Say “processed food,” and most people think “cheese spread.” They’re right, of course. Cheese spread is, in fact, a processed food. But so are baked potatoes, canned tuna, frozen peas, skim milk, pasteurized orange juice, and scrambled eggs. In broad terms, food processing is any technique that alters the natural state of food — cooking, freezing, pickling, drying, and so on.
This chapter describes how each form of processing changes food from a living thing (animal or vegetable) into a component of a healthful diet — and at the same time
Lengthens shelf life
Reduces the risk of foodborne illnesses
Maintains or improves a food’s texture and flavor
Upgrades the nutritional value of foods
Preserving Food: Five Methods of Processing
When you’re talking about food, the term natural doesn’t necessarily translate as “safe” or “good to eat.” Food spoils (naturally) when microbes living (naturally) on the surface of meat, a carrot, a peach, or whatever reproduce (naturally) to a population level that overwhelms the food (naturally).
Sometimes you can see, feel, or smell this happening. You can see mold growing on cheese, feel how meat or chicken turns slippery, and smell when the milk turns sour. The mold on cheese, the slippery slickness on the surface of the meat or chicken, and the odor of the milk are caused by exploding populations of microorganisms. Don’t even argue with them; just throw out the food.
Food processing reduces or limits the growth of food’s natural microbe population, thus lengthening the shelf life of food and lowering the risk of foodborne illnesses.
For simplicity’s sake, here’s a list of the methods used to extend the shelf life of food:
Temperature methods
Cooking
Canning
Refrigeration
Freezing
Air control
Canning
Vacuum-packaging
MAP (Modified Atmosphere Packaging) and CAP (Controlled Atmosphere Packaging), processes that remove or lower the amount of oxygen in the package and replace it with nitrogen, carbon diosixe (to inhibit bacterial growth) and, if the package contains meat, carbon monoxide to maintain the meat’s red coloring
Moisture control
Dehydration
Freeze-drying (a method that combines methods of controlling the temperature, air, and moisture)
Chemical methods
Acidification
Mold/bacteria inhibition
Salting (dry salt or brine)
Irradiation
High-pressure processing
For the record, two or more of these methods may be used at the same time, such as vaccum or reduced atmosphere packaged items may be refrigerated to further reduce the rate at which the food inside the package spoils.
Temperature control
Exposing food to high heat for a sufficiently long period of time reduces the growth of the naturally occurring population of bacterial spoilers. For example, pasteurization (heating milk or other liquids such as fruit juice to 145 to 154.4 degrees Fahrenheit for 30 minutes) kills nearly all pathogens (disease-causing microorganisms) and most other bacteria, as does high-temperature, short-time pasteurization (161 degrees Fahrenheit for 15 seconds).
Chilling also protects food by slowing the rate of microbial reproduction. For example, milk refrigerated at 50 degrees Fahrenheit or lower may stay fresh for almost a week because the cold prevents any organisms that survived pasteurization from reproducing.
Removing the water
Like all living things, the microbes on food need water to reproduce. Dehydrate the food, and the bugs won’t reproduce, which means the food stays edible longer. That’s the rationale behind raisins, prunes, and pemmican, a dried mix of meat, fat, and berries adapted from East Coast Native Americans and served to 18th- and 19th-century sailors of every national stripe. Natural dehydration (loss of water) occurs when food is
Exposed to air and sunlight
Heated for several hours in a very low (250 degrees Fahrenheit) oven or smoked (the smokehouse acts as a very low oven)
Freeze-drying is a modern way to achieve the same result.
Controlling the air flow
Just as microbes need water, most also need air. Reducing the air supply almost always reduces the bacterial population.
Foods are protected from air by vacuum-packaging. A vacuum — from vacuus, the Latin word for “empty” — is a space with virtually no air. Vacuum-packaging employs a container (generally a plastic bag or a glass jar) from which the air is removed before it’s sealed. When you open a vacuum-packed container, the sudden little pop you hear is the vacuum being broken.
If there’s no popping sound, the seal has already been broken, allowing air inside, and that means the food inside may be spoiled or may have been tampered with. Do not taste test; throw out the entire package, food and all.
Chemical warfare
Preservatives have had bad press, blamed (inaccurately) for a range of problems they never caused. In fact, the chemicals used as food additives or food preservatives keep your food and you safe by slowing or preventing spoilage. The most common preservatives used in food are
Acidifiers: Most microbes don’t thrive in highly acidic settings, so a chemical that makes a food more acidic prevents spoilage. Wine and vinegar are acidifying chemicals, and so are citric acid, the natural preservative in citrus fruits, and lactic acid, the natural acid in yogurt.
Mold inhibitors: Sodium benzoate, sodium propionate, and calcium propionate slow (but do not entirely stop) the growth of mold on bread. Sodium benzoate also is used to prevent the growth of molds in cheese, margarine, and syrups.
