Reheating food safely: steaming hot and once only

What you are trying to achieve

Food that you cooked earlier, cooled, and stored in the fridge has to be protected twice: once while it was cooling and sitting cold, and again when you bring it back up. Bacteria that survived cooking, or that landed on the food afterwards, can multiply in the fridge if the fridge is warm, and they multiply much faster while the food passes through 8°C to 63°C. Reheating is the step that takes the food back out of that band quickly, and far enough that the centre is safe. It is not a way to rescue food that was cooled too slowly, left on the side, or kept for longer than your method allows.

The Food Standards Agency's Safer Food, Better Business pack tells caterers to reheat food so it is steaming hot all the way through. That is the check the pack expects you to be able to show. In England, Wales and Northern Ireland there is no single criminal offence written as "you served food at 74°C". The duty is to keep food safe. Most SFBB kitchens turn "steaming hot" into a probe check of 75°C in the centre, because that is a number two people can agree on and an officer can repeat. If your safe method says 75°C, that is the standard you record against. Do not probe the edge of the tray and call it the centre.

In Scotland the legal reheating temperature is 82°C. CookSafe tells you to reheat to not less than 82°C. A lower combination, such as 70°C for two minutes, belongs in a Scottish kitchen only where your own pack says the higher temperature would spoil that dish and you have written the alternative down. Do not import an English 75°C working figure into a Scottish service that has not agreed it. The rest of this guide uses 75°C as the example house check for England, Wales and Northern Ireland, and says so when the Scottish figure is different.

Reheat only once

Cook, cool, store cold, reheat, serve. That is one cycle. Food that has been reheated and not sold is finished. You do not cool it again for a third service. Each trip through the warm band gives surviving bacteria and spores another chance to multiply, and some toxins are not destroyed by the next blast of heat. If half a tray of curry sells at lunch, the rest of that reheated tray is served as part of that same service, held hot in line with your hot-holding method, or thrown away. It does not go back in the fridge labelled "evening".

Write the rule where the food is portioned, not only in a folder. The person plating at 18:00 needs to know that the tub marked "reheated lunch" is not a raw ingredient for a new cook-cool cycle. A day dot that says when it was first cooked is not enough if nobody can see whether it has already been reheated. Many kitchens mark the container "reheated" or only reheat what is still in the original cooled, dated tub and then discard the leftover of that reheated batch. Pick a rule the team can follow when the pass is loud.

There is a narrow difference between a second life and a corrective action during the same service. If food in a hot hold dips below 63°C and you bring that same batch back to steaming hot and return it to the hold, that is the hot-holding correction, and you only get it once. It is not permission to cool the batch overnight and reheat it again tomorrow. If you are unsure which situation you are in, throw the food away and write the reason. The cost of a tray is smaller than a food-poisoning complaint you cannot defend.

What to reheat, and what not to

Reheating is for food you cooked yourself, or food a manufacturer tells you to reheat, that has been stored as the label or your method requires. It is not for food that is already ready to eat and meant to be served cold. A slice of ham, a dressed salad, or a cream cake does not get "the chill taken off" in a microwave and then sit on the pass. That is the worst of both methods: you have left the cold chain and you have not reached a hot-holding temperature.

Do not reheat food that was cooled too slowly, food with no date, food that smells or looks wrong, or food that has already been reheated. Do not reheat rice that sat warm in the cooker all afternoon. Bacillus cereus spores survive boiling. If the rice was in the danger zone long enough to form toxin, a thorough reheat will not make it safe. Rice is either served hot from cooking, held at 63°C or above, or cooled quickly and refrigerated as the cooling guide describes, then reheated once until steaming hot. If you cannot tell which of those happened, bin it.

Cook-chill and frozen meals from a supplier come with a method on the pack. Follow that method. A regeneration time that was written for a single portion is not the time for a full hotel pan. A product that says "cook from frozen" is not thawed on the side first and then given the frozen time, or the reverse. The thawing guide covers how to defrost when the product is meant to be thawed before cooking. If the pack and your safe method disagree, the stricter instruction wins until a competent person rewrites the method. Do not let the team invent a shorter programme because the oven is full.

