Fresh Fruits And Vegetables
( Originally Published 1939 )
Application of the newer knowledge of nutrition to the dietary of the public has brought about great changes in the nature of the food supply. Fruits and vegetables now constitute a much greater percent-age of the food consumed than formerly—a fact which has opened production areas increasingly distant from great metropolitan centers of population. Transportation methods have responded to the change, and long-distance automotive hauling has facilitated delivery. This has scattered the terminals, so to speak, in that deliveries are made at a greater number of points and at more or less irregular and unscheduled times, in contrast to the practice heretofore in railroad freight and express service which delivered food at a few depots or yards on good schedule. This development has greatly increased the difficulty of official supervision because the inspector must cover a greater number of receiving depots.
On the other hand, the adoption of aggressive advertising programs and the marketing of widely publicized brands have led to development of improved packaging and to products better both in appearance and in quality. Great packing houses in the growing areas now assemble, clean, grade, and pack fresh fruits and vegetables to improve their appearance and their keeping quality. In order to maintain their own standards of quality and protect their preferred place in consumer demand, growers have united to form great cooperative enterprises which are financially able to maintain programs of research to improve their products, and also of education in correct methods of crop production and handling. This newer development of large-scale production and long-distance transportation has raised an entirely new set of problems of quality control as, for example, the widespread use of insecticides, the deterioration of food in transit, and proper conditions of storage.
Apples. Apples are produced in numerous varieties and to a greater or less extent in every state in this country, particularly in Washington and the Northwest. Their cultivation requires the control of plant diseases and insect and fungus pests, and their storage presents an additional series of parasitic as well as plant physiological problems. Attacks by insects and some fungi are fought with poisonous sprays, especially lead arsenate. Sometimes the fruit is treated with sodium hypochlorite rinse. Great care must be exercised to pre-vent bruising or breaking the skin; otherwise deterioration and microbic infection may occur. Apples are now carefully graded and usually are packaged attractively. The more fancy stock is wrapped individually in paper. Apples are held in good condition in storage at temperatures about 36° F. The use of carbon dioxide in the storage atmosphere has contributed to the reduction of deterioration and certain types of fungus spoilage.
Citrus fruit. Production of oranges in extreme southeastern and southwestern parts of the country, far removed from great population centers, requires careful handling if they are to be delivered in proper condition for marketing. Some varieties of ripe oranges do not always have the familiar orange color but may be green. Sometimes they are orange colored before turning green. The standard requirement for determining ripeness is not color but a ratio of acid to sugar in the pro-portion of 1 to 8. Consuming markets demand that the fruit have typical orange color. Exposure of the fruit to ethylene gas (and possibly acetylene) brings about a destruction of green chlorophyll, thereby revealing the orange pigments, without otherwise changing the composition. Immature fruit is not given this treatment. Frozen fruit develops a dry, pithy condition in the pulp which does not become noticeable until it has reached market. No detrimental effects are observed from eating cold-stored oranges which had been frozen on the tree. Efforts have been made to color the fruit with dyes, but this is considered to be fraudulent by some official groups. In order to protect oranges from rot and to facilitate storage, they are often immersed in a 6-8 percent borax solution, which may be heated to 117° F., for a few minutes. Sometimes the fruit is washed with alkaline astringents, then rinsed in clear water, and dried. The fruit may be polished by treating with an emulsion of 20 percent paraffin and 80 percent carnauba wax, and then brushed with rotating horse-hair brushes. This not only improves the appearance but also serves to protect the surface from microbic invasion and, at the same time, reduces respiration and moisture loss, improving the storage quality.
Oranges are graded for size, wrapped individually in paper, crated, and stored at temperature of about 40° to 45° F.
Grapefruit are handled very similarly to oranges. Large quantities are canned both as slices and as juice. The flesh of the fruit usually has a typically light yellow color, but a few varieties, produced in Texas, have a pink flesh. Lemons are picked green and allowed to ripen under controlled conditions to secure better quality of flavor and storage. They are graded for size, and are individually wrapped in paper.
Peaches. Peaches are grown all over the United States but their greatest commercial production is in temperate Georgia and California. The fruit is delicately flavored and does not lend itself well to long shipment and storage. Peaches used to be packed in the circular, slatted so-called peach basket, holding about 1/2 bushel, but now the fancy grades are individually wrapped and packed in small, flat baskets in crates.
Pears. Pears are much more difficult to market in a satisfactory condition than apples. They are quite susceptible to disease and parasitic attacks, and must be picked before fully ripe in order to develop a satisfactory quality. The fruit is boxed and ripened in a well ventilated room at about 70° F. It may be cold-stored satisfactorily for only several weeks.
Bananas. The banana is one of the most perishable of fruits and yet it is marketed in fresh condition all the year round. It has not been preserved successfully, although a large amount of research effort has been expended on this problem. The fruit is picked green at the plantations in the Caribbean region and shipped in refrigerated steamers. Great care is necessary in order to avoid bruising the fruit, or allowing the temperature to vary much from 57° F. The flavor of the banana on the tree is insipid, but it develops its pleasing quality when the green, immature fruit is allowed to ripen at temperatures of about 60-62° F., requiring from 4 to 9 days.
Potatoes. White potatoes are subject to a large number of plant diseases and insect infestations. Some of these are controlled by the application of various chemicals such as Bordeaux mixture or other arsenic compounds and nicotine sulphate and by the use of clean seed, proper cultivation methods, careful crop rotation, and other agronomic measures. The tubers are harvested by elevator diggers in large-scale operations but many are hand-dug. They are often stored before marketing, and must be dry to prevent spoilage. Potatoes respire in storage, and accordingly are not piled deeper than about 5 to 6 feet to allow free circulation of air and removal of the respired carbon dioxide. Likewise, temperatures and humidity must be controlled to prevent drying out and sprouting. Storage practice usually calls for 33-40° F. temperature and 85 to 90 percent humidity.
