To the problem of melanoidin structure formation in aqueous-ethanolic media

The overwhelming majority of research works is devoted to studying of a melanoidin formation in aqueous media, only the small number of the publications covering results of carrying out reactions in non-aqueous or mixed solvents is known. At the same time difference of mechanisms of formation of target structures in the ethanolic media, which also are biologically important, is noted, besides, aryl amines are also poorly studied as brown reaction reagents. The electronic spectra removed during process of formation of melanoidin structure by selection of microprobes from a reaction system with the subsequent dilution and absorption measurement show existence of several maxima of absorption in visible and UV-areas: legible peak in the field of 305-315 nanometers and two weak shoulders to areas 405 and 480 nanometer respectively. The first maximum is probably caused by cooperative absorption, the main contribution to which is made by oligomeric condensation products of 5-hydroxymethylfurfural with side chains in $\alpha$-position, which are intensively formed in ethanol in the presence of amine. The absorption maximum in ethanol in the region of 400-410 nanometers may be attributed to substituted pyrrolecarboxaldehydes and it is possible to assume the intermediate formation of the composite chromophore due to substituted pyrrole structure. In FTIR spectra it is possible to note the presence of bands, the reference as to substituted pyrroles, and to furan structures, besides, the bands which are due to oligomeric heterocycles. Its formation can be a consequence of the spontaneous condensation of the furan compounds activated by donor groups initiated by oxygen. The possible pathways of melanoidins structure formation, which are formed in D-lactose - p-toluidine interaction in aqueous-ethanolic solution, are offered based on UV-Vis-spectrophotometry and IR-spectroscopy data obtained. It is shown that carrying out reactions in aqueous-ethanolic (62 % EtOH) promotes the function substituted five-membered heterocycles formation, including condensed as base in structure brown products units.