SWEET CORN.

This is a variety of maize which develops a high sugar content and is eaten while the starch is yet soft, in other words, in an unripe state. It is a food product of immense importance in the United States, although almost unknown in Europe. The content of sugar varies from 5 to 8 percent in the fresh, soft kernel. The sugar which is present in the kernel rapidly disappears after the husking or removal from the stalk. In order to secure the maximum sweetness the corn should be cooked and eaten as soon as possible after removal from the stalk. Where it is not possible to do this it should be placed in cold storage after removal from the stalk and remain unhusked until it is ready for cooking. Green corn is universally eaten hot. It is usually cooked by boiling in water, although it may also be roasted before the fire. It has a high food value, and the composition of the grains of fresh, soft, green corn is shown in the following table:

Composition of Fresh Green Indian Corn:

Moisture,73.00percent
Starch,13.50„
Sugars,6.00„
Protein,5.00„
Crude fiber,1.20„
Ash,.70„
Fat,.60„

Maize Proteins.

—The proteins of maize are composed principally of two zeins. The two forms are differentiated by their behavior toward alcohol. The first form constitutes the zein soluble in alcohol and the second the zein insoluble in alcohol. There are two other proteins in maize existing in small quantities which have been named myosin and vitellin, respectively. There is also a third unnamed variety and small quantities of albumin.

Variation in Maize, under Different Climatic Conditions.

—It is possible that most of the varieties and subvarieties of maize are simply the existing standard varieties modified by changing environments. There are certain conditions of climate, soil, and distribution of rainfall which tend to produce a large, starchy, soft grain, while other conditions tend to produce a small, hard grain richer in protein. The variations of importance are those of the carbohydrates and the protein, which are complementary, since as the protein rises the carbohydrates fall in relative proportion. There is also a marked variation in the carbohydrates, due to variety and climatic conditions combined. It is, for instance, the increase of the sugar at the expense of the starch that produces the body known as sweet maize eaten in the green state, as already described. Even in the sweet variety the relative proportion of sugar varies in different localities and under different conditions of growth.

Early Varieties.

—There are certain varieties of maize which are of especial value on account of their early maturation. This is a property extremely valuable in the sweet variety of maize or that eaten in the green state, since it is important to get these varieties into the market as early as possible and to continue them as long as possible. This is secured by planting the early variety at as early date as possible and planting later maturing varieties at intervals thereafter. By the selection of varieties of different periods of maturing it is possible in the climate of Washington to offer green corn from neighboring fields on the market from July until the advent of a killing frost which is usually the last of October or first of November. This gives a period of nearly four months during which the green corn may be delivered to the local market. Further south the period of supply is longer.

Canned Corn.

—Immense quantities of green corn are grown for the purpose of canning in order to supply the market during the closed season. The canning industry for green corn is located chiefly in the north. In the eastern states the industry is of great importance, from Maryland to Maine. The northern-grown corns are often preferred as they are supposed to be sweeter and more palatable. In the central western states, northern Indiana, Michigan, Wisconsin, northern Illinois, and Iowa are the principal centers of the canning industry, although it is practised to a greater or less extent in almost all parts of the country.

Adulterations of Canned Corn.

—Unfortunately in the canning process of corn additions have been made to the product which are of an objectionable nature. Chief among these is the use of bleaching agents such as sulfur in the form of burnt sulfur or of sulfite or bisulfite of soda or potash. These bleaching agents impart to the corn a white color which some consumers prefer, but at the expense of introducing a substance which must be regarded as deleterious to health. Still more objectionable is the practice of using saccharin instead of sugar as a sweetening agent. Saccharin is a coal tar product which has an intense, sweet taste, very persistent, and when used alone becomes disagreeable. A very small quantity of it is sufficient to impart a very sweet taste to the canned corn at a much less expense than could be secured by using the pure sugar. This form of adulteration is extremely reprehensible both because it deceives the consumer and adds a substance which by most hygienists is regarded as prejudicial to health. The bleaching agent and the artificial sweetener are wholly unnecessary. The manufacturers of sweet corn are expected to use the best and freshest and sweetest materials and cannot be excused for tampering with them in any way which either produces deception or injury to health.