Bacteria-busters: Salt is hydrophilic (hydro = water; phil = loving). So is sugar. When you cover fresh meat with salt (or sugar), the salt (or sugar) draws water up and out of the meat — and up and out of the cells of bacteria living on the meat. The bacteria die; the meat dries. And you get to enjoy sugar-cured ham or corned beef (which gets its name from the fact that large grains of salt were once called “corns”).
Irradiation
Irradiation is a technique that exposes food to electron beams or to gamma radiation, a high-energy light stronger than the X-rays your doctor uses to make a picture of your insides. Gamma rays are ionizing radiation, the kind that kills living cells. As a result, irradiation prolongs the shelf life of food by destroying microbes and insects on plants (which also make food safer longer) and slowing the rate at which some plants ripen. For more about the history and effects of food irradiation, check out Chapter 21.
Improving Food’s Appeal and Nutritional Value
Some food processing really does make your food taste better. For example, although steak tartare (chopped fresh steak) does have its devotees, most people consider a steak processed by heat — cooked — even tastier. Processing also improvers your diet by allowing you to sample a wide variety of seasonal foods (mostly fruits and vegetables) transported from grower to you by refrigerated trains or trucks all year long. And processing enables food producers to improve the nutritional status of many basic foods, such as grains and milk, by enriching or altering them to meet optimal nutrition needs.
Intensifying flavor and aroma
One advantage of food processing is that it can intensify aroma and flavor, almost always for the better. Here’s how:
Drying concentrates flavor. A practically water-free prune has a different, darker, more intensely sweet flavor than a juicy fresh plum.
Heating heightens aroma by quickening the movement of aroma molecules. In fact, your first tantalizing hint of dinner usually is the scent of cooking food. Chilling has the opposite effect: It slows the movement of the molecules. To sense the difference, sniff a plate of cold roast beef versus hot roast beef straight from the oven. Or sniff two glasses of vodka, one warm, one icy from the freezer. One comes up scent-free; the other has the olfactory allure of pure gasoline. Guess which is which.
Warming foods intensifies flavors. This development is sometimes beneficial (warm roast beef is somehow more savory than cold roast beef), sometimes not (warm milk is definitely not as popular as the icy-cold version).
Changing the temperature changes texture. Heating softens some foods (butternut squash is a good example) and solidifies others (think eggs). Chilling keeps the fats in pâté firm so the stuff doesn’t melt down into a puddle on the plate. Ditto for the gelatin that keeps dessert molds and dinner aspics standing upright.
Adding nutrients
The addition of vitamins and minerals to basic foods has helped eliminate many once-common nutritional deficiency diseases. The practice is so common that you take the following for granted:
Breads, cereals, and grains are given extra B vitamins to replace the vitamins lost when whole grains are stripped of their nutrient-rich covering to produce white flour or white rice or degermed cornmeal. The vitamin enrichment reduces the risk of the B vitamin–deficiency diseases beriberi and pellagra.
Breads, cereals, and grains are also fortified with iron to replace what’s lost in milling.
All milk sold in the United States contains added vitamin D to reduce the risk of the bone-deforming vitamin D–deficiency diseases rickets (among children) and osteomalacia (among adults).
Added fat-free milk proteins turn skim milk — milk from which the fat has been removed — into a creamier liquid with more calcium but less fat and cholesterol than whole milk.
Combining benefits
Adding genes from one food (such as corn) to another food (such as tomatoes) may make the second food taste better and stay fresh longer. You can bet that this is one hot topic; for more about genetic engineering at the dinner table, check out Chapter 22.
Faking It: Food Substitutes
In addition to its many other benefits, food processing offers up some totally fake but widely appreciated substitute fats and sweeteners. Actually, these may be just the tip of the iceberg, so to speak. In 1985, the Brits introduced Quorn, a brand-name meat substitute made from mushrooms that had become the number-1 meat substitute worldwide when it was first brought to the United States in 2002. Quorn seems to have slipped back into the nutritional netherworld in the United States, but as processing becomes more adventurous, who knows what strange and wonderful dishes lie just beyond the entrance to this Nutritional Twilight Zone.
Alternative foods No. 1: Fat replacers
Dietary fat (the fat found naturally in food) carries flavors and makes food taste and feel “rich.” But it’s also high in calories, and some fats (the saturated and trans fats described in Chapter 7) can clog your arteries. One way to deal with this problem is to eliminate the fat from food, as in skim milk. Another way is to head for the food lab and create a heart-safe no- or low-calorie substitute.
Classifying fat replacers
Over the years, food technologists have created three types of fat replacers:
Carbohydrate-based fat replacers comprise complex carbohydrates that thicken food but aren’t absorbed by the body. (For more on the different types of carbohydrates in plant foods, see Chapter 8.) Examples include carrageenan (a seaweed extract), guar gum (from guar beans), cellulose (insoluble dietary fiber), inulin (from the chicory root), and food starches (dextrins and maltodextrins) that may be treated chemically to change the texture or make the starch easier to dissolve and digest.
