According to current scientific thought, the universe is approximately 15 billion years old and the Earth is approximately 4.5 billion years old. Fossil microorganisms have been found in rocks 3.3 to 3.5 billion years old (1). They were the first forms of life to appear on Earth. They were likely the blue-green algae, which contain a pigment enabling them to use the sun's radiation to synthesize carbohydrates. They contain deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) similar to all other forms of life today. They also contain the enzymes, proteases, amylases, lipases, and other enzymes required to hydrolyze proteins, starches, and lipids necessary for recycling. This was very fortunate because microorganisms have been required ever since as recyclers of organic matter. Without them, the Earth would be a giant dumping ground containing all forms of organic matter and dead bodies. Initially, microorganisms consumed organic matter, including dead organisms, as food for their own energy requirements. Later, after plants and animals evolved, microorganisms consumed dead plants and animals and became able to invade plants and animals, causing disease—in some ways the first stage in recycling.
The next forms of life, evolving about a billion years later, were plants, also based upon DNA/RNA and having the ability to convert carbon dioxide and water to carbohydrates using the sun's radiation for energy. The plants became the food supply for future evolution of animals, including humans. Microorganisms recycled the plants, consuming them as food/energy as they died, returning them to soil for future plant growth. Plant life evolved in a sea of microorganisms and thus had to have means of resisting invasion (plant disease) even when alive. They did this by developing a ligno-cellulose structure that resists microbial invasion. A seed germinating in the soil has to survive the onslaught of billions of microorganisms that, given the opportunity, would destroy the seed and/or recycle the developing plant. Plants, their leaves and roots—cassava, sweet potatoes, yams—berries, fruits, nuts and cereal grains—particularly wheat, rice, maize, barley, rye, oats, millet, and sorghum—and legumes, beans, and peas are major staples of our food supply today.
Millions of years before humans appeared on earth, all the chemical and enzyme reactions needed for food fermentations were present as part of the recycling reactions used by microorganisms to digest and recycle plant components; for example, fermentation of fruits and fruit juices to wine and vinegar, germination of grains as the first step in brewing alcoholic beverages, and souring of milk. When humans and other animals evolved on Earth, they had to consume the food supply either before it was invaded by microorganisms and recycled or while in various stages of recycling—the fermented foods. When microbes produced unpleasant aromas or flavors in the food or produced toxins that caused illness or death, the food was spoiled and humans learned to avoid it. If the invasion of the food components by microorganisms yielded attractive aromas, flavors, and textures, humans learned to appreciate and desire such foods. These were the beginning of fermented foods, including sour milk, cheeses, wines and beers, vinegar, lactic acid products such as sauerkraut, and hundreds of other fermented foods consumed today.
There is another factor related to fermented foods and lost in antiquity, and that is salt: common salt, sodium chloride, or sea salt—a mixture of sodium, potassium, magnesium, and calcium salts found in seawater. Salt has been highly prized for thousands of years. In ancient times, soldiers received part of their pay in the form of salt (or salary) and, even today salt is vital to producing savory foods, based primarily on its condiment value, but it was also valued throughout history as a preservative. Salt in suitable concentrations, prevents putrefaction and leads to a controlled protein hydrolysis.
When ponds of seawater dry up under the influence of temperature and wind-flow (actually a method of producing sea salt even today), the seawater may contain fish and other sea animals that isolated in the seawater die their bodies are self-autolyzed by their enzymes, leading to amino acid/peptide concentrations. It is likely that humans discovered that such animal residues in high salt brines were savory condiments.
Humans also discovered very early that salt could preserve fish or other animal tissues, especially when they were sun-dried, and such salted, sun-dried fish are staple foods in many marine areas of the world today.
Seawater also may have played a role in primitive lactic acid fermentation/preservation of plant materials because such materials stored in seawater would likely undergo lactic acid fermentation as well.