The darkening of cooked potatoes is attributed to the presence of abnormally large proportions of free amino acids, especially of tyrosine. The protein in such abnormal potatoes is relatively unstable and is easily hydrolyzed. This condition is associated with relatively low content of potassium in the soil.
Sweet potatoes are usually hand-dug because they are subject to injury by harvesting machinery. Bruising entails loss from spoilage. The roots are given a preliminary sweating treatment by storing at about 85° F. and at about 90 percent relative humidity for about 2 weeks to reduce moisture at the exterior for protection against attack by fungi. They can then be stored at temperatures of about 50° F. for several months and kept in good condition.
Corn. Numerous varieties of corn are grown, having kernels colored red, black, brown, blue, yellow, and white, but the white is preferred. Sweet corn is usually harvested when the kernel contains the maximum content of sugar. This is known as the milk stage. Ripening continues after picking so that, if it is piled deep, heating will spoil it. It is usually marketed near its place of production, but long-distance shipment in refrigerator cars is possible.
Asparagus. Large quantities of asparagus are now marketed. Green asparagus is harvested by cutting the spears off at the ground level. Green asparagus with a white butt is cut off below the surface of the ground. White asparagus, mostly for canning, is protected from the light by hilling up the soil. Changes in quality continue after harvesting so that the bundles of spears must be kept cool. Long-distance shipping must be done under refrigeration.
Tomatoes. Tomatoes constitute a widely grown and increasing vegetable crop. When intended for distant markets, they are picked in their mature green stage. For local consumption within a few days, they are picked when about three-fourths of their surfaces have a pink color. Canning and manufacture require that tomatoes be taken from the vines fully ripe with maximum color. Rate of ripening after harvesting can be controlled by storing at various temperatures.. Some tomatoes are reported to be ripened under the accelerating effect of ethylene gas, but this treatment is not used on any considerable portion of the crop. After picking, the product is sorted and graded for size, color, ripeness, and quality, and sometimes wrapped in paper, especially for shipping long distances. Tomatoes cannot be kept very long in cold storage, and so are manufactured into several products, mostly canned tomatoes, and catsup, pulp, paste, soup, juice, and various sauces.
Soybeans. Soybeans are being grown in increasing acreage. They are not used much for human food, although food products are made from them, such as flour, oil, and various sauces. When canned, the product has a flavor and general quality that does not find much favor among the American public. Soybean milk is extensively used in the Orient, and it is beginning to be available in this country.
For more information on the technology of the fruits and vegetables, see Prescott and Proctor.'
Cultivation and fertilization. Intensive production of fruits and vegetables for profitable marketing has forced producers to adopt drastic measures to protect their crops from ravages of insects and fungi, and to apply fertilizer for plant food. Various insecticides and fungicides have been used, but lead arsenate is the most general. Other agents are lime and sulphur, copper sulphate and lime, fluorides, and selenium compounds. Pyrethrum and derris have been used to some extent on vegetables, although poisonous compounds have been used on crops also. To prevent their washing off, adhesives and oil are added to the poisonous mixture before spraying.
Some of the vegetable truck crops have been fertilized with human manure, or night soil, as it is called. The material is suspended in water and sprinkled on the growing plants. Although no definite knowledge is available as to the extent of the practice in this country, it is not believed to be very prevalent, although it is extensively done in foreign lands. However, a real source of similar contamination is the use of sewage to irrigate field crops.
Removal of insecticide-spray residues. In the great warfare between man and insects, it has been found that poisonous insecticides are necessary to control depredations of insects. The health hazard of these toxic products to consumers led control officials to set maximum limits for the most dangerous of these, namely, lead arsenic and fluorides.
Adoption of tolerances for poisonous-spray residues on fruit and vegetables, both in this country and abroad, has forced the industry to process its stock in order to remove them. Both dry and wet cleaning methods are used. In the dry process, the fruit is dry wiped with a cloth or brush, either by hand or by passing the stock on a conveying belt through a row of bristle brushes or wiping cloths. However, such treatment is only indifferently effective, removing on an average only about 15 to 35 percent of the residues, and sometimes even increasing them. Wet treatment is quite generally effective, but none is automatically completely reliable without supervision. In general, the wet processes involve dissolving the residues with hydrochloric acid or sodium silicate, sometimes in combination with oils and other products to facilitate wetting and solution. Hydrochloric acid in strength of about 1 percent is a better wash for lime sprays and fluorine residues, and sodium silicate is better for the oil or wax treatment. The usual procedure is to immerse the crated fruit in tanks by hand for about 2 to 3 minutes, or to pass the loose fruit through cleaning machines. After this treatment, the fruit is rinsed in clean water, and then dried by wiping or by an air blast to insure proper storage life.
Packing operations. Although methods of handling the many different kinds of fruits and vegetables vary with the product and the practices of the particular producing area, similar treatment must be given all harvested crops to prepare them for market. When these are picked in the fields or orchards and collected in baskets of one kind or another, the products must be cleaned of adhering earth, insects, and miscellaneous field debris. Immature fruit or vegetables must be sorted from those which are riper, decayed portions must be discarded, and all must be culled for size, variety, grade, and other quality considerations. Some of the firm vegetables and fruits are conveyed on endless belts between rows of operators who pick out the misshapen, decayed, or unripe products. Much of it is washed under forced sprays of water, and dried. Some is polished with dry brushes. Much of the better-grade fruit is individually wrapped in paper before packing in crates or baskets. The outer leaves of the leafy vegetables must be trimmed off. There is an increasing tendency to market the products in attractive packages under brand names.
