Temperature control in the kitchen forms part of the food safety pillars which is critical in ensuring the prevention of bacterial growth and overall quality of foods.
Temperature control ensures that foods that are meant to be served hot are kept at the required temperature and foods meant to be served cold are not left out at dangerous temperatures.
One of the best ways to kill bacteria is by heat. Rapid changes in temperature also prevent bacteria from surviving. So heating foods quickly kills bacteria.
Cold temperatures actually only slow or minimise the growth of bacteria.
Think about the foods in your fridge. When foods are kept in the fridge for longer than three days foods start to food off. This is caused by food spoilage bacteria and takes a few days to happen in the fridge due to the minimum growth rate.
However, when foods are left out at 20+ °C (68+ °F) food spoils a lot quicker. This is why we talk about the danger zone.
The Danger Zone is a temperature range in which bacteria grow and multiple at its fastest. This ranges from 20 – 45 °C (68 – 113 °F). Bacteria can, however, grow and survive between 5 – 65 °C (41 – 149 °F). But the most common food-related bacteria grow at their best in the danger zone.
This is because our internal body temperature is at 37 °C (98 °F) and food poisoning bacteria are related to us by the food we eat. 37 °C (98 ° F) is, therefore, the optimum performance zone for these bacteria. This is true for bacteria such as E.coli and Salmonella.
Therefore keeping foods outside this range prevents rapid growth of bacteria.
How to manage hot foods
All hot foods, but especially those on display at a buffet or servery must be kept above 65.0 °C (149 °F) at all times.
In order to achieve this, hot foods must be kept in a pre-heated hot display that is above this temperature. If you place hot foods in a cool display it will take too long to get back up to the required temperature allowing bacteria to survive. The same is true for placing cooled foods into a hot display. Remember we need high and quick temperatures to kill bacteria.
Keeping records for both the hot and cold display of foods is an important factor in temperature control. Remember that if it is not being monitored then it’s not being managed. Temperatures should be recorded at least 1 hour into service in order to ensure that everything is in order.
When it comes to the reheating of food, they should be heated to a temperature of 70 °C (158 °F) for at least 10 minutes in order to ensure all bacteria has been killed. Warmers and Bain maries cannot be used to reheat foods because they do not rapidly increase the temperature, allowing time for bacteria to grow and survive.
How to manage cold foods
In the case of high-risk cold foods such as prepared salads, deli meats and dairy, these foods must be displayed below 5 degrees C (41 °F). Foods such as sliced fruits and juices can be kept below 7 degrees C (45 °F). This requires that a cold display be used to keep food cold and out of the danger zone.
This also means that these foods should be pre-chilled in a fridge or freezer for at least 30 minutes, and the cold display should be operating below the required temperatures before foods are placed out on display.
Cold displays must be either refrigerated or kept on ice. We would recommend both in warmer climates. Crushed ice works particularly well as a display that is both appealing and functional.
How to manage the refrigeration of foods
Much like the display of foods. All perishable foods need to be refrigerated. This is so that foods do not spoil sooner than the expiry date. Remember that cold temperatures only minimise bacterial growth, but in some cases, bacteria such as Listeria monocytogenes actually thrive at refrigerated ranges.
This is why all five of the food safety pillars are essential in a food safety management system.
Nevertheless, high-risk foods need to be kept below 5 degrees C (41 °F). Fruit and vegetables should be kept below 7 degrees C (45 °F) as is the case when displayed. Frozen foods need to be kept at -12 degrees C (10 °F).
However, colder temperatures up to -20 °C (-4 °F) will allow you to keep food for up to six months.
Ice-cream is particularly unique due to its consistency and must be kept below -18 °C (0 °F). This keeps ice-cream solid, preventing crystallization and therefore minimising layers in the ice-cream in which bacteria can survive.
Maintaining refrigeration units is vital to ensuring safety and quality and should also be monitored on a daily basis, to ensure correct temperatures are kept.
Keeping records will also allow you to detect ongoing maintenance concerns or whether the doors were left open for too long due to negligence.
How to keep temperature records
- List each fridge/freezer in the kitchen
- Record at least 4 hot and 4 cold foods if you display your foods
- Purchase a hand-held digital probe thermometer (you can review the different types here)
- Place a vial of water or stick of butter in each fridge/freezer
- Use the thermometer to record the core temperature
- Record these temperatures twice daily and/or at each buffet service for the foods.