Feasibility of Using a Multistage Drying Method Including Infrared Heating, Tempering and Sun Drying for Wet Paddy

Abstract

This paper presents the practical multistage drying process of wet paddy with high moisture content in the range of 20 to 30%wet basis. The drying with infrared radiation was firstly used and followed by tempering and sun drying with variation of drying time for 2-6 min, 0-60 min and 180-300 min, respectively, in order to investigate their effects on milling qualities in terms of head rice yield and whiteness index. The response surface methodology was used to analyze the interaction effect of variables. The results showed that the optimum drying time with infrared radiation should not be up to 6 minutes. When overlapping the contour graphs, the superimposed response surface plots showed the boundary conditions in which head rice yield and whiteness index of milled rice were approximately equal to those of reference rice. The testing condition was finally selected to verify the proposed method. The results of milling qualities, cooking properties and pasting properties of tested sample were found to be acceptable.