2. Materials and methods
2.1. Materials
Native normal and waxy rice flours were purchased from Patum Rice Mill and Granary Company (Pathum Thani, Thailand). Distilled water, a commercial-grade glycerol product, and analytical-grade chemicals were used in the study unless otherwise noted.
2.2. Heat-moisture treatment
Normal and waxy rice flours were heat-moisture treated using a modified method of Gunaratne and Hoover (2002). The flour moisture content was brought to 20% and 30%, respectively. Flour samples were then quickly transferred to glass jars and tightly sealed. All samples were heated in a hot-air oven (FD 53; Binder GmbH, Germany) at 100 °C and 120 °C for 4 and 16 h. Later, the sample-containing jars were opened and the samples were cooled down at ambient temperature (30 ± 3 °C). The hmt flours were then spread evenly ∼2 cm thick on aluminum trays and dried in a hot-air oven at 40 °C to the moisture content of 10–12%. Later, the hmt flour samples were passed through a 100-mesh sieve and kept in polypropylene bags at ambient temperature.