NATURE 



[May 7, 1903 



a large percentage of proteid and oily matter, in con- 

 sequence of which the nutritive value is high. But 

 the proteid matter contains an active ferment, and the 

 oil is of a highly oxidisable nature, readily becoming 

 rancid. For these reasons they do not hesitate to 

 assert that the germ, as well as the bran, should be 

 rejected in the act of making f^our, the farinaceous 

 endosperm being the only component of the wheat 

 grain which ought to be used as human food. It is 

 interesting to note that the problem of the utilisation 

 of germ has been much more successfully attacked in 

 England than on the Continent. The credit is due i 

 to an English miller of discovering the fact that on ! 

 subjecting germ to the action of slightly superheated | 

 steam the diastasic properties of the proteids are de- 

 stroyed, while the oil is so fixed as to lose its natural 

 tendency to rancidity. Germ treated in this manner j 

 and then mixed with ordinary white flour produces a 

 bread of pleasant flavour and of high nutritive value. 



The endosperm or kernel of wheat consists princi- 

 pally of proteid matters, starch, and products of starch 

 hydrolysis. Of these substances the proteid matter has 

 received the closest attention, the whole general 

 character of each particular variety of wheat, and o. 

 its resultant flour, being governed by the quantity and 

 quality of the proteid bodies contained. It has been 

 recognised from the time of Liebig to the present that 

 the proteid matter of wheat is not a single compound, 

 but a mixture of several distinct substances. Among 

 these are small quantities of bodies soluble in water 

 or dilute saHne solutions respectively (albumins and 

 globulins) ; but the greater portion is not soluble in 

 either of these reagents, but forms with water a tough 

 india-rubber-like body, to which the name of gluten 

 has been given. This substance is readily prepared by 

 carefully kneading and washing in a stream of water 

 a piece of dough from wheaten flour. The starch and 

 soluble matters are thus eliminated, and the gluten 

 remains behind. The body thus obtained, known as 

 wet gluten, contains about two-thirds of its weight of 

 water, the remainder being approximately pure proteid. 

 By appropriate means, gluten is capable of being 

 separated into two, and possibly three, different sub- 

 stances, possessing distinct and characteristic chemical 

 and physical properties. 



The most exhaustive examination of these bodies 

 has been made by Osborne and Voorhees, who in 

 1893 communicated their results to the American 

 Chemical Journal. Following much the same lines 

 of research as other investigators, they treated gluten 

 and flour itself respectively with dilute alcohol (0-90 

 specific gravity). This reagent dissolves a consider- 

 able quantity of proteid matter from both the previously 

 washed gluten and the untreated flour, the proteid 

 being the same in both instances. (Albumin and 

 globulin are insoluble in dilute alcohol.) To this pro- 

 teid the name of gliadin has been given. Of gluten, 

 the insoluble portion has been called glutenin. 

 Osborne and Voorhees describe gliadin as being, when 

 obtained in the dry state from a solution in weak 

 alcohol or water, an amorphous transparent substance 

 closely resembling pure gelatin in appearance. It is 

 slightly soluble in distilled water, but is instantly pre- 

 NO. 1749, VOL. 68] 



cipitated by a trace of common salt. Gliadin is 

 very soluble in dilute alcohol (70 to 75 per 

 cent.). As may be assumed from its mode of prepara- 

 tion, glutenin is insoluble in such alcohol, and also 

 in water and dilute saline solutions. When freshly 

 precipitated and hydrated, glutenin is soluble in o-i 

 per cent, potash solution, and also in the slightest 

 excess of sodium or potassium carbonate solution. 

 Osborne and Voorhees made analyses of spring and 

 winter American wheat flours respectively, each of 

 which is a perfect flour of its kind, and found them to 

 yield gliadin and glutenin in the following propor- 

 tions : — 



Spring flour. Winter flour. 



(Hiadin 45'8 ... 4^'4 



Glutenin 54*2 ... 51 '6 



These quantities are roughly, it will be noticed, half 

 and half, whereas M. Fleurent, whose results are 

 adopted by MM. Girard and Lindet, states that the 

 ideal composition of gluten is 75 parts of gliadin to 

 25 parts of glutenin. With such a composition the 

 resultant bread will be well-risen and easy of diges- 

 tion ; but if the proportion of gliadin is higher, the 

 bread will rise well during fermentation, but will fall j 

 in the oven, thus producing a heavy loaf as the j 

 result of the liquefaction of gliadin in the presence .' 

 of water, under the influence of heat. But if the 

 glutenin be in excess, the dough will be comparatively 

 inelastic, and will not rise in baking. J 



There is evidently a great discrepancy between the! 

 results obtained by Osborne and Voorhees and those 

 given in the work before us. It is to be regretted 

 that MM. Girard and Lindet do not point out more 

 clearly that in determining the percentage of gliadin 

 M. Fleurent has made a radical departure from the 

 method of Osborne and Voorhees. Instead of using 

 pure dilute alcohol as a solvent, M. Fleurent employs 

 70 per cent, alcohol containing 3 parts of caustic 

 potash per 1000. If, as stated by Osborne and 

 Voorhees, glutenin is soluble in o-i per cent, potash 

 solution, it is evident that it is readily soluble in a 

 solution of the strength employed by M. Fleurent. 

 After thus dissolving in dilute alcoholic potash solu- 

 tion, M. Fleurent passes carbon dioxide gas to satura- 

 tion ; but although potassium carbonate is insoluble ir> 

 absolute alcohol, it is soluble in alcohol of 70 per cent., 

 and so one has at the close of the experiment, not a 

 solution of gliadin in dilute alcohol, but a solution of 

 gliadin and a portion of the glutenin in a dilute alcohol- 

 and- water solution of potassium carbonate. It is in 

 consequence of this difference in their respective 

 methods that the proportions of gliadin and glutenin 

 found by these investigators differ so markedly from 

 each other. No reflection whatever is cast upon the 

 method of M. Fleurent as a means of judging the 

 quality of a sample of flour, but it is unfortunate that 

 the separation thus obtained is throughout spoken of 

 by MM. Girard and Lindet as being one of gluten 

 into gliadin and glutenin. 



The examination of the more purely chemical part 

 of this book has occupied space to the exclusion of 

 the other subject-matter of the book. In later chapters 



