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, 2.92 grams

Moisture, 10.06 percent

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, 6.93 percent

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, 7.66 percent

Protein, 15.48 „

Ether extract, 7.46 „

Crude fiber, 1.20 „

Ash, 1.29 „

Starch and sugar, 67.61 „

In the dry substance:

Protein, 16.77 percent

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.

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.