Archiv. der AALERS.-Méthode pour essayer la pureté de l'arrowroot. BÉCHAMP.-Compt. Rend,, xxxix. 653; xlii. 1210. DELFFS.-Poggend. Annal., cix. 648; N. Jahrb. Pharm., xiii. 1. GREENISH, T.-Pharm. Journ. [3], vol. vii., &c. GUERIN, VARRY.-Ann. Chim. Phys. (2), lvi. 525; lvii. 108; lx. 32; lxi. 66. GUIBOURT.—Ann. Chim. Phys., xl. 183. 66 HANBURY and FLUCKIGER.- 'Pharmacologia." Lond. 1874. HASSALL." Food and its Adulterations." JONES, H. W.-Pharm. Journ., 1876, p. 23. JESSEN.-Poggend. Annal., cvi. 497; Journ. Pract. Chem., cv. 65. MASCHKE, J.-Pract. Chem., lvi. 409; lxi. 1. MUTER, J.-" Organic Materia Medica." Lond. 1878. NÄGELL.-Die Starke-Mehlkörner. 1858. PAYEN.-Ann. Chim. et Phys. (2), liii. 73; Ivi. 337; lxi. 355; lxv. 225; (4), iv. 286. Compt. Rend., xiv. 533; xviii. 240; xxiii. 337; xxv. 147; xlviii. 67. ROYLES.-" Materia Medica." SCHARLING.-Journ. Pharm. et Chim. [3], 1856, t. ii., p. 246. TRIPE, I. W.-On the Discrimination of Starches by Polarised Light. Analyst, 1879, vol. iv., p. 221. WIESNER-Einleitung in die Technische Mikroscopie. 8vo, Wien, 1867. WHEAT-WHEATEN FLOUR. The § 82. The wheat cultivated in this country is the Triticum vulgare, of which there are two varieties-the T. aestivum, or summer wheat, and the T. hybernum, or winter wheat. mean composition of wheat from 250 analyses is as follows [König]: Per cent. 13.56 12:42 1.70 1.44 2.38 64.07 2.66 1.79 Fibre, Ash,. These analyses do not include Russian wheat. In the central parts of South Russia a wheat is grown which has an amount of nitrogenous substances quite uncommon-the mean of twentyfour analyses giving a percentage of 3.45 nitrogen and 21.56 nitrogenous substances. The mean composition of the ash of entire wheat is as follows: According to the researches of M. Duvivier, of Chartres, the external part of the envelope of the grain is covered with fatty, odorous, and nitrogenous matters, which are in a particular combination, and form on the grain a very tenacious coating-a sort of preservative, and communicating an odour quite sui generis. These substances, which are named cerealin, tritisecaline, &c., are isolated by treating the entire grain with cold ether, and then allowing the ethereal extract to evaporate spontaneously. However, neither the nature nor even the presence of these matters can be considered satisfactorily established, and further investigation seems necessary. $83. Constituents of Flour.-Flour, in the common acceptation of the term, is ground wheat freed from bran. B The physical characters which flour should possess are as follows:-It should be an almost perfectly white, fine powder, with only the slightest tinge of yellow; the odour should be sweet, and it should be free from acidity. It should exhibit no trace of bran when pressed smooth with a polished surface; and it should have a Fig. 20 is a representation of the microscopical certain amount of costructure of wheat when a fine section of the seed hesiveness sufficient is made, x 199. a is the cells of the bran; b the to retain for sometime cells of the thin cuticle; c the gluten cells; d the any shape impressed starch cells; B, wheat starch, x 350. upon it by squeezing. The microscopical characters of good flour are: the absence of foreign starches, of fungi, &c., and the presence alone of the elements of ground wheat. (See pp. 142, 144, and 146, for measurements of the starches.) The chemical composition of ground wheat is represented in the following table, giving the mean of fourteen analyses by Peligot: The percentage of ash from the whole wheat is much higher than that of ordinary flour, the bran containing much ash. Thus, 100 parts of bran contain The analyses of Millon* and Kekulé give the following: whilst 100 parts of flour, according to Wanklyn, contain The nitrogenous matter of the cereals has been usually determined by a combustion and subsequent estimation of the nitrogen. Mr. Church has, however, shown that this method of estimation is not perfectly reliable as a measure of the