eaten with rich, fatty meats. Consider the global pairings of lamb and yogurt, sausages and sauerkraut, or a hamburger with dill pickles.

Indigenous fermented foods, which evolved worldwide, are linked to local cultures and traditional practices. Preparation methods have been handed down like heirlooms through the generations. Whether artisanal or factory made, most people now consume at least one fermented food daily, such as yogurt, sauerkraut, cheese, dry-cure salami, sourdough, olives, dill pickles, hot sauce, vanilla pods, and cider vinegar. The greatest diversity of fermented foods is, not surprisingly, in Asia. Japan’s fermentation traces back to ancient China. The Japanese are masters of tsukemomo or “pickled things.” A vast array of colorful vegetables, fruits, roots, and fish are preserved in various fermenting agents: salt, rice bran, sake lees, koji, and miso. Enzyme-rich natto (sticky soybeans) is produced by bacterial fermentation.

Kimchi, one of Korea’s oldest fermented traditions, is a category of seasonal, salt-preserved vegetables that can be spicy and ripened to pungency or mild. Doenjang (soybean paste) and gochujang (spicy red pepper paste) are also indispensable. Fermented fish sauces like Vietnamese Nước mắm and Filipino patis add great savor to foods. India’s vast array of ferments include dosa (lentil-rice crepes) and idli (steamed lentil rice cakes).

Many substrates are used for fermented beverages: cereal grasses, fruits, milk, vegetables, nuts, roots, and tea. In Russia, rye bread is used to make kavass. Wine, beer, and cider are the best-known fermented alcoholic beverages. Production of distilled spirits, such as whiskey and gin, is partly based on grain fermentation. Coffee beans, cocoa beans, and China tea (pu-erh) also involve fermentation during processing. Honey, flower nectar, sugar cane, and palm tree sap are natural, sweet liquids that can be fermented as well.

A taste must be acquired for some fermented foods and beverages, including Sudanese garis (camel’s milk), Central Asian koumiss (mares’ milk), and Kenyan mursik (smoked milk). Masato is a “mouthwatering” cocktail in the Peruvian rainforest made from cooked yuca. Amazonian tribal women masticate the tuber, then spit the chewed pulp into a container with local fruit and spices. Enzymes in their saliva break down the starch into sugar for fermentation.

French chemist Louis Pasteur (1822-1895) was at the forefront of a new branch of science — microbiology — when he discovered the biological basis of fermentation and showed that microbial growth was a common feature of all fermentation processes. Under anaerobic conditions, which are without oxygen, microbes (yeasts) convert natural sugars to ethanol during alcoholic fermentation; they also convert natural sugars to organic acids during lactic acid fermentation. Different types of fermentations are associated with specific microbes. Due to the lack of oxygen during the process, pathogens are killed off.

Pasteur said, “Fermentation is a property of living cells.” He described the process as “la vie sans l’air” or “life without air.” The word fermentation derives from the Latin verb “fervere” meaning “to boil.” Like bubbles on top of boiling water, effervescence or bubbliness is a noticeable characteristic of fermenting food.

Alcoholic and lactic acid fermentations are the most commonly used methods to ferment food. Wine, bread, and beer are produced with alcoholic fermentation. Pasteur showed how bacteria (Acetobacter aceti) converts ethanol to acetic acid for vinegar. Found in soil, flowers, bees, and fruits like grapes, this bacteria is not the vintner’s friend; it turns wine into vinegar. Many quick homemade or commercial vegetable pickles are made with vinegar, but they differ from traditional lacto-fermented vegetables preserved with dry salting or brine.

Many genera of bacteria produce lactic acid. Lactic acid bacteria are among the most important groups of microbes for food fermentations. The friendly bacteria lactobacillus is found on plant surfaces and in the gastrointestinal tracts of humans, where it helps break down foods, absorb nutrients, and fight off pathogens. LAB gives the characteristic tangy taste to sauerkraut, kimchi, labneh, lassi, fermented fish and meat, kefir and even silage — fermented animal feed. Sourdough is fermented with lactic acid and yeast. Acidic foods are less susceptible to spoilage, and the acid causes milk protein to form a solid curd. Some LAB are used as probiotics in foods like yogurt. Lactic acid fermentation can also occur in our muscle cells when we exercise strenuously.

