While little study appears to have been made of the digestibility of cereal proteids when cooked for a long time at a low temperature, it is probably fair, in the absence of further definite information, to assume that, like animal proteids, it is better to cook them at a low temperature such as that of the fireless cooker, than at the temperature of boiling water or higher.
In the bulletin entitled “A Precise Method of Roasting Meat,” by Elizabeth A. Sprague and H. S. Grindley, published by the University of Illinois, a study is made of the temperatures at which the changes take place from raw meat to “rare”; from “rare” to “medium rare,” and from this to “well done” meat. The authors found that if the centre of the meat is between 130 degrees and 148 degrees Fahrenheit (55 degrees and 65 degrees Centigrade), it is rare; if it is between 148 degrees and 158 degrees Fahrenheit (65 degrees and 70 degrees Centigrade), it is medium rare; and if it is between 158 degrees and 176 degrees Fahrenheit (70 degrees and 80 degrees Centigrade), it is well done. They found no advantage in cooking meat in a very hot oven (385 degrees Fahrenheit, or 195 degrees Centigrade), but rather a difficulty to keep it from burning; that in an oven which was about 350 degrees Fahrenheit (175 degrees Centigrade), the meat cooked better; and that in an Aladdin oven which kept the meat at about 212 degrees Fahrenheit (100 degrees Centigrade), it cooked best of all; that is, it was of more uniform character all through, more juicy, and more high flavoured. This seems to point to an advantage in fireless cookery for meats, and practical experience bears it out.
The initial heat of the insulated oven serves to sear and brown the meat, and when this heat is reduced by the cooling of the stones, the low temperature found to be best for completing the roasting is obtained. With regard to meats cooked in water in the cooker, experience has shown that they become well done and are more tender than when boiled, showing that the temperatures necessary to reach that degree of cooking are obtained even in the centre of a large piece of meat, without toughening or hardening the outside of the meat, as is done when more intense heat is applied.