Influence of hot air fluidized bed drying on quality changes of purple rice

ABSTRACT

The influence of drying using a fluidization technique on the quality of purple rice was investigated in this study. The results demonstrated that the initial moisture of rice was 28.3% dry basis (db). Compared to the sun-dried or reference purple rice samples, the influence of drying at temperatures ranging from 100 to 150°C did not affect the quality of color, anthocyanin content, total phenolic content, or antioxidant activity. At this initial moisture level, samples should be dried at 150°C air because such temperatures yield the highest drying rate. Drying at this temperature also causes an increase in the head purple rice yield because of the gelatinization of starch. In the case of an initial moisture content of 33.3% (db), the drying temperature should not exceed 130°C.

KEYWORDS:

• Anthocyanin content
• antioxidant activity
• fluidized bed drying
• purple rice
• total phenolic content

Acknowledgments

The authors express their sincere appreciation to Assoc. Prof. Dr. Chanakan Thebault Prom-u-thai from the Purple Rice Research Unit, Department of Plant Science and Natural Resources, Faculty of Agriculture, Chiang Mai University, Thailand for the sample. Thanks also to the Postharvest Technology Program, School of Bioresources and Technology, King Mongkut’s University of Technology Thonburi, and Postharvest Technology Innovation Center, Commission on Higher Education for use of their equipment.