Measurement of resistant starch content in cooked rice and analysis of gelatinization and retrogradation characteristics

Abstract

Digestion-resistant starch (RS) has many physiologic functions. The RS content is measured by enzymatically degrading flour samples according to the method of the Association of Official Analytical Chemists. Experiments have been performed with wheat, corn, and other grains, but there are no data for cooked rice grains in the form ingested by humans. Thus, we investigated a method to measure RS that is suitable for cooked rice grains using rice cultivars that are reported to differentially increase postprandial blood glucose in humans. Using a method for cooking individual rice grains and optimized enzyme reaction conditions, we established an RS measurement method. We also found that the amylopectin crystal condition affects the RS content measured using our method.

Graphical abstract

The order of RS content measured by our method that optimized the sample form and enzyme reaction time is consistent with that of digestibility in humans.

Key words:

• resistant starch
• rice
• retrograde
• cooked rice grain
• amylopectin

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

Abbreviations: RS, resistant starch; DSC, differential scanning calorimetry