46 Chemical Properties of Wheaten Flour. 



to about 70 per cent., most attention has been directed to the 

 proteins. When flour is made into a dough and the starch 

 removed from this by agitation with water, a sticky, elastic mass 

 of a light-brown colour remains ; this is known as gluten and 

 consists almost entirely of protein. 



The definition of " strength " now generally adopted (see 

 Humphries, p. 40), based as it is on the character of the final 

 product — the loaf — covers so many factors that it cannot be 

 strictly correlated with chemical composition. It is, however, to 

 be supposed that the determination of certain factors or groups 

 of factors should enable some idea of the relative baking values 

 of flours to be gained in the laboratory ; experience has con- 

 firmed this view. The chemist requires the miller and the baker 

 to define, as precisely as possible, the particular points they look 

 for in a satisfactory wheat or flour. Mr. Humphries has rendered 

 great service by his attempts to do this. 



In the following a brief review is given of the factors with 

 which strength has been associated in the past. The explanation 

 of "strength" from the chemical point of view must be treated 

 as a separate problem. 



The preparation of sample loaves from a given flour still 

 remains the most satisfactory test. It is essential that such 

 loaves be prepared with scientific accuracy, under definitely 

 standardised conditions, so that the only variable is the flour 

 itself and possibly the amount of water used for doughing. Every 

 mill desiring to produce uniform products is bound to have a 

 laboratory for this purpose. 



Gluten. 



The oldest idea is that " strength " is due to gluten ; that in 

 virtue of its elasticity this retains in the dough the gas produced 

 during panary fermentation, and enables the dough to distend 

 and keep up when baked. Flours containing most gluten should 

 be the strongest. Experience has shown that a high gluten con- 

 tent is usually associated with strength, but in a great number 

 of instances it has been found that of two flours, that with the 

 higher gluten content behaves as the weaker when baked. 

 Scientifically, therefore, gluten content cannot be considered an 

 absolute measure of strength, although obviously connected with 

 it. 



Total Nitrogen. 



Some of the proteins of flour are soluble in water, and therefore 

 are removed during the process of washing out the gluten. The 

 determination of total nitrogen in a flour is less liable to the errors 

 affecting the empirical methods of estimating gluten, but the 

 results of such determinations are roughly parallel to the gluten 



