Why is Temperature Control Important?
Poor temperature control is a major causal factor in many reported outbreaks of food poisoning. Food business operators have a moral and legal duty to ensure validated time and temperature controls are in place and followed in practice. Failure to implement and follow these simple rules by food handlers and management has led to major outbreaks of food poisoning, substantial fines and imprisonment.
The maximum legal temperature (recommended in Scotland) for foods that support the growth of pathogens or formation toxins is 8OC, but there are some exemptions to this requirement. Food on display or service can be kept above 8OC for a single period of up to four hours, but most organisations will set a target level of two hours. Other exemptions include raw food intended for cooking or further processing and where a scientific assessment can demonstrate there is risk to health.
Chilled storage of food products between 5OC – 8OC in most cases is an effective control measure, but problems in food safety can still happen. Listeria monocytogenes is psychotropic pathogen that can multiple at a temperature as low as -1.5OC and growth can double at temperatures above 5OC1. It is recommended good practice for healthcare and social care organisations to maintain a cold chain of chilled ready to eat (RTE) food at 5OC or below from delivery to service1.
Scombrotoxic food poisoning is a foodborne illness that typically results from eating spoiled fish. Poisoning occurs when histidine, an amino acid found in dark fleshed fish, converts to histamine due to spoilage. This can happen when fish is stored above 4OC. Correct chilled storage between 1OC -4OC is recommended as heat resistant toxins cannot be destroyed by cooking.
Freezing and Defrosting
Never accept frozen prepacked food products delivered below -15OC. Put frozen food in the freezer as soon as it is delivered and at store at 18OC or below. Ice-cream can be safely served from a suitable display freezer operating between -10OC to 15OC2, but bulk storage of closed tubs must be storage at 18OC or below.
Anisakiasis is a disease caused by the consumption of raw or undercooked fish contaminated with parasitic nematodes (worms) that attach to the wall of the oesophagus, stomach or intestine. There is a legal requirement for all food businesses to freeze fish that will be consumed raw with all parts of the product to achieve a time and temperature combination of -20OC for not less than 24 hours or -35OC for not less than 15 hours3. Farmed salmon is exempt from this requirement3.
Foods that require refrigeration should be defrosted in the fridge or defrosting cabinet (10OC -15OC) to minimise the growth of bacteria and formation of toxins. Once food has been defrosted, it should be consumed within 24 hours or follow manufacturer’s instructions for prepacked products.
Cooking food is an effective method used to destroy most pathogenic bacteria and parasites found in food products. The Food Standards Agency has produced a useful guide on different time and temperature combinations:
- 80OC for 6 seconds
- 75OC for 30 seconds
- 70OC for 2 minutes
- 65OC for 10 minutes
- 60OC for 45 minutes
Food that will processed below a time and temperature of 60OC for 45 minutes5 will need scientific evidence to prove the method is safe. Sous vide is popular method for processing a variety of food products at low temperatures. You should trial and document a safe method to demonstrate the correct time and temperature combination for each type of product. Local government has produced an excellent guidance document that navigates caterers through necessary steps to validate the process: http://www.torbay.gov.uk/media/9853/sous-vide-guidance.pdf
Food must be cooled as quickly as possible to prevent the growth of pathogenic bacteria and formation of harmful toxins. Slow cooling times can trigger germination of spore forming bacteria and formation of toxins. Exotoxins are produced when bacteria multiply on food. They can survive high temperatures for long periods of time during the reheating process. Endotoxins form part of the bacteria cell wall, and usually released after the organism grows and then dies in human gut.
Cooling times and temperature can vary. In most cases food products should be cooled from 55OC to 20OC within two hours4. Guidance for sous vide cooking and cook-chill recommends cooling food to 5OC within 90 minutes and cook-chill states 30C within two hours of cooking5,6.
Reheating food is major food safety hazard if the correct temperature and time limit has not been achieved. Food should be reheated rapidly to a minimum core temperature of 75OC for 30 seconds (legal limit in Scotland is 82OC)4. Food can only be reheated once. Preheating equipment will reduce the time needed to achieve the correct core temperature. Always follow the manufacturers instructions for prepacked foods on standing and stirring to make sure all parts of the product is heated to the correct temperature.
Hot food must be held at 63OC or above. Food may be kept below 63OC for a single period of no more than two hours or longer if a scientific assessment demonstrates there is no risk to health. Following this two-hour period, food must be discarded, chilled rapidly to 8OC or below, or reheated once (75OC or 82OC) and held above 63OC.
Percipio Training provides guidance on time and temperature controls on all its food safety/hygiene and HACCP courses. We will make sure your team knows why temperature controls are important, and what happens when things go wrong. Check our website to find out more about accredited courses at levels 2,3 and 4.
1. Food Standards Agency (2016) REDUCING THE RISK OF VULNERABLE GROUP CONTRACT LISTERIOSIS. GUIDANCE FOR HEALTHCARE AND SOCIAL CARE ORGANISATIONS. [ Online]. Available at: https://www.food.gov.uk/sites/default/files/media/document/listeria-guidance-june2016-rev.pdf (Accessed 27/08/2019).
2. West Lothian Council (2015). Guidelines for the Storage and Sale of Ice Cream [ Online]. Available at: https://www.westlothian.gov.uk/media/2784/Storage-and-Sale-of-Ice-cream-Information-Sheet-FH10/pdf/FH10_ICE_CREAM.pdf (Accessed 27/08/2019).
3. Food Standards Agency (2018). Freezing fish and fishery products: How to freeze fish and fishery products that are intended to be eaten raw or lightly cooked in food businesses and restaurants. [ Online]. Available at: https://www.food.gov.uk/business-guidance/freezing-fish-and-fishery-products Accessed 27/08/2019)
4. British Hospitality Association (2016) Industry Guide to Good Hygiene Practice: Catering Guide Regulation (EC) 852/2004 on the Hygiene of Foodstuffs. London BHA.
5. Torbay Council.Guidance on Sous Vide Cooking. [Online]. Available at: http://www.torbay.gov.uk/media/9853/sous-vide-guidance.pdf ( Accessed on 27/08/2019).
6. DEPARTMENT OF HEALTH (1989) Chilled and Frozen guidelines on Cook-Chill and Cook-Freeze Catering Systems, London: HMSO.