Sugar added to make an ordinary corn taste like sweet corn is to be regarded as an adulteration unless its use is noted on the label.

Maize starch is also often added to sweet corn at the time of canning and this practice can only be regarded as an adulteration.

Detection of Adulterations in Sweet Corn.—Test for Sulfurous Acid.

—To about 25 grams of the sample (with the addition of water, if necessary) placed in a 200-c.c. Erlenmeyer flask, add some pure zinc and several cubic centimeters of hydrochloric acid. In the presence of sulfites, hydrogen sulfid will be generated and may be tested for with lead paper. Traces of metallic sulfids are occasionally present in vegetables, and by the above test will indicate sulfites. Hence positive results obtained by this method should be verified by the distillation method.[24] It is always advisable to make the quantitative determination of sulfites, owing to the danger that the test may be due to traces of sulfids. A trace is not to be considered sufficient as indicating either a bleaching agent or a preservative.

[24] U. S. Dept. Agr. Bureau of Chemistry, Circular No. 28, pp. 11-12.

Detection of Saccharin.

[25]—Add from 25 to 40 c.c. of water to about 20 grams of the sample; macerate and strain through muslin; acidify with 2 c.c. of sulfuric acid (1 to 3) and extract with ether. Separate the ether layer, allow the ether to evaporate spontaneously, and take up the residue with water. If saccharin be present its presence will be indicated by the sweet taste imparted to the water. To confirm this test add from one to two grams of sodium hydroxid, and place the dish in an oil bath. Maintain the temperature of the oil at 250° C. for 20 minutes, when the saccharin will be converted into salicylic acid. After cooling and acidifying with sulfuric acid, extract in the usual way and test for salicylic acid. This test, of course, presupposes the absence of salicylic acid in the original sample. If salicylic acid is present in the original sample it must be removed before making the test for saccharin.

[25] Ibid., Bul. 65, p. 51.

Fig. 27.—Indian Corn Starch. × 200.—(Bureau of Chemistry.)

Starch of Indian Corn.

—Maize starch has characteristics which enable it to be easily detected by the microscope. The granules of this starch are of a more uniform size than those of wheat and vary from 20 to 30 microns in diameter. Occasionally very much smaller granules occur which probably are more of the original size and which have been arrested in growth by the ripening of the grain. The granules of maize starch are more or less polyhedral in form with round angles. The only common cereal starch which they can be mistaken for is rice, but they are generally larger than the granules of rice. Under the microscope with ordinary light they give only the faintest sign of rings but show in most cases a well developed hilum, which is at times star-shaped or like an irregular cross, while at other times it has the appearance of a circular depression. The maize starch granular is a type of the angular, as the wheat is of the sphere or spheroid form. The characteristic appearance of maize starch kernels is shown in the accompanying [Fig. 27]. Viewed with polarized light the starch grains of Indian corn present deep, well marked crosses, which divide each grain into four distinct parts as shown in [Fig. 28]. It is interesting to note that the angularity of maize starch is greatly influenced by the hardness of the kernels from which the grains are taken. The hard varieties, such as popcorn, have very angular grains while those from soft varieties have a great many almost spherical forms.

Fig. 28.—Starch Grains of Indian Corn, under Polarized Light. × 200.—(Courtesy of Bureau of Chemistry.)

Maize Flour (Corn Meal).

—Formerly the maize kernel was ground between stones, bolted to remove the bran, and the maize flour or corn meal thus produced used directly as a human food. Modern milling operations have changed the method of producing maize flour so that not only is the outer bran removed but also, to a large extent, the germ itself, thus diminishing the quantity of fat in the prepared meal. This is notably true of the maize flour which is prepared for exportation. Leaving in the flour such a large quantity of fat tends to produce rancidity during shipment. To avoid any change of a deleterious nature which the flour may undergo during shipment, it is also frequently kiln-dried before being sent to foreign shores and even when intended for domestic consumption at points remote from the mill.