RELATION TO PUBLIC HEALTH
Composition. Fruits and vegetables are generally characterized among foodstuffs by their high content of water, fiber, minerals, vitamins, and organic acids, by their flavor, and also by their low content of protein and fat. Their proximate composition is not constant, even in the same variety, by reason of effects of soil, climate, moisture, elevation, and other meteorological conditions. Average values for some common fruits are given in Table XXXVI compiled from Chatfield and McLaughlin.
Generally speaking, fruits (with the exception of the banana) contain no starch, and most of the carbohydrate is in the form of utilizable sugars. Fresh fruits contain about 80 to 90 percent water; vegetables, 66 to 95 percent. Both are low in protein and fat. Potassium is always present, averaging above 100 milligrams per 100 grams of fruit. The content of calcium, phosphorus, and iron in fruit is appreciably lower than, and the copper about the same as, their content in the common vegetables.
The figures for the composition of vegetables, as presented in Table XXXVII are taken from Chatfield and Adams.
McCance and associates have reported their analyses 5 on fresh fruits bought in the English market. They present the carbohydrate as consisting of "unavailable" and "available" forms. The "unavailable" consists of cellulose and pentosans which may constitute as much as 90 percent of total carbohydrate but supply only a small fraction of the energy requirements. The available carbohydrates are the sum of the reducing sugars, sucrose, and starch. Some of the analyses by McCance are presented in Table XXXVIII.
Fruits and vegetables have unique food values which can be sup-plied by no other products. Ponderable aspects of these values comprise constituents which can be identified objectively and measured, such as their proximate composition (e.g., content of water, carbohydrate, fats, proteins, vitamins, minerals). Imponderable aspects are their palatability, variety of flavor, and eye appeal-factors which are difficult to appraise but found to be of great subjective value and contributory to comfortable and effective assimilation of food.
Fiber. The fiber content of fruits and vegetables has not acquired a very definite meaning. Some reports comprise it in roughage, and others give it other designations. McCance and Lawrence state 6 that the pentosans (or hemicelluloses) should be included with the fiber or cellulose, because both are unassimilable and are excreted as roughage. These unassimilable constituents act as laxatives whether by absorbing water and increasing fecal bulk, or by stimulating peristalsis by their rough physical form, which, however, is much milder and less irritating than the fiber from the whole cereals. This property of fruits and vegetables to contribute bulk and roughage to the dietary regimen is one of their important functions as food.
Minerals. As research in nutrition continues to reveal need of an increasing number of inorganic constituents, it has usually been found that they are present in plant foodstuffs. Oxidation of these foods in the digestive processes yields alkaline residues. Although most fruits and vegetables are more or less acid in taste and in chemical reaction, they contain minerals in the form of organic salts. When foods are metabolized, these salts furnish bases which neutralize acid residues of other foods, and enable the body to maintain a desirable acid-base ratio.
Fruits and vegetables are among our most important sources of calcium, phosphorus, manganese, iodine, copper, and iron to some extent, and the base-forming elements. Numerous investigators have reported that calcium in plants is well utilized in human nutrition, and Fincke and Sherman showed that calcium in kale was nearly as well utilized as calcium from milk, but that in spinach "very poorly if at all," on account of the content of oxalic acid which forms the in-soluble and inert calcium oxalate, eliminated as such.
The iron content of fruits and vegetables has been shown by Stiebeling 8 to be poor (0-0.00040 percent) in a group consisting almost entirely of fruits; fair (0.00040-0.00079 percent) in a group comprising half the fruits, and the seed pods, blanched leaves and stalks, roots and bulbs; good (0.00080-0.00159 percent) in potatoes and thickly pigmented stalks and leaves; and excellent (above 0.00160 percent) in chiefly immature leguminous plants and thin green leaves. Generally, it is associated with chlorophyll. The total iron content is not a measure of its nutritional utility.
Vitamins. The vitamin content of many fruits and vegetables has been collected from the literature and published by Daniel and Munsell. Some of these are given in Table XXXIX. [See also the tables of Fixsen and Roscoe, Nut. Abs. Rev. 7, 823 (1937-8) .] Many reported determinations of vitamin G are unreliable because of the failure of the investigators to distinguish between vitamin G and riboflavin. Other values may be expected to change as improvements are made in analytical methods, and particularly as the contributing effects of variety of plant, nature of soil, methods of cultivation, influence of climate and season, conditions of harvesting and storage, and industrial practices are better understood and correlated with the assay determinations. Methods of preparation, cooking, and serving also affect the final vitamin content [see Fixsen, ibid. 8, 281 (1938)1
The vitamins are widely distributed throughout the plant king-dom. Green leafy parts and highly colored vegetables are outstanding in their content of vitamin A (or its precursors), and to a less degree in the vitamins B1, C, and B2; they also contain some vitamin E. The fruits, especially the citrus varieties, are very rich in vitamin C, and many are good sources of A and B1.
Vitamin A and its precursor carotene are insoluble in water and accordingly are not leached into cooking water. Although both substances are subject to destruction by oxidation, the ordinary processes of cooking are not likely to cause significant loss of either of them.
Vitamin B1 (thiamin) is water soluble, and is resistant to destruction by heat in an acid environment. Vegetables and fruit when cooked without neutralization of their acidity (e.g., addition of sodium carbonate) do not lose significant amounts of thiamin by destruction but may lose a considerable proportion if the cooking water is discarded. Vitamin B2 (riboflavin) and the pellagra-preventive factor (nicotinic acid and its derivatives) are soluble in cooking water and are relatively stable in non-alkaline media at the temperatures of ordinary cooking.
