VISCOSITY OF GLUTEN DISPERSED IN ALKALI, ACID AND NEUTRAL SOLVENTS

Abstract

The viscosity of gluten dispersed in urea and sodium salicylate was higher, and showed a greater increase with increasing protein concentration, than that of dispersions of the same age and concentration, in sodium hydroxide and acetic acid solutions. Calculations, based on these measurements, indicated that the effective particle size is larger in the former pair of solvents. In urea solutions the viscosity of dilute gluten dispersions was independent of the hydrogen ion concentration between pH 6.1 and 9.2, and within this range the system was stable. Beyond this pH range the viscosity at first increased, but the system was unstable as shown by a subsequent rapid decrease in viscosity with time.Dilute dispersions in sodium hydroxide, urea and sodium salicylate solutions decreased in viscosity at first, whereas the viscosity of dispersions in acetic acid decreased continuously. Some evidence was obtained of coagulation in concentrated dispersions in the neutral solvents at 0 °C. and 25 °C.The character of the precipitate obtained by salting out dispersions in each of the four solvents after storage at 25 °C. indicated that the neutral solvents alter the gluten less than alkali or acid. This conclusion is supported by the fact that glutens obtained from flours of different protein quality had essentially the same viscosity when dispersed in alkali or acid, but in the neutral solvents exhibited markedly different viscosities which were partially correlated with the quality of the gluten.