Kitchen food safety: clean, separate, cook, chill

Four steps

FoodSafety.gov, run by the US Department of Health and Human Services, organises home food safety into four steps: clean, separate, cook and chill. They are a useful way to think about a kitchen, because each step blocks a different route by which harmful bacteria reach a plate. This guide follows them in order, with the details taken from the USDA Food Safety and Inspection Service (FSIS).

Clean: hands, surfaces and produce

Hands carry bacteria from raw food to everything else they touch. FSIS describes five steps for washing them:

1. Wet your hands with clean, running water, warm or cold, turn off the tap and apply soap.
2. Lather by rubbing your hands together, including the backs, between the fingers and under the nails.
3. Scrub for at least 20 seconds. FSIS suggests humming "Happy Birthday" from beginning to end twice as a timer.
4. Rinse well under clean, running water.
5. Dry with a clean towel or let them air dry.

Wash before you start, and again after handling raw meat, poultry, seafood or eggs or their packaging. FSIS says handwashing after touching raw meat or poultry or its packaging is a necessity.

Surfaces need the same attention. FSIS advises washing countertops and sinks with hot, soapy water to remove raw meat and poultry juices, and sanitizing them for extra protection. Cutting boards are washed in hot, soapy water after each use; the knife skills guide covers boards in more detail.

Produce is different from meat: it should be washed. Mississippi State University Extension advises washing vegetables under cool, running water before cooking or eating them, gently scrubbing off visible dirt, and not using soap.

Do not rinse raw meat or poultry

Many cooks rinse raw chicken or meat under the tap out of habit, or because they were taught to. FSIS addresses this directly: USDA research found that washing or rinsing meat or poultry increases the risk of cross-contamination in the kitchen, and from a food-safety point of view washing raw poultry, beef, pork, lamb or veal before cooking is not recommended. Water splashing off raw meat can carry bacteria to the sink, the counter and nearby food, while rinsing does not make the meat itself safe. Cooking to the right internal temperature is what does that.

FSIS gives the same advice about eggs bought from a shop: do not wash them before putting them in the refrigerator, because washing is already part of commercial egg processing.

Separate: stopping cross-contamination

FSIS defines cross-contamination as the transfer of harmful bacteria to food from other foods, cutting boards and utensils when they are not handled properly. It is especially likely with raw meat, poultry, eggs and seafood, so their juices need to be kept away from cooked and ready-to-eat food and from fresh produce.

In practice that means a few habits:

• Use one cutting board for fresh produce and bread and a separate one for raw meat, poultry and seafood, as FSIS suggests.
• Never put cooked food back on the plate or board that held it raw, unless it has been washed.
• Keep raw meat, poultry and seafood apart from produce and ready-to-eat food in the shopping bag, and wrapped or contained in the refrigerator so their juices cannot drip.
• Throw away packaging from raw meat and poultry straight after use, and wash your hands afterwards.

Cook: use a thermometer

Cooking is what makes raw meat, poultry, seafood and eggs safe, but only when the inside reaches a high enough temperature. You cannot judge that by colour or by time. FSIS advises using a food thermometer, placed in the thickest part of the food. Its Safe Minimum Internal Temperature Chart gives these figures:

A thermometer is only as good as its accuracy. FSIS describes checking one in ice water, where it should read 32°F (0°C). The safe temperatures page gathers every figure on this site in one place.

Chill: the danger zone and the 2 hour rule

FSIS calls the range from 40°F to 140°F (4.4°C to 60°C) the danger zone, because bacteria grow most rapidly in it, doubling in number in as little as 20 minutes. Two rules follow:

• Do not leave perishable food out for more than 2 hours. If the room or the outdoor air is above 90°F (32.2°C), the limit is 1 hour.
• Keep hot food hot and cold food cold. Hot food that is being held for serving should stay at 140°F (60°C) or above. Cold food belongs below the bottom of the danger zone, at 40°F (4.4°C) or colder.

The 2 hour clock includes the time food spends cooling on the counter after cooking and the time it spends on the table during a meal. A long, relaxed dinner can use most of it.

Leftovers

FSIS's guidance on leftovers comes down to three numbers and one habit:

• Within 2 hours: get leftovers into the refrigerator within 2 hours of cooking.
• Shallow containers: divide large amounts, such as a pot of stew, into shallow containers so they cool quickly, rather than putting one deep pot in the refrigerator.
• 3 to 4 days: eat refrigerated leftovers within 3 to 4 days, or freeze them.
• 165°F: reheat leftovers until they reach 165°F (73.9°C), checked with a thermometer.

When reheating in a microwave oven, FSIS warns that microwaves can heat unevenly and leave cold spots where bacteria survive. Stir the food or turn it partway through, and check the temperature in several places.

Example: a roast chicken dinner

None of these habits takes long, and together they cover the main ways food goes wrong at home.

That rounds off the series. Pin the safe temperatures table somewhere near the stove.