Vitamin C (ascorbic acid) is readily oxidized, especially in alkaline media and in the presence of metals such as copper. When the ascorbic acid oxidase is destroyed by a high temperature (boiling) quickly attained, subsequent cooking entails no significant loss other than the aliquot portions readily dissolved in the liquors. There may be an additional slow loss of ascorbic acid in cooked vegetables by oxidation if considerable time elapses between cooking and consumption—as in restaurant food.
Vitamin D has been believed to be present in fruits and vegetables in too small amounts, if at all, to be significant. However, the work of Kohman and associates (see page 436) showed that plant products were quite adequate for normal calcification, growth, and reproduction of several generations of rats and guinea pigs, indicating the possible adequacy of these foods in their content of all vitamins including vitamin D.
Cooking losses. Peterson and Hoppert found that, during cooking, varying percentages of the minerals are extracted from vegetables (and fruits, when they are similarly cooked) and lost in pot liquor. These losses may amount to 15 to 30 percent when the food is steamed or pressure cooked, and 30 to 40 percent when boiled in water. Culp and Copenhaver found that, when vegetables were boiled and drained, they lost about 30 percent of their iron, copper, and total solids, and about 40 percent of their manganese. Leaching accounts for all the losses of soluble salts and sugars, is greatest in boiling, and varies directly with time and inversely with size of the piece. Skins of potatoes prevent the outward diffusion of solubles, and when food is cooked in air or fried in fat, there is no loss except water.
The data in Table XL show results obtained by McCance et al . on the same vegetables, raw and boiled. The upper figure in each pair is the raw value; the lower figure is the boiled value. The "factor" in the last column enables calculations to be made on the basis of purchased weight. Amounts which can be derived from 100 grams of food as purchased can be obtained by multiplying the figures given in the table by the respective factors.
The dietary mineral, calorific, and vitamin values of fruits and vegetables have little practical significance unless they are determined on the products as served for the table.
Protective foods. The consumption of fruits and vegetables helps to prevent and correct such specific pathologic conditions as the anemias, sprue, dental caries, diabetes, and celiac disease. Their property of furnishing so many nutrients which are now recognized as necessary to human well-being led McCollum 14 to designate them "protective foods." This idea is based on the nutritional need of the organism for food which supplies additional constituents to diets de-rived predominantly from the milled cereals, tubers, and muscle meats. When persons subsisted entirely on diets composed of these latter food-stuffs, they developed syndromes of diseases which were diagnosed as having been caused by the absence of certain necessary nutrients, such as the vitamins and minerals. This need is supplied by milk and by salads composed of fresh food such as lettuce, cabbage, celery, tomatoes, and other leafy, fresh vegetables, together with a liberal supply of citrus fruits. Sherman enlarges on this conception 15 by calling attention to the value of fruits and eggs not only as supplying some of the protective factors to prevent deficiency, but also as contributing positively to "the enhancement of vitality and the promotion of buoyant health." As McCollum states, a liberal use of the fresh and leafy vegetables and fruits materially helps to preserve "the characteristics of youth."
Epidemiology. Fresh fruits and vegetables have relatively infrequently been incriminated in reports of food-borne infections and intoxications. The use of night soil (human manure) to fertilize gar-den and farm vegetables, exposure of fruits and vegetables on sale to contamination by street dust, animals, insects, and promiscuous handling by dealers and customers, and practice of eating some of them untreated have directed attention to the possibility of serious infection from these sources. This has led to numerous researches to ascertain whether fruits and vegetables can actually carry a load of pathogenic microorganisms picked up from polluted soil or from market handling and exposure.
Several rather clear-cut instances of typhoid fever have been traced to contaminated vegetables. An outbreak in England involving 110 cases was traced to watercress which was grown on beds fed with sewage. An outbreak affecting 18 persons in this country was also reported to be caused by eating watercress sandwiches. The organism could not be isolated from the cress beds, but circumstances pointed to this source. Rhubarb from soil known to be fertilized with typhoid excreta caused 2 cases. Celery has been incriminated in an outbreak of 49 cases in an institution where there had been typhoid fever some months previously and where the hospital sewage had been used on the celery beds. The disease developed soon after the celery came into use. Cholera is reported to have been spread by eating strawberries from an infected district. Several workers connect the incidence of summer diarrhea and also summer typhoid fever with the increased consumption of fruits and vegetables. An outbreak of 7 cases of illness is reported by Savage and White 18 from eating fresh tomatoes which seem to have been infected with Salmonella aertrycke. This organism was not found on any of the vegetables, but the agglutinins were demonstrated.
Indirect evidence has been supplied as to the possibility of typhoid infection from night soil. Human manure is sometimes applied to fertilize crops before planting and also during cultivation. Numerous investigators agree that the typhoid organism may live in the soil for a considerable time and survive on the exterior of the crops. Creel isolated this organism after 31 days from the leaves and stem of lettuce and radishes grown in artificially contaminated soil. The weather was partially dry, which favored the early death of these organisms, so that it would be expected that in wetter weather their viability would be prolonged. Rain did not wash them off. In fact, Creel washed the leaves three times in separate lots of sterile water without removing all the organisms. Likewise Melick grew radishes and lettuce under natural conditions in soil contaminated with typhoid organisms, and isolated viable bacteria from the radishes after 37 days, and from the lettuce after 41 days, which is ample time for the maturing of such vegetables. Ordinary washing did not remove the organisms. Johnston and Kaake sprayed a tomato and 2 apples with a saline suspension of Shigella paradysenteriae var. sonnei (B. dysenteriae Sonne). Positive cultures were obtained from the skin of the tomato up to the end of 2 days but not 6 days, and from the flesh in a tissue 10 days but not 18 days. From the skin of the apple, it was obtained for 6 days but not for 8 days. Numerous investigators agree that fruit and vegetables may become infected with intestinal pathogenic organisms, and remain viable for several days on the unbroken surface but die off in a shorter period if exposed to the acid juices.
