Potato

POTATO (Solanum tuberosum), a plant of the nightshade family (Solanaceae). It differs from root vegetables in that its underground organs, which are rich in carbohydrates and have great nutritional value, are not roots but underground stem formations-tubers, which is why potato is classified as a tuber crop. The homeland of potato is considered to be South America, where it grows wild as a perennial plant (in temperate zones, potato is an annual). The first Europeans to become acquainted with potato were the Spanish (1533). In 1565, it was brought to Ireland, and then gradually spread throughout Europe. In Russia, it is believed to have penetrated during the time of Peter I, while its cultivation was begun under Anna Ioannovna, and the spread of potato occurred at a slow pace, sometimes accompanied by undesirable complications ("potato riots"), and only crop failures of grain in the 1840s gave impetus to the wider use of potato culture. In terms of total yield, European Russia before the war occupied second place (24,557,614 tons per year). The amount of potato per capita, however, was at that time for Russia about 245 kg, and for Germany about 800 kg per year. Many varieties of potato are known, and depending on the duration of the development period, early, medium, and late varieties of potato are distinguished; the first with a vegetative period of 70-90 days, the second 120-130 days, and the third up to 180 days. The purpose of tubers and the requirements for them, in turn, establish the following 3 groups of potato varieties: table, feed, and industrial varieties. The chemical composition of potato tubers is not constant and depends on the variety and growing conditions. According to data from the Central Statistical Administration, the average chemical composition of Russian potato is expressed by the following figures: water-76.13%, carbohydrates-19.56%, proteins-2.14%, fiber-0.99%, fat-0.22%, ash-0.98%. The nitrogenous substances of potato consist of approximately half asparagine and amino acids, the other half are proteins and in very small amounts peptones. Carbohydrates in potato are (according to König) in the following forms and amounts: sugars-0.33%, dextrins and gum-0.69%, starch-17.27%, nitrogen-free extractive substances-1.24% and pentosans-0.92%. The main nutrient in potato is starch. The fat content in potato is negligible. The ash of potato is rich in potassium (60%), the other cations are present in small amounts. Among anions, the main place belongs to phosphoric acid (16.86%). One of the components of potato is the poisonous glycoside solanine (Solanin, C₄₈H₇₃NO₁₅). Symptoms of solanine poisoning manifest as a bitter, scratching taste sensation and burning of the tongue, irritation of the mucous membranes, heaviness in the stomach, nausea and vomiting. The content of solanine in normal potato is from 0.002% to 0.01%. Potato with a content of more than 0.02% solanine can apparently cause the above-mentioned disorders. Nevertheless, solanine is more harmful to animals than to humans, since for human consumption, potato is used peeled and without the outer parts, in which solanine is mainly contained. In addition, the process of cooking potato significantly reduces its solanine content both by extraction from the tubers and by its decomposition. The largest amount of solanine is contained in sprouted potato tubers, and therefore they are considered harmful to health. Potato contains all three vitamins (A, B, C), although in moderate amounts (vitamin A is present in small amounts). Usually, preparation and cooking of potato little destroy its vitamins, so that cooked, especially steamed potato still contains a noticeable amount of them. When calculating the nutritional value of potato, it is necessary to take into account the amount of waste that is not used for food, which for potato constitutes about 25% of its weight. The caloric value of 1 kg of potato is approximately 625 calories. The digestibility of potato by humans is quite good, namely (according to the Central Statistical Administration) from 100.0 raw substance: proteins-1.39, fats-0.19 and carbohydrates-18.58 are digested. The methods of using potato are not the same everywhere. In our country to this day potato is mainly consumed for food purposes, then for technical production and least of all for animal feed. Germany, however, before the war, spent about half of the entire harvest on animal feed, somewhat less than a third for the food of the population and about a third for everything else; absolutely Germany provided more potato to each consumer than Russia. In food technology, potato is a very important raw material product, used for obtaining starch, molasses, alcohol, etc. In years of grain crop failure or severe economic crises, potato was repeatedly used as a good surrogate additive in baking bread from rye flour. In Germany, for this purpose, both raw potato (30%) and flour obtained from dried potato (in the amount of 10% by weight of rye flour) were used. The quality of bread made from such a mixture depended on the perfection of processing this bread product. In Germany during the war, it was possible to obtain acceptable potato bread that caused no complaints from consumers, but when the content of potato flour was increased to 20%, an unpalatable bread was obtained, which was reluctantly consumed by the population. In Russia, Erisman, Popov and others, in case of flour shortage, considered it more expedient to use additional potato as a separate dish, because the taste qualities of potato bread baked at that time were very low, although its digestibility approached that of black bread. Potato should be stored in dry, cool and non-freezing premises, on wooden bedding. To prevent greening, warehouses for its storage are usually made dark. The richness of water in the potato tuber makes it particularly sensitive to temperature effects. The lower limit of the temperature of the room intended for storing potato should not go below 0°. The upper limit does not have such a precise boundary, however above 3.75° the respiration of potato becomes noticeable, there is a risk of its sprouting and rotting; therefore the optimal temperature limits for storing potato are from 0.6° to 2.5°. For storing potato, various devices are used, which can be reduced to two main types: storage pits (cellars, pits) and above-ground (sheds and mound-stacks). Storage in cellars is more convenient but expensive. Pits are a cheap way of storing potato, but they require sufficiently dry soil and taking certain precautions both in the construction of the pit itself and in filling it with potato. For mass storage of potato, it is often placed in above-ground heaps, and the covering of such heaps should consist of an inner air-bearing and an outer earth layer. Covering with earth alone causes rotting of potato in humid weather. When storing potato, losses from rotting and other causes reach 12-15%. These disadvantages are not possessed by potato stored in a dried form. The drying process developed in Germany from 1902 and especially during the 1914-18 war. The chemical composition of dried potato according to data from the Central Statistical Administration is as follows: water-5.0%, protein substances-8.20%, carbohydrates-82%, fats-0.8%, fiber-4.0%. From 100.0 dried potato, digested are: proteins-5.33%, fats-0.68% and carbohydrates-67.24%. The caloric value of 1 kg is 3,040 calories. The advantages of such a product consist in eliminating losses from rotting, sprouting and respiration, stability in storage, the possibility of its use at any time of the year, facilitating its transportation and the possibility of its use as a feed. Disadvantages: worse taste than fresh potato and reduced vitamin content. Diseases of potato. Among the diseases of potato, first of all, a group of diseases of fungal origin should be noted. These include the so-called "potato disease" (not to be confused with potato disease of bread), caused by the fungus Phytophthora infestans, "dry (or white) rot" of tubers, caused by fungi of the genus Fusarium, scab (species Actinomyces) and others. Bacterial lesions include: "wet rot" (Clostridium butyricum), "ring rot" and others. Recently, the so-called "degeneration diseases" (mosaic disease, twisting and curling of leaves, etc.) have become very important, which are apparently caused by disorders of enzymatic functions and have the character of viral diseases. Among diseases not related to the life activity of microorganisms, "sprouting of tubers" should be mentioned, consisting in the fact that young tubers are formed directly from the eyes of primary tubers, and "thread-like disease", expressed in the formation of very thin thread-like shoots from the tuber. Among insects, the Colorado potato beetle does the greatest harm to potato, eating the tops in the adult state and in the larval stage. A special category of defective product is frozen potato. At 0° potato does not freeze yet and can be supercooled to -4°. Frozen potato as a dead product is unsuitable for sowing, but can serve for feed purposes and for distilling needs. Frozen potato in a cooked state has the well-known sweet, unpleasant taste that sometimes makes it completely unfit for food. The characteristic sweetness inherent in frozen potato, as Müller showed, depends on the accumulation of glucose in the tubers and partially sucrose.

