White corn flour is the food prepared by so grinding and bolting cleaned white corn that when tested by the method prescribed in paragraph (b)(2) of this section, not less than 98 percent passes through a No. 50 sieve and not less than 50 percent passes through No. 70 woven-wire cloth. Its moisture content is not more than 15 percent. In its preparation, part of the ground corn may be removed, but in any such case, the content (on a moisture-free basis) of neither the crude fiber nor fat in the finished white corn flour exceeds the content (on a moisture-free basis) of such substance in the cleaned corn from which it was ground.

For the purpose of this section, moisture, fat, and crude fiber are determined by methods therefore referred to in § 137.250(b)(1).

The method referred to in paragraph (a) of this section is as follows: Weigh 5 grams of sample into a tared truncated metal cone (top diameter 5 centimeters, bottom diameter 2 centimeters, height 4 centimeters), fitted at bottom with 70-mesh wire cloth complying with the specifications for No. 70 wire cloth in “Official Methods of Analysis of the Association of Official Analytical Chemists,” 13th Ed. (1980), Table 1, “Nominal Dimensions of Standard Test Sieves (U.S.A. Standard Series),” under the heading “Definitions of Terms and Explanatory Notes,” which is incorporated by reference. Copies may be obtained from the AOAC INTERNATIONAL, 481 North Frederick Ave., suite 500, Gaithersburg, MD 20877, or may be examined at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/ code_of_federal_regulations/ibr_locations.html.Attach cone to a suction flask. Wash with 150 ml. of petroleum ether applied in a small stream without suction, while gently stirring the sample with a small glass rod. Apply suction for 2 minutes after washing is completed, then shake the cone for 2 minutes with a vigorous horizontal motion, striking the side against the hand, and then weigh. The decrease in weight of sample, calculated as percent by weight of sample shall be considered the percent passing through No. 70 wire cloth. Transfer the residue from cone to a No. 50 sieve having a standard 20.3 centimeter (8-inch) diameter full-height frame, complying with the specifications for wire cloth and sieve frame in “Nominal Dimensions of Standard Test Sieves (U.S.A. Standard Series).” Shake for 2 minutes with a vigorous horizontal motion, striking the side against the hand; remove and weigh the residue; calculate the weight of residue as percent by weight of sample, and subtract from 100 percent to obtain the percent of sample passing through the No. 50 sieve.