Volume 9

Seventh International Congress of Applied Chemistry : London, May 27th to June 2nd, 1909.

  • International Congress of Applied Chemistry
Date:
1910
Catalogue details

Licence: In copyright

Credit: Seventh International Congress of Applied Chemistry : London, May 27th to June 2nd, 1909. Source: Wellcome Collection.

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    ■as tlie conditions of temperature and moisture during liarvest must be largely responsible for thè quality of a resulting flour; they also aid in throwing tight upon thè clianges which flour undergoes during agemg, for in thè presence of moisture there is a tendency to soften thè hard gluten, to weaken thè soft gluten and to render thè starch granules more suitable for gas production in thè presence of added yeast ; thè agents which bring about these changes are thè proteolytic and diastatic enzymes mainly secreted around tlie embryo ; thè former was found by Ford and Guthrie (J. Soc. Chem. Ind. 1908, 27, 389) in flour, while thè lattei' has long been recognised as existing in flour in apreciable quantities in spite of thè fact that during thè milling thè germ is practically excluded. It is also cerfcain that, if there are visible changes in thè starch granules in wheat grains during 36 hours wetting, changes must also be taking place in thè protein matter, and that, as these altered conditions are noticeable within that part of thè grain divided from thè embryo by thè wall of thè embryo sac, this quantity of altered endosperm fìnds its way into thè flour so that thè degraded gluten and pitted starch granules wiìl each appreciably affect thè quality of “ strength ” from thè baker's point of view, and it is conceivable that a strong dry wheat wetted for even so short a time as 24 hours would fail to live up to its reputation when thè flour milled from it was subjected to thè bakehouse test. During thè microscopie examination of a number of flours of different strengths and of various ages, it became evident that there existed a dose relation between thè quantity of gluten in a flour and thè number of aggregated starch granules which appeared as practically opaque areas in thè microscopie fìeld. Yarious methods for estimating thè dark areas were devised, such as determining thè amount of light cut off by tliem and also direct estimation of thè areas by means of a micrometer scale, but it was soon apparent that no approximation to accuracy could l>e obtained by observations made on thè minute portion of thè fìeld directly under thè objective. The most satisfactory method and thè one I now employ is thè adoption of standards of flours of known gluten content against which any other flour can be compared. The standard flours are set up in Canada balsam on microscope slides, and with a little practice a rapid microscopical survey of thè
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