2.3 Preventing illness: hands, heat and cross-contact

What bacteria need: FATTOM

Bacteria can only grow when conditions suit them. If the kitchen controls those conditions, bacteria already in raw food cannot multiply to a harmful level. The six conditions spell the memory word FATTOM.

FATTOM and its six conditions.

Potentially hazardous foods

A food that offers bacteria these conditions is called a potentially hazardous food (PHF). PHFs are perishable: left at room temperature, they spoil. They either let pathogens grow or survive, or may already carry them.

As a general guide, these foods count as PHFs:

• foods from an animal — meat, poultry, fish, shellfish, milk or eggs — or anything containing one of these;
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• plant foods that have been cooked or heat-treated;
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• raw sprouts, such as bean, alfalfa or radish sprouts;
• cooked starches, such as rice or pasta;
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• soya proteins, such as tofu or soya milk.

Some pairs show how handling changes the risk:

• Uncooked rice is not a PHF, but cooked rice is.
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• Raw onions are not, but fried onions are.
• Fresh garlic is not, but fresh garlic kept in oil is.
• A dry soup mix is not, until water is added.
• An unopened can is not (unless its label says to keep it refrigerated), but an opened one is.

Bread, flour, cooking oil, powdered eggs and beef jerky are non-PHFs; tofu, gravy, coffee creamer and pastries filled with meat, cheese or cream are PHFs.

The danger zone

Key temperatures and the danger zone.

Minimum temperatures

There are commonly accepted minimum time and temperature controls for PHFs. Other time and temperature controls can be used if scientific data show it gives safe food.

Guests may at times request food preparation that deviate from common controls. Guests who order a runny egg yolk, raw marinated fish or raw shellfish such as oysters should know that only full cooking makes these safe.

Heat: cooling, holding and reheating

The ten handling mistakes do not cause equal harm. Ranked by the share of foodborne illness each causes:

• Improper cooling: 30%
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• Advance preparation: 15%
• An infected person: 12%
• Poor reheating: 10%
• Improper hot holding: 8%
• Contaminated raw food: 4%
• An unsafe source: 3%
• Leftovers: 2%
• Cross-contamination: 2%
• Inadequate cooking: 1%

All other causes together account for the remaining 3%.

Cooling. Cooking does not kill everything. Some bacteria form spores, a tough resting form that survives heat. As cooked food cools through the danger zone, the spores wake and multiply. So cooked food has two deadlines. It must fall to 20°C (70°F) from 60°C (140°F) within two hours. It must then fall on to 4°C (40°F) within the next four hours.

A walk-in cooler alone will not cool a large roast, a whole bird or a big pot of soup in time; a pot of 4 L (1 gal.) or more can take a day or longer. Ways to speed it up:

• Spread food in shallow pans, with the food 5 cm (2 in.) deep at most. Never stack the pans, so cold air reaches each one.
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• Leave food loosely covered or uncovered while it cools; a tight lid traps heat.
• Cut big roasts or whole birds into smaller, thinner pieces before panning them.
• Stir the food in a container sitting in ice water, or use cooling wands (also called cooling sticks).
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• Choose stainless steel or aluminum containers, which pass heat well; plastic does not.
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• Use ice as an ingredient in soups or stews, and split a large batch of custard into single servings.
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• Cool in a walk-in with wire shelves and good air flow; household-style and reach-in fridges cool food poorly.

Advance preparation. Food made long before service often spends too long in the danger zone: it sits at room temperature, is not heated or cooled properly, or goes in and out of the zone again and again. To prevent it:

• Cook as close to service as you can, for use the same day.
• Cool food properly before you cover it tightly.
• Label food kept in the cooler more than 24 hours with the date made and a "serve by" date.
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• Throw out most PHFs after three days.

Reheating for hot holding. Food that is cooked, cooled, then reheated crosses the danger zone twice, and a hot-holding unit keeps it near the edge of that zone. To reheat safely:

• Do not reheat in the hot-holding unit; it is not built for that.
• Bring the food to 74°C (165°F) and hold that heat for at least 15 seconds before it goes into the unit.
• On a stove or in an oven, reach that point within two hours, with a thermometer to hand.
• In a microwave, which heats unevenly, stir or turn the food at least once, reach 74°C (165°F), then let it stand covered for two minutes.
• Do not take crackling sounds as proof the food is hot; use a thermometer.

