When making stock from the carcass and scraps from a cooked chicken, how safe is it to re-heat the stock afterwards? It is not always convenient to make the stock immediately after cooking the chicken, so the cold carcass is re-heated when making the stock, and then re-heated again when using the stock. Is this safe?
It is usually fine to make chicken stock from the carcass of a roasted chicken that has been refrigerated but it is best to make sure that the carcass is refrigerated as quickly as possible after cooking and carving (and within 2 hours). The chilled carcass can also be frozen for up to 3 months, sealed tightly in a container or resealable bag, then thawed in the fridge and used to make stock at a conveneient time (some people like to save up 2 or 3 carcasses in the freezer and then make stock in larger quantities).
When you are making stock it is also a good idea to bring the pan of water, chicken and vegetables up to boiling point, before reducing the heat to a low simmer. This "scalding" will help to reduce the risk of salmonella as it cannot survive high temperatures.
Once the stock has finished its cooking time it should be strained immediately. Don't let the chicken bones and vegetables sit in the cooling stock. Cool and refrigerate the strained stock as quickly as possible (again within 2 hours of cooking). The stock can be reheated once from here. The stock can also be frozen for up to 3 months for later use, but again it is safest to reheat it only once after thawing.