All these preservations affect taste/odor and appearance (browning/oxidation).
Before describing the preservation methods, some definitions: Firstly, “edible” is personally and socially defined, but is also biologically defined as able to pass through the digestive system without serious negative effects.
Some substances start out as edible–fruits off the tree, parts of other plants, and most all animals. Cooking alters the chemistry to increase digestibility, but most all parts of animals can be eaten raw as well. (We have to look hard for the exceptions, such as part of the fugu fish and polar bear livers). There are edible minerals, too, some with no effect at all, and some that are used/needed by the body such as iron and iodine, but these are normally available from animal and vegetable (renewable after 10,000 BC) sources.
Allan Griff is a frequent commenter on this site. He represents an older generation who has much to add to our understanding of the world. I believe that intergenerational conversations are critical to solving the problems we face today. There are times when I wish to myself that I could discuss a current topic with someone only to realize that that person is no longer around. Allan has a unique perspective on food and our culture. He also has a unique way of expressing himself. I don’t agree with everything he writes, but I do value his perspective. Food scientists like Allan and me realize that food is a precious resource that is in short supply. Food preservation prevents food waste.
There are plenty of plant toxins, such as oleander leaves, castor beans, and cotton seeds. The toxic bioactivity of many fungi (mushrooms) is well known, too.
The problem of storage came when agriculture and animal keeping allowed us to have at times more food than we could eat at one time, either because of the annual cycles of plants, or the availability of a lot of fish at one time, or a large animal caught and killed. Those that managed the best had more food and more survived, as did the food habits they followed. Food sharing thus became connected to belonging, and thus to religious separation principles. Eat like us, not like them, as ”us” is the group that protects you.
The objectives of preservation were to slow down or stop deterioration that would reduce or eliminate nutritional value, or introduce danger by supporting harmful bacteria, molds or parasites.
It is important to know the differences between spoilage and danger, and between toxicity and infection.
When an edible substance spoils, it is chemically changed but may still be edible. We throw away a lot of food which is not dangerous, but just unappetizing because of our experiences, or maybe because we are not desperate enough. Often the driver is fear of the unknown: if it smells or looks changed, we don’t know if the change is dangerous, and if there is an alternative (including just not eating it) we will reject the food. Sometimes the food can be “saved” by cooking it; heat kills most bacteria, but isn’t perfect, and past experience, often culturally transmitted, is necessary.
The case of milk is interesting; milk is fermented to give buttermilk, yogurt and cheese, but we use specific strains of microorganisms for these, so if milk starts to smell from being unused for a while, even in a refrigerator, most of us nonfarm people will discard it. Farm people may know more about what they can still do with it, and may also have options of feeding animals that we don’t have.
Toxicity is when a toxic substance enters the body (or sometimes even on the skin) and has a negative reaction, ranging from irritation to death. The substance is not alive, although it may have been produced by a living organism, like the botulism toxin that has gotten so much fame as a tissue contracting agent.
Allergy is when an individual person has an unusual reaction to a food, typically a protein in that food, that can vary from mild to life-threatening. Allergies are usually diagnosable, but need expertise and evidence. This is an incendiary statement to some who are convinced they or their children have an allergy but do not want to verify or quantify; if it’s so important, why not prove it and get a handle on how much produces what reaction? Many allergies change their intensity with time, or even go away, so if the avoidance of the allergen is a problem, verify from time to time.
Infection is the entry of an organism which continues or even starts to grow within the body. The agent can enter through the air and through food, and sometimes through the skin or open wounds on the skin (including insect bites), and a few such as AIDS and STDs enter otherwise.
Our digestive system protects us, as the stomach is highly acid (pH 1.5 to 3.5) in which almost all bacteria can’t survive. That’s one reason chewing is good for us. The rest of the system is alkaline, not enough to destroy bacteria but they shouldn’t have gotten that far anyway.
Here are some questions I’d like answered: Do antacids or proton inhibitors increase the pH and thus kill less bacteria? If I eat a lot of absorbent food at one meal, with limited digestive fluids, is the pH higher so more bacteria survive?
All bacteria are not equal, but mystery (not-knowing) makes them so. The favorable public image of probiotics needs responsible clarification, including numbers to show how much is useful to whom. I want to avoid the image that something is “good for you,” a popular but deceptive phrase as it implies equal biology for all, and ignores quantity – how much of what? Nor can we assume that all bacteria are either good or bad. There are some, maybe most, that are neither. What about viruses? I don’t know all the answers but I do know the questions and am uncomfortable when I see them avoided.
