42 



Quality in Wheaten Flour. 



correlated with it. That proposition is untenable. A very large 

 proportion of the gas evolved in panary fermentation is lost, 

 either as a result of the mechanical handling of the dough or by 

 gradual diffusion. The leak is not the same in the cases of all 

 flours, and it was shown at the last International Congress of 

 Applied Chemistry (Humphries and Simpson) that the gas- 

 retaining capacity of a set of flours indicated with substantial 

 accuracy their relative strength. The gas-making capacity of 

 any flour can be most materially modified by the baker or by the 

 very latest developments of flour milling. The gas produced in 

 the earliest stages of panary fermentation is lost so far as effective 

 aeration of dough is concerned. All flours afford much gas in the 

 early stages ; and while some afford enough at all stages, very 

 many do not. The total amount of gas evolved must be useless 

 as an index of strength ; for working purposes the gas evolved in 

 the later stages of fermentation only may be used as an index. 

 Even then any gas produced beyond what is necessary to overcome 

 the leak and the relatively small quantity required for the inflation 

 of the dough is wasted. It follows, therefore, that the problem 

 before the miller or the baker is to make certain that any given 

 flour should yield enough gas for practical working purposes 

 whenever panary fermentation is to be taken into account. 



It is obvious that the requirements of the yeast have to be 

 considered ; it must have a sufficiency of proper food. In other 

 words, it must have sufficient sugar, soluble nitrogen, and mineral 

 food (phosphates). An addition of sugar sometimes increases the 

 quantity of gas evolved in panary fermentation, sometimes 

 diminishes it. My colleague, Mr. A. G. Simpson (Humphries and 

 Simpson — International Congress of Applied Chemistry, 1909), 

 explained that point as follows : When a mixture of flour and 

 water is made, a large proportion of the water goes into com- 

 bination, and this proportion increases as time passes. The food 

 of the yeast is that part of the flour which goes into solution 

 when w r ater is added in dough-making. The quantity of sugar 

 found in a flour before a dough is made with it is not a correct 

 index of the quantity which will be formed by diastatic action when 

 water is added. The quantity so produced will depend not only 

 upon the enzymes concerned in diastatic action, but also upon the 

 physical state of their pabulum. It is known that yeast cannot 

 thrive in a liquid containing sugar if the concentration of the 

 sugar be high, and it has been ascertained that for optimum 

 results the concentration should not exceed 15 per cent. From 

 the foregoing considerations it will be gathered that during 

 fermentation the proportion of water available to hold sugar in 

 solution is diminishing, while a relatively large proportion of sugar 

 is being produced as the result of diastatic action. It follows, 



