In order to acquire milled rice with maximum removal of PA and minimum losses of weight and minerals, it is imperative to determine the effect of DOM on the contents of PA and mineral elements in rice. This agrees with the objective of the present study which is to optimize the appropriate milling treatment.
For all these cultivars, both the levels of PA and minerals in brown rice decreased as a function of DOM, and the contents showed significant difference (P < 0.05) at different levels of DOM according to Fig. 2. This is in conformity with the previous study ( Itani et al., 2002) that mineral elements (P, K, Mg, Ca and Mn) decreased from the outermost fraction to the inner portion. Moreover, it appeared here that the levels of PA and Mg decreased at a higher rate compared with the other mineral elements. Moreover, the average loss of PA and Mg in the three cultivars increased from 46.94% to 97.05% and 50.92% to 93.41% as the DOM increased from 9% to 25%, respectively. In contrast, milling had little detectable effect on Zn and Se contents. With an increase in DOM from 9% to 25%, the average loss of Zn and Se only increased from 15.60% to 39.36% and 22.84% to 51.07%, respectively. This suggested that PA and macro-elements such as Mg seem to be more highly concentrated in the outer layer, whereas microelements such as Zn and Se seem to be relatively evenly distributed in the grain, followed by the other mineral elements. The results partially agreed with the previous studies reported by Das et al. (2008) and Liang et al. (2008).