title: Turmeric (Curcuma longa L.) drying: an optimization approach using microwave-vacuum drying.
abstract: This study investigated the effect of microwave power (2,400-4,000 W) and drying times (10-30 min) on the quality of dried turmeric in terms of colour (L, a*, b*), moisture content, water activity (aw), ash, antioxidant activity (2,2-dipheneyl-1-picrylhydrazyl; DPPH), total phenolic and curcuminoids content. In addition, Response Surface Methodology (RSM) was implemented to optimize the drying conditions for turmeric. A range of quality parameters, microwave power (W) and time (min) were fitted to quadratic models using a central composite design. The Analysis of Variance (ANOVA) statistic results suggested that the optimal qualities (i.e., aw, value, moisture content, phenolic content, curcuminoid content and EC50 and L value) of dried turmeric were achieved at high vacuum-microwave power (3,500-4,000 W) and long duration (27-30 min). The improvement in the quality of dried turmeric microwave-vacuum drying in these conditions was illustrated through the enzymatic browning reaction via inhibition of polyphenol oxidase which suppressed the formation of the brown pigments and increased the phenol substrates.
authors.affiliation: Division of Food Science and Technology, Faculty of Agro-industry Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Sathira
authors.initials: S
authors.lastname: Hirun
authors.affiliation: Division of Product Development Technology, Faculty of Agro-industry Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Niramon
authors.initials: N
authors.lastname: Utama-Ang
authors.affiliation: School of Environmental and Life Sciences, University of Newcastle, Ourimbah Campus, Ourimbah, NSW 2258 Australia.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Roach
keywords: Curcuminoids; Dehydration; Microwave-vacuum; Optimization; Turmeric