MICROSCOPY OF RICE STARCH GRANULES DURING COOKING

Starch from five cultivars of rice was pasted in the Brabender viscograph and then held al 95 degrees C for 60min. Granules were examined by light and scanning electron microscopy. In concentrated (12%) pastes,low-amylose rice starch showed total granule disintegration after 60min of cooking at 95 degrees C, but highamylose granules showed only marginal disorganization, Waxy starch granules were disintegrated even at 70 degrees C. In dilute (1%) pastes, on the other hand, granules swelled without appreciable disruption, apparently more in low than in high amylose starch. Clearly low amylose starch granules were weak and fragile and so swelled as well disintegrated easily, while high amylose rice starch was relatively strong and rigid and so resisted swelling as well as disintegration. This relative rigidity/fragility of starch granules seemed to be the key to differences in rice quality.