Implications as to the effects of insanitary conditions of handling are shown by an early investigator in this field who claimed to have cultivated tubercle bacilli from grapes bought in a market opposite a clinic which was attended by tuberculous patients. Flies are known to carry the organisms of typhoid and dysentery.
Vasquez-Colet quotes Barber as finding that cholera vibrios -survived in cockroach feces for at least 16 hours at room temperature, on fresh beef, lettuce, fish, and clams. On fruits acid to litmus and on lettuce, the cholera vibrios from human feces survived more than 20 hours but not 48 hours. Varquez-Colet artificially contaminated various common fruits with suspensions of cholera, typhoid, and dysentery organisms (Flexner and Shiga types), and found that cholera germs would live from a few hours to 6 days, typhoid bacillus from a few minutes to at least 3 days, and dysentery organisms from a few minutes to at least 5 days. It seems that such products may convey infection but not to any marked extent.
Numerous other studies listed by Tanner have been made on fruit artificially infected with several varieties of pathogenic organisms. In brief, the acid fruit juices are bactericidal to Eberthella typhosa, and Salmonella paratyphi and schottmülleri, and uncertainly destructive to Clostridium botulinum and its toxin. However, a death was traced to botulism from a ripe persimmon 23 Spores, experimentally injected into ripe persimmons with a pH of 5.6-5.8, vegetated and produced toxin, whereas the spores cannot vegetate in foods with a pH below 5.4. This explains why botulism is so rarely associated with fruit.
The actual presence of pathogenic organisms on fruits and vegetables for market has occasionally been demonstrated.
Fresh fruit could be disinfected without impairment of organoleptic qualities by rinsing in 0.2 percent solution of chloride of lime, but results on vegetables are uncertain.
The progressive increase in the number of coliform organisms is interpreted as an indication of more or less fecal contamination. Tanner 22 reviews the work of several investigators who found that Escherichia coli is quite generally found on common fruits and vegetables. Johnston and Kaake 20 studied the bacteria on fresh fruit in Toronto displayed for sale either inside or outside the front of the shop, quite accessible to insects. They found that the majority of the species identified were probably of soil origin, although a strain of Shizella dispar (B. dispar) which was present is held to be a cause of a dysenterylike disease in man. Mills, Bartlett, and Kesel showed that normal uninjured fruits and vegetables do not contain living bacteria within their tissues, but, judging by the coliform test organ-ism, pathogens can gain entrance through injured or decayed portions where they may remain viable for as long as 42 days. They may persist on moist skin 15 days or more. Smeall found no frankly pathogenic organisms on grapes and cherries but did find several intestinal types.
Chapman reports that much of the irrigation of the state of Colorado comes from grossly polluted streams, and often solid constituents of sewage can be seen in irrigation ditches to be deposited "on the hands of the workers, on the soil of the fields, and on the vegetables growing in the fields." Examination of vegetables many miles below the source of pollution showed bacterial infection to be high, even after the products were thoroughly washed.
As Melick points out, only occasionally is the attempt to trace an epidemic to vegetables successful, owing to the distribution of such food among a wide circle of consumers after passing through the hands of several dealers, and the difficulty of discovering weeks afterward what vegetables were eaten and by whom, and the final tracing of them to their sources. Rosenau remarks 26 that in large cities it is practically impossible to trace infection to such causes, and that "It therefore remains more a suspicion than a conviction."
Vermin infestation. The larvae or maggots of the common 2-winged fly (such as the common house fly) can live on human food materials. The eating of such infested food may produce gastro-intestinal disturbances, known as intestinal myiasis. In this disease, larvae develop and penetrate the intestinal wall. Banks 28 has compiled a list of dipterous larvae found in different foods, and he de-scribes their identification.
Mushroom poisoning. Mushrooms are reported to have caused 10,000 cases of illness with 200 deaths in France in 1 year. Some European cities have established careful inspection of their mushroom supplies, and seek to educate the public as to edible kinds of mushrooms.
In this country, there seem to be an increasing number of cases of mushroom poisoning, caused by mistakingly eating poisonous varieties instead of wholesome ones. The species most frequently incriminated are the deadly Amanita phalloides and the A. muscaria. There is no antidote to their poisons, which are the complex chemical substances muscarin and amanito-toxin, both of which are partially resistant to heating and drying. The poisonous mushrooms are generally characterized by a so-called death cup at the base of the stem. This is the remains of the ruptured bag called the volva, which at first enclosed the whole plant. In some specimens, this sign may be largely obliterated.
Symptoms of mushroom poisoning may be a sudden intense pain in the abdomen, vomiting, diarrhea, thirst, loss of flesh, prostration, contraction of pupil, mental symptoms, coma, and, in children, death in 3 to 4 days, and in adults, in 6 to 8 days, although death may be avoided if the stomach is emptied quickly enough.
There is no simple test for distinguishing poisonous from edible types. There are said to be 80 species growing in this country that are inedible. In general, mushrooms that grow in fields are usually edible, and those that grow in woods are often poisonous, but this is not a hard and fast rule. The only safe procedure is to learn to recognize edible varieties by their appearance. A good popular description of edible and inedible mushrooms has been writted by L. C. C. Krieger. A more technical and comprehensive description of many varieties has been published by Patterson and Charles, and by Ford.
Even commercialized growing of mushrooms must be watched because an outbreak is on record where an inedible variety became dominant in a commercial cultivation.