It has been hypothesized by anthropologists (2) that it was alcoholic fermentation and the desire for alcohol that motivated humans to settle down and become agriculturists. Humans could not have survived over the millennia without fermented foods. Fermentations preserve foods, improve digestibility and enrich substrates with essential vitamins, amino acids, and fatty acids. They also convert vegetable proteins to savory meat-like flavors and textures and yield the diverse flavors and aromas that enriched the human diet in the past, enrich our diets today, and will continue to do so in the future.
II. HISTORY OF SELECTED FERMENTED FOODS A. Alcoholic Fermentations
Mead/Honeywine. Honeybees have been producing honey from flowering plants and probably also from honeydew for 10 to 20 million years before humans appeared on earth (3). Honey was the world's first concentrated sweet. Its sugar concentration (about 80%) is too high for honey to undergo fermentation or even spoilage without dilution. It was the reserve food for the honeybees themselves but also sought after by humans and animals such as bears. Diluted with water such as rain, however, it will undergo fermentation by yeasts that live in the surrounding environment. So it is likely that honey/mead fermentation was occurring long before humans arrived and continues as a fermentation today.
Primitive wines and beers are vastly different from our modern wines and beers. The former are generally cloudy, effervescent beverages containing not only liquid but particles of the fermenting substrate, yeast cells along with the alcohol, and B vitamins. They are very nutritious and energy-rich.
An example is African kafir/sorghum beer. The art of kafir beer production goes back to prehistoric times. In the villages, kafir beer is made by women: girls learn how to make kafir beer for their husbands before they marry (4). Sorghum grains or millet are germinated, sundried, ground, and mixed with sorghum, millet, or maize flours and water, and then cooked, cooled, and fermented by the residual yeasts and the dregs in the containers. Fermentation is carried out in large crocks or drums (5).
Fermentations involving production of ethanol are among the most ancient fermentations known. The most primitive methodology utilizes chewing the grains to introduce saliva (ptyalin) as a source of amylase to hydrolyze the starch to sugar and has been used for centuries. An example is chicha, produced in the Andes region of South America (6). Even today, women and children sit in a circle chewing maize kernels. The gobs are then removed from the mouth and sundried. Later they are placed in crocks covered with water and allowed to ferment with yeasts in the environment. The yellow colored cloudy liquid contains as much as 6% ethanol and a wide variety of B vitamins. In ancient Incan times, the emperor himself could hold office only as long as he delivered sufficient chicha to the citizens. In ancient Japan, rice wine/sake was also produced using chewing of grains as a source of amylase to convert the starch to sugar (7). Later it was discovered that rice overgrown with Aspergillus, Rhizopus, or Mucor molds also became sweet and could be fermented to rice wine. Among the more complex sweet/sour alcoholic foods are tapay, tapai, tape' and Chinese Lao-chao. These generally rely on two or more fungi for their production. These can include Amylomyces rouxii, a yeast-like mold, and Endomycopsis fibuliger, a mold-like yeast (8).
Thousands of years ago in Egypt, wheat grains/flour were made into lightly baked bread that was then moistened with water and fermented to a primitive beer—bouza.
Still earlier in human history, at the dawn of agriculture, when grains were collected in crocks, it is highly likely that such grains, on occasion, became moistened with rain, germinated, and fermented to primitive beers.
The most ancient Mexican alcoholic beverage is pulque, made by fermenting pulp juices from the Agave plant. Leuconostoc mesenteroides produces dextrans that add texture to the beverage. The alcohol is produced by Saccharomyces cerevisiae, a yeast, or by Zymomonas mobilis, an alcohol-producing bacterium. Pulque is very rich in B vitamins and plays a vital role in the nutrition of, in particular, the economically disadvantaged in Mexico (4).
B. Vinegar—the Acetic Acid Fermentation
Primitive alcoholic beverages generally contain some acetic acid, but the amount is limited as long as the fermentation remains anaerobic. The rapid production of carbon dioxide helps maintain anaerobiosis by providing a layer of CO2 on the surface of the fermenting materials. However, when the alcoholic fermentation stops, Acetobacter sp. become active as soon as oxygen becomes available, and a portion of the ethanol is converted to acetic acid—vinegar. Vinegar is an ancient condiment and extremely useful as a pickling agent or even as a medicinal because it is germicidal.
