Background: The whiter the rice, the more it is preferred by consumers and the more value it has in the market place. The first objective of this study was to determine the interrelationships of raw colour, cooked colour, amylose content and protein content in rice. The second objective was to assess whether or not the colour of cooked rice can be predicted from raw rice colour in conjunction with amylose and protein contents.
Results: Protein and amylose contents were not significantly correlated with the colour measurements for raw rice. Protein and amylose showed moderate, significant associations with L* and a* and a*, b* and C* respectively for cooked rice. Only the colour variable a* of cooked rice could be predicted using protein, amylose and raw rice colour with high enough precision to be useful, and this was only for modelling using samples cooked in the same manner (rice cooker). Cooking method (rice cooker versus excess water) affected the colour of cooked rice.
Conclusion: Being able to predict a* in cooked rice is likely of limited value. Only the model that used samples where postharvest handling conditions were controlled (US-grown rice) was able to predict C*, a more useful measure, and then with only moderate ability. L*, a measure of brightness/whiteness, was not predicted well by any of the models.
Copyright © 2011 Society of Chemical Industry.