Most food safety recommendations are for cooking foods to particular temperatures based on the identity of the food item. This requires that the user periodically check the temperature of the food being cooked to see if the desired temperature has been reached, and depending upon the recommendation being used, begin a timer for a period of time while keeping the food at the particular temperature for that time period.
Most recipes on the other hand are for cooking a food for a particular time period in an environment of a certain temperature on the theory that the food being cooked will reach the needed temperature shortly before or at the expiration of the time period. This approach cause problems, because the oven or other cooking device typically do not obtain the correct cooking temperature or the user does not provide sufficient heat to the food, for example, during stove top cooking or grilling.
Today given the increase in utility costs, it is desirable to not place a hot food directly into the refrigerator. In addition, however, if a food remains out in or at room temperature for to long or is in the temperature range of 70° F. to 140° F. for over two hours, then a variety of bacteria will start to grow that may cause food borne illnesses for the consumers of the food.