Studies on the texture of cooked rice. III. Varietal differences in the texture of cooked rice.

Abstract

Ninety seven rice cultivars including nonglutious and glutinous rice both of japonica and indica subspecies were investigated to clarify the varietal influence on the textural parameters of cooked rice. A General Foods Texturometer was used for the analysis of the physical parameters. Value of chewiness which is well expressive of hard character of cooked rice was very high in indica nonglutinous rice especially in long kernel varieties. Stickiness which generally represents a sticky character of cooked rice, on the other hand, was highest in japonica lowland varieties and it's followed by japonica upland and indica lowland varieties. Glutinous rice showed exceedingly low value of chewiness and high stickiness, although varietal differences in the textural parameters among the glutinous rice groups were rather small. Textural palatability index (TPI) which has been thought to be indicative or eating quality of cooked rice was high in japonica rice and very low in indica rice. The order of TPI value among the nonglutinous variety groups was japonica lowland > japonica upland > indica short culm > indica medium kernel > indica long kernel. In the japonica lowland groups, early maturing varieties had a rather higher TPI than the intermediate or late maturing varieties. Chewiness as a whole negatively correlated with stickiness. Length-width ratio of kernel positively correlated with chewiness and negatively correlated with stickiness and TPI. In nonglutinous varieties, hundred kernel weight showed a negative correlation with chewiness and a positive correlation with stickiness and also with TPI.