Effects of different color fixative technologies on quality of dried longan

Different color fixatives and technology of heat dump drying were studied to dried longan in this paper. The parameters such as color fixative time，drying temperature and drying time were investigated during longan drying process. Results showed that the total sugar content of dried longan increased with color fixative time extending，and it increased firstly and then decreased with drying temperature increasing. The acidity of dried longan increased firstly and then decreased with the increase of drying temperature and drying time. The color fixative of 1% sodium metabisulfite and 0.5% ascorbic acid was used to inhibit the browning of longan，and the optimal processes of heat pump drying of dried longan were as follows：color fixative time of 4 minutes，drying at 60℃，for 12 h. The dried longan plum had uniform color，the total sugar content was 2.55%，the acidity was 25.7%. Thus，different color fixatives and technologies of heat dump drying had influences on the quality of dried longan，and the optimal technology of heat dump drying of longan was reliable and advisable and the product had better quality using the process.