Molds are food preservers that impart characteristic flavors to some foods. They are aerobic and tolerate high concentrations of salt and sugar. Usually associated with spoilage, molds can also be beneficial to charcuterie (salami) and mold-ripened cheeses, such as the French Roquefort and Camembert. Molds are commonly used in Asian food fermentation. Indonesian tempeh, a soybean product reminiscent of tofu, is made with whole, cooked beans inoculated with mold (genus Rhizopus). In Japan, koji mold spores (Aspergillus oryzae) are used for soy sauce, miso, sake, mirin, amazake, and daikon-zushi — fermented daikon, herring, and malted rice.

The notion of allowing bacteria to grow uncontrolled on unrefrigerated food seems a bit daring — like dancing on the razor’s edge. But home fermentation is completely reliable if careful sanitation and fermentation practices are followed. USDA microbiologist and fermentation safety specialist Fred Breidt, Jr., Ph.D., says fermentation is “extremely safe and effective … the scientific literature has never recorded a case of food poisoning from raw vegetables that have been fermented properly.”

It is essential to differentiate between beneficial and pathogenic microbes and understand how they affect fermentation. Bubbling is a normal function. Whitish foam or fuzzy spots that resemble a weird science project may appear on fermenting veggies. It is probably harmless Kahn’s yeast, which can be removed. But if a colorful or a dark mold (or something worse) is spotted on the surface or under the brine, throw the entire substance out. Mold spores are everywhere, but through careful handling, they can be kept under control. Many resources provide tips for dealing with unfriendly microbes.

Probiotics are live and especially beneficial microbes that help establish healthy gut microbiota. In a 2017 Chinese-Canadian study, researchers worked with a group of super-healthy Chinese seniors, some100 years old, who had microbiome profiles resembling those of healthy 30-year-olds. The centenarians’ diets were high in Chinese probiotic fermented foods and prebiotic foods, which are undigestible substances that feed beneficial bacteria and lower disease risk factors. All prebiotic foods are fiber, yet not all fiber is prebiotic. Good choices include collards, kale, soybeans, whole grains, bananas, dragon fruit, seaweed, blueberries, onions, beans, garlic, asparagus, artichokes, and burdock root. Researchers concluded that a biomarker of healthy aging may be to continually maintain a diverse community of microbial species in the GI tract.

Not all fermented foods are created equal. Heat can kill beneficial microbes through canning and pasteurization. Nearly every supermarket has a refrigerated grocery shelf with live, fermented foods. Check labels to discover foods with active cultures. Active culture yogurts with live, beneficial “bugs” such as Lactobacillus acidophilus include FAGE and Stonyfield.

Do-it-yourself fermenting, however, is not high tech and does not require specialized equipment. You can start with a large Mason jar. Fermenting does require careful attention to detail and regular monitoring. A large body of information on fermentation exists today through Facebook groups, websites, cookbooks, and festivals dedicated to the art. Progressive chefs and restaurants are adopting fermentation methods to create new flavors. Plenty of inspiration is available from which to draw. Research the techniques, gather safety tips, discover new recipes, and explore the nuances of fermentation. Experience counts for a lot. Crocks and jars are bubbling at my house at this very moment. Happy fermenting!

Fermenting Vegetables

Select high quality, seasonal produce. Vegetables for dry-salting can be thin sliced, chopped, or grated; smaller cuts ferment faster. Prepare a brine to ferment whole vegetables or large pieces.

Practice good sanitation to avoid pathogens. Wash equipment in very hot, soapy water; wash whole produce in cool water and dry with paper towels. Trim off the blossom end of cucumbers to remove enzymes that can make vegetables soft and slippery. Choose a salt like unrefined sea salt, pickling salt, or Himalayan salt. Avoid those with anti-caking agents or iodine, which inhibit microbe action and cause a metallic taste. Reduced-sodium salts and flaked salts, which vary in density, are not recommended. Use filtered or purified water for brines. Hard water can interfere with acid formation. Chloramine, an antimicrobial disinfectant in most city water systems, could impact successful fermentation. Weaker brines allow faster fermentation because microbes are not suppressed, but the chance for spoilage is greater. Higher salinity slows fermentation (good in warm weather) and minimizes spoilage risk. Salt ratios are a balancing act, with many variables. For brines, try 1 to 3 tablespoons salt per quart of water, and for dry-salting try 2 to 4 teaspoons salt per pound of vegetables.