Chilling food to preserve it is a technology which has been around for longer than you may expect. Archaeologists have found evidence dating back to 1780 BC of ice houses. What the exact purpose was is unclear but the use of ice has been going on for centuries.
Cooling food correctly
Bacteria need 4 elements to multiply:Food, Water, Time and warmth or Temperature. If any of these are changed from the best level , then the multiplication will reduce or stop. Heating food can make food safe by killing bacteria and viruses. Once the target temperature has been reached, for “high risk” foods such as dairy and meat, the temperature must be reduced quickly through the danger zone of 5C to 63C. The time that the food is in the danger zone is important with food needing to be cooled to less than 5C in less than 90 minutes. In Scotland, high risk food must then be stored at less than 5C. In the rest of the UK, it is a maximum of 8C (less than 5C is best practice). Other countries will vary. Check your local laws.
Don’t forget to keep records!
Chilling food quickly
One of the methods that can be used is a blast chiller which drives cool air through the compartment and is used in commercial premises.
Always try to reduce the size of the food that is being chilled, by cutting meat into smaller pieces, baking smaller portions, or using flatter containers. Chilling food quickly is all about the surface area to volume ratio. The smaller the surface area to volume ratio, the slower the food will cool.
Food poisoning and spoilage bacteria thrive between 8C and 63C. this is known as the Danger Zone. Some bacteria can multiply below 8C slowly, and some can survive temperatures above 75C. The ones that can survive above 75C contain spores. Spores act as seeds, and will lie dormant until favourable conditions arise, sometimes for hundreds of years. FInd out more about microbiology here.