﻿UNITED STATES DEPARTMENT OF AGRICULT1 



DEPARTMENT BULLETIN No. 1130 



Washington, D. C. T January 26, 1923 



SIGNIFICANCE OF WHEAT HAIRS IN MICROSCOPI- 

 CAL EXAMINATION OF FLOUR. 



By George L. Keenan, Microanalyst, Microchemical Laboratory, Bureau of Chemistry. 



CONTENTS. 



Page. Page. 



Purpose of method 1 Examination of commercial flours -i 



Method 1 Examination of experimental series of flour.. 6 



Examination of mill stocks 2 Summary 7 



PURPOSE OF METHOD. 



Since the publication of United States Department of Agriculture 

 Bulletin 839, "The Microscopical Examination of Flour, further 

 study has suggested that the number of wheat hairs present in a 

 weighed portion of the sample might be of value in classifying it. 



Heretofore the grading of a flour by the original method has 

 depended upon a count of the bran particles and hairs in a weighed 

 portion of the sample. In practice, however, the identification of 

 bran particles appears to be a more difficult task for the untrained 

 eye than the recognition of wheat hairs or fragments of hairs. The 

 bran particles occur in the flour in such a variety of forms that an 

 analyst unaccustomed to the differentiation of histological sections 

 under the microscope may encounter difficulties in obtaining con- 

 sistent bran-particle counts. The wheat hairs and hair fragments, 

 on the other hand, are readily identified and the quantity present in 

 a sample has been found to be indicative of the flour grade. 1 



METHOD. 



The method employed, which is similar to the one described in 

 Department Bulletin 839, with some modifications, is as follows: 



Carefully weigh out upon an accurate balance a 5-milligram portion 

 of flour and transfer the weighed portion to the center of a microscope 

 slide the surface of which has been ruled with lines running lengthwise 

 and 1 millimeter apart. The flour having been transferred to the 

 slide, mix about 4 drops of chloral hydrate solution (1:1) with the 

 flour by means of a preparation needle. After making a uniform 

 mixture of the flour and the chloral hydrate solution, apply a cover- 

 glass 22 millimeters square and gently warm the slide on the hot 



1 The term " grade " is here used in a general way, to classify the assembled types of flour. 

 16243—23 



