USING GREEN DRYING TECHNOLOGY TO MAINTAINHIGHER LEVELS OF ACTIVE COMPOUNDS: AN EXAMPLEOF ROSELLE (HIBISCUS SABDARIFFA L.) DRYING

摘要

In this research, a novel patented Solar Energy-assisted PhotocatalyticClosed-type Dryer (SEPCD) was used to dry roselle (Hibiscus sabdariffa L.). Itwas designed to replace traditional sun drying and hot-air drying, in which thequalities of dried products are easily affected by meteorological conditions andsanitary environment. The operation of SEPCD is to advance the concept of greendrying technology in terms of energy saving, active compounds maintenance andbactericidal effect during drying process. The results showed that, by usingSEPCD at 45°C, the total bacterial count of dried roselle was average below 5CFU/g which is much lower than that dried by commercial hot-air-drying. Theconcentrations of anthocyanins, total polyphenols, and flavonoids were 6.31,22.92 and 8.07 mg/l, respectively, which are higher than those by hot-air drying.