The glass transition temperature and expansion behavior of rice extrudates.

• Main Authors: Chia-Mao Chen, 陳家茂
• Other Authors: An-I Yeh
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/46589105142159457084

博士 === 國立臺灣大學 === 食品科技研究所 === 89 === This study was to investigate the expansion behavior of rice pellets. To understand the role of amylose content, three different flours (TS10, TG9, TSG1)and reconstituted flour from TS10 and TSG1 were used to prepare pellet by single screw extrusion at 50% feeding moisture. The Tg and Te of pellets were determined using DSC and non-contact infrared thermometer, respectively. The results showed that amylose content did not significantly affect Tg and Te. But the increase in amylose content results in the decrease in both transparency and expansion ratio. The pellet exhibited maximum expansion ratio at equilibrium moisture of 10%. Addition of dextrin resulted in the decrease in intrinsic viscosity, Tg and Te. The addition of dextrin and increase in feeding moisture resulted in more transparent pellet with higher expansion ratio. The data illustrated that the transparency can be an index