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Cereal Chem 68:606-609   |  VIEW ARTICLE

Exothermic Transitions in Whole Grain Milled Rice and Milled Rice Flour Studied by Differential Scanning Calorimetry.

W. E. Marshall and F. L. Normand. Copyright 1991 by the American Association of Cereal Chemists, Inc. 

Cooling curves for long, medium, and short grain varieties and very low amylose varieties of whole grain milled rice and their milled rice flours were generated by differential scanning calorimetry at a constant cooling rate of 1.0 C/min. Two successive heating and cooling cycles were run, but data were reported only for the two cooling cycles. Exothermic transitions were produced from all varieties, at least during the first cooling cycle. Exotherms were attributed to the crystallization of amylose-lipid complexes within the starch granule and were quantified by determining enthalpies (DeltaH) for the crystallization process. Exotherm formation during the first cooling cycle was influenced by the amount of rice lipid removed from the kernel or flour, the presence of intact kernel structure, and the amylose content of the rice. In most cases, exotherms were produced during the second cooling cycle and were smaller in magnitude than those originating from the first cooling. The degree of amylose-lipid complex formation during the second cooling was independent of rice lipid, kernel structure, and amylose content. These exotherms appeared to depend only on the particular rice variety examined.

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