Studies on the influence of the solvent on the contribution of single Maillard reaction products to the total color of browned pentose/alanine solutions - A quantitative correlation using the color activity concept

As recently reported, thermal treatment of an aqueous solution of xylose, alanine, and furan-2-carboxaldehyde (mixture I) led to the formation of a variety of Maillard reaction products, among which four compounds, contributing the most to the brown color, could be differentiated from the less color-active compounds by using the color dilution analysis (CDA) and, thus, be proposed for identification experiments. To study the influence of the solvent on the colored compounds, this screening procedure was applied in the present investigation on colorants formed in the Maillard mixture heated in water/methanol (mixture II). In addition to the four colorants identified in mixture I, three additional compounds were evaluated with high color intensities in mixture II. To evaluate the color impact of these color-active compounds more exactly, their absolute color contribution was measured by correlating quantitative data to the color detection threshold. On the basis of the color activity values (CAVs) obtained, it could be shown that the presence of methanol conversely influenced the color contribution of 1- and 3-deoxyosone-derived compounds and that additional compounds were involved in the overall color of mixture II. By application of this concept, 13.4 or 16.5% of the total color of Maillard mixture I or II, respectively, was shown to be caused by four or seven colorants of known structures.