While this preparation of maize flour is doubtless important for transportation purposes, it impairs the palatability and nutritive value of the product. It is advisable to continue to have the maize flour prepared in the old-fashioned way and sent directly into consumption.

Method of Preparation.

—One method of preparing the maize flour is as follows: The grains are broken into large pieces and dried with steam heat at a temperature of from 105° to 110° C. (221°-239° F.). The mass while still hot passes into a mill composed of two stones which revolve rapidly in opposite directions. The smaller portions of the meal, which have been reduced to a kind of gum by the high temperature, are separated by this process from the covering or the bran of the kernel. A small mass of the starchy matter leaves the mill in the form of small noodles, which are freed from any particles of bran by sifting. In this manner a mass is obtained which is quite free from fiber and fat.

The composition of maize meal prepared by the above process is as follows:

Moisture,9.70percent
Protein,12.68„
Ether extract,1.19„
Ash,.60„
Fiber,.35„
Starch, sugar, and dextrin,71.48„

This method of preparing maize meal is not used to any extent in this country, but is said to be commonly employed in Germany.

Composition of Maize Flour.

—The color of maize flour depends upon the color of the corn from which it is produced,—it may be white or yellow. The starch granules when heated in water to 62.5° C. swell up and become deformed, except a few, usually the small ones, which resist the action of water at that temperature. The starch granules of maize flour under polarized light present a black cross, very marked and very distinct when the field is obscured. When viewed under polarized light with a selenite plate the starch grains of maize are colored red with a green cross or reciprocally, and this coloration is very brilliant.

As has already been said, the composition of Indian corn meal made by the old-fashioned method of grinding and removing only the bran is practically that of the whole grain itself.

The composition of degerminated maize meal (Indian corn flour) is shown by the following average data:

Moisture,12.57percent
Protein,7.13„
Ether extract,1.33„
Ash,.61„
Fiber,.87„
Starch and sugar,78.36„
Calories calculated on the moist meal,3,837   

The above data show that the refined Indian corn meal has lost more than three-fourths of its fat, a large portion of its mineral matter, and also a very considerable proportion of its protein, due to the separation of the bran which is extremely rich in protein and the germ which is rich both in oil and protein. A mere glance at the data shows that this refined Indian corn meal is much less nutritious than the natural meal in so far as its content of tissue-forming bodies and its faculty to furnish heat and energy are concerned. In other words, the calories are very much lower than in the natural corn meal. This is another reason for urging our people to return to the consumption of the old-fashioned material.

The Adulteration of Indian Corn Meal.

—Owing to the cheapness of Indian corn in so far as is known there is no adulteration practiced. The refined Indian corn flour itself is sometimes used as an adulteration for buckwheat flour, wheat flour, and other cereal flours, but has not itself been subjected to adulteration.

Corn Bread (Indian Corn Bread).

—Corn bread is a very common diet among all classes of people in the southern states and also to a considerable extent in the north.

Owing to the lack of agglutinating powers of the nitrogenous constituents of Indian corn flour, corn bread cannot be aerated or raised, as is the case with wheat bread. It is often eaten in an unleavened state. It may be partially leavened by the usual agent, namely, yeast or a chemical baking powder. Two varieties of bread are very commonly used, namely, that made of white flour or meal and that made of yellow. There is apparently no difference in the nutritive values of these two kinds. Some consumers prefer the white loaf and some the yellow.

Composition of Indian Corn Bread.

—The composition of bread depends upon whether the whole grain flour is used from which only the coarse bran has been removed by bolting or whether the decorticated and degerminated meal is used. In the first case bread is made richer in fat and protein and in the second case richer in starch. In the bread will also be found the materials used in its preparation, namely, salt, lard or other fats, milk, yeast, or baking powder residues. The best bread is made from the freshly ground flour of the whole grain from which only the outer covering, namely, the coarse bran has been removed. As offered at many of our hotels and some private houses, corn bread has been so manipulated as to lose a large part of its palatability, without any compensating improvement of its nutritive properties.