fleshformers, or albuminous matters properly so called. In a valuable recent series of researches on this point, with regard to wheat, barley, and oats, Mr. Wigner has shown that these nitrogenous flesh-forming constituents have been over-estimated, since nitrogen combined as nitric acid, nitrous acid, and alkaloids, is present in larger quantities than has been hitherto supposed. This is more especially true as regards the husk and bran, very little non-coagulable nitrogenous matter being contained in the flour properly so called. These analyses were carried out as follows: 50 grains of the sample were ground in a warm porcelain mortar with enough carbolic acid to form a paste. Two or three drops of dilute acid were added, and the paste then diluted with hot carbolic acid and allowed to cool, filtered, and the filter washed with carbolic acid of the same strength. By this treatment all the true albuminoids were coagulated and remained in the filter, while any nitrogenous matter, either as nitrates, nitrites, alkaloids, or gluten, passed through the filter. The residue in the filter was washed down into the point as far as possible, and the filter dried; the residue detached, and the filter itself finely shredded with scissors and ground to powder, and then burnt in a combustion-tube in the usual way. The samples were collected so as to give examples of every class of wheat, barley, and oats, and ground by the operator. Treated in this manner, Mr. Wigner found that 17.7 per cent. of the total nitrogen in wheat, 17.6 per cent. of that in oats, and 14.7 per cent. in that of barley, as an average, deduced from the examination of fifteen samples of each, was present in such a form as not to be capable of coagulation by carbolic acid. The extremes in various samples differed widely, and it would appear as though we may have by this process a method of distinguishing the true nutritive value of one sample of grain from another.* In a recent research by the author (still proceeding), the nitrogen as nitrates in the bran was estimated as 0071 grm. per cent.; an alkaloidal peptone was precipitated by phosphomolybdic acid; and found to exist in the proportion of about .75 per cent. In whole meal the nitrogen as nitrates was 043 per cent., the alkaloidal peptone 1.00 per cent. The nitrogenous constituents of flour comprised under the name of gluten are probably, from the recent researches of T. Weyl and Bischoff, not ready formed in the flour, but the result of the action of a ferment like myosin, which, however, has not been isolated. This theory would account for the fact that (as observed by Mitscherlich and Krocher) wheat in which no sugar could be found before being sent to the mill, on being moistened and ground yielded as much as 4 per cent. of sugar. Gluten is composed of at least four bodies-gluten-caseine, gluten-fibrine, mucedin, and gliadin. Gluten may be obtained by merely kneading the flour into a paste, and then washing all the starch out of the paste in a thin stream of water. As thus obtained it is, in the moist state, a yellowish-grey, very elastic, adhesive mass; and when dry, somewhat horny. It dissolves for the most part in alkaline liquids and in acetic acid. From the gluten the four bodies mentioned may be separated as follows: 1. Gluten-caseine.-The well-washed gluten is digested a few days with potash solution (for every 100 grms. of gluten about 3 to 4 grms. KHO). The clear solution is decanted from the insoluble residue, and precipitated by acetic acid in the least excess. The precipitate is exhausted successively with 60 per cent. and with 80 per cent. alcohol, then with absolute alcohol, and lastly with ether. The insoluble portion now consists of gluten-caseine, which may be purified by solution of weak potash lye, precipitated by acetic acid, washed with water and alcohol, and dried in a vacuum. It forms a whitish-grey, voluminous, *See Analyst, July, August, 1878. + Ber. der Deutsch. Chem. Gesellschaft, 1880, p. 1064. |