Trading Standards Institute Advice

Temperature control: hot food

This leaflet is for all food businesses including those involved in food preparation and production, retail premises, catering, restaurants, pubs, cafes, takeaway and fast-food shops or businesses working from home.

What is temperature control?
Temperature control is the term used for making sure food is kept at a temperature that will keep it safe and limit the growth of food poisoning bacteria. The safety of food is preserved by good temperature control. For hot food the important temperatures are those achieved when processing, cooking and keeping food hot before and during service.

When food is cooked, food poisoning bacteria are reduced to a safe level. Storing hot food is referred to as 'hot holding'.

What happens if food temperature is not controlled?
Certain micro-organisms (called pathogens) can contaminate food, grow in it and then, if eaten, make you ill. These organisms multiply to high levels in a warm environment. You cannot see them or know they are there - food will look, smell and taste completely normal. Symptoms of food poisoning appear later if the food was contaminated and unsafe.

'High risk' is the term used for food that is most likely to cause food poisoning, such as any food that is ready to eat (including cooked rice, cooked meats, shellfish and dairy products such as milk and cream).

These foods should always be kept either below 5°C or above 63°C. Between these two temperatures is the area known as the danger zone - the temperature range within which bacteria grow most quickly. Temperature above or below these limits gives the bacteria as little chance as possible to multiply. The average room temperature is approximately 21°C - an ideal temperature for bacteria to grow.

We can eat pathogens and our body can deal with them - but only up to a certain level. Taking in too many organisms is known as taking an 'infective dose', and this will make you ill. Controlling the growth of bacteria to make sure levels always stay below the infective dose level is the method used to keep food safe.

What do I need to do?
THINK ABOUT THE MENU AND THE FOOD YOU USE AND HOW YOU PROCESS IT
Identify dishes and products that are high risk. It is important that all food handlers are trained to identify high-risk food and how to process it safely. One of the main causes of food poisoning is not cooking things properly.

MAKE SURE YOU HAVE THE RIGHT EQUIPMENT FOR THE JOB
You should have enough room in your oven and on top of the stove for the amount of food that you cook and process. You will also need suitable equipment to keep food hot if you are not going to use it immediately.

Make sure that anyone preparing and cooking food knows how to use this equipment, and that they are familiar with recipe or product cooking times and temperatures.

USE A PROBE THERMOMETER
It is good practice to use a probe thermometer to check that food is properly cooked. Probe thermometers are designed to take the 'core' temperature of the food. This means measuring the temperature at the thickest part of the food - normally the middle. The thickest part will always be the last area to experience temperature change, so the correct reading here shows that the food will have reached the right temperature throughout.

When you are cooking food, you must make sure it reaches a minimum core temperature of 70°C for two minutes (or an immediate reading of 75°C). In Scotland the minimum core temperature is 82°C. The food can certainly be hotter than this, but the quality of some food may suffer if it is overcooked or heated.

It is important to periodically check that the probe is working properly - it must be accurate. You check this by putting the probe into a mixture of cold water and ice. It must read between -1°C and +1°C. Then put it into boiling water where it must read between +99°C and +101°C. Any reading beyond these temperatures shows that the probe is not accurate and it must be correctly adjusted or replaced.

REHEATING FOOD THAT HAS BEEN COOKED
The same rule applies to food that is reheated.

If you use a microwave to reheat food, make sure there are no cold spots. Cold spots are areas that receive the lowest thermal energy.

You should thoroughly reheat food to a minimum core temperature of 75°C. (In Scotland it must be reheated to a minimum of 82°C)

You can only reheat food once and if you do not use it after reheating, you must throw it away. At 63°C bacteria stop growing and above this temperature start to die. At 75°C enough of them have been destroyed to reduce levels to below the threshold that would make you ill, making the food safe to eat.

Not all bacteria may be destroyed by reheating. Some may survive, especially those that are able to form a 'spore' (create a tough outer layer to protect themselves). Spores can survive cooking, which means they may be present in cooked food. If the food temperature falls back into the danger zone, organisms which have survived will start to grow again. To prevent this, you must store hot food above 63°C.

How do I store hot food safely?
There are several ways of storing hot food - you can use whichever method suits your business and the food product. For example, you could use:

  • traditional equipment such as an oven or the top of the stove
  • a bain-marie
  • a heated trolley or hot cupboard

Using the oven or the top of the stove will keep food hot but there is a risk the food will dry out and its quality spoil.

A bain-marie provides a layer of heat around the food, while not leaving heat in direct contact with food. A very simple form of bain-marie is to put a pan into a tray of very hot (simmering) water on the stove. You can buy a bain-marie as a piece of equipment - this could be a unit designed for kitchen use or a display counter. They can be heated by either electricity or gas (please note: electric models, unlike gas versions, use dry heat and must not be filled with water).

Whichever method you choose, you must not use hot-holding equipment to heat food. You must heat the food quickly and thoroughly to a minimum core temperature of 75°C using cooking equipment, and then transfer it to the hot-holding unit.

How do I cool food safely?
If you are going to cool cooked food, either to use as a cold dish or to reheat, you must do this as quickly as possible. Do not cool hot food by putting it into a fridge or freezer - this warms the fridge or freezer and puts the entire contents as risk. Cool it by:

  • leaving it in a cool place
  • taking it out of the original cooking container
  • using a fan to circulate cool air
  • cooling foods like rice and pasta by running them under the cold tap
  • putting the container in cold water
  • breaking down the food into smaller quantities, which will cool much quicker than large amounts

You should never leave high-risk food to cool for longer than 90 minutes before storing it in the fridge. Read our 'Temperature control: cold food' leaflet for more information.

You can leave low-risk food to cool and then store it appropriately. It is not as important to cool low-risk food so quickly.

Some food can be cooked and rather than kept hot, served as it is cooling.

You should only keep hot food out of temperature control for two hours at the most. You can only reuse this food if, after two hours, you return it immediately to at least 75°C (for example, by reheating it quickly). You must keep the food above 63C from that point as hot food can only be kept out of temperature control once. Depending on the type and quality of the food and what you are going to use it for, it may be better to throw it away.

A quick reminder
Remember, it is a criminal offence to use food that is not fit for people to eat. By using spoiled, out-of-date or unsafe food, you are risking your customers' health and your reputation. If in doubt, throw it out.

More information
You will find further guidance in our other leaflets on this website. Information can also be found on the Food Standards Agency website.

Alternatively, contact your local environmental health service for advice.

Please note
This leaflet is not an authoritative interpretation of the law and is intended only for guidance.

© 2017 itsa Ltd.