Formation Process of Coffee Brown Pigments during Roast

Abstract

To confirm the formation process of three coffee brown pigments A, B and C, which were produced by thermal reaction between chlorogenic acid and sucrose during roast, the pigments B and C were isolated by Sephadex G-25 column chromatography from roasted coffee beans or the brown product obtained by heating the mixture of chlorogenic acid and sucrose using the model roast method. Pigment B or C was heated at 170°C by the improved model roast method and analyzed to clarify the time course of the change of B or C. Dark brown pigment A was formed from red brown pigment B and B was from yellow brown pigment C. These results show the formation process of three pigments as follows: Moreover, it has been observed that (i) the interconversion of the pigments was ceased when the reaction mixture dried, (ii) retention time of C produced by the model roast method on the Sephadex G-25 column chromatography became smaller as the roast proceeds, and (iii) citric acid in Mcllvain buffer promoted the browning but was not necessary for the formation of three pigments.