Human Foods and Their Nutritive Value by Harry Snyder (dark academia books to read .TXT) ๐
CHAPTER XXI
LABORATORY PRACTICE 299
Object of Laboratory Practice; Laboratory Note-book and Suggestions for Laboratory Practice; List of Apparatus Used; Photograph of Apparatus Used; Directions for Weighing; Directions for Measuring; Use of Microscope; Water in Flour; Water in Butter; Ash in Flour; Nitric Acid Test for Nitrogenous Organic Matter; Acidity of Lemons; Influence of Heat on Potato Starch Grains; Influence of Yeast on Starch Grains; Mechanical Composition of Potatoes; Pectose from Apples; Lemon Extract; Vanilla Extract; Testing Olive Oil for Cotton Seed Oil; Testing for Coal Tar Dyes; Determining the Per Cent of Skin in Beans; Extraction of Fat from Peanuts; Microscopic Examination of Milk; Formaldehyde in Cream or Milk; Gelatine in Cream or Milk; Testing for Oleomargarine; Testing for Watering or Skimming of Milk; Boric Acid in Meat; Microscopic Examination of Cereal Starch Grains; Identification
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Fig. 34.โBarley Starch.
147. Barley Preparations are not so extensively used as wheat, oats, and corn. Barley contains a little more protein than corn, but not quite so much as wheat; otherwise it is quite similar to wheat in general composition. Sometimes in the preparation of breakfast foods barley meal is mixed with wheat or corn. Barley is supposed to be more readily digested than some of the other cereals, because of the presence of larger amounts of active ferment bodies, and it is frequently used for making an extract known as "barley water," which, although it contains very little nutritive value, as less than one per cent of the weight of the barley is rendered soluble, is useful in its soothing influence and mechanical action upon the mucous membrane of the digestive tract.
Fig. 35.โRice Starch.
148. Rice Preparations.โRice varies somewhat in composition, but usually contains a slightly lower percentage of protein than corn and also a smaller amount of fat. It is particularly rich in starch, and has the least ash or mineral matter of any of the cereals. In order to make a balanced ration, rice should be supplemented with legumes and other foods rich in proteids. It is a valuable grain, but when used alone it is deficient in protein. Rice is digested with moderate ease, but is not as completely absorbed by the body as other cereals, particularly those prepared by fine grinding or pulverization. Of late years rice culture has been extensively introduced into some of the southern states, and the domestic rice seems to have slightly higher protein content than the imported. Rice contains less protein than other cereals, and the starch grain is of different construction. Rice does not require such prolonged cooking as oatmeal; it needs, however, to be thoroughly cooked.
149. Predigested Foods.[56]
"It is questionable whether it would be of advantage to a healthy person to have his food artificially digested. The body under normal conditions is well adapted to utilize such foods as the ordinary mixed diet provides, among them the carbohydrates from the cereals. Moreover, it is generally believed that for the digestive organs, as for all others of the body, the amount of exercise they are normally fitted to perform is an advantage rather than the reverse. It has been said that 'a well man has no more need of predigested food than a sound man has for crutches.' If the digestive organs are out of order, it may be well to save them work, but troubles of digestion are often very complicated affairs, and the average person rarely has the knowledge needed to prescribe for himself. In general, those who are well should do their own work of digestion, and those who are ill should consult a competent physician."โWoods and Snyder.
150. The Value of Cereals in the Dietary.โCereals are valuable in the dietary because of the starch and protein they supply, and the heat and energy they yield. They are among the most inexpensive of foods and, when properly prepared, have a high degree of palatability; then, too, they are capable of being blended in various ways with other foods. Some are valuable for their mechanical action in digestion, rather than for any large amount of nutrients. They do not furnish the quantity of mineral matter and valuable phosphates that is popularly supposed. They all contain from 0.5 to 1.5 percent of mineral matter, of which about one third is phosphoric anhydrid. In discussing the phosphate content of food, Hammersten states:[59]
"Very little is known in regard to the need of phosphates or phosphoric acid.... The extent of this need is most difficult to determine, as the body shows a strong tendency, when increased amounts of phosphorus are introduced, to retain more than is necessary. The need of phosphates is relatively smaller in adults than in young developing animals."
In the coarser cereals, which include the bran and germ, there is the maximum amount of mineral matter, but, as in the case of graham bread, it is not as completely digested and absorbed by the body as the more finely granulated products which contain less. The kind of cereal to use in the dietary is largely a matter of personal choice. As only a small amount is usually eaten at a meal, there is little difference in the quantity of nutrients supplied by the various breakfast cereals.
