Combination of rice varieties and cooking methods resulting in a high content of resistant starch

Background and objectives With the interest in increasing resistant starch (RS) of cooked rice, lowering its digestibility has been attempted but not established yet. Herein, we aimed to develop a simple cost-effective method to prepare RS-enriched cooked rice. Various combinations of rice types, cooking methods, and additives were investigated to increase the RS content. Findings The high-amylose cultivar (similar to 28% amylose), retort-type cooking (121 degrees C, 30 min, 15 psi), and brown rice resulted in higher RS content than that of normal rice, conventional cooking, and white rice, respectively. The effect of various food additives in soaking water on additional RS formation was marginal except for citric acid or soybean oil. Conclusions The method for producing RS-enriched cooked rice was successfully established using high-amylose brown rice via soaking in 30-40 mg/ml citric acid solution, retort-type cooking, and drying. Its high RS content is likely due to collective effects from starch retrogradation, amylose-lipid complex, restricted starch swelling/gelatinization by bran layer and non-starch dietary fiber, and chemical cross-linking. Significance and novelty A simple cost-effective method was developed resulting in the highest RS content reported to date for intact cooked rice (7.60%), which can be consumed as-is or as a rice product ingredient requiring low glycemic index properties.