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Digestibility of Different Starches

Many investigations have been carried on upon the digestibility of starches from different sources.1 Raw starch digests much more slowly than starch in the form of paste. "Potato, arrowroot

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FIG. 11. Some common starches. 1, Potato starch.; 2, rice starch; 3, wheat starch; 4, wheat starch with polarized light; 5, maranta starch-polarized light; 6, bean starch-polarized light. (Yearbook U. S. Dept. Agric., 1907, by permission.)

and probably tapioca and sago starch pastes are not made more easily digestible by long cooking. On the other hand the cereal starches are made more digestible by long cooking though the 'Day. U. S. Dept. Agri. Office Exp. Sta. Bull. No. 202.

change occurs very slowly. . However, in the case of starch still inclosed in cellulose walls, as in many starchy foods, the long-continued cooking may be necessary. The commercial preparations of corn starch require 30 to 40 minutes cooking because of the improvement of flavor which results."

Without going into detail in regard to the digestion of starch, it is known that the starch is acted upon to a small extent by the ferments of the saliva, but starch digestion takes place largely in the small intestine. Here the amylopsin from the pancreas, and the lactase, maltase and sucrase in the intestinal secretions act on the carbohydrates, and prepare them for absorption.

CHAPTER III

BREAD AND OTHER CEREAL PRODUCTS

BREAD AND BREAD-MAKING

History

In making edible foods from the cereals or their products, various methods for grinding the grain, for making the dough light and for baking have been in use from the earliest times. In the primitive stages of the civilization of all peoples, their methods have been very crude and imperfect, but as bread of some kind has so long been the most important food of the race, the improvements in the methods used for preparing bread, have kept pace with the advancement of the race toward civilization. References to bakers, and baking are numerous throughout the earlier literature: not only the writings of the Jews but those of the Egyptians and Romans, are full of these references. In 170 B. C. baking became a regular trade in Rome. The use of fermented bread was no doubt carried to Britain by the Romans, but strangely enough they seem to have returned to unfermented bread after the Romans left England. Wine "must" was very early used in Greece and Rome, and "barm" from beer in Spain.

Going back to the earliest times, both leavened and unleavened bread were used. The simplest product would, of course, be that which was unleavened, but as the mixture of flour or meal and water undergoes spontaneous fermentation, deriving yeast and other organisms from the air, it would not be long before this fact would be taken advantage of to produce a light bread of different texture and flavor from that which was baked as soon as mixed. The next step to allowing the dough to stand for some time and

become sour, would be to add some of the sour dough or "leaven" to the fresh batch of dough to induce fermentation. Thus it is evident that the whole process would be gradually evolved through experience.

The making of bread is possible because of the presence of gluten in the flour. Gluten is a protein or mixture of proteins, which becomes viscid or sticky when mixed with water, and this mass may then be blown up with air or any other gas, and finally the mass sets in this condition in the process of baking. If the walls of the cells are not stable enough to stand, when the gas has been expelled by heat, the bread falls, or is said to be heavy.

Unleavened Bread

Unleavened bread is prepared by simply mixing the ground, crushed or bolted flour with water and salt and baking before a bonfire, in the ashes, or on a pan in the oven. No attempt is made at "aeration" or making the product light. The Passover cake of the Isrealites, sea biscuit, and hard tack as used on shipboard and in the army, the Scotch oat cake and the corn-meal "pone" are examples of this kind of bread. Crude ovens built of clay are often used in baking these unleavened breads. (Fig. 12.) Graham flour and whole-wheat flour are often prepared in this way in dietary establishments, and these products require very thorough mastication.

"Biscuit" as they are sometimes called, or "crackers," are made either from the leavened or the unleavened dough. (See p. 75.) "Hard tack" is rapidly baked, and while in the oven the generation of steam and the expansion of the starch causes it to rise slightly. After being baked it is stored in a warm room for a week or two to "cure" and dry, and in this condition, will, if dry, keep for years without deterioration. Under the influence of heat and moisture dextrin is formed and the starch granules swell so that gelatinous starch is formed.

Not only will unleavened bread keep for a long time, but another advantage is that as it is so hard and dry it requires thor

ough mastication and will when eaten become mixed with large quantities of saliva which aids digestion. This variety of bread is not, however, usually considered very appetizing, and so for general use it has never taken the place of raised bread.

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There are two general methods in use for making dough lightI Non-fermentation methods; II. Fermentation methods.

I. Bread not Raised by Fermentation

Much time and labor are expended in the making of raised or fermented bread. Not only is the product of the fermentation somewhat uncertain in the hands of the ordinary cook, but some of the nutritive ingredients of the flour are used up in furnishing the materials which raise the dough. In Germany, as well as in America,1 more than fifty years ago, numerous attempts were made to produce good products without employing fermentation. Liebig calculated that in Germany the daily loss of material by the 1 Bread and Bread Making, Farmers' Bull. No. 389, U. S. Dept. Agri.

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