Abstract:

The effects of four different drying methods on the contents of total flavonoids, total organic acid and ascorbic acid and color were studied to select a suitable drying method for hawthorn. Colorimetry method was applied to determine the content of total flavonoids in hawthorn dried by four drying methods with hyperoside as the contrast; acidbase titration method was used to determine the content of total organic acid with phenolphthalein as indicator; 2,6-dichloro-indophenol titration method was used to determine the content of ascorbic acid and color data were measured by a color difference machine. The results showed that the contents of total flavonoids, total organic acid and ascorbic acid of hawthorn treated by four different drying methods were significantly different. Freeze drying had the highest contents of total organic acid and ascorbic acid(133.25 mg/g and 0.322 4 mg/g, respectively), while sun drying contained the lowest (94.55 mg/g and 0.163 1 mg/g, respectively). Hawthorn dried by microwave had the highest contents of total flavonoids (42.26 mg/g), while sun drying contained the lowest (32.25 mg/g). Vacuum freezedried hawthorn presented the best effect on color. Vacuum freeze drying method could reduce the loss of total flavonoids to a certain extent and showed the best color on the basis of preserving ascorbic acid to the greatest extent.

Key words: drying method, total organic acid, color, hawthorn, total flavone, ascorbic acid