Monitoring for the color formation of a Doraji tea by soaking of threonine and sucrose solution and roasting

摘要

Response surface methodology (RSM) was used for monitoring the changes of Hunter's color and organoleptic colors of roasted doraji tea with variations in threonine concentration of soaking solution and roasting condition. In soaking and roasting processes based on the central composite design with variations in threonine concentration of soaking solution, roasting temperature and roasting time, coefficients of determinations (R~2) of the models were above 0.87 (p<0.05) in Hunter's color parameters and organoleptic color. Hunter's color L value of roasted doragi tea was maximized in 0.09% threonine concentration of soaking solution, 142.37 deg C and 21.94 min in roasting condition. Hunter's color a value of roasted doragi tea was maximized in 1.24% threonine concentration of soaking solution, 154.01 deg C and 28.59 min in masting condition, minimized in 1.67% threonine concentration of soaking solution, 137.61 deg C and 24.62 min in roasting condition. Hunter's color b value of roasted doragi tea was maximized in 1.10% threonine concentration of soaking solution, 154.72 deg C and 27.12 min in roasting condition. The maximum quality of organoleptic color of roasted doragi tea was soaked in 1.25% threonine concentration, and roasted at 141.81 deg C for 34.14 min.