ASSESSING THE APPLICABILITY OF VACUUM MICROWAVE DRYING PROCESS BY THE CHANGES OF NUTRITIONAL COMPONENTS IN PURPLE SWEET POTATO

Abstract

Microwave vacuum drying is one of the most advanced drying techniques being investigated recently for applying. In the microwave vacuum drying process, the material is heated by electromagnetic energy, under vacuum conditions. This report presents the results of research on the effect of microwave vacuum drying on drying time, total sugar content, and protein content of purple sweet potato under different conditions of vacuum pressure (65, 75, 85 kPa) and microwave power (80, 240, 400 W); compared with hot air convection drying process when the same samples at moisture content ≤ 5.0%. The results show that vacuum pressure and microwave power affect the samples' total sugar and protein content after drying. The maximum total sugar and protein contents were 13.46 g and 3.27 g, respectively, at a microwave power of 80 W, the vacuum pressure of 85 kPa. The vacuum microwave dried purple sweet potato samples had lower total sugar and protein losses than those dried under forced convection drying by hot air with a significant difference (p ≤ 0.05)