Predicting color kinetics during red Asian ginseng (Panax ginseng) preparation

A red Asian ginseng preparation was prepared as follows: fresh Asian ginseng (Panax ginseng) roots were first steamed for half an hour to several hours, and then the steamed roots were dried into died roots (red Asian ginseng, 10% moisture content, on a dry basis). During steaming, the color of ginseng (white) turned yellow and brown during subsequent steaming. Color is an important index for grading red Asian ginseng. In this study, the effects of drying time and temperature on the surface color formation (L, a/b) of the Asian ginseng, and the color formation (L, a/b) of the red Asian ginseng powder were investigated. The value of L decreased, while the value of a/b increased as drying proceeded; the value of L was slightly influenced by the drying temperature, but the value of a/b was markedly influenced. With respect to the color of the final product (red ginseng), the value of L was slightly influenced by steaming time and temperature, while the value of a/b was increased as steaming time and drying temperature increased. Based on the nth-order rate equation and Arrhenius equation, a kinetic model for describing these effects was established, and the results were satisfactorily fitting.