Thermal characteristics and state diagram of extruded instant artificial rice

Abstract

Instant artificial rice was developed by extrusion method using corn flour, glycerol monostearate (GSM), and glucomannan and guar gum. Moisture sorption isotherm and thermal characteristics of the artificial rice with glucomannan and guar gum were measured and modeled to develop different regions of a state diagram. The freezing point, glass transition, and solids-melting were measured and modeled by Chen’s model, modified Gordon–Taylor model, and Flory–Huggins model, respectively. The ultimate maximal-freeze-concentration conditions were found as (Tm′)u (i.e., annealed end glass transition temperature for the sample with moisture 0.40g/g sample) equal to −8.3°C and (Tg‴)u (i.e., annealed onset glass transition temperature for the sample with moisture 0.40g/g sample) equal to −8.4°C, and the characteristic solids content, Xs′ as 0.76g/g sample (i.e., un-freezable water, Xw′ equal to 0.24g/g sample). Similarly the characteristic glass transition temperature, Tgiv (i.e., intersection of vertical line passing through Tm′ and glass transition line above Xs′) was estimated as 29.8°C.