A food is unsafe when something in it can make a person sick or hurt. Kitchens sort those dangers into three kinds, because each is prevented a different way.
Key idea
Biological hazards: bacteria, viruses and parasites, and the toxins some bacteria make. Chemical hazards: cleaning chemicals, pesticides, too much of an additive, and food allergens. Physical hazards: objects such as glass, metal shavings, bone, plastic or a bandage. Most foodborne illness comes from biological hazards.
| Bacteria need | So the kitchen… |
|---|---|
| Food (especially protein-rich, moist foods) | treats meat, dairy, eggs, cooked rice, cut melons and cut leafy greens as foods that need time and temperature control |
| Warmth | keeps food out of the danger zone, 41°F to 135°F |
| Time | limits how long food stays warm |
| Moisture | knows dry foods (crackers, flour) are lower risk |
| The right acidity and oxygen | follows tested recipes for pickles and sealed foods |
Why it works
Foods that support fast growth of germs are called TCS foods in the Food Code: foods that need Time and Temperature Control for Safety. Cooked rice, cut tomatoes and cut leafy greens are on that list, not just meat.
Worked example: Which kind?
A chip of glass from a broken jar falls into a salad.
- It is an object, not a germ or a chemical.
Answer: A physical hazard. Throw the salad away.
Common mistake
Thinking you can smell or see unsafe food. The germs that cause most illness usually don't change the smell, look or taste of food. Spoilage germs do, but they are a different group.
Practice at home
- Look through your refrigerator and list the TCS foods: cooked leftovers, dairy, eggs, meat, cut fruit. These are the ones to watch for time and temperature.
The science behind it
- How bacteria multiply: doubling, and why time matters
- Helpful and harmful microbes: the germs in yogurt and the ones in food poisoning
In Meal Prep
- Food Safety Basics: clean, separate, cook and chill at home