How to reheat so the centre actually gets hot

Start from chilled food, not from food that has been sitting on the pass "to take the edge off". Stir soups, stews, sauces and rice so there is no cold pocket. Split deep containers into shallower ones if the centre will not catch up. Cover food where the equipment needs a cover to heat by steam, especially in a microwave or a combi oven, and uncover or vent if the method says the cover will stop you probing.

1. Hob or range. Bring sauces and soups back to a proper simmer, stir, and probe the centre. A gentle warm that never bubbles is how the middle stays short of 75°C.
2. Oven. Spread food so the tray is not doubled up. Probe the centre of the largest piece and the middle of the tray, not the corner that faces the fan. A programme that usually works will not work if the oven was overloaded or the door was open for service.
3. Combi or regeneration oven. Use the programme you were shown for that dish and that load. Then probe. The programme is not the record. The temperature of the food is the record. If the food went in still frozen because the thaw was late, the programme will not save it.
4. Microwave. Microwaves heat unevenly. Stir or turn the food part way through, then leave it to stand for the time your method gives so the heat evens out. Probe in more than one place. A steaming edge and a cold centre is not a reheat. Covering helps. It does not replace the probe.
5. Fryer or grill for products designed for it. Follow the pack. A frozen battered product has a cook time. A reheated cooked product may not belong in the same oil. Do not assume the fryer has reheated a dense item all the way through because the coating is brown.

A bain-marie, a hot cupboard, a heat lamp and a soup kettle on "keep warm" are not reheating equipment. They are for food that is already hot. If you drop a cold tray into the well, you warm the outside, cool the water, and leave the centre in the danger zone for the service. Take it back to a real heat source. The same is true of a plate warmer and of a low oven used as a holding drawer.

Probe with a thermometer you have checked. Between foods, clean and disinfect the probe so you are not carrying allergens or juices from one dish to the next. If the centre has not reached the target, keep reheating. Check again. Write both readings. Do not serve the hot outer portions and put the cold centre back in the fridge. If a second check is still short and the equipment is not recovering, stop that product, tell the person in charge, and do not serve it. The probe guide is the standard for the iced-water and boiling-water checks that make the number worth writing down.

After the reheat

Serve the food straight away, or move it into hot holding at 63°C or above. Do not leave a reheated tray on the side "until the lunch rush". That is an untimed spell in the danger zone after you have already used your one reheat. If it will not be served at once, it needs a hot-hold temperature and a time, as the hot-holding guide describes. If hot holding is not realistic for that dish, reheat in smaller batches closer to the order.

Cooling a reheated dish to use again is the step your method should forbid, with rare exceptions a competent person has written down for a specific product. The default for a cafe, restaurant, takeaway, pub, school or care kitchen is: leftover from a reheated batch is waste. Record it. If the same dish is thrown away every Friday, the review should change the batch size, not hide the waste.

Plated meals for a hospital, school or care setting need the same centre temperature as a tray in a restaurant. A regeneration trolley that displays a cavity temperature has not probed the mash in the middle of the stack. Check a sample of plates, including one from the slowest position your method has identified. If you deliver meals, they leave hot and they are eaten within the time your method allows. An insulated box is not a second reheat and it is not a hot cupboard.

What to record

Record the food, the temperature in the centre, the time, and who checked. If the first probe was short and you continued, write the fail and the pass. If you threw food away, write what it was, why, and roughly how much. A column of identical 75s written at the end of the week from memory is not a reheating check. Officers trust a page with a low reading and a second reading more than a page that never varies.

You do not need a separate novel for every slice of toast. You do need a record for the dishes you reheat as a method: the curry, the chilli, the pie filling, the rice, the cook-chill meals, the Sunday meat for Monday sauce. Link the record to the cooling record. If Tuesday's chilli has no cooling time and no date, Wednesday's reheat temperature does not prove the chilli was safe to reheat. The diary is the place for the exception. A reheating sheet at the oven is the place for the daily numbers. The corrective action guide covers how to write the note so it shows what you did and what you will change.

Dates on the container should let the cook see when it was made and that it is still inside the house life. Many caterers use the day of production plus one day for a reheated dish, or follow a manufacturer life if it is shorter. Put the life you actually use in the safe method. An undated tub is not "probably from yesterday". If you cannot tell, you do not reheat it.

