Microscopy of rice starch granules during cooking.

Starch from five cultivars of rice was pasted in the Brabender viscograph
and then held at 95°C for 60 min. Granules were examined
by light and scanning electron microscopy. In concentrated (12%) pastes,
low-amylose rice starch showed total granule disintegration after
60 min of cooking at 95°C, but highamylose granules showed only
marginal disorganization. Waxy starch granules were disintegrated
even at 70°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.