Viscosity of melanoidins formed by oxidative browning validity of the equation for a relationship between color intensity and molecular weight of melanoidin.

Abstract

To demonstrate the validity of an equation, E=k1 Mα1 (E:1%1cm E450, absorbance of 1% solution in 1 cm path at 450 run, M: molecular weight, k1, α1: constant), intrinsic viscosity of the color components of melanoidin from a glycine-, diglycine- or triglycine-xylose system and of the color components of shoyu, separated selectively by utilizing their change of elution position on DEAE-cellulose chromatography during oxidative browning, has been investigated in connection with their color intensity or molecular weight. The intrinsic viscosity increased with an increase of molecular weight of the color components from each of melanoidins. The Staudinger's equation, [η]=k2Mα2, was observed to fit the relationship between the intrinsic viscosity ([η]) and molecular weight of color component from each of melanoidins. On the other hand, an experimental equation, E=k3[η]α3 was obtained from a linear relationship between logarithmic intrinsic viscosity and logE of color components from each of melanoidins. The last equation can also be derived from the first two equations. Therefore, the equation, E=k1 Mα1 was judged by this experiment to be valid for these melanoidins. Moreover, these melanoidins including the color components of shoyu was suggested to consist of a homologous series of symmetrically flexible chain polymer with different degrees of polymerization and color intensity, since the equation, [η]=k2 Mα2 was applicable for the melanoidins solutions and none of color components from melanoidins showed optical rotation in visible wavelength region. Mechanism of the representation of color from the chromophore of melanoidin has been also discussed.