Relationship between amylose content and expansion characteristics of parboiled rice.

Factors influencing expansion of rice were studied because of the importance of expanded rice as a snack food in India. Rice was soaked, parboiled by steaming at various pressures, and expanded by roasting with sand at 250 degree C for 10-12 s. Expansion ratio was determined from the bulk vol. of 20 g. 7 rice cv. with differing amylose contents were studied. Optimal amylose content for best expansion varied with parboiling condition, increasing with increasing steaming pressure, and was e.g. 21% total amylose for 0.5 kg/cm-2 vs. 28% for 2 kg/cm-2. Highest overall expansion (index 6.5-6.7) was given by 27-28% total amylose and 13.5% water-insoluble amylose.