Savory/Meat Flavored Sauces and Pastes. It is not known who discovered how to transform bland vegetable protein into meat-flavored sauces and pastes. It may have been an accident; nevertheless, it was one of the great discoveries in food science. When seeds fall upon the ground, they either germinate, forming new plants, or they become overgrown with microorganisms as the first step in recycling. The seed coat is rather resistant to microbial growth, so the first organisms to penetrate into the cotyledons are often molds that produce proteases, lipases, and amylases that hydrolyze the various components in the seed. Thus, the mold-overgrown seeds become a source of enzymes. Of scientific importance, such moldy seeds are described as a ''koji'' and can be used to hydrolyze the proteins, lipids, and starches in other vegetable or animal products. The first koji in recorded literature was a millet kogi. Millet koji was mixed with meat, fish, or fowl and salt and stored in a bottle for 100 days. The first reference to meat-flavored pastes was made about 3000 years ago during the Chou dynasty in China (9). The first reference to soybeans as a substitute for meat was in the world's oldest encyclopedia of agriculture, published in a.d. 535 in China.
Soybeans, rich in protein, are an excellent source of nutrition. In order to be palatable, they must be hydrated/soaked and cooked. As long as soybeans remain dry they are not susceptible to microbial spoilage. After being hydrated, however, they become susceptible to overgrowth by bacteria and molds, as is true of most seeds. The first savory products were all mashes or pastes. It was not until about a.d. 25-220. that liquid sauces appeared in the literature in the Han dynasty (9).
In a simple primitive process of producing savory soybean paste, soybeans are soaked and cooked and made into a ball covered with rice straw and placed under the ceiling of the house where it is warm. Aspergillus molds present in the straw overgrow the soybeans in approximately 30 days. The mold-covered soybeans are then mixed with sea salt brine and allowed to digest for a year or longer. Enzymes from the mold digest the proteins, lipids, and carbohydrates, yielding savory amino acid/peptide-flavored soybean paste. Liquid released from the soybean paste is a tamari-type soy sauce very rich in savory amino acid/peptide flavors (10).
We can only guess what effect soybean paste and soy sauce had on consumers used to eating predominately bland rice. It was one of the great discoveries of food science, and along with soy sauce and miso we have Nestle '' Maggi''-type meat flavors and bouillon cubes in today's markets.
Indonesian tempeh fermentation is closely related to soy sauce fermentation as the first stage is an overgrowth of soybeans with amold, Rhizopus oligosporous or related strains (4,11,12). The fungal mycelium knits the soybean cotyledons into a compact cake that can be sliced thin and deep-fat fried or cut into cubes for use in soups. This fermentation has been carried out in Indonesia for hundreds of years by people untrained in microbiology or chemistry— yet they have the ability to produce high-quality tempeh.
The most surprising thing about tempeh fermentation is that in recent years a new high-technology industry has developed with the objective of producing meat substitutes (4,13-15). There are two major methods. The first is to extract soybean protein and spin it into fibers by passing the protein strands through a chemical bath. The resulting fibers are oriented to a meat-like texture and meat flavors are added. The dehydrated chunks are used in soups and other food products as vegetarian meat substitutes. It is a very sophisticated and relatively expensive food processing technique. Indonesian tempeh achieves much the same objective by fermentation in which mold mycelium provides the meat-like texture and the resulting products are within the financial means of the average Indonesian.
A second method of producing meat substitutes is even more closely related to the tempeh process in that it involves growing edible strains of Fusarium graminearum mold mycelium, harvesting the mycelium by centrifugation/filtration and adding meat flavors, and then dehydration. This process was developed by Rank, Hovis, MacDoughall (RHM) in England (16,17). The nuggets are based on mold mycelium for texture plus added flavors. This technology is advanced and sophisticated and relatively expensive compared to the tempeh process.
Indonesian tempeh achieves a similar degree of texture as a meat substitute by overgrowing soaked, dehulled, cooked soybean cotyledons with Rhizopus oligosporous mycelium.
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