The safest ways to defrost food are:
1. In the fridge: this might take at least 24 hours if the item is large.
2. Under cold water, provided the food is in a water-tight container so that outside bacteria are not able to contaminate it.
3. In the microwave, as long as you are planning to cook it right away - parts of the food might become warm during the process, resulting in bacterial growth. High heat is required to kill these bacteria.
Of course, these precautions alone are not enough. When cooking, follow these guidelines:
1. Processed and rolled red meat, poultry, and any food containing egg must get to a core temperature of at least 75° Centigrade in order to kill bacteria.
2. Food that is kept hot for longer than two hours must not fall below 63° degrees centigrade.
3. You should not put hot food into the fridge or freezer.
Depending on the ratio of volume to surface area of food, the cooling time can be between 30 minutes and four hours. If possible, keep it within 90 minutes by following these steps:
1. Transfer food from hot pans to cool containers
2. Place soups, stocks, stews, etc, into smaller containers
3. Sit containers, especially large ones like lasagna pans, in ice-cold 'bain-maries' (water baths)
4. Turn on the fan to keep the air moving so that heat is dispersed away from the food
5. Joint whole chickens, and cut meat and fish into individual portion sizes.