The proteins of the wheat kernel

LITERATURE. 9 2 to 3 per cent of the gluten was obtained, which corresponds to 0.25 to 0.35 per cent of the flour.The actual quantity he considered to be much more, and that in different varieties of wheat the proportion of gluten-fibrin varied greatly.Ritthaiisen described gluten-fibrin as insoluble in water, but by boiling with water it was decomposed and rendered insoluble in alcohol.In alcohol of 30 to 70 per cent it dissolved readily when heated, and separated again on cooling, more completely from the more dilute alcohol.From dilute solutions on concentration and from concentrated solutions on cooling the gluten-fibrin separated on the surface of the liquid as a thick, soft skin, which was renewed as often as it was removed, which property Ritthausen considered distinguished it from mucedin and plant-gelatin.In cold alcohol of 80 to 90 per cent the gluten-fibrin was soluble to a considerable degree.Dilute acids and alkalis dissolved this protein freely, yielding solutions from which it was precipitated on neutralizing to a slight acid reaction.The composition of gluten-fibrin is shown in the table on page 8. Plant-gelatin or gliadin formed the fraction of the alcohol-soluble protein that dissolved freely in alcohol of 60 to 70 per cent.The solubility of this protein decreased rapidly when the proportion of alcohol to water fell below or above this strength.It was very slightly soluble in cold water, more so in hot water.By boiling with water it was gradually rendered insoluble in alcohol.Extremely dilute acids and alkalis dissolved plant-gelatin readily.The amount of plant-gelatin which different wheats contain was not determined, owing to the impossibility of separating it from the other proteins.The composition of this protein is shown in the preceding table.Mucedin formed the fraction of the alcohol-soluble proteins which was soluble in the most dilute alcohol.Except for its greater solubility in water and in very dilute alcohol, mucedin does not appear to differ greatly in its properties from plant-gelatin.Its composition is given in the table on page 8.Mucedin yielded 25 per cent of glutaminic acid when boiled with sulphuric acid, but other decomposition products were not determined.Only a very small quantity of mucedin was obtained in a pure state, and no estimate of its total amount was made.The relative proportion, however, Ritthausen considered to vary greatly in different sorts of wheat.Albumin was obtained by heating the acidified wash-waters of the gluten.This, however, he considered as possibly derived from the soluble part of the gluten-proteins.The composition of this albumin is given in the table on page 8. IO THE PROTEINS OF THE WHEAT KERNEL.Weyl1 was the first to recognize the presence of globulin in wheat flour, and states that besides vegetable-vitellin, vegetable-myosin, which coagulated at 55° to 60°, was also present.Weyl & Bischoff2 considered the protein matter of wheat to consist chiefly of a myosin-like globulin which they called vegetable-myosin, and that, if so, this must be the substance from which gluten is derived, for other proteins are present only in small quantity.Extraction with 15 per cent salt solution left a residue from which they obtained no gluten.They therefore considered it probable that the gluten forms from the myosin in consequence of a ferment action similarly to the formation of fibrin from fibrinogen.No ferment, however, could be detected.They also found that large amounts of sodium chloride, sodium sulphate, and magnesium sulphate hindered the formation of gluten in the same way that sodium and magnesium sulphates hinder the formation of fibrin.As no gluten was obtained from flour extracted with alcohol, they concluded that the myosin had been coagulated.By warming flour 48 to 96 hours below 60°, the coagulation point of myosin, no gluten was obtained from the meal after adding a little unwarmed flour, showing that the gluten-forming substance had been coagulated.Balland3 found that nearly the same amount of gluten was formed with water at 2°, 15°, and 60°, and therefore concluded that no ferment action took part in its formation.According to Martin,* alcohol extracts from gluten but one protein substance.This is soluble in hot water, but insoluble in cold ; hence is insoluble phytalbumose.The residue remaining after treatment with alcohol is uncoagulated protein, soluble in dilute acids and alkalis.This he called " gluten-fibrin."The insoluble phytalbumose is not present, as such, in flour, since direct extraction of the meal with 75 per cent alcohol removes no protein.Extraction with water yields less globulin and soluble albumose than extraction with sodium chloride solution of 10 to 15 per cent.Martin therefore concluded that the insoluble phytalbumose is formed from the soluble by the action of water, the gluten-fibrin being formed by a similar action of water on the globulin ; that is, conversion into an albuminate.This albuminate and the insoluble phytalbumose together constitute gluten.W. Johannsen5 believed that there was no ferment action in the formation of gluten.Dough was obtained by grinding dried gluten and mixing with starch, and also by mixing moist gluten with starch.