Potato poisoning. Green parts of potatoes contain the glucoside solanin which may cause illness if it has accumulated in sufficient quantity. It is present in greater or less degree in all potatoes. Sound, normal potatoes contain it in amounts of 0.04-0.116 gram of solanin per kilogram of potato, varying with the season. The solanin con-tent of some early potatoes has been found to have the unusually high value of 450 milligrams per kilogram, whereas seed potatoes of the same strain and wintered over 3 years yielded about one-tenth as much. When the potato is diseased or sprouted, its content of solanin may increase to more than 1 gram. It is known to be toxic in amounts of 0.2-0.4 gram per kilogram of potato. Ordinary cooking does not seem to destroy it.
Farm animals, as well as human beings, have been made ill when they ate green potato sprouts or parings. Several outbreaks of illness have been reported from the consumption of potatoes which contained about 0.4 gram of solanin per kilogram. In a well-authenticated out-break, Hansen 33 reports that 7 persons in a family ate potatoes green from exposure to sunlight, and 2 died. Six physicians worked on these cases. Trembles and other possible causes were eliminated, and the diagnosis of solanin poisoning seemed warranted.
In spite of the facts known about the toxicity of solanin, there is increasing doubt among some authorities as to whether most, if not all, of the reported cases are not due to a bacterial infection. The organism Proteus vulgaris Hauser (B. proteus) is known to grow well on potato média, and all the symptoms in the outbreaks are some-what similar to typical illness of bacterial origin.
Rosenau points out that many of our standard articles of diet contain poisonous substances in minute amounts, and that extractives that are pharmacologically active may be obtained from practically every one of our wholesome foods. The amounts of solanin in normal potatoes cannot be considered to have any public-health significance.
Other poisonous plants. Other plants, poisonous in themselves, are the castor bean, ergotized rye, Cicuta (water hemlock), white snake-root, and occasionally rhubarb. The castor-bean seed contains the violently poisonous albuminoid substance ricin. In the manufacture of castor oil, no trace of the ricin is found in the finished oil. Ergotism is caused by eating bread and other products made from rye diseased with the fungus Claviceps purpurea. The disease is commonly encountered in eastern Europe, but it is only rarely found in America. Cicuta, the water parsnip and a common weed which grows in wet places, was the plant used by the ancient Greeks in the "cup of hemlock."
White snakeroot is the cause of many animal deaths in the West each year. Trembles in cattle is a serious disease caused by eating this white snakeroot or richweed, as it is sometimes called. It is more prevalent during periods of drought when the cows are forced to eat any green plants they may find in the pasture. When human beings drink milk from cows ill with trembles, they develop milk sickness, which is highly fatal.
Rhubarb, spinach, and several other leafy edible plants contain salts of oxalic acid in amounts sufficient to cause symptoms of poisoning. Rhubarb stalks and leaves contain from 0.2 to 0.4 percent oxalic acid, which is thought to cause the harmful effects.
Insect infestation. Many fruits and vegetables are subject to infestation by insects. Tomatoes have been sporadically attacked by corn-ear worm which crawls under the calyx, burrows down to the core, and feeds on the tomato from within, or they may only cut small feeding holes around the calyx which permit the entrance of organisms of decay. When the fruit is pulped, as in the manufacture of catsup or paste, the insects and excreta are broken up and distributed. Dusting with calcium arsenate early in the season reduces the infestation about 50 percent.
Raspberries and loganberries are particularly subject to attack by a small light brown beetle which burrows back and forth through the core, causing the berry to become more or less dry. Patches have varied from zero to about 25 percent infestation. Blueberries have often been found to contain maggots. Most of these can be removed by washing the berries in revolving drums immersed in clean water. Apple butters, syrups, and molasses have also been found to contain objectionable material such as flies and other insects, hair or rodents and other animals, and nondescript debris from various sources.
Spray residues on fruits and vegetables. Although the problem of possible toxicity of insecticides on fruits and vegetables has been recognized for many years, the finding of heavy residues of arsenic on a shipment to Boston of western peas, and later a notice from British officials that American fruit would be refused importation if it carried an excess of arsenic trioxide over 0.01 grain per pound of solid food, forced food-control officials to give serious attention to remedying this increasing public-health hazard." The best insecticide to fight the codling moth is lead arsenate, although compounds containing fluorides are also used. Selenium is also used in insecticides and sprays. To increase the effectiveness of these poisons, various ingredients, particularly casein and oil, are added to make them adhere firmly to the fruit and avoid waste by rain-washing. However, they also make it difficult to remove the poison from the fruit before it is shipped. Such sprays are useless unless they are sufficiently poisonous to destroy the insects. The residues remaining on the fruit are dangerous to consumers. The problem is particularly serious because fruit is often eaten by the sick and infirm whose resistance to illness has been lowered by infection or organic disease. Arsenic and lead have been found in substantial amounts on market cabbage, cauliflower, and apples, and the medical profession has called attention to the possibly serious public-health hazard. Heeren and Funk 41 re-port a case of severe dermatitis caused by the eating of three apples from which a whitish coating had been wiped with a handkerchief, although human subjects who ate two uncooked, sprayed apples daily from fall to early spring gave no indication of toxic effects, and these negative results were confirmed by collateral tests on guinea pigs. Cogswell and Forbes 42 report the death of a 15-year-old girl from eating fruit bearing spray residues. The whole subject of the toxicity of these sprays needs thorough study in the interest of public health.
Nelson and Mottern showed that lead arsenate sprays greatly reduce the vitamin C content of oranges, and Miller, Bassett, and Yothers showed that the chemical composition is changed. Their work raises the question as to what are the possible effects of these sprays on the food values of apples and other fruit.
A full discussion of the problem was presented in a symposium of papers published in the Journal of Industrial and Engineering Chemistry, 25, 616-642 (1933).