What environmental health officers check

Officers ask what you reheat, how you know it is hot enough, and whether anything is reheated twice. They may probe a dish that is about to be served. They look at the fridge for tubs with no date, for food that is still hot from a slow cool, and for trays marked in a way that suggests yesterday's service is going round again. They listen for "we just zap it" as the whole method.

• The safe method names the foods, the equipment, and the temperature or "steaming hot" check, including 82°C where the business is in Scotland.
• Staff can show a probe of the centre, and can say what they do if the reading is short.
• Records show real variation, or an honest failure, not a week of identical numbers.
• Reheated leftovers are not going back into the fridge for another day.
• Rice and other high-risk dishes have a cooling history, not only a reheat temperature.
• The microwave, if you use one, has a stir and stand step that staff can describe.
• Hot-holding equipment is not being used as the reheating step.

A perfect reheat log next to a cold centre is a confidence-in-management problem as well as a hygiene problem. The person who signs the 4-weekly review should have watched a reheat, not only filed the sheet. If the probe is missing, out of calibration, or too thick to reach the centre of the dish you actually serve, say so in the review and replace it. Training records should show that the people who reheat have been shown this method, including the once-only rule.

Worked example

A cafe cooks a beef chilli on Monday afternoon, cools it in shallow trays, and refrigerates it by 16:00. The safe method says chilli is reheated once, to 75°C in the centre, stirred, and then held at 63°C or above for the Tuesday lunch, which runs 12:00 to 14:00. Anything left at 14:00 is thrown away. The tub is labelled "chilli Mon, reheat Tue only".

On Tuesday at 11:20 the cook tips the chilli into a wide pan, stirs it as it heats, and probes the centre at 11:40: 68°C. The pan goes back on. At 11:55, after another stir, two probes in different parts of the pan read 76°C and 77°C. The sheet shows 68°C then 76°C, the time, and the name. The first reading is not rubbed out. The chilli goes into a preheated bain-marie and is probed at 12:30 at 71°C. That is a normal reheat.

At 14:05 about a third of the tray is left. A member of staff wants to cool it for a jacket potato topping in the evening, because waste annoys the owner. The method says no. The chilli has already been reheated. It is binned, and the diary says "chilli leftover binned after lunch reheat, about 2 litres". The following week they cook a smaller Monday batch. The 4-weekly review mentions the change. The temperature record from Tuesday still shows the 68°C that was corrected, which is what makes the log believable.

The same week a frozen lasagne from a supplier is regenerated for a function. The pack says cook from frozen, 40 minutes for two portions in a single tray at the stated oven temperature. The kitchen puts four portions in one deep dish and pulls it at 40 minutes. The centre is 61°C. They split what is left into two shallow dishes, return them to the oven, and probe again at 83°C. The note says the pack load was not followed and the portion count is now written on the function sheet. They do not serve the first reading. They do not cool the lasagne for another day.

Common mistakes

• Calling a bain-marie or a hot cupboard a reheat.
• Probing the edge of the tray, or trusting the oven timer with no centre check.
• Microwaving without stirring, standing, and probing more than one spot.
• Reheating food that was never cooled properly, especially rice.
• Cooling reheated leftovers for a second service.
• Using an English 75°C figure in a Scottish kitchen whose pack says 82°C.
• Writing 75 in every box at the end of the week.
• Reheating an undated tub because it "looks like Tuesday's".

Where this comes from

This guide follows the Food Standards Agency Safer Food, Better Business safe method on reheating, which expects food to be steaming hot all the way through and reheated only once. The Food Standards Agency's page on cooking your food covers cooking and reheating for businesses, and the pack itself is published as Safer Food, Better Business for caterers. In Scotland, the Food Hygiene (Scotland) Regulations set 82°C as the reheating temperature, and CookSafe is the working pack. A house probe check of 75°C is a common way for kitchens in England, Wales and Northern Ireland to demonstrate steaming hot. Write the check you will actually use, train the people who reheat, and keep the cooling record and the reheat record for the same batch where an officer can read them together.