Effect of dehydration techniques on bioactive compounds in hawthorn slices and their correlations with antioxidant properties.

Hawthorn fruits are rich in nutrients and antioxidant compounds. Dehydration is the major processing and preservation method for hawthorn fruits. The rates of moisture loss; polyphenol, flavonoid and triterpenoid acid contents; and antioxidant activities and their relationships were investigated in hawthorn slices that were dried by four dehydration techniques (microwave drying, solar drying, hot air drying and freeze drying) under different operation conditions. The results showed that both the drying method and the processing parameter affected the antioxidants. Microwave drying and hot air drying at high temperatures (≥ 80 °C) resulted in the degradation of the polyphenols, flavonoids and triterpenoid acids in the hawthorn slices. These antioxidant compounds were best preserved by freeze drying and hot air drying at 60 °C. Epicatechin and chlorogenic acid were the major phenolic compounds identified in this research, and these compounds were significantly affected during processing. The antioxidant activities of the hawthorn fruits were significantly related to the total polyphenol, flavonoid and triterpenoid acid contents. Hot air drying at proper temperatures could be suitable for hawthorn slice dehydration processing that conserves the antioxidant properties of the fruit.