Abstract: The low-temperature vacuum drying of natural Gardenia yellow pigment was in vestigated in this paper. Parameters of heating temperature, vacuum, sample concentration and sample thickness were taken as affecting factors. L₉(3⁴) orthogonal experimental design was used to optimized the process. After the dried products reached the homogeneous moisture content, color value(CV), color difference(CD) of the product and drying time were analyzed. It was found that color value, color difference and drying time were significantly affected by the heating temperature. Color value were affected greatly by the sample thickness. Form the comparison experiment of single-factor, drying time for heating temperature at 55℃ was 21.05% shorter than that at 35℃. Sample concentration and the vacuum had relatively less impact on product quality and drying time. The optimal conditions were obtained as follows: heating temperature 45℃, sample concentration 20%, sample thickness 5 mm and the vacuum of 0.09MPa. Under these conditions, the properties of Gardenia yellow pigment powder were:moisture content of 4.35%, color value of 87.8, and color difference of 74.12. The whole drying time was 1360min.

Key words: low-temperature vacuum drying, Gardenia yellow pigment, color value