OATS (Genus Avena).

This cereal is an important food product, being used very largely in Europe, especially in Scotland, and also very extensively in this country as human food. The chief use of oats is for cattle food, especially for horses. It is extraordinarily rich in its nutritive constituents and, therefore, is prized highly as a food in the building and restoration of nitrogen tissues, such as the muscles. The variety in common cultivation is Avena sativa L.

Oats are grown in almost every part of the United States, but chiefly in the northern and western portions. In the southern states the crop is planted in the late autumn or early winter. In the northern states it is chiefly a spring crop, being sown early in the spring as soon as the ground is in fair condition. The oat crop is one which requires a rather abundant and well-distributed rainfall. A spring drought is very detrimental to the growth of oats, much more so than wheat or rye. It is a crop which is well suited to be grown under irrigation.

There are many varieties of oats in cultivation, but in general characteristics they all correspond to one description. The husk adheres firmly to the grain, and when threshed the grain of a common variety of oat carries the first layer of husk or chaff with it. Oats, as bought in the market, therefore, consist not only of the kernel or grain but also of this outer, chaffy envelope. The magnitude of the crop in the United States is very great, but only an inconsiderable proportion of the whole is used for human food, and this chiefly in some form of oatmeal. The statistics of the crop grown in the United States during 1906 are given in the following table:

Acreage,30,958,768  
Yield per acre, bushels,31.2
Total yield, bushels,964,904,522  
Price per bushel, cents,31.7
Total value at farm,$306,292,978  

Ratio of Kernel to Hull.

—Numerous examinations of unhulled oats show that the average percentage of kernel to hull for 100 parts is as 73 to 27. In the oats grown in the western states the proportion of kernel is relatively higher and in the southern states lower.

In the analytical process if the hull or chaff is ground with the grain the proportion of fiber or crude cellulose is very considerably higher than in the class of cereals ground without the chaff. The mean composition of unhulled kernels of oats of American growth is represented by the following table:

Weight of 100 unhulled grains,2.92grams
Moisture,10.06percent
Protein,12.15„
Ether extract,4.33„
Crude fiber,12.07„
Ash,3.46„
Starch and sugar,57.93„

A study of the above data shows that the flour of unhulled oats is rich in fat, fiber, and ash. The large percentage of fiber and ash is due to a great degree to the composition of the hulls or chaff. The fat or oil comes chiefly from the germ.

Composition of Hulled Oats.

—Inasmuch as the chaff is always separated from the oat flour when the latter is to be used for human food, the composition of the oat in the hulled state is of greater importance to the present purpose than in the unhulled condition. The means of 179 analyses show the hulled oats to have the following compositions:

Moisture,6.93percent
Protein,14.31„
Ether extract,8.14„
Crude fiber,1.38„
Ash,2.15„
Starch and sugar,67.09„

The removal of the hulls, as is seen, and the partially dried condition of the grain in the above analysis increases the percentage of other ingredients. The protein and fat are especially large in quantity. Oatmeals may be regarded as the richest of the cereal flours, both in protein and in oil.

The Protein of Oat Kernels.

—There are three principal products in the oat kernels characterized by their different degrees of solubility, namely, protein soluble in alcohol, protein soluble in dilute salt solution, and protein soluble in alkali. The protein soluble in alcohol constitutes about 1.25 percent of the whole grain, the protein soluble in dilute salt solution about 1.5 percent, and the protein soluble in alkali the remainder, viz., 11.25 percent. The protein of oats has very little agglutinating power and, therefore, oat flour is not suitable for making bread, or rather it is very little used for that purpose.

Oat Products.

