Influence of moisture, particle size and pulse flour composition on phase transition behavior of rice flour.

Study on the phase transition characteristics is an important parameter in extrusion processing. The influence of Moisture Content (MC), particle size and level of cereal-pulse blend on the glass transition (Tg) and melt (Tm) temperatures of a ready to eat cereal-pulse formulation was determined. All samples were moisture conditioned in a 9 to 27 % with 3 % interval. Tg and Tm were measured by phase transition analyser (PTA). A substantial decrease in Tg and Tm was observed as moisture content level increased from 9 to 27 %. However Tg and Tm values could not be clearly defined below 9 % moisture content and above 27 % moisture content. The Tg and Tm values of the cereal-pulse formulation were found to be increased with increasing pulse composition (5 to 30 % with 5 % interval). Increase in particle size (150, 180, 212, 300, 425 and 500 μ) exhibited significant increase effect on Tg while less significant effect on Tm. This may be due to crystalline regions which play a role in cross linking amorphous regions of the polymeric network and thus suppress the mobility of amorphous regions. The observed differences in Tg and Tm induced by the moisture content, concentration of Bengal gram and particle size will be useful in simulation and optimization of barrel temperature set during extrusion processing.