Ethylene treatment of fruits. Extensive use of the gas ethylene to hasten the ripening, to improve the quality, and to develop a desirable color in fruit more quickly and more uniformly has raised a question as to the effect on the nutritive value of the treated food. Chace states 45 that the changes are natural ones in that the phenomenon is a speeding up of natural ripening processes. Neither ethylene itself nor any of its impurities have been observed to be poisonous in the concentrations used, and consumption of the fruit has never resulted in any recorded illness.
With regard to the possible effect on the vitamin C content, tests were conducted on split samples of oranges picked at the same time from all sides of the same tree. One part was allowed to stand at room temperature, and the other part was treated with ethylene immediately after picking. There were no differences in the vitamin C content of the treated and untreated samples. Jones and Nelson likewise found that ethylene-ripened tomatoes contained as much vitamin A, B, and C as green ones in the same stages of development, although naturally ripened tomatoes were better sources than any other of the treated or untreated, less mature products. Inasmuch as these less mature products were reddened to the color of commercially ripened tomatoes but contained only the lower vitamin content, it follows that the ethylene ripening of tomatoes does indeed lead the consumer to expect a normal supply of the vitamin whereas the vitamin content is actually below this expected level.
Dyed fruit. Dermatitis has been reported in 2 cases where the patients handled fruit which had been treated and dyed. Yellow OB was shown to be the prime offender. It was confined exclusively to the outside of the peel, and none penetrated to the pulp or juice. This dye, as well as associated ones used in coloring, is not a general irritant because the majority of individuals do not react to it.
Vegetable milk. Soybeans—preferably yellow-seeded varieties—are soaked for a few hours and macerated in water and boiled in the proportion of 1 part of mash to 3 parts of water, and strained. The dense liquid which is formed looks like cows' milk. It is also made by suspending refined soybean flour in water. Various salts, sugars, oils, and other products may be added to balance the formula, and the mixture may then be homogenized and spray-dried to produce a powder. This may be packed in cans and sealed. Table XLI gives the analyses of several soybean milks. Soybean will not only look like cows' milk; it is used as a substitute for cows' milk, is useful in special cases of difficult baby feeding, has a composition which simulates milk in certain aspects, and is finding markets in what has heretofore been an exclusively dairy field. It has also been used as an evaporated milk, and as constituents of ice cream, ice-cream cones, and bakery products of many kinds. The protein glycinin of soybeans is quite similar in its content of important amino acids to proteins of cows' milk. It is a completely nutritive protein. It will maintain life and will provide for normal growth of the young when it is the only protein consumed, and therefore it is similar to the proteins of milk and eggs. Miller and Wen showed by digestion tests on 3 men that protein of soybean milk digested in 2.7, 2.7, and 3 hours respectively, whereas those of cows' milk required 3.5, 3.9, and 4.3 hours. The calorific value of a glass of this milk is about 170 calories. It contains a fair amount of vitamin A and plenty of vitamin B, but is deficient in vitamins C and D. Its keeping qualities are reported to be about the same as those of cows' milk. Buddhist monks live chiefly on soybean cheese, and are recognized as a robust group. Several investigators state that soybean milk is a satisfactory infant food, and Stearns re-ports that infants retain adequate quantities of its calcium, potassium, and nitrogen when they are in the same proportions as in cow's milk. Adolph and Chen report 52 that calcium is as well utilized from the curd of soybean cheese as from cows' milk. Hepburn and others state that soybean milk is not the nutritive equivalent of cows' milk, and several clinical tests show that, for satisfactory infant feeding, it must be fortified with various food factors which it naturally lacks.
The use of the word "milk" and the enthusiastic approval given to soybean milk for infant feeding raise a new problem for food-control officials. The word milk is liable to be misleading to the public in this country, who have been acquainted with only one milk, namely, that of mammals. When the public substitute this product for cows' milk, they should recognize that it does not contain the full quota of nutrients of cows' milk. Unless this deficiency is supplied from other sources, there may be serious nutritive deprivation. In addition, the microbiology of soybean milk has not been worked out, so that its possibilities as a vehicle for the transmission of communicable disease is unknown. Inasmuch as soybean milk does not have the composition of cows' milk, and especially lacks soluble carbohydrate, the micro-biology of this product would be expected to be quite different from that of cows' milk. Its role as a culture medium for pathogenic microorganisms needs to be studied. The size and nature of this problem can be visualized when it is realized that there are 5000 different varieties 50 of soybeans.
Standards. Fresh fruit is defined as "fruit which has undergone no material change other than ripening since the time of gathering." Standards are established for the citrus fruits which require that grapefruit juice must contain not less than 7 parts of soluble solids (Brix reading expressed as sucrose) to each part of acid calculated as citric acid without water of crystallization, and that orange juice must contain not less than 8 parts of soluble solids to each part of acid.
The adoption of the above ratios of soluble solids to acid was found necessary to differentiate normal fruit from that which had been damaged by freezing.
The increasing use of insecticides has led the U. S. Department of Agriculture to adopt the following tolerances as the maximum substances which may be present on interstate shipments of fruit and vegetables:
Arsenic (as As2O3) .. 0.01 grain per pound of fruit
Lead 0.025 grain per pound of fruit
Fluorine 0.01 grain per pound of fruit
This limit for arsenic is known as the international tolerance, because it is based on the findings of the British Royal Commission which investigated an extensive outbreak of beer poisoning.
Congress has authorized the Secretary of Agriculture to establish and promulgate uniform standards of classification of farm products. The Bureau of Agricultural Economics has defined the several grades of many of these products and, in some instances, has set them up as scores by which the quality is given a numerical rating. These items may comprise such considerations as color, size, ripeness, tenderness of texture, freedom from disease or decay or blemishes or signs of rough handling, flavor, and other such factors which govern quality either from the standpoint of consumer appeal or of fairness in the marketing of claimed commercial grades. These standards are drawn up by regulatory officials in collaboration with trade groups. They are first issued as tentative standards and then later as Service and Regulatory Announcements of the Bureau of Agricultural Economics. Most of the common fruits and vegetables are now covered by either tentative or official standards. These are not mandatory on the industry but serve as the basis on which certificates of grade are issued by the licensed graders.
