It is important that the housekeeper not only understand the nature and composition of foods, but she should also know something of their digestive properties, since food, to be serviceable, must be not only nutritious, but easily digested. Digestion is the process by which food rendered soluble, and capable of being absorbed for use in carrying on the various vital processes.
The length of time required for stomach digestion varies with different food substances. The following table shows the time necessary for the stomach digestion of some of the more commonly used foods:
|Beans, pod, boiled||2||30|
|Apples, sour and raw||2||00|
|Apples, sweet and raw||1||30|
|Potatoes, Irish, boiled||3||30|
|Potatoes, Irish, baked||2||30|
|Eggs, hard boiled||3||30|
|Eggs, soft boiled||3||00|
|Salmon, salted, boiled||4||00|
|Beef, lean, rare roasted||3||00|
|Beef, lean, fried||4||00|
|Beef, salted, boiled||4||15|
|Pork, salted, fried||4||15|
The time required for the digestion of food also depends upon the condition under which the food is eaten. Healthy stomach digestion requires at least five hours for its completion, and the stomach should have an hour for rest before another meal. If fresh food is taken before that which preceded it is digested, the portion of food remaining in the stomach is likely to undergo fermentation, thus rendering the whole mass of food unfit for the nutrition of the body, besides fostering various disturbances of digestion. It has been shown by recent observations that the length of time required for food to pass through the entire digestive process to which it is subjected in the mouth, stomach, and small intestines, is from twelve to fourteen hours.