EFFECT OF COOLING METHODS AND MILLING PROCEDURES ON THE APPRAISAL OF RICE MILLING QUALITY

The objective of this research was to appraise the quality of medium-grain rice as affected by cooling and two different Federal Grain Inspection Service (FGIS) milling procedures. Milled rice quality was measured in terms of total rice yield (TRY), head rice yield (HRY), and whiteness. The cooling study used an internal and an external heat exchanger developed for the McGill No. 3 mill with room-temperature water and ice cooled water as cooling media. Californian M202 rough rice samples of three different qualities were milled using the McGill No. 3 mill with and without cooling following the standard FGIS Western rice milling procedure. The cooling methods increased the TRY and HRY, but decreased whiteness. Every 10°C reduction in the milled rice temperature due to cooling corresponded to an increase of 0.9 percentage points in TRY and 1.7 percentage points in HRY. The rice samples of M202 from California and Bengal from the Southern region milled with the Western milling procedure had lower TRY (1.0 to 1.4 percentage points) and HRY (2.3 percentage points) compared with the Southern milling procedure. Similar quality results obtained using the Southern milling procedure might be produced using the Western milling procedure with heat exchanger cooling.