TRANSACTIONS OP SECTION B. ■ 365 



MONDAY, SEPTEMBER 4. 



Joint Discussion with Sub-Section K on the Part played by Enzymes in 

 the Economy of Plants and Animals. 



(i) Opened by Dr. E. P. Armstrong. 



(ii) The Velocity of Formation of Enzyme Systems. 

 By Professor H. Euler. 



In studying the alteration of enzyme activity during the culture of micro- 

 organisms in different mediums varying results have been obtained by previous 

 investigators depending on the species of yeast selected, the condition of the 

 yeast before the cultivation, and the nature and duration of the ' training.' No 

 experiments having been published on the velocity of the increase of enzyme 

 action, preliminary researches in this direction have been undertaken in continua- 

 tion of experiments made two years ago with Miss af Ugglas on the increase 

 of the amount of invertase in yeast after cultivation in sucrose solutions. The 

 amount of this increase appears to be characteristic for each species of yeast 

 and the form of the curve connecting the increase of inverting power with the 

 period of cultivation is in all cases the same. Experiments on the fermentation 

 of glucose and galatose gave similar results. 



It" seems that the power of micro-organisms to adapt themselves to the cul- 

 tural conditions can be expressed by constants which are characteristic for every 

 species. 



The following Paper was then read : — • 



Some Points concerning the Treatment of Wheaten Flour. 

 By A. E. Humphries. 



At the Leicester and Winnipeg meetings of this Association the author dealt 

 with some phases of the complex questions concerning the quality of wheaten 

 flour. Great importance must be attached to 'strength,' a flour's capacity for 

 making big, shapely, and therefore well-aerated loaves. The nice appearance 

 of food is a factor affecting its dietetic value. The whiteness of bread depends 

 to a very great extent upon the ' strength ' of the flour used, for the good ap- 

 pearance of bread depends very largely on the perfect aeration of the loaf. 

 ' Strength ' does not depend upon any one factor. A flour with a high protein- 

 content is not necessarily strong. A flour with a low protein-content is probably, 

 but not necessarily, weak. 



The size of the loaf depends upon the production of sufficient gas during 

 fermentation, more particularly during the later stages, and upon the gas- 

 retaining capacity of the dough. The yeast must have a sufficiency of sugar, 

 nitrogenous and mineral foods in forms which it can assimilate. Flour itself 

 does not contain sufficient sugar for the requirements of the yeast. As a general 

 proposition it is true to say that flour made from wheats harvested in moist 

 atmospheric conditions yield as a result of diastatic action during panary fer- 

 mentation a sufficient quantity of sugar, those harvested in hot dry conditions 

 do not. The yeast requires its nitrogenous food in a very simple form. Flours 

 containing a very high percentage of nitrogenous matter do not necessarily pro- 

 vide a sufficiency of nitrogeneous yeast-food. It is believed that yeast can ob- 

 tain all the mineral matter it requires from flour, but there are cases in which 

 the addition of mineral phosphates does increase the yield of gas in panary 

 fermentation conducted under commercial conditions. A flour may possess a 

 high percentage of gluten, but unless it yields in fermentation sufficient gas to 

 overcome the great and variable leak, and thoroughly to inflate the dough in the 

 latest stages of the breadmaking process, it would be accounted weak. 



Furthermore, a flour may yield more than sufficient gas at all stages of 

 fermentation and may even possess a high percentage of nitrogenous matter and 



