Relating raw rice colour and composition to cooked rice colour

Area of Science:

• Food Science
• Agricultural Science
• Sensory Science

Background:

• Consumer preference and market value of rice are strongly linked to its whiteness.
• Understanding the factors influencing rice color is crucial for the rice industry.

Purpose of the Study:

• To investigate the interrelationships between raw rice color, cooked rice color, amylose content, and protein content.
• To evaluate the predictability of cooked rice color using raw rice color, amylose, and protein content.

Main Methods:

• Colorimetric measurements of raw and cooked rice samples.
• Analysis of amylose and protein content in rice grains.
• Statistical modeling to assess correlations and predictive capabilities.

Main Results:

• Raw rice color showed no significant correlation with protein and amylose content.
• Cooked rice color (L*, a*, b*, C*) exhibited moderate associations with protein and amylose content.
• Cooked rice 'a*' (redness/greenness) was predictable using raw rice color, protein, and amylose, but only for samples cooked uniformly (rice cooker).
• Cooking method significantly impacted cooked rice color.

Conclusions:

• Predicting 'a*' in cooked rice has limited practical value.
• Predicting 'C*' (chroma) was moderately successful only for US-grown rice with controlled postharvest conditions.
• Brightness/whiteness (L*) could not be reliably predicted by any tested models.