F. Okopov.

Potato as a nutrient medium was first proposed by Schroter; Koch widely used it in bacteriological practice. At present, potato is used primarily as a special nutrient medium, being employed either in its natural form or as one of the components of the medium. Not all varieties of potato are suitable for preparing the medium. The most suitable is the yellow potato that does not disintegrate during sterilization, giving a smooth and dense, rather than loose and rough, surface when cut after cooking. Preparation of the medium begins with thorough disinfection of the potato skin, as extremely resistant spore-bearing bacteria are often present on its surface. For disinfection, the potato is brushed and immersed for 1 hour in a 1%₀ solution of mercuric chloride. Then the potato is rinsed several times with water, the skin is cut off from both ends, and cylinders are removed with a special drill or an ordinary knife, which are then cut diagonally into two wedges. These wedges are immersed for 15-30 minutes in distilled water—if the medium does not need to be neutralized—or in a 1% solution of soda if a neutral or slightly alkaline reaction is desired (potato usually has a slightly acidic reaction). Then each wedge is slightly dried with gauze or filter paper and placed in a Ru potato tube, which is a slightly wider tube than usual with a circular narrowing or constriction at some distance from the bottom; the potato wedge rests on this constriction. Distilled water, or physiological NaCl solution, or 5% glycerin water (the latter specifically for cultivating tubercle bacilli) is poured into the bottom of the tube in such an amount that the lower edge of the potato wedge slightly touches the liquid. The medium prepared in this way is sterilized in an autoclave for 20 minutes at 115°. After checking for sterility in an incubator, the medium is ready for use. For preparing the potato medium by the above method, Koch dishes were formerly used, but at present almost exclusively Ru tubes are used, as this provides greater assurance of medium sterility. Potato media are used mainly for growing tubercle bacilli. Such media containing potato include Pavlovsky's glycerin potato (preparation method indicated above), Anzilotti's glycerin potato, Yurevich's glycerin-potato broth, Wodremmer's potato broth, etc. As a component of the medium, potato is used either in the form of a mashed mass (boiled and grated potato is sterilized with a small amount of water) or potato extract, to which, depending on the purpose, peptone, meat extract, gelatin, agar, blood, glycerin ETC. are added