Abstract:

Rough rice was dried with different drying methods to the safe moisture content of 12% (wet base), and head
rice yield (HRY), fatty acid value and RVA parameters were determined after drying process. The results showed that i)
as for single-pass drying, there was a critical tempering duration which could significantly improve HRY, and the critical
temperature was more obvious when the drying temperature was higher; HRY did not reach 70% by extending the tempering
duration when the drying temperature was above 60 ℃ and the moisture content reduction was higher than 9.4%, and
tempering temperature was the same as drying temperature; ⅱ) as for drying-aerating process, the HRY was more than 72%,
especially for drying with high temperature above 60 ℃ and tempering with drying temperature or even higher temperature,
RVA parameters of rice post-drying: the peak viscosity, low viscosity, breakdown value, final viscosity, setback viscosity all
increased with the extension of the tempering time; the higher the drying temperature and tempering temperature were, the
greater the value was, and there were some fluctuations; the influence of tempering temperature on RVA values was more
significant than the drying temperature or tempering duration. The trends of fatty acid value of both drying methods were
different from that of constant low temperature drying process.

Key words: rough rice, single-pass drying, drying-aerating, head rice yield, fatty acid value, RVA parameters