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How safe are the insulated casserole carriers that are now available?
I do not have any research-based recommendations. As far as I know, nobody has conducted this type of consumer research. Therefore, the following are simply educated guesses. Maintaining hot (>140 F) or cold <40 F) temperatures is dependent on a variety of factors but most importantly: 1) the temperature of the food upon packing in the container; 2) the type of materials used to construct the insulated container; 3) the thickness of the insulated container; and 4) any other barrier to environmental temperatures. (1) The hotter or colder the food is upon packing, the longer it will stay at a safe temperature. However, the temperature of the insulated container is also important. Immediately before packing hot foods, heat the container by pouring boiling water in it, letting it sit for several minutes, and then emptying it. Before packing cold foods, put the insulated container in the refrigerator even if it has a freezer pack. (2) Stainless steel has better heat transfer properties. Therefore, is NOT a good material to use for keeping hot foods hot and cold foods cold in an insulated container. The energy from the food will easily be transferred through the stainless steel. Thus the temperature of the food will change more rapidly. A better material for keeping foods hot or cold is plastic. The reason that you find so much variation with temperature keeping qualities of insulated containers, is that there are many types of plastics being used in these containers. I have no information about the benefits of each type. I have also seen ceramic pans used and then inserted into an insulated nylon bag. I think these are also effective. (3) Another factor is the thickness of the plastic or ceramic or nylon bag - the thicker the better. If one is comparing brands, they can take them and look at them simultaneously to compare the thickness. (4) Also, putting the container in another container, bag, etc. will help retain the temperatures for a longer period. (5) Many thermos labels state that the food is safe for between two and four hours. I would agree with this. Furthermore, within that time frame the food is safe to eat. Finally, when packing food in an insulated container, also remember it is very important to ensure that the food is thoroughly cooked and packed in a sanitary manner. To me, these two preparation steps are more critical than hot- or cold-holding - that is if the hot or cold-holding is less than four hours.