Types of adulteration and spoilage. Many shipments of fruits and vegetables have been seized because of extensive content of poisonous insecticide residues. In the last few years these have involved such common products as apples, cherries, crabapples, peas, cauliflower, currants, plums, quinces, cabbage, celery, as well as some of the products manufactured from several of them. Seizures have been made of wormy food, products infested with insects or insect debris, food containing more or less decomposed material, food that was artificially colored, and also food contaminated by harmful chemicals from one cause or another.
Physical examination. Insecticide-spray residues appear as a whitish coating or small white spots near the calyx. Apples and pears are particularly likely to show these residues of lead or arsenic sprays, although they may be observed on other fruit and vegetables.
Citrus fruit, substandard by freezing, is recognized by a pithy, dry condition of the pulp, not evident immediately after a freeze, but developing into unpalatability by the time the fruit reaches the consumer.
Insects and their debris and excreta in tomatoes are determined by a microscopic procedure based on Wildman's technic 57 of disintegrating the fruit and shaking it vigorously in a water and an oil such as kerosene or gasoline. The insect parts collect in the oil layer, which is poured onto a rapid-action filter disk in a Büchner funnel. The foreign particles are counted and identified with the aid of a wide-angle magnifying glass.
The determination of maggots in blueberries requires that 20 ounces of the berries be boiled with a little water for about 3 to 5 minutes, then passed through a sieve with 6 to 7 meshes per inch. The residue is poured into a dark pan, and the maggots counted against the dark background. Canned blueberries are tested the same as the fresh fruit.
Raspberries and loganberries are examined for the presence of larvae of insects, especially the light brown beetle Byturus unicolor, by pouring a No. 2 can full of the berries into a No. 10 can, crushing with a spoon, and cooking until soft. About 1 to 2 ounces of gasoline are added, the contents stirred vigorously, and water added. The insects are picked from the surface.
Chemical examination. Inasmuch as fruits and vegetables do not lend themselves to adulteration which usually involves the determination of the proximate constituents, only those analytical methods are given which are used to determine the presence of spray residues, and the solids-acid ratio. General analytical methods for fruits and fruit products and for vegetables are given in the official compilation of the Association of Official Agricultural Chemists.
For the determination of the normal ratio of the soluble solids to acidity, the percentage of soluble solids is determined by drying a weighed sample until consecutive weighings do not vary more than 3 milligrams. The acidity is ascertained by titrating 25 milliliters of the juice, diluted to 250 milliliters, with 0.1 N alkali, using phenolphthalein as the indicator, but if highly colored, with azolitmin solution or phenolphthalein powder on a spot plate.
Lead arsenate residues do not exist in any fixed ratio because the washing or solution removes the arsenic and lead irregularly, leaving the lead in greater amount. Accordingly, the lead is the more significant. A rapid method for this determination is reported by Samuel and Shockey. The arsenic is distilled off as arsenic trichloride, and can be determined by the official bromate or Gutzeit method. The lead is precipitated with sodium sulphide solution, and the quantity is determined by comparison against a prepared graph of standards.
Bacteriological examination. Although fresh fruits and vegetables are known to carry a miscellaneous microbiological flora, no evidence is available as to its regulatory significance.
Supervisory procedure. The function of the food-control officials in supervising the handling and sale of fresh fruits and vegetables from the public-health standpoint is mostly limited to inspecting it for evidence of excessive insecticide residues, for reasonable sanitation in handling, for wholesome fruit, for removal of all decomposed products, and for the prevention of sale of poisonous or harmful food.
The control of insecticide residues on export shipments of sprayed fruit is handled by the certificate plan. The fruit industry pays for the employment of field analysts whose qualifications are passed upon _ by competent state and federal chemists. Every export shipment is accompanied by a certificate of analysis, showing compliance with the established tolerance. A few states have adopted standards of tolerance, and are carrying on educational and cooperative programs with the producers to insure safe products for public consumption.
The application of dyes to impart a typically ripe color to fruit of uneven or otherwise unattractive color has been tolerated because its use has not concealed immaturity. Immaturity is measured by the solids-to-acid ratio. However, it is becoming increasingly accepted that the use of dyes is a fraudulent practice, to say the least, and the Food and Drug Administration has notified the trade that the practice of dying citrus fruit renders it liable to seizure.
The sale of fresh fruits and vegetables should be surrounded with ordinary sanitary safeguards. The stock should be held and displayed high enough above the sidewalk to prevent contamination from dogs and human expectoration. The trimming of the bulky, leafy vegetables is often done on the public streets and in the open markets, and the attendant litter is not carefully removed. This probably constitutes no appreciable health hazard but it violates the desire for ordinary cleanliness, shocks the public sense, and indicates that carelessness in this respect may be expected to be accompanied by worse infractions of sanitation.
The control of safe mushroom distribution requires special training of the inspectors to recognize the more common dangerous varieties. The source of supply of new retail outlets should be investigated. The markets and other direct outlets of selling farm products should be especially carefully patrolled.
The increasing interest in the sale of soybean milk products directs attention to the need of food-control officials to give this industry the same type of sanitary supervision as is accorded the regular fluid-milk industry. Very little information is available concerning the health hazards involved by the transmission and culture of pathogenic organ-isms. Furthermore, it is known to be somewhat lacking in its nutritive equivalence to milk. Therefore, its sanitary handling, its bacterial culture characteristics, and its proper labeling are problems to be worked out by control officials.
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