Molecular degradation of rice starch during processing to flakes

✍ Scribed by Mujoo, Rajni; Ali, Syed Zakiuddin

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 127 KB
• Volume: 79
• Category: Article
• ISSN: 0022-5142
• DOI: 10.1002/(sici)1097-0010(19990515)79:7<941::aid-jsfa309>3.0.co;2-l

✦ Synopsis

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 ¯aker did not cause any further appreciable change in the proportion of Fraction-I and Fraction-II. Flaking in the roller-¯aker 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 ¯akes but substantially in roller-¯aker ¯akes. 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 l max of the peak of this fraction. When retrogradation was induced in the ¯akes under appropriate conditions of moisture and temperature, the content of the high-molecular-weight Fraction-I of total starch increased slightly in edge-runner ¯akes but markedly in roller-¯aker ¯akes, indicating an aggregation or reassociation of starch molecules or its fractions.