Touched by an Angel?
Unlike many animals, humans are capable of digesting myriad substances. Evidence that the bulk of the prehistoric human diet consisted of plant materials, probably gathered by women, is extensive. Animals trapped or hunted by men occasionally supplemented the plant foods. Probably any member of a shore-dwelling family would gather seafood, particularly crustaceans and other shellfish. But any prehistoric food could carry harbingers of sickness or death.
Presumably, animal feeding behavior was the first guide to the edibility of plants and their parts. This can be a treacherous guide, however: That pale white mushroom eaten with impunity by rabbits and squirrels could be the destroying angel, or death cap (Amanita phalloides) — an age-old favorite of poisoners.
With rare exceptions — such as polar-bear liver, which contains vitamin A in toxic amounts — the flesh of most prehistoric prey would have been wholesome over the short term. Kept for too long, however, flesh can spoil and become toxic, even deadly. Thus, having found by trial and error which plants and animals were edible, primitive humans had to learn how to preserve such foods. In climates with cold winters or long arid spells, human survival might have depended on preserving food for many months.
Each of the five basic methods of food preservation — drying, heating, freezing, fermentation, and chemical preservation — is in use today in some form. We will never know exactly how prehistoric people discovered them, but it seems certain that magic and practicality were inseparable. As reasoning (if not always reasonable) creatures, ancient people sought, and expected, explanations for everything. In the days before science, humans turned to religion for explanations. And sometimes religious interventions were indeed beneficial: Although many dietary taboos set forth in the Old Testament are scientifically inexplicable, the biblical prohibition of pork consumption clearly served to prevent trichinosis.
Saints Preserve Us?
Successful food preservation often involves combining at least two or more of the five basic methods:
Desiccation: Desiccation (dehydration, or drying) prevents the rotting of meat, the germination of stored grains, and the sprouting of certain vegetables. It also inhibits the growth of microorganisms, but some of these dormant germs can become dangerous with rehydration of the food. (The Chinese and the Italians really used their noodles when, independently, they invented starchy dried foods with a very long shelf life.)
Heating: Heat can increase shelf life by temporarily sterilizing food. Meats can be spit-roasted — held over a fire on a pointed rod. But our ancient ancestors could not adequately cook many plant foods until they developed pottery cooking vessels.
Freezing: Ancient peoples living in areas with cold winters would observe that frozen foods remained in good condition (at least to unsophisticated taste buds) almost indefinitely — whereupon humans developed rudimentary cold storage by cooling the recesses of caves and other shelters with ice and snow.
Fermentation: Fermentation is a gradual chemical change caused by the enzymes of some bacteria, molds, and yeasts. Fermented beverages were ubiquitous in the earliest civilizations of Mesopotamia and Egypt. Not only did wine facilitate conviviality; it was usually more potable than the available water. Winemaking also served as a means of storing nutrients from grapes almost indefinitely. Similarly, Asian steppe dwellers turned mare's milk into koumiss — a fermented beverage that keeps much longer than unprocessed milk. Many cheeses with a long shelf life are produced by lactic-acid fermentation. One means of pickling — a very early form of food preservation — is to treat foods with vinegar, a liquid obtained by further fermenting alcoholic beverages.
Chemical preservation: Many people consider food additives a modern innovation, but humans have used preservatives for millennia. Today it is hard to understand how precious salt was in ancient times, when it was valued partly as an effective preservative. Salted herring were exported in large quantities from North Sea fishing communities and consumed throughout most parts of Middle Europe.
During the Middle Ages the winter feeding of livestock was often so difficult that only animals selected for breeding were kept alive. Meat from the slaughtered livestock was salted for consumption over the winter. (Considering how high salt intakes affect many people with high blood pressure, the church's annual late-winter proscription of meat consumption during the 40 days of Lent must have prolonged many medieval lives.)
Smoking is another ancient and common means of chemical food preservation. Smoked foods include bacon, kippered herring, and lox. Smoking introduces antioxidants — butylated hydroxyanisole (BHA) and butyl gallate, for example — in large amounts. Permitted levels of such antioxidants as additives are far below levels found in smoked meat.
Spices are rich in antioxidants and even bactericides (substances that kill bacteria). The hot curries and chili dishes popular in the tropics — where food safety is most difficult to achieve — tend to be high in such natural preservatives.