per lb. % % % % % % % % % % Cal. Oat Preparations: Oats, whole grain 11.0 11.8 5.0 59.7 9.5 3.0 -- -- -- -- -- Oatmeal, raw 7.3 16.1 7.2 66.6 9.9 1.9 12.5 6.5 65.5 1.4 1767 Rolled, steam-cooked 8.2 16.1 7.4 65.2 1.3 1.8 12.5 6.7 64.5 1.4 1759 Wheat: Whole grain 10.5 11.9 2.1 71.9 1.8 1.8 -- -- -- -- -- Cracked wheat 10.1 11.1 1.7 73.8 1.7 1.6 8.1 1.5 68.7 1.2 1501 Rolled, steam-cooked 10.6 10.2 1.8 74.4 1.8 1.5 8.5 1.6 70.7 1.1 1541 Shredded wheat 8.1 10.6 1.4 76.6 2.1 1.8 7.7 1.3 71.1 1.4 1521 Crumbed and malted 5.6 12.2 1.0 77.6 1.7 1.0 9.1 0.9 73.7 1.4 1623 Farina 10.9 11.0 1.4 75.9 0.4 0.4 8.9 1.3 72.9 0.5 1609 Rye: Whole grain 11.6 10.6 1.7 72.5 1.7 1.9 -- -- -- -- -- Flaked, to be eaten raw 11.1 10.0 1.4 75.8 1.7 7.8 1.3 71.1 1.3 1516 Barley: Whole grain 10.9 12.4 1.8 69.8 2.7 2.4 -- -- -- -- -- Pearled barley 11.5 8.5 1.1 77.5 0.3 1.1 6.6 1.0 73.0 0.3 1514 Buckwheat: Flour 13.6 6.4 1.2 77.5 0.4 0.9 5.0 1.1 73.1 0.7 1471 Corn: Whole grain 10.9 10.5 5.4 69.6 2.1 1.5 -- -- -- -- -- Corn meal, unbolted 11.6 8.4 4.7 74.0 1.3 6.2 4.2 73.2 1.0 1728 Corn meal, bolted 12.5 9.2 1.9 74.4 1.0 1.0 6.8 1.7 74.6 0.8 1602 Hominy 10.9 8.6 0.6 79.2 0.4 0.3 6.4 0.5 78.7 0.2 1671 Pop corn, popped 4.3 10.7 5.0 77.3 1.4 1.3 7.9 4.5 77.8 1.0 1882 Hulled corn 74.1 2.3 0.9 22.2 0.5 1.7 0.8 21.8 0.4 492 Rice: Whole rice, polished 12.3 6.9 0.3 80.0 0.5 5.8 0.3 78.4 0.4 1546 Puffed rice 7.1 6.2 0.6 85.7 0.4 5.1 0.5 84.0 0.3 1639 Crackers 6.8 10.7 8.8 71.4 0.5 1.8 9.1 7.9 70.5 1.4 1905 Macaroni 10.3 13.4 0.9 74.1 1.3 11.6 0.8 72.2 1.0 1660
151. Use for Bread Making.โWheat is particularly adapted to bread-making purposes because of the physical properties of the gliadin, one of its proteids. It is the gliadin which, when wet, binds together the flour particles, enabling the gas generated during bread making to be retained, and the loaf to expand and become porous. Wheat varies in chemical composition between wide limits; it may contain as high as 16 per cent of protein, or as low as 8 per cent; average wheat has from 12 to 14 per cent; and with these differences in composition, the bread-making value varies.
Fig. 36.โStarchy (light-colored) and Glutinous (dark-colored) Wheats.
Fig. 37.โLongitudinal
Section of Wheat Kernel:
a, pericarp;
b, bran layers; c, aleurone cells;
d, germ. (After Kรถnig.)
152. Winter and Spring Wheat Flours.โThere are two general classes of wheat: spring wheat and winter wheat. The winter varieties are seeded in the fall, and the spring varieties, which are grown mainly in the Northwestern states, Minnesota, and North and South Dakota, and the Canadian Northwest, are seeded in the spring and mature in the late summer. Winter wheat is confined to more southern latitudes and regions of less severe winter, and matures in the early summer. There are many varieties of both spring and winter wheat, although wheats are popularly characterized only as hard or soft, depending upon the physical properties. The winter wheats are, as a rule, more soft and starchy than the spring wheats, which are usually corneous or flinty to different degrees. There is a general tendency for wheats to become either starchy or glutinous, owing to inherited individuality of the seed and to environment. There are often found in the same field wheat plants yielding hard glutinous kernels, and other plants producing starchy kernels containing 5 per cent less proteids. Wheats of low protein content do not make high-grade flour; neither do wheats of the maximum protein content necessarily make the best flour. For a more extended discussion of wheat proteids, the student is referred to Chapter XI.
153. Composition of Wheat and Flour.โIn addition to 12 to 14 per cent proteids, wheat contains 72 to 76 per cent of starch and small amounts of other carbohydrates, as sucrose, dextrose, and invert sugar. The ash or mineral matter ranges from 1.7 to 2.3 per cent. There is also about 2 per cent fiber, 2.25 per cent ether extract or crude fat, and about 0.2 per cent organic acids.
12.0 { Ash Potash
Soda
Lime
Magnesia
Phosphoric anhydrid
Sulphuric anhydrid
Other Substances Per Cent
2.25 { Protein Albumin 0.4 Globulin 0.9 Gliadin 6.0 Per Cent
13.0 Glutenin 5.3 Other proteids 0.4
Fig. 38.โGranular
Wheat Flour Particles.
154. Roller Process of Flour Milling.โFlours vary in composition, food value, and bread-making qualities with the character of the wheat and the process of milling employed. Prior to 1870 practically all wheat flour was prepared by grinding the wheat between millstones; but with the introduction of the roller process, steel rolls were substituted for millstones.[60] By the former process a smaller amount of flour was secured from the wheat, but with the present improved systems about 75 per cent of the weight of the grain is recovered as merchantable flour and 25 per cent as wheat offals, bran, and shorts[61].
The wheat is first screened and cleaned, then passed on to the corrugated rolls, or the first break, where it is partially flattened and slightly crushed and a small amount of flour, known as the break flour, is separated by means of sieves, while the main portion is conveyed through elevators to the second break, where the kernels are more completely flattened and the granular flour particles are partially separated from the bran. The material passes over several pairs of rolls or breaks, each succeeding pair being set a little nearer together. This is called the gradual reduction process, because the wheat is not made into flour in one operation. More complete removal of the bran and other impurities from the middlings is effected by means of sieves, aspirators, and other devices, and the purified middlings are then
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