April, 1913. 



KNOWLEDGE. 



137 



In the case of the Mummy Wheat the fibrous 

 nature was completely lost and the friable powder 

 resulting from the crushed husk was as though the 

 oerries had been roasted. 



Acidity. 



The acidity of the samples lias already been fully 

 discussed under former headings. 



Diastatic Power. 



With the exception of that from the newest wheat 

 the aqueous extracts of all the samples examined 

 failed to render starch soluble. It should be of 

 importance to determine the connection between 

 " loss of vitality " and " diastatic power." 



In a letter from Mr. Humphries it is stated that 

 wheat more than fifteen months old is rarely used in 

 commerce, and, consequently, the changes which 

 have been found to take place within the berry after 

 a period of fifty or more years are not likely- to be 

 encountered by the practical miller. 



The chemical and physical alterations which 

 take place within the wheat grain, however, are the 

 same, only to a much more retarded extent, as 

 those which flour undergoes during storage, and they 

 mav, therefore, be taken as a guide for the latter 

 purpose. 



Flour improves, in most respects, from the bread- 

 making point of view over a period extending for 

 about two months, but beyond this limit there will 

 be a deterioration, more or less rapid according to 

 the quality and conditions of the flour and the 

 conditions of storage. 



Evaporation of moisture will be in proportion to 

 the amount of heat occurring during storage, and the 

 giving out and taking in of moisture are the prime 

 factors which influence the changes, biological and 

 chemical, which take place within the flour. 



Balland (Contpt. Rend. CXIX, 565) found the 

 variations in chemical composition of flour during 

 storage, for a range of over two thousand samples, to 

 be principally due to fluctuations in moisture content, 

 which reached a maximum in February of about 16-2 

 per cent., and a minimum in August of 9 • 40 per cent. 

 The lowest percentage of acid was found by the 

 same author to be 0-013 per cent, in January, while 

 samples drawn in August contained nearly three 

 times that amount. 



Humphries, in his researches on the conditioning 

 of wheat (Brit. Assoc, 1911), points out that the 

 mere addition of moisture to Southern Plate wheat 

 was not sufficient to produce a marked change on 

 the baking qualities of the resulting flour (this flour 

 contained fourteen and a half per cent, of moisture), 

 but that great improvement was noticed if the flour 

 was also conditioned by addition of further water 

 until it contained fifteen and a half per cent, of water. 



Humphries observed that the improved Hour 

 showed a marked diminution in acidity (a statement 

 certainly not in accord with expected results, unless 

 the additional percentage of moisture had not been 



taken into account), and a decrease in the percentage 

 of ash. 



The production of inorganic phosphate by the 

 addition of water was believed to be the chief 

 cause of improvement. 



In the light of Wood's experiments on the influ- 

 ence of salts on gluten, the perpetual though slow- 

 passage of a saline solution, such as that of a 

 phosphate, through the cells of the wheat berry or 

 in flour during storage, would undoubtedly tend to 

 retard the degradation of the gluten, which we 

 find to have taken place only in the most ancient 

 wheats and which is principally due to the formation 

 of acid, and to improve the gluten of a flour by 

 increasing the ratio of conditioning salt to degrading 

 acid. 



The moisture content is the greatest variable, 

 whilst acidity always increases with age, the period 

 of time taken to produce absolute "inefficiency" of the 

 gluten being greatly retarded by the presence of salts. 



The passing of the moisture in and out of the 

 flour or grain makes it possible for these changes to 

 take place, and the extent of the alternations 

 determines the rate of change. 



Changesdueto enzymic action undoubtedly proceed 

 when the water content of the samples is high, such 

 as is seen, for instance, when sufficient moisture is 

 present to induce germination*, and it would be 

 interesting to observe the minimum amount of 

 moisture that would be necessary for such process. 

 It is quite certain, however, that, in the conditions 

 under which the examined wheats existed, this 

 point was never reached. 



The minimum moisture content necessary to 

 maintain life within the seed is another interesting 

 figure to consider, and lies between fifteen per cent, 

 and forty-five per cent, in the case of wheat if the 

 action of bacteria and moulds be prevented. 



In order to obtain this limiting figure, and also 

 with a view to furthering the present knowledge of 

 vitality and its duration in seeds, a number of 

 experiments have been undertaken with the hope that 

 the future examination of them may throw some 

 certain light on the conditions that influence the 

 retention of life within the seed. A full description 

 of these experiments and the objects for which they 

 have been undertaken have been reserved for a later 

 paper, when a complete discussion on their import 

 can be made. 



Summary. 



The influence of age on wheat grains is not very 

 pronounced when measured by chemical analysis, 

 the principal change which occurs being a marked 

 decrease in the ash content. 



This fact, which has been noticed previously by 

 other experimenters, is mainly brought about by the 

 absorption and expulsion of moisture under changing 

 conditions of the atmosphere, whereby the soluble 

 mineral matter is brought to the surface of the grains 

 and, sooner or later, rubbed off. 



Whymper (Internal. Conn, App. Clwni. 1009). 