I consider parasites (worms, including trichinella) a form of infection, although the medical world may differ. A living thing is inside of us and causing trouble. BTW, if you ask about pork and trichinosis, Wikipedia says there are a few cases in the US every year (under 20), it is treatable, symptoms may be severe but it eventually goes away and is not usually fatal.
But don’t use this as an excuse for eating undercooked meat or poultry. Animals can and do carry many other nasty organisms, and that justifies thorough cooking as well as washing hands and any surfaces that touched raw meat. I know that this challenges the macho positive image of juicy rare steaks, but I’ll have mine fully cooked and let others do as they will.
The Thirteen Preservations
1-Heat (Cooking ). Frying = hot oil, roasting, baking, grilling, boiling. Time and temperature matter. I like frying because I’m more worried about sterility than the lower-class popular image or eating the added fat. In fact, sometimes the fat is less if fatty foods are fried, as the food fat melts and combines with the frying oil which is uneaten.
Pasteurization uses heat to stop bacterial activity especially in milk, although Pasteur dealt with stopping fermentation in wine. Temperature depends on time: 30 minutes is needed at 63 C but only 15 seconds are enough at 72 C. Problem is to ensure that all the content of a vessel is at the desired temperature for the necessary time. It doesn’t kill bacterial spores, but if that’s necessary we can go hotter or pack aseptically.
Roasting and boiling of large items may leave centers too cool to be sterile. Use meat thermometers. This surprises some people who know boiling occurs at 100 C — less at higher altitudes, but Celsius, who based his scale on water, lived at sea level. Heat takes time to move and even if the surface is hot enough to sterilize quickly, it takes time to get through to the centers. This annoys people who want less-cooked interiors (rare) but with today’s relatively safe food supply, they are relatively safe, especially as the roast/boil will quickly get the bacteria on the surfaces.
Baking is hot enough to kill bacteria and is associated with grains to make cakes, bread and cookies, which keep longer than the original grains, especially if grain-drying ability is limited.
But since I’m talking about preservation, what matters is how the cooked food is managed after cooking. Eating it right away works, but isn’t always possible for everything. Options include sharing with friends and relatives, selling it, refrigeration (which in some climates just means outside storage) and a variety of packaging methods where volume justifies, including other preservation methods noted below. If in doubt, reheat it. Microwaving will help but may not be enough. That’s why we have an immune system to fall back on.
Canning and jarring at 120 C+ was invented by Appert in France to keep Napoleon’s troops well-fed in the early 19th century. If you get otherwise susceptible (low-acid) foods, which include meats, starches and vegetables, hot enough long enough, everything including the spores is killed. There are exceptions (prions, some staphylococci) but they are rare enough that such methods became the basic preservation method before electricity made cold storage popular. Pressure cookers, which allow heating above 120 C, were popular about 50 years ago, and allowed home-based preservation of the susceptible foods noted above.
2-Acidifying (pickling). Adding acids to low-acid foods to get pH below 4 will preserve them, and the most common and available acid is acetic acid (vinegar), made by carrying fermentation to its stable conclusion. Concentration matters. Many fruits are acidic, and straight lemon juice will help, but most vinegar is made by fermentation of other fruits such as grapes and apples. To the naturalists (fearers of humanipulation), added acid is worse than “natural” acids, maybe (or maybe not) if the acid was made by fermentation of a natural product such as a fruit. To the bacteria, acid is acid, and its origin doesn’t matter.
3- Drying removes water needed for pathogen growth. Examples are fruit (raisins, apricots, dates), jerky, prosciutto, yakinori (seaweed), fish (with salt), powdered milk. Grain needs drying to 10% or less to be safely stored in air. Water activity relates to the amount of water left in a substance. Grinding and baking the grain also gets water down, but needs appropriate packaging and storage to keep it that way. Many consumers have a negative image of hard baked goods that were softer when made, calling them “stale”, but certain dry baked products remain popular. In USA they are crackers, in Europe biscuits.
4-Salting binds water, limiting bacteria to prevent growth, deactivate/kill them. Common for fish (cod) and meat (pork). Question: on long sea voyages, if sailors caught fish, could they preserve them with sea salt?