—As has been intimated before, the principal oat products, as far as food is concerned, are the various forms of oatmeal commonly classed as breakfast foods. These products are prepared in various forms of agglutination and physical texture but if made from genuine oats, as there is little cause for doubt, they have essentially the same composition and nutritive power. It is doubtful if there is any preparation of oatmeal any more nutritious or palatable than the plain oat grain properly cooked. The forms in which the oat products are offered to the public are perhaps more convenient for use and in some cases by reason of heating and preparation require less trouble, but otherwise they apparently have no advantage over the simple product.

The mean composition of a number of oat flour products is shown in the following table:

Moisture,7.66percent
Protein,15.48„
Ether extract,7.46„
Crude fiber,1.20„
Ash,1.29„
Starch and sugar,67.61„

In the dry substance:

Protein,16.77percent
Ether extract,8.08„
Crude fiber,1.38„
Ash,1.94„
Starch and sugar,73.20„
Calories,4,875   

It is evident from the above average analysis that the products examined are made from the whole kernel without the removal of the germ but with a very careful removal of the hull and bran. The composition of these products compares very favorably with the typical composition of the kernel itself. These data show the high nutritive value of these oat products, both in respect of fat and protein.

Fig. 29.—Oat Starch. × 200.—(Courtesy of Bureau of Chemistry.)

Adulterations.

—There are very few adulterations of oatmeal. Fortunately the price of this cereal is such that the admixture of other cereals would not be profitable. Doubtless such admixtures have often been made but evidently, from the examination of the products upon the open market, they are not very frequent. The characteristic appearance of oat starch is shown in [Fig. 29].

Oat starch grains average about 10 microns in diameter. There are usually present some grains of somewhat oval shape, which assist in identifying oat products when present. The starch granules also have a tendency to agglutinate into masses of varying size, as shown in the [photograph].

Detection of Adulterations.

—The adulteration of oatmeal with the flour of other cereals can easily be detected by the use of the microscope. Oat starch when highly magnified presents a peculiar cellular structure of pentagonal character which might be compared to the effect produced by grinding a large number of faces upon a precious stone. This peculiar appearance is caused by the tendency of the starch granules in oats to become compacted in large masses. The appearance of the separate granules and also the compact aggregate are shown in the figure on the preceding page. The large aggregated masses are of different sizes, ranging from .02 to 1.2 millimeters in length. These masses are usually broken up by grinding or pressure and, therefore, are not found in very great abundance in the commercial oatmeal. When separated into single granules these are found to be irregular in outline, due to the compression to which they have been subjected, more or less pentagonal in structure, and from .015 to .02 millimeter in diameter. The starch granules do not show any very marked characteristics under polarized light and have neither lines nor hilum. The above statements can easily be verified by any one who can operate an ordinary microscope, but before attempting to detect adulteration a careful examination of starch granules, prepared by the investigator himself, should be made.

RICE (Oryza sativa).

Rice is one of the most important food cereals. It furnishes a large part of the food of the inhabitants of China and Japan. It is a food rich in starch and poor in protein, and furnishes, therefore, heat and energy, and is well adapted for the nourishment of those engaged in hard labor or who undergo extreme physical exertion. The cultivation of rice is rapidly extending in the United States, especially in Louisiana and Texas. The statistical data relating to the rice crop for 1906 are as follows:

Acreage,575,014  acres
Production,17,854,768  bushels
Yield per acre,31.1„
Price per bushel,90.3cents
Total value,16,121,298  dollars

The adulteration of rice is confined to coating it with talc, paraffin, and glucose. The object of this treatment is to give a better appearance to the grain and to protect it from the ravages of insects. The use of indigestible substances such as talc and paraffin is scarcely justifiable. The starch granules of rice have distinctive properties which enable them to be readily recognized under the microscope, as shown in [Fig. 30].

The rice starch grains are polygonal in form and have sharp angles. The grains vary in size from 2 to 10 microns, though the latter size is seldom reached, the most of the grains being about 6 microns. The hilum is seldom visible. The grains occur in the rice kernels mostly in groups of a considerable number of the individual grains forming starch masses of ovoid or angular form.

Fig. 30.—Rice Starch. × 200.—(Courtesy of Bureau of Chemistry.)