Human Foods and Their Nutritive Value, Harry Snyder [free e books to read TXT] 📗

51. Squash and Pumpkin.—Squash has much the same general composition and food value as beets and carrots, although it belongs to a different family. Pumpkins contain less dry matter than squash. The dry matter of both is composed largely of starch and sugar and, like many other of the vegetables, they are often combined with food materials containing a large amount of nutrients, as in pumpkin and squash pies, where the food value is derived mainly from the milk, sugar, eggs, flour, and butter or other shortening used.

52. Celery.—The dry matter of celery is comparatively rich in nitrogenous material, although the amount is small, and the larger proportion is in non-proteid form. When grown on rich soil, celery may contain an appreciable quantity of nitrates and nitrites, which have not been converted into amids and proteids. The supposed medicinal value is probably due to the nitrites which are generally present. Celery is valuable from a dietetic rather than a nutritive point of view.

53. Sanitary Condition of Vegetables.—The conditions under which vegetables are grown have much to do with their value, particularly from a sanitary point of view. Uncooked vegetables often cause the spread of diseases, particularly those, as cholera and typhoid, affecting the digestive tract. Particles of dirt containing the disease-producing organisms adhere to the uncooked vegetable and find their way into the digestive tract, where the bacteria undergo incubation. When sewage has been used for fertilizing the land, as in sewage irrigation, the vegetables are unsound from a sanitary point of view. Such vegetables should be thoroughly cleaned and also well cooked, in order to render them sterile. Vegetables to be eaten in the raw state should be dipped momentarily into boiling water, to destroy the activity of the germs present upon the surface. They may then be immediately immersed in ice-cold water, to preserve the crispness.

54. Miscellaneous Compounds in Vegetables.—In addition to the general nutrients which have been discussed, many of the vegetables contain some tannin, glucosides, and essential oils; and occasionally those grown upon rich soils have appreciable amounts of nitrogen compounds, as nitrates and nitrites, which have not been built up into proteids. Vegetables have a unique value in the dietary, and while as a class they contain small amounts of nutrients, they are indispensable for promoting health and securing normal digestion of the food.

55. Canned Vegetables.—When sound vegetables are thoroughly cooked to destroy ferments, and then sealed in cans while hot, they can be kept for a long time without any material impairment of nutritive value. During the cooking process there is lost a part of the essential oils, which gives a slightly different flavor to the canned or tinned goods.[17] In some canned vegetables preservatives are used, but the enactment and enforcement of national and state laws have greatly reduced their use. When the cans are made of a poor quality of tin, or the vegetables are of high acidity, some of the metal is dissolved in sufficient quantity to be objectionable from a sanitary point of view.[18]

56. Edible Portion and Refuse of Vegetables.—Many vegetables have appreciable amounts of refuse,[19] or non-edible parts, as skin, pods, seeds, and pulp, and in determining the nutritive value, these must be considered, as in some cases less than 50 per cent of the weight of the material is edible portion, which proportionally increases the cost of the nutrients. Ordinarily, the edible part is richer in protein than the entire material as purchased. In some cases, however, the refuse is richer in protein, but the protein is in a less available form. See comparison of potatoes and potato skins.

57. General Composition.—Fruits are characterized by containing a large amount of water and only a small amount of dry matter, which is composed mainly of sugar and non-nitrogenous compounds. Fruits contain but little fatty material and protein. A large portion of the total nitrogen is in the form of amid compounds. Organic acids, as citric, tartaric, and malic, are found in all fruits, and the essential oils form a characteristic feature. The taste of fruits is due mainly to the blending of the various organic acids, essential oils, and sugars. Although fruits contain a high per cent of water, they are nevertheless valuable as food.[20] The constituents present to the greatest extent are sugars and acids. The sugar is not all like the common granulated sugar, but in ripe fruits a part is in the form known as levulose or fruit sugar, which is two and a half times sweeter than granulated sugar. Sugars are valuable for heat-and fat-producing purposes, but not for muscle repairing. Proteids are the muscle-forming nutrients. The organic acids, as malic acid in apples, citric acid in lemons and oranges, and tartaric acid in grapes, have characteristic medicinal properties. The sugar, proteid, and acid content of some of our more common fruits is given in the following table:[21]