5- Packing in oil (some fish) keeps water/oxygen from the food. Fats/oils are lighter than water, so if a mix is in a container the fat will go to the top and can block water/air entry from above. The oils themselves don’t support pathogens, but some (the unsaturated) can oxidize in air and change color and taste (rancid).
6- Additives. Nitrites are used for some meats, absorb oxygen and thus delay spoilage. “But they are chemicals,” I hear my neighbors say, “and therefore bad for you.” Some chemicals may be bad for us, but not all, and I need to know what they are, the concentrations and what harm? Hops, a plant bud, adds and preserves flavor of beer. IPA = India Pale Ale has a high amount of hops, to preserve the British unpasteurized beer across the long sea voyage to India. “Yes,” my neighbors say, “but hops are natural.” “So are poison mushrooms,” I think, but don’t bother to preach the counter-gospel to the converted. Instead, I think about why they are so chemophobic. There are some good reasons, but that’s too much to go into here.
7-Sugaring opposes bacteria by making water less available but still can be a substrate for molds. They also make the food taste better to many people, especially children, but have a low popular image. Chocolate is a good example, aided by oil content. Fruitcakes are still made, given at Christmas to last “forever.” Preserves get their name from the ability of sugars to deactivate bacteria. Pectin is a component of some fruits and allows gelling = jellies (this word means different things in different cultures, fruits and contexts), jam.
8-Fermentation is noted above as a maker of acid, but on the way there, the sugars and starches become ethyl alcohol. Starting materials are usually grains (beer) and fruits (wine). Reboiling this initial product (distilling) concentrates the alcohol further into whiskeys and brandies. Some start with cane sugars (rum). The alcohol opposes bacteria and yeast growth, and very-high-alcohol product (161-proof rum, for example) can be used to preserve otherwise susceptible fruits. Another branch of this “family” converts milk to cheese/yogurt, where less water and (with cheese) higher oil content allow longer useful life.
9-Cooling, wine cellars, root cellars, refrigerators, freezers. Even freezing doesn’t kill pathogens but slows their rate of reproduction enough to allow long-term storage. Since it is very dry in freezers, packages must be managed to control water content.
10-Packaging: keep pathogens out, barrier may also maintain flavor/appearance (including carbonation). Polyethylene/polypropylene best for water, poly(ethylene/vinyl-alcohol) good barrier against oxygen and carbon dioxide, aluminum foil and very thin aluminum coating (metallized film) are important. PET is good enough for carbonated soft drinks. Vacuum packaging = coffee and wheat germ, avoids oxidation. MAP = modified atmosphere packaging, CAP = controlled atmosphere packaging: need some oxygen to avoid anaerobic bacteria (botulism) but minimal to avoid oxidation of product. Example: prepacked New Zealand lamb, gas proportions in sealed packages allow shipping refrigerated to be sold ”fresh,” rather than frozen, which is more costly to ship and commands a lower retail price.
11-Leave alive, as parsnips, other roots and potatoes, also kept animals. If plant remains die over winter, they convert to new food as fertilizer for more and later yield next year.
12- Use as feed to animals, they convert to other forms (e.g., cellulose to protein/fat).
13- Personal storage: eat it, store the calories as fat, use them when needed. Bears, bats and woodchucks do it every winter. So would people if they could, to overcome poor crops and famine, which accounts for the positive image of fat people in history.
Next Week: Formerly Known as Food: How the Industrial Food System Is Changing Our Minds, Bodies, and Culture
Allan Griff was born in New York City, June 1933. His mother was a nurse and father a social worker. He has lived in New York, New Jersey, Maryland, Washington DC, and resides now in East Bay, California. He has degrees in Chemical Engineering (Cornell) and Anthropology (Columbia). He worked for professors on bond energies, rocket fuels, semiconductors, liquid-liquid extraction, and archeology maps. His varied professional experience includes Gulf Oil refinery, Union Carbide Plastics, and the United Nations (UNIDO, food packaging expert in Latin America).
Allan authored the first practical book in US on plastics extrusion and a training manual for extrusion. In addition, he is an independent consultant and trainer, industry reporter, and trade-fair exhibit manager. He has travelled around the world extensively, presented seminars and webinars on extrusion, environment and plastics chemistry. He has also written five book-length studies of plastic beverage bottles and related products. He is an advocate of health and environmental benefits of plastics, and is especially interested in reasons for their negative popular image.