Food safety centers on temperature control and preventing cross-contamination. The USDA danger zone spans 40°F to 140°F (4°C to 60°C), the range in which bacteria multiply most rapidly. Perishable food should not sit out for more than 2 hours at room temperature, and only 1 hour when the temperature is above 90°F. Safe internal cooking temperatures are: 165°F for whole poultry, 160°F for ground meats, 145°F (with a 3-minute rest) for fresh beef, pork, and fish, and 160°F for egg dishes. Eggs in raw preparations like Caesar dressing or mousse should be pasteurized to ensure safety. USDA safe storage times allow leftovers for 3 to 4 days in the refrigerator, with reheating to 165°F before consumption.
Cross-contamination is the transfer of harmful bacteria between foods, and preventing it requires systematic habits. Raw meat should be stored on the bottom refrigerator shelf to prevent drips onto other foods, and separate cutting boards should be used for raw meat and produce. Color-coded boards are common in professional kitchens: red for raw meat, yellow for poultry, blue for seafood, and green for produce. Hands should be washed with soap for 20 seconds — about the time it takes to sing "Happy Birthday" twice — after handling raw meat or eggs, and surfaces should be sanitized with hot soapy water followed by a bleach solution of 1 tablespoon per gallon of water. Marinades used on raw meat should never be reused without first being brought to a rolling boil.
Safe defrosting has only three reliable methods: in the refrigerator (slowest and best quality), in cold water changed every 30 minutes for sealed packages, and in the microwave (with immediate cooking afterward). Defrosting at room temperature is dangerous because the outer layers reach the danger zone before the interior thaws. The differences between use-by and sell-by dates are also important: sell-by dates are inventory tools for stores, while use-by or best-by dates indicate quality, not safety. Spoiled food often has an off odor, slimy texture, discoloration, or visible mold, but pathogenic bacteria frequently have no smell or taste, so when in doubt, throw it out.