WINNIPEG, 1909. , 777 
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 con- 
cerned. 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 addi- 
tion 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 combination and this 
proportion increases as time passes. The food of the yeast is that part of 
the flour which goes into solution when water 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 con- 
taining 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, therefore, that the 
concentration of sugar in the uncombined water may easily get beyond the 
proportion at which the optimum proportion of gas can be obtained. It follows 
also that, in certain cases, sugar can be added advantageously when an 
increased production of gas is desired ; it can also be added advantageously 
in some cases when it is desirable to retard fermentation. 
It may be asked whether the same principles apply in other cases of 
enzymic action. Can beneficial enzymic action be assisted or undesirable 
enzymic action retarded on such lines? Are there any reasons for believing 
that conditions favourable or unfavourable to alcoholic fermentation equally 
affect enzymic action? Has sugar a direct effect on the physical state of 
the gluten ? 
Mr. Whymper (in the Starch Section of the last International Congress 
of Applied Chemistry) showed by photo-micrographs and lantern slides 
that only a very small proportion of the starch particles is attacked by 
diastase. The small or smaller grains were shown to be unaffected by the 
diastase. Mr. Simpson has shown that, under certain conditions, a small 
proportion of flour converted into sugar a quantity of ungelatinised starch 
equal to 8 per cent. of the weight of the flour, but that under identical 
conditions the same quantity of the same flour converted a quantity equal to 
400 per cent. of its own weight into sugar when gelatinised starch was used. 
