FLOURS. 25 



SECTION II. 



FLOURS. 



Attention has already been directed to the difference in composi- 

 tion between starch and flour ; under the latter heading we propose 

 dealing with the principal cereal flours that serve as food-stuffs fo r 

 civilised peoples. 



The determination of the quality and purity of the various flours 

 is a matter of great importance and of some difficulty, often 

 demanding considerable skill and experience. The microscopist 

 may not be able to pronounce an opinion as to the nutritive value 

 of a flour submitted to him, but he can obtain valuable information 

 which should always supplement a chemical examination. In any 

 case, microscopical examination can alone detect the admixture of 

 one flour with another, and that is the form that adulteration 

 usually takes. The most common of such admixtures is that of 

 rye, maize, or rice flour with wheat flour. 



The principal factor in the identification of a flour is the form 

 and relative size of the grains of starch which it contains, but it is 

 nevertheless absolutely necessary for the microscopist to be ac- 

 quainted with the structure of the vegetable debris that are usually 

 to be found in it, as these also furnish valuable indications of iden- 

 tity ; moreover, he must avoid the error of attributing these to 

 foreign substances, the presence of a limited proportion of the 

 debris of the pericarp and seed coats being always tolerated in com- 

 mercial flours. 



