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Molecular degradation of rice starch during processing to flakes
Author(s) -
Mujoo Rajni,
Ali Syed Zakiuddin
Publication year - 1999
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/(sici)1097-0010(19990515)79:7<941::aid-jsfa309>3.0.co;2-l
Subject(s) - starch , roasting , fraction (chemistry) , amylose , fractionation , solubility , parboiling , retrogradation (starch) , food science , chemistry , extrusion , amylopectin , moisture , materials science , chromatography , organic chemistry , composite material
Roasting of the soaked paddy (roasting‐parboiling) appeared to cause an increase in the proportion of the high‐molecular‐weight component of starch, separated in Fraction‐I, probably due to retrogradation. The solubility of starch also decreased. Flaking of roasted‐parboiled paddy in the traditional edge‐runner flaker did not cause any further appreciable change in the proportion of Fraction‐I and Fraction‐II. Flaking in the roller‐flaker unit, on the other hand, caused a decrease in the proportion of Fraction‐I, indicating molecular breakdown of starch. The total starch solubility increased marginally in edge‐runner flakes but substantially in roller‐flaker flakes. Fractionation of starch that was soluble in hot water showed that the major amount of amylose equivalent resided in this portion as revealed by a higher proportion of Fraction‐II and a high λ max of the peak of this fraction. When retrogradation was induced in the flakes under appropriate conditions of moisture and temperature, the content of the high‐molecular‐weight Fraction‐I of total starch increased slightly in edge‐runner flakes but markedly in roller‐flaker flakes, indicating an aggregation or reassociation of starch molecules or its fractions. © 1999 Society of Chemical Industry