What’s Cooking?

You can bet that the first cooked dinner was an accident involving some poor wandering animal and a bolt of lightning that — zap! — charred the beast into medium sirloin. Then a caveman attracted by the aroma tore off a sizzled hunk and forthwith offered up the first restaurant rating: “Yum.”

After that, it was but a hop, a skip, and a jump, anthropologically speaking, to gas ranges, electric broilers, and microwave ovens. This article explains how these handy technologies affect the safety, nutritional value, appearance, flavor, and aroma of the foods that you heat.

Ever since man discovered fire and how to control cooking — rather than having to wait for a passing thunderbolt — the human race has generally relied on three simple ways of heating food:

  • An open flame: You hold the food directly over — or under — the flame or put the food on a griddle on top of the flame. The electric heating coil is a 20th-century variation on the open flame.
  • Hot air: You put the food in a closed box (an oven) and heat the air in the oven to create high-temperature dry heat.
  • Hot liquid: You submerge the food in hot liquid or suspend the food over the liquid so that it cooks in the steam escaping from the surface.

Cooking food in a wrapper such as aluminum foil combines two methods: open fire (the grill) or hot air (the oven) plus the steam from the food’s own juices (hot liquid). Here are the basic methods used to cook food with heat generated by fire or an electric coil:

  • Open Flame
  • Hot Air
  • Hot Liquid

Cooking with electromagnetic waves

A gas or electric stove generates thermal energy (heat) that warms and cooks food. A microwave oven generates electromagnetic energy (microwaves) produced by a device called a magnetron (see Figure below).

Microwaves transmit energy that excites water molecules in food. The water molecules leap about like hyperactive 3-year-olds, producing friction, which then produces the heat that cooks the food. The dish holding food in a microwave oven generally stays cool because it has so few water molecules.

Cooking away contaminants

Many microorganisms that live naturally in food are harmless or even beneficial. For example:

  • Lactobacilli (lacto = milk; bacilli = rod-shaped bacteria) are used to digest sugars in milk and convert the milk to yogurt.
  • Nontoxic molds convert milk to blue cheese. The blue ribbons in the cheese are safe, edible mold.

Some organisms, however, carry the risk of food poisoning. For example:

  • Clostridium botulinum (C. botulinum), a bad bug that thrives in the absence of air (as in low-acid, canned food), produces the potentially fatal toxin that causes botulism.
  • Campylobacter jejuni (C. jejuni), which flourishes in raw meat and poultry and unpasteurized milk, has been linked to Guillain-Barré syndrome, a paralytic illness that sometimes follows flu infection.

Are you surprised to find out that, every year, several million Americans experience diarrhea and other more-serious symptoms of food poisoning after eating food contaminated with such an organism? Take a look at some of the incidences of food poisoning in the United States:

  • In 2003 alone, the USDA estimated 1,341,873 cases of food poisoning due to Salmonella.
  • Since 1995, the Food and Drug Administration has tracked at least 19 incidents, 409 cases of reported illness, and two deaths linked to fresh and freshly cut lettuce and leafy greens contaminated by diseasecausing organisms that were transmitted by exposure to sewage and animal waste.
  • In the winter of 1998–1999, Americans were reported to be suffering illness and death caused by consumption of packaged meats contaminated with Listeria monocytogenes. This incident was particularly troublesome, because the contaminated products (packaged meats) were made to be served cold.

The only way to reduce the risk would have been to heat the cold cuts — unlikely except with hot dogs, which must be boiled or broiled (not microwaved) to reach a safe internal temperature of 165 degrees Fahrenheit.

Note: During pregnancy, a fetus whose mother consumes Listeriacontaminated food may suffer damage or, in extreme cases, may die.

  • Children and adults have died in this country following consumption of undercooked chopped meat containing Escherichia coli 0157:H7 (sometimes called pathogenic E. coli).

Although simply heating food to the temperatures shown in Table 20-2 is not a guaranteed protection against food-borne illness, cooking food thoroughly and keeping it hot (or chilling it quickly) after it has been cooked destroys many dangerous bugs or slows the rate at which they reproduce, thus reducing the risk.

The Bug Where You Find It
Campylobacter jejuni Raw meat and poultry, unpasteurized milk
Clostridium botulinum Poorly processed canned low-acid foods or vacuumpacked smoked fish
Clostridium perfringens Foods made from poultry or meat
E. coli Raw beef
Listeria monocytogenes Raw meat and seafood, raw milk, some raw cheeses
Salmonella bacteria Poultry, meat, eggs, dried foods, dairy products
Staphylococcus aureus Custards, salads (that is, egg, chicken, and tuna salads)

USDA Meat and Poultry Hotline

Table 20-1 lists some common pathogens (disease-causing organisms) linked to foodborne illnesses and notes the foods likely to harbor them; Table 20-2 shows the recommended safe cooking temperatures for various foods.

This Food . . . Is Done (Generally Safe to Eat) When Cooked to This Internal Temperature
Eggs and Egg Dishes
Eggs Cook until yolk and white are firm
Egg dishes 160°F
Ground Meat and Meat Mixtures*
Turkey, chicken 165°F
Veal, beef, lamb, pork 165°F
Fresh Beef*
Medium rare 145°F
Medium 160°F
Well-done 170°F
Fresh Pork
Medium 160°F
Well-done 170°F
Chicken, whole 180°F
Turkey, whole 180°F
Poultry breasts, roasts 170°F
Poultry thighs, wings Cook until juices run clear
Stuffing (cooked in bird) 165°F on thermometer inserted into the center of the stuffing**
Duck and goose 180°F
Fresh (raw) 160°F
Precooked (to reheat) 140°F

* Undercooked hamburger is a major source of the potentially lethal organism E. coli 0157:H7. To be safe, the internal temperature of the meat must read 165°F
** After the bird is cooked, the stuffing should be removed immediately and stored separately in the refrigerator. USDA Food Safety and Inspection Service, “A Quick Consumer Guide to Safe Food Handling,” Home and Garden Bulletin, No. 248 (August 1995)

Use a food thermometer to make sure you reach the recommended temps. Because some things are more complicated than they seem, read the directions that come with the thermometer to be sure you’re doing it right. Really.