This section is from the book "A Handbook Of Invalid Cooking", by Mary A. Boland. Also available from Amazon: Handbook of Invalid Cooking.
Mush is meal or grain cooked in water to the consistency of rather thin pudding. Porridge is like mush, only thinner. The most important point connected with the preparation of these is thoroughness in the cooking. Made as they generally are of coarsely ground or of rolled grains, they need long boiling to soften the cellulose and to cook the starch properly.
Oatmeal. Oatmeal should be cooked for at least three hours in a double boiler. It is at its best prepared the day before it is needed, and then reheated as it is wanted. If it is done in this way, the flavor is fine, and there is no danger that the grains will be hard. When taken from the kettle, the oatmeal should be of the consistency to pour, and on cooling it ought to form into a tender, jelly-like pudding. Sometimes oatmeal is cooked so that the grains are whole and separate, but it is not easily digested so, and lacks the delicious flavor which long cooking gives.
Oatmeal for those for whom there is no objection to its use is a valuable nutrient, furnishing more for the money than almost any other food.1
1 Composition of oatmeal:
Nitrogenous matter..................................... 12.6%
Carbohydrates, starch, etc.............................. 63.8%
Fatty matter............................................ 5.6%
Mineral matter.......................................... 3.0%
Water.................................................... 15.00%
Total......................................100.00%
LethErbY. From Prof. Mott's Chart of the Composition, Digestibility, and Nutritive Value of Food.
Indian Meal. Indian meal also requires many hours' cooking. Even if it be in a single vessel and actually boiled, not less than an hour and a half of exposure to heat is safe.
Farina. Farina having been already subjected to a high degree of heat in its preparation, is thereby partially cooked, and does not require as long a time as the raw grains.
Mushes and porridges made from oatmeal, cracked wheat, or any grain on which the tough outside covering remains, are to be avoided in all cases of irritation or disease of the alimentary canal, particularly in diseases of the intestines, for the hard hulls are very irritating to the delicate lining membranes. Young children have exceedingly delicate digestive powers, and are often made ill by coarse, starchy food. For them it is always safest to use the prepared grains, such as farina, granula, and Imperial Granum.
All of the grains given in these recipes may be made into porridges by following the rules given for mushes, except that a larger proportion of water should be used. Porridges are like mushes, only thinner.
 
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