Cereal Chem 67:7-10 | VIEW
Effect of Lipids on the Retrogradation of Cooked Rice.
Y. Hibi, S. Kitamura, and T. Kuge. Copyright 1990 by the American Association of Cereal Chemists, Inc.
The effect of lipids on the aging process of cooked rice stored at 5 C was studied by measuring enzyme digestibility and X-ray diffraction patterns. For normal rice, simultaneous digestibility with beta-amylase and pullulanase, which is a good measure of degree of gelatinization, increased after 3 hr of storage and then continuously decreased. X-ray diffraction patterns of normal rice immediately after cooking showed a V-type pattern that may be attributed to helical complexes of amylose with lipids in starch. V-type pattern intensity became faint in 5 hr, whereas B-type pattern intensity increased, implying that the starch-lipid complexes were metastable and changed to a more stable structure partly characterized by B-type X-ray pattern via an amorphous state. This can illustrate the way in which lipids affect the retrogradation process of cooked rice. Water-soluble carbohydrates from aged pastes of normal rice starch were also measured and found to increase and then decrease after 5 hr of storage. This may also closely correlate with the behavior of the starch-lipid complex. Gel permeation chromatography of the water-soluble carbohydrates indicated that an increase in solubility by defatting was due not only to the amylose fraction but also to the amylopectin fraction.