Glycemic response to brown rice treated by different drying media

• Drying rice with SHS exhibited the highest degree of starch gelatinization, followed by HHA and HA drying.
• The extent of the amylose–lipid complex formation related to the degree of starch gelatinization and rice variety.
• The GI values increased when the degree of starch gelatinization was higher than the critical value.
• The HA and HHA are suitable media for drying rice that has low gelatinization temperature.
• The SHS is suitable media for drying rice that has high gelatinization temperature.

During high-temperature treatment, starch is gelatinized and amylose can simultaneously form with lipids to be the amylose–lipid complexes. These complexes can resist to enzymatic attack and useful for decreasing risk of developing type 2 diabetes and cardiovascular disease. The effects of drying media, hot air (HA), humidified hot air (HHA) and superheated steam (SHS), and their operating conditions on drying characteristics and the glycemic index (GI) of three rice varieties i.e. Phitsanulok 2, Kao Dok Mali 105 and RD 31 was therefore investigated experimentally. Drying temperature and drying medium strongly influenced the drying rate, degree of starch gelatinization, amylose–lipid complex formation and the GI value. Rice variety also took an effect on the starch gelatinization and GI value. To obtain the GI value as low as possible, the SHS should be applied to dry rice with high gelatinization temperature while HA or HHA should be used for drying rice with low gelatinization temperature.