Hot holding. Keep held food at 60°C (140°F) or above.

• Check the unit every day with a thermometer.
• Heat it to at least 60°C before loading it.
• Put in only food that is already at 74°C (165°F).
• Never switch a unit off after service and leave the food in it to cool. The food then sits in the super danger zone, 20–49°C (70–120°F), where pathogens grow very fast. Take food out after service and cool it at once.
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Leftovers. Leftovers cause outbreaks because their time in the danger zone adds up during cooling, reheating and portioning.

• Reheat leftovers once only, and discard any that have already been reheated.
• Do not mix them with fresh food.
• Cool them uncovered and apart from raw foods, then cover them tightly.

Cooking. Cooking food properly kills every pathogen apart from spores, or brings their numbers down to a level that will not cause illness. Cooks under-cook by accident, for example by cooking meat that is still frozen, or giving a stuffed bird the same time as an empty one.

• Check the internal temperature rather than trusting the clock.
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• Test large items in several places.
• Allow extra time for partly frozen food, which can hide cold spots.
• Cook grilled or fried meat until the juices run clear and fish until it flakes easily, and shape hamburgers thin.

Hands: the infected worker

Many people carry pathogens in the gut, nose, mouth or on the hands without feeling ill. People who do have symptoms — diarrhea, fever, vomiting, jaundice, a sore throat with fever, or an infected hand — are much more likely to spread them. Some, such as Salmonella, E. coli and Campylobacter, can make guests very ill in small numbers. Ready-to-eat food is the greatest risk, because no cooking follows to kill what a hand puts on it.

• Wash your hands well after any task that could soil them: using the toilet, eating, smoking, blowing your nose or handling raw meat.
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• Cover any infected cut, burn or sore on a hand or arm with a waterproof bandage and then a glove or finger cot (a small rubber sleeve for one finger) before touching food or utensils.
• Gloves do not replace handwashing. Change a glove or cot when it is dirty or torn, and at the end of each day.
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• A worker with signs of infection must not handle food or utensils and should be sent home.
• Where you can, handle food, especially ready-to-eat food, with utensils or gloves rather than bare hands.
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Cross-contamination and allergens

Cross-contamination means something harmful moves by accident into a food that did not have it — for example germs from raw meat reaching sliced deli meat, or nuts getting into a tomato sauce that should have none. Expect raw meat, poultry and seafood to carry pathogens.

• Keep separate boards, knives, cloths, sinks and work areas for raw and ready-to-eat food. If you must share them, wash with detergent and sanitize with bleach between uses.
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• Store ready-to-eat food on shelves above raw food, and dry food above wet food.
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• Prepare ready-to-eat items first thing in the day, before any raw food.
• Wash your hands after touching raw food, before you do anything else.
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• Keep wiping cloths in fresh bleach solution between uses: 30 mL (1 oz.) of bleach to 4 L (1 gal.) of water.
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• Handle cooked and ready-to-eat food with clean utensils, not your hands.
• When a guest reports an allergy, follow every one of these steps and prepare their food with separate or freshly sanitized tools.
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Raw foods and suppliers

Some foods are often served raw even though raw they have always carried risk:

• oysters in the shell
• raw egg in dishes such as Caesar salad or eggnog
• rare hamburger
• sushi and sashimi
• steak tartare (raw chopped beef)
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These foods have caused many outbreaks, and smell, taste and look will not reveal germs. To lower the risk:

• Buy from approved suppliers, ideally ones with their own food safety plans.
• Use pasteurized products, such as pasteurized liquid egg, where you can.
• Never serve such foods to people at high risk: older people, young children, people in poor health, and people in hospitals or care homes.
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An approved source is a supplier checked by a government food inspector. Cheap food from an unreliable seller may carry high levels of pathogens, may have been taken illegally, and may not have been stored or moved safely. Shellfish from closed harvesting areas are a particular danger. If you are unsure whether a supplier is approved, ask your local environmental health officer.