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Chapter 9: Rough-Rice Drying–Moisture Adsoprtion and Desorption

Otto R. Kunze (retired), Texas Agricultural Experiment Station and Texas A&M University, College Station, Texas; David L. Calderwood (retired), U.S. Department of Agriculture, Agricultural Research Service, Beaumont, Texas

RICE: Chemistry and Technology, Third Edition
Pages 223-268
DOI: https://doi.org/10.1094/1891127349.009
ISBN: 978-1-891127-34-9


Rice is usually harvested at a moisture content higher than that at which it can be safely stored and, therefore, must be subjected to some type of conditioning. Drying, the principal method of conditioning rough rice for storage, must be discussed in terms of its relationship to the nature of the grain, high-moisture rice, different types of dryers, and various drying procedures. This chapter emphasizes the hygroscopic character of the rice grain and the handling of high-moisture or field rice, and it shows how ambient air conditions before and during harvest can have a marked influence on subsequent rice quality.

High-moisture rice of a given moisture content and variety is not necessarily uniform from one season to the next, nor from one load to the next within the same season. Head-rice (whole-grain) yields resulting from different lots of rice at the same moisture content and subjected to the same drying treatments may be quite different. Freshly harvested field rice must be characterized for quality so that further quality losses during drying, storing, and milling operations can be credited to the appropriate process or procedure.