As with chemical preservation, many people consider freeze-drying — a combination of two of the time-tested methods described above — a modern innovation. But native South Americans living on the Altoplano, in the Andes, have subsisted on freeze-dried potatoes of a sort for thousands of years. The plateau dwellers carry the potatoes up into areas where the atmospheric pressure is very low, the sky is usually almost cloudless, and the nighttime temperatures fall well below the freezing point of water. The natives slice and crush the potatoes and "freeze-dry" the result by spreading it on rocks. (In modern food-processing facilities, freeze-drying involves freezing foods hard and then drying the result in a vacuum.)
When Animalcules Attack
Anthropologist Loren Eisley has attributed the human population explosion to the invention of the microscope, before which understanding of endemic diseases had been impossible. The invention of the microscope enabled the observing of germs and, thus, control of the diseases they can cause. The invention was also a major factor in increasing humanity's food supply.
As early as 1675 Antonie Van Leeuwenhoek, the inventor of the microscope, reported seeing animalcules — minute organisms — through his device. But two centuries passed before such organisms were recognized as causes of food poisoning and other diseases.
Louis Pasteur was the perfect exemplar of his famous dictum: "Chance favors the prepared mind." His microscopic viewing of animalcules led not only to his understanding their ability to cause disease, but to his development of methods to control pathogenic bacteria. The most well-known of Pasteur's methods is milk pasteurization, which destroys the bacteria that can cause tuberculosis. Pasteurization originally involved keeping milk at approximately 42 degrees Celsius (161 degrees Fahrenheit) for about 30 minutes. But flash-pasteurization — also known as the high temperature-short time method (HTST) — has the same effect. Flash-pasteurization is widely used in the food industry, not only to semisterilize liquids but also to inhibit deteriorative enzyme action in beverages such as orange juice.
The development of heat sterilization as the basis of what would become the canning industry resulted from Napoleon's offer of a prize for a means of preserving food for his armies. The winner was Nicolas Appert, who showed that foods could be preserved by placing them in glass containers, heating them, and then sealing the containers. Shortly afterwards, Peter Durand received a British patent for canning with tin-coated steel cans, the solder in which became a new source of an ancient problem: lead poisoning. (In the mid nineteenth century Sir John Franklin's efforts to find the Northwest Passage ended when ice crushed his ships. His crewmen took to the ice with ample canned foods. All died — not of exposure, but of lead poisoning.) The development of the double-fold canning seal has enabled commercial canners to eliminate this hazard.
The emphasis in commercial canning and bottling practices has shifted, as in surgery, from the chemical inhibition of germs to the prevention of bacterial contamination — in other words, to making chemical preservatives (such as sodium benzoate, sodium nitrite, and sulfur dioxide) unnecessary. Today, cases of food poisoning from commercial canned goods are rare and usually involve anomalous products. Raw chopped garlic cloves in olive oil, for example, can harbor Clostridium botulinum, which secretes the toxin that causes the paralytic disease botulism. The risk of botulism is much greater with home-canned foods than with commercially canned foods. Growth of Clostridium botulinum can result from incomplete sterilization of alkaline foods, such as green beans, potatoes, and sweet corn. (Home canning alkaline foods in tomato juice, which is acidic, is safer than canning them in water.)
Give Me That Old-Time Religion?
Storage and processing are not the only avenues of food contamination: Raw shellfish raised in contaminated water can harbor extremely toxic organisms, and unpasteurized milk from infected cows can cause tuberculosis and undulant fever. Great strides have been made in developed countries toward eliminating infected milk cattle.
Plant-related toxins include ergotic alkaloids, aflatoxin, and hydrogen cyanide. Throughout European history, long cold and rainy periods have coincided with outbreaks of ergotism, a disease caused by toxins from the fungus Calviceps purpurea. This fungus infects grain of all kinds, but its chief target is rye, on which it forms purple masses called "sclerotia." These sclerotia contain several alkaloids that are related chemically to the hallucinogenic compound LSD. The dreadful cycle of infection occurred repeatedly throughout the Middle Ages; its effects were always "explained" by religion. Crops were blighted; women and livestock aborted. Individuals — even whole populations — suffered such symptoms as burning in the extremities, convulsions, and hallucinations. In France alone, tens of thousands of people convulsed to death. Some sufferers made pilgrimages to the shrine of St. Anthony and reportedly obtained relief. Hence the disease became known as Saint Anthony's fire. (The dietary absence of ergot at the shrine's locale may have contributed to the pilgrims' relief.)
