298 SCIENCE PROGRESS 



and therefore the greater the strength, but this view has proved 

 inadequate. It is now known that the tenacity of gluten is 

 conditioned by the presence of various salts or acids. Wood 

 and Hardy have shown that gluten itself has no tenacity, this 

 property depending on salts or acids contained in the flour 

 or added in the process of working. Any salt confers cohesion 

 on gluten ; any acid or alkali, when sufficiently dilute, lessens 

 it. The actual amount of gluten in flour is therefore only one 

 factor in determining strength ; account must also be taken of 

 the acids and salts also present. No practical method has yet 

 been devised for doing this but a beginning has been made 

 by Wood. 



The second factor in determining strength is the production 

 of sufficient gas to keep the gluten fully distended. The gas 

 is formed during panary fermentation, partly from the sugars 

 already existing in the flour and partly from those produced 

 by action of the diastatic enzyme of the flour on the starch. 

 Three factors are here involved : the amount of sugar already 

 present ; the amount of diastase ; the condition of the starch, 

 especially as concerns its resistance to the attack of diastase. 

 E. F. Armstrong points out that the sugar already present 

 would not suffice to give the necessary volume of gas and in 

 any case is ot little importance, as sugar is found directly the 

 flour is wetted. He shows also that ordinary flours contain 

 more than enough diastase to produce the necessary sugar. 

 There are flours, however, that do not, and these give better 

 loaves when a little more is added as malt extract or in some 

 other form. The condition of the starch must, therefore, be 

 regarded as the most significant factor. The starch granules 

 are each surrounded by an envelope which has to be disinte- 

 grated before the diastase begins its action. The larger the 

 granule the greater becomes the liberation of starch when 

 the envelope is destroyed ; a flour containing 30 or 40 per cent 

 of its starch as large granules — 30 or 35 /a — therefore more 

 rapidly undergoes the necessary change than another in which 

 only 10 per cent of the starch occurs in this form, the rest being 

 present in smaller granules. 



In the meantime while these problems are being cleared 

 up, the percentage ot nitrogen in the grain — which runs parallel 

 to the percentage of gluten — is a rough indication of "strength " 

 and in conjunction with other simple tests is taken as a first 



