Differences in Hollow Volumes in Cooked Rice Grains with Various Amylose Contents as Determined by NMR Micro Imaging

The presence of hollows in cooked rice grains found before in the cultivar Koshihikari was confirmed for 4 more cultivars with various amylose contents. The size, shape, and total volume of hollows differed between cultivars. Hollow volumes increased with grain volume and length before 100 °C was reached, but subsequently decreased during prolonged boiling. The previously proposed mechanism, describing sealing by gelatinized starch of cracks formed during soaking, seemed accurate for all 5 cultivars. Based on the hypothetical model of their formation, a relationship between amylose content and hollow formation was assumed. However, no correlation existed between final hollow volume and shape on 1 side and individual parameters such as flour gelatinization and amylose content on the other side.