RICE When Treated for Milling Acquires Desirable Qualities

The most valuable product obtained in the milling of rice is the whole kernels, or head rice. The medium- and short-grain rice varieties are more extensively grown in the United States, owing largely to a higher yield of head rice in milling, than the long- and long-slender-grain varieties. The better long- and long-slender-grain varieties are, however, quoted on the principal clean-rice markets at higher prices than the medium- and short-grain varieties. If the milling quality of the long- and long-slender-grain rices could be improved it should lead to a larger production and consumption of these types in the United States.

The Process
In certain rice-producing countries of the Far East some rough rice is treated prior to milling. It is claimed that the treated rice mills better, and that the milled rice has a more pleasing and distinctive taste, contains more vitamin B, keeps better, and is more nourishing than untreated rice. The process consists in soaking rough rice in water, then steaming it under pressure. After steaming, the rice is dried and milled. The type or types of rice that are so treated in the Far East and the exact procedure followed are not generally known.  It appears that the method of treatment varies more or less in different countries, but the effects of the treatment are essentially the same.

In experiments conducted by the writers on parboiling rough rice the long-grain varieties Fortuna, Rexoro, Edith, and Iola, the medium-grain variety Blue Rose, and the short-grain varieties Colusa and Caloro were used. These, with the exception of Iola, are important commercial varieties in the United States. Rexoro is a long-slender-grain variety of the same general type as the Patna rice from India.  The more extensive tests were made with Fortuna and Rexoro.

The rough rice was first soaked in water, drained, and then steamed under pressure. The treated samples were thoroughly air-dried before they were submitted for shelling tests.

Treated and untreated samples of each variety were sent to the Federal-State rice grading office at Crowley, La., for shelling tests.  These were made with the Smith shelling device, which indicates the probable yield of head rice that may be obtained from a given lot of rice when milled.

Results of Experiments

For the samples of rough rice soaked for 24 hours at room temperature and steamed for 25 minutes the increase in the indicated yield of head rice ranged from 2.6 percent for Blue Rose to 25.5 percent for Rexoro; for Fortuna the increase was 9.8, for Iola 19.9, and for Edith 23.4 percent. The increases for Colusa and Caloro, steamed 45 minutes, were 19.1 and 28.0 percent, respectively.

In the more extensive experiments, samples of Fortuna and Rexoro were soaked at constant temperatures and steamed for different lengths of time. The increases in the indicated yields of head rice were essentially the same regardless of the length of the soaking period, the temperature of the water in which the rice was soaked, or the length of the steaming period. The color and texture of the treated rice were, however, affected by these factors.

The average increase in indicated yield of head rice for all Fortuna samples soaked at constant temperatures and steamed for different periods was 29.7 percent, and for all Rexoro samples 25.2 percent.

Color of Treated Rice

   The treated rice obtained in these experiments when milled varied in color from translucent to amber, whereas untreated milled rice is white or more or less opaque. However, even though the treated milled rice is darker than the untreated, it is nearly as white when boiled.

Cooking Quality

Treated kernels when boiled retained their shape better than did untreated kernels of the same variety. When boiled and sterilized in water or canned soup the treated kernels retained their shape much better than did the untreated kernels of the same variety or those of Patna rice (fig. 55).

FIGURE 55.—Samples of boiled and sterilized rice: A, a, Fortuna untreated; b, Rexoro untreated. B, a, Fortuna parboiled; b, Rexoro parboiled. C, Patna.

A considerable quantity of Patna rice grown in India is imported duty free each year largely for use in commercially canned soups. In the past American-grown varieties that have been compared with Patna in canned soups have not been so satisfactory. However, in comparing parboiled Fortuna and Rexoro rices with imported Patna, the former appear to have all the desirable characteristics of the latter when boiled and appear even more desirable for use in canned soups.

The information obtained shows that treated rice has desirable characteristics that are at present largely unknown to the rice trade of the United States.

Jenkin W. Jones and JOHN W. TAYLOR, Bureau of Plant Industry.