Protein-based fat replacers are commonly made by heating and blending proteins from egg whites and milk into tiny balls (technical term: microparticulatedprotein) that form a substance that feels and tastes like fat. Simplesse is a protein-based fat substitute. Note: These products don’t provide significant amounts of dietary protein.
Fat-based fat replacers are made from fatty acids such as the emulsifiers, naturally occurring compounds in foods that enable fats and water to mix. For use as fat replacers, they have been modified so they are indigestible and block the body’s absorption of other fats.
Table 19-1 lists several examples of fat replacers currently found in various foods.
Regardless of their source, the three important nutrition questions about fat replacers are
Do these additives contribute to weigh loss?
Do these additives enhance the nutrient value of food?
Are these additives safe?
DO FAT REPLACERS HELP PEOPLE LOSE WEIGHT?
Maybe. Fat replacers are designed to reduce the amount of fat and therefore the number of calories in ordinarily high-calorie foods such as cakes, cookies, and potato chips. But lowering the fat content may mean increasing calories from other ingredients such as sugar. In the end, the calorie count of the low-fat food may not be much lower than that of the regular product.
On the other hand, even if the calorie count stays the same, simply adding the fat replacer may alter, in a good way, how the food affects your body. In 2008, a team of nutrition researchers from the University of Copenhagen published a report in the American Journal of Clinical Nutrition showing that when volunteers were given one of two meals — the first with foods with their normal fats in place, the second with foods whose fats had been replaced with a fat substitute — those who got the second meal were less hungry for a longer period of time after eating. Why? The authors explain that the substitute isn’t absorbed by the body and inhibits the body’s absorption of other fats in food. As a result, more food fat stays in the intestines longer, creating the feeling of fullness that decreases appetite.
That being said, calorie control, a balanced diet, and a reasonable amount of exercise remain the most healthful tools for weight loss.
ARE FAT REPLACERS NUTRITIOUS?
Carbohydrate-based fat replacers do add carbs to food in the form of soluble or insoluble dietary fiber (see Chapter 8). But neither protein-based fat replacers nor fat-based fat replacers contribute anything but infinitesimal amounts of nutrients. In addition, because natural food fats help your body dissolve and absorb fat-soluble nutrients (see Chapter 10), foods made with these substitute fats commonly contain added vitamin A, vitamin D, vitamin E, and vitamin K.
ARE FAT REPLACERS SAFE?
The adverse effects of carb-based fat replacers are usually limited to minor gastro discomfort such as flatulence (intestinal gas) due to an increase in dietary fiber.
Fat-based replacers — or at least one fat replacer — may be more problematic. Olestra (brand name: Olean) is a sucrose and fatty acid compound approved by the FDA in 1996. But along with the approval, the FDA required a warning on the label that olestra may cause abdominal cramping and loose stools. In 1998, an 18-member FDA food advisory committee reaffirmed the agency’s original decision that olestra is safe for use in snack foods and concluded that the fat alternative’s gastrointestinal effects didn’t significantly affect public health. Five years later, following a review of several studies conducted after foods with olestra went on sale, the FDA concluded that the statement was no longer required. But the fact is that eating excess amounts of foods containing olestra may lead to uncomfortable results. Be smart: Read labels and limit the chips.
A second class of fat-based fat replacers is made of milk and egg proteins, which means it may be trouble for people who are sensitive to these foods.
Conclusion? As the American Heart Association has written, while “fat replacers on the market are considered safe by the U.S. Food and Drug Administration (FDA), their long-term benefits and safety are not known. The cumulative impact of using multiple fat replacers as they increase in the marketplace is unknown. Still, within the context of a healthy diet that meets dietary recommendations; fat replacers used appropriately can provide flexibility with diet planning.”
Alternative foods No. 2: Substitute sweeteners
Most substitute sweeteners were discovered by accident in laboratories where researchers touched a paper or a pencil and then stuck their fingers in their mouths to discover, “Eureka! It’s sweet.” As Harold McGee wrote in the first edition of his wonderful On Food and Cooking (Collier Books, 1988), “These stories make one wonder about the standards of laboratory hygiene.” Alas, when Mr. McGee updated and expanded his book for the second edition, he took out most of the entertainingly arch observations such as this one. Get the second edition for the details; keep the first for the fun.
