Rice millers aim for maximizing HRY and whiteness for
maximum profitability. The present study was undertaken
with the objective to quantify reduction in HRY and variation
of whiteness during milling in relation the physicochemical
properties of the selected Thai rice varieties.
The reduction in HRY during milling was found be best
represented by a non-linear power model with R2 of fitting
ranging from 0.974 to 0.997 and the RMSE values of less
than 1.0% for the selected rice varieties. The regression
parameters of the model were found to be the function of
physicochemical properties of the milled rice. The HRY
during milling of selected rice varieties could be estimated
from their physicochemical properties within ±10% of
the actual values using the developed relationships
kernel whiteness of milled rice increased with the milling
duration with an increasing rate in the beginning followed
by a diminishing rate and heading towards an asymptotic
value. The relationship could be satisfactorily modeled by
a non-linear relationship with R2 of fitting ranging from
0.972 to 0.998 and the RMSE of 0.3–1.0 WI for all selected
varieties. It was found that the model parameters of the
developed relationship were the function of physicochemical
properties of the selected rice varieties. It was possible
to estimate the whiteness using physicochemical properties
satisfactorily within ±5% of the actual values. Thus it
could be concluded that the milling characteristics, namely,
HRY and kernel whiteness could be estimated from the
physicochemical properties of the rice.
This result could be used by rice millers in deciding the
cut off milling time for maximizing HRY and whiteness
combination of the milled rice for different varieties varying
in the physicochemical properties. These two properties
decides the price of the milled rice.