Glass transition effects on milling yields in a cross-flow drying column

ABSTRACT

Drying treatments were selected based on the glass transition temperature of rice kernels and applied in an experimentally simulated drying column. When kernels were dried in the glassy state, there was negligible head rice yield reduction (HRYR), regardless if samples had been tempered or not. But when kernels transitioned to the rubbery state during the initial stages of drying and subsequently developed sufficient intra-kernel material state gradients, significant HRYRs occurred, and HRYRs of tempered samples were significantly less than those of non-tempered samples throughout the column. Sample HRYRs near the heated-air plenum were much greater than those into the column.

KEYWORDS:

• Drying
• glass transition
• head rice yield
• milling yield
• rice quality
• rough rice

Acknowledgments

The authors express their gratitude to Redentor Mijares Burgos and Joanne Baltz-Gray of the University of Arkansas Rice Processing Program for their assistance with processing samples. The authors thank the Arkansas Rice Research and Promotion Board and the corporate sponsors of the University of Arkansas Rice Processing Program for financial support of this project.