THERMOPHYSICAL PROPERTIES OF MILLED RICE STARCH AS INFLUENCED BY VARIETY AND PARBOILING METHOD

Rices differing in amylose content and starch final gelatinization tem peratures (GT) were parboiled at 100, 120, and 127-degrees-C to determ ine the formation of amylose-lipid complex I (melting at <100-degrees- C) and complex II (melting at >100-degrees-C), which are observed in m odel systems. In rices parboiled at 100-degrees-C, only the low-GT (<7 0-degrees-C) nonwaxy rices exhibited the amylose-lipid complex I melti ng, without residual (unmelted) starch crystallites. Intermediate-high -GT starches (greater-than-or-equal-to 70-degrees-C), with residual an nealed starch, did not form complex I, nor did waxy IR65. The amylose- lipid complex II melting endotherm was observed in all rices parboiled at 120 and 127-degrees-C. It was highest for IR64 parboiled at 120-de grees-C. Reduction in hot-water-soluble amylose and increase in X-ray diffraction peak at 2theta = 19.9-degrees for V complex corresponded t o Maximum DELTAH of amylose-lipid complex II melting for the pressure- parboiled samples of intermediate-high-amylose rices.