Medieval churchgoers held that witchcraft was the cause of Saint Anthony's fire,* most cases of which were probably due to ergotic toxins. A guide for spotting, capturing, and persecuting witches — Malleus Maleficarum (The Hammer of the Witches) — first published circa 1484 in Germany, influenced church inquisitors to torture thousands of people to death. The authors of the Malleus Maleficarum — Dominican inquisitors Jakob Sprenger and Heinrich Institoris (also known as Henry Kramer) — had a reputation for brutalizing their "interviewees," and it seems certain that they had written the "witch hunter's textbook" to defend their extreme methods. Needless to say, neither the book nor the inquisitorial pursuits it "justified" suggested any effective preventive for ergotism — such as separating sclerotia from infected grain by floating the grain in a 30-percent potassium chloride solution.
Aflatoxin poisoning, unlike ergotism, is subtle. Aflatoxins are powerful liver carcinogens produced mainly by Aspergillus flavus, a mold that grows on grains and seeds. Corn and peanuts are especially vulnerable to A. flavus. Aflatoxins are easily controllable in stored grains by treating the grains with very dilute solutions of certain fatty acids. Because A. flavus is ubiquitous on peanuts, the U.S. Food and Drug Administration has set a residue limit for aflatoxin of one part per billion — a concentration our livers can easily handle. For centuries natives of the Amazon jungle have thrived on a potentially poisonous staple food: Manihot esculenta, better known as cassava or manioc. The cassava plant has a large, starchy, tuberous root that often contains hydrogen cyanide (HCN) at high levels. Long before the arrival of the Europeans, Amazon natives had learned how to detoxify cassava root: They pounded the plant; placed it in long, narrow baskets; placed the baskets in water, thus leaching out HCN; wrung the baskets repeatedly; and cooked the result, thus dissipating any residual HCN. Today, strains of cassava with negligible amounts of HCN are cultivated throughout the humid tropics.
Ray Ban?
Scientific technology has replaced witchcraft as the prime target of superstitious fanatics. Resistance to food irradiation, for example, is considerable.
Gamma rays at low doses (less than 100 kilorads) can almost perfectly sterilize biologically inert foods, such as meat and poultry, and highly storable foods, such as grains and dry beans. At very low doses (15 to 20 kilorads), gamma rays can inhibit the sprouting of onions and potatoes and can control insect infestations. But despite scientific approbation and widespread legal approval of such uses of radiation, an alarmist opposition hinders their commercial acceptance.
A few widely publicized cases of food poisoning due to contaminated hamburgers have led to political clamor for extending federal meat inspection to bacteriological contamination. But not only would such an expansion be inordinately expensive; it would be ineffective. No legislation or inspection procedure can prevent postinspection undercooking (or other mishandling) of meat. A safe and dependable preventive for such food poisoning, however, has been available for at least 40 years: Gamma rays at low doses can completely sterilize meat and poultry products without any other effects.
The leader in the fight against food irradiation is Food and Water, Inc. This obviously well financed outfit claims, for example, that consuming irradiated foods can shorten lives and cause birth defects. One can only guess why Food and Water disseminates such claims despite the absence of evidential support. Fearmongering has become a boom industry for alarmists and a popularity prop for politicians.
In a speech delivered in March 1997, U.S. Environmental Protection Agency administrator Carol Browner proposed compulsory in-store labels that would name any residual pesticides that might be present in fresh produce. "It is the consumer's right to know," declared Browner. But is it the politician's right to panic consumers? Consider that in the United States there has never been a documented case of anyone becoming ill from the residue of a pesticide when the pesticide was used lawfully.
Common sense must supplement government regulation. Anyone who uses the same knife and cutting board for raw chicken — a frequent carrier of salmonella, which is destroyed by cooking — and cooked meats that they don't intend to recook invites serious illness. And no food code could have protected the man who, during a cholera epidemic, carried crabmeat from South America to New York in an unrefrigerated plastic bag. (He nearly killed himself and the seven friends who shared his crab salad.)
Increasingly, however, irrational fear — of food irradiation, of gene-splicing, of hormone-stimulated milk production, and of pesticide residues — supersedes common sense. It seems as if the Dominican friars who wrote Malleus Maleficarum are alive and well — and busy "justifying" their activities.
By Bill Grierson, Ph.D., Professor Emeritus, University of Florida. published in 1997, Volume 9, Number 3 of American Council on Science and Health (www.acsh.org/publications/). Edited to be posted by Leopoldo Costa
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