5o Chemical Properties of W heat en Flour. 



size. The microscopic examination of a large number of flours 

 of different origin has shown that the large granules vary in 

 number from 6 to ij per cent, of the total number of granules. 

 In other words, in one flour as much as 30 to 40 per cent, of 

 the total weight of starch is in the form of large grains, whilst in 

 another only 7 to 10 per cent, is in this condition. 



Before a starch grain can be converted into sugar the cellular 

 envelope has first to be destroyed. Obviously, when the envelope 

 of the large granule is destroyed a much larger proportion of starch 

 is rendered available than when the contents of a small granule 

 are liberated. 



Whymper has recently made a microscopic study of the changes 

 occurring during the germination of wheat. He finds that the 

 larger and more mature granules are the most readily attacked 

 by the enzymes of the plantlet. Though there is no general rela- 

 tion between the size of starch granules of different origin and 

 the ease with which they are attacked by diastase and other 

 agents, it appears that the larger granules of any particular 

 starch are affected sooner than the smaller granules. 



The destruction of the cellular envelope of the granule is 

 undoubtedly effected by an enzyme (cytase) about which very 

 little is known. Julian Baker has suggested that poor flours 

 lack a sufficient quantity of cytase, and in confirmation of this 

 view showed that the addition of powdered malt, which contains 

 such an enzyme, improves the size of the loaves obtained from 

 such flours. 



Mineral Matter. 

 The amount of ash in flour seldom amounts to 0*5 per cent., 

 more than one-half consisting of phosphates. There is un- 

 doubtedly some relationship between the mineral constituents and 

 the gas-retaining power of gluten, though no complete analyses 

 have as yet been published directly connecting strength with the 

 composition of the ash. Wood, however, states that the soluble 

 ash of Fife flour (milled from a strong English-grown wheat) 

 shows a relatively high proportion of phosphate and magnesia 

 and a low proportion of chloride, sulphate, and lime ; whereas the 

 ash of a weak flour contained small proportions of phosphate and 

 magnesia but much more chloride, sulphate, and lime. The 

 influence of small quantities of acids and salts on gluten is dealt 

 with more fully by Mr. Hardy in the following paper. 



Fat. 



The amount of fat in flour varies from 1 to if per cent., the 

 higher value being a feature of flours from the Canadian North- 

 West. The oil is present to the extent of about 15 per cent, of 

 the wheat germ. It easily turns rancid, and is characterised by 

 a high iodine number (115). 