Because substitute sweeteners aren’t absorbed by your body and don’t provide any nutrients, scientists call them by their proper name: non-nutritive sweeteners. The best-known (listed in order of their discovery and/or FDA approval) are
Saccharin (Sweet ’N Low): This synthetic sweetener was discovered by accident (the fingers-in-the-mouth syndrome) at Johns Hopkins in 1879. A ban on saccharin was proposed in 1977, after it was linked to bladder cancer in rats; however, it’s still on the market, and diabetics who have used saccharin for years show no excess levels of bladder cancer. In 1998, the executive committee of the National Toxicology Program (NTP) recommended that saccharin be taken off the list of suspected human carcinogens; in 2010, it was. Note: Most people think saccharin is very sweet, but if you hate broccoli, you’re likely to think saccharin’s bitter. Check out Chapter 15 to see why.
Cyclamates: These sweeteners, created in 1937 at the University of Illinois, were subsequently linked to cancer in laboratory animals and banned (1969) in the United States. Since then, the FDA has stated that follow-up studies show no such link, but cyclamates — which are legal in Canada and many other countries — remain banned in the United States.
Aspartame (Equal, NutraSweet): Another accidental discovery (1965), aspartame is a combination of two amino acids, aspartic acid and phenylalanine. Aspartame is safe for most healthy people; the exception is those born with phenylketonuria (PKU), a metabolic defect characterized by a lack of the enzyme needed to digest phenylalanine. In the body (or when it is exposed to heat), aspartame breaks down into its constituent ingredients, and if you lack the required enzyme, the excess phenylalanine can pile up in brain and nerve tissue. Newborns are usually tested for PKU because for them the excess phenylalanine may lead to mental retardation, epilepsy, and retarded growth.
Sucralose (Splenda):Sucralose, discovered in 1976, is a no-calorie sweetener made from sugar. But the body doesn’t recognize sucralose as a carbohydrate or a sugar, so it zips through the intestinal tract unchanged. More than 100 scientific studies conducted during a 20-year period attest to its safety, and the FDA has approved its use in a variety of foods, including baked goods, candies, substitute dairy products, and frozen desserts.
Acesulfame-K (Sunett): The K is the chemical symbol for potassium, and this artificial sweetener, with a chemical structure similar to saccharin, is found in baked goods, chewing gum, and other food products. In 1998, the FDA approved its use to prolong the shelf life of soft drinks.
Neotame: Neotame is a modified version of aspartame. In 2002, the FDA approved Neotame for use as a tabletop sweetener as well as for use in jams and jellies, syrups, puddings and gels, fruits, fruit juices, and non-alcohol beverages.
Stevia (Truvia): In 2008, the FDA ruled that Truvia, a sweetener made from stevia (a South American plant member of the sunflower family) can be designated GRAS (“generally regarded as safe”). Stevia (Truvia), used to sweeten some carb-free soft drinks, is estimated to be 200 to 300 times sweeter than sugar.
Tagatose (Naturlose, Shugr): In 2003, the FDA approved the use of tagatose, a white powder made from lactose (the sugar in milk), in cereal, soft drinks, frozen desserts, candy, chewing gum, and cake frosting. Tagatose may cause gastric upset (gas and diarrhea); paradoxically, it may also act as an aid to digestion.
Table 19-2 compares the calorie content and sweetening power of sugar versus the substitute sweeteners. For comparison, sugar has 4 calories per gram.
Table 19-2 Comparing Substitute Sweeteners to Sugar
* The range of sweetness reflects estimates from several sources.
** Aspartame has 4 calories per gram and tagatose 1.5, but you need so little to get a sweet flavor that you can count the calorie content as 0.
A Last Word: Follow That Bird
You can sum up the essence of food processing by following the trail of one chicken from the farm to your table. (Vegetarians are excused from this section.)
A chicken’s first brush with processing is, ugh, slaughtering, after which it’s plucked and shipped off to the food processor (in some instances the company doing the slaughtering also processes the chicken into other products) or the supermarket, packed in ice to slow the natural bacterial decomposition. In the food factory, your chicken may be boiled and canned whole, or boiled and cut up and canned in small portions like tuna fish, or boiled into chicken soup to be canned or dehydrated into bouillon cubes, or cooked with veggies and canned as chicken à la king, or fried and frozen in whole pieces, or roasted, sliced, and frozen into a chicken dinner, or … you get the picture.
If destined for the supermarket, a raw chicken will be packed and dated. When you buy it and bring it home, you’ll do your own processing. First, the chicken goes to the refrigerator (or freezer), then to the stove for thorough cooking to make sure that no stray pathogenic bacteria contaminate your dinner table (or you), and then back to the fridge for the leftovers. In the end, the chicken’s been processed. And you have eaten. That’s the point of this story.
If there’s no popping sound, the seal has already been broken, allowing air inside, and that means the food inside may be spoiled or may have been tampered with. Do not taste test; throw out the entire package, food and all.
Because substitute sweeteners aren’t absorbed by your body and don’t provide any nutrients, scientists call them by their proper name: non-nutritive sweeteners. The best-known (listed in order of their discovery and/or FDA approval) are