Important Questions Answered.
WILL you please answer the following in your columns?— 1. What is the chemical difference between fresh and stale bread, rendering the latter more digestible? 2. What change takes place when milk is boiled, making it more constipating than when raw? and does heating it to, perhaps, 140° produce the same effect? 3. What effect does soda have on the digestive organs, making it injurious? 4. What is the digestibility and nutritive quality of caramel? 1. Fresh bread contains a large amount of water, about forty-five per cent., much of which is in a pure or uncombined state. Within two or three days after baking, chemical changes take place in the interior of the loaf, in which the greater portion of the water enters into a combination with the starch and gluten of the grain, giving to the bread the appearance of being lighter, although if placed upon the scales it will be found that it has lost scarcely anything in weight. This fact can be easily demonstrated by placing a stale loaf in a closely covered vessel, and putting it in a hot oven for half an hour. On breaking open such a loaf it will be found to possess all the characteristics of a newly baked loaf, the water having been driven out from a combination with the constituents of the flour by the heat. A portion of the inside of a freshly baked loaf, when rubbed between the fingers, or when chewed, forms a sticky, pasty mass, which is permeated by the digestive fluids with difficulty. Pieces of stale bread treated in the same manner separate into small particles, which are readily acted upon by the digestive fluids. It is for this reason chiefly that stale bread is so much more wholesome and digestible than freshly baked bread. It should be added that the indigestibility of warm bread is greatly increased by the addition of butter. 2. The nutritive constituents of milk are casein, albumen, milk-sugar, fat, and salts. Boiling or heating to a temperature of about 140° coagulates the albumen, but does not materially affect the other constituents. The skin that forms upon the top of the milk, heated to near a boiling point, consists of this coagulated albumen, one of the most important nutritive elements of the milk. Milk is digested chiefly in the duodenum, by the action of the pancreatic juice, and the pepsin produced from it is found to be slightly constipating in character. The change produced by boiling seems to increase this natural tendency of milk, though whether this is due to the effect of heat upon the albumen or not, it is, perhaps not possible to say with certainty. Experience shows, however, that heating milk to 130 or 140 degrees temperature does not increase its natural constipating tendency. 3. The gastric juice, one of the most important of the digestive fluids, is very strongly acid in character, the degree of acidity being equal to that of a solution containing one five-hundredth part of pure hydrochloric or muriatic acid. In order that digestion should be properly performed, it is necessary that this degree of acidity should be retained in the stomach. The use of soda, or any other such article, neutralizes the acid in the food, and so checks the digestive process. The use of soda in cooking, in the form of baking-powders, etc., is a pernicious practice, and one that should be discarded, as well as the common practice of taking soda, magnesia, and other alkalies, to relieve acidity of the stomach. The only defense possible is that it is sometimes the least of two evils; but healthful living would dispense with both. 4. Caramel is a chemical substance produced by the action of heat upon sugar, and is neither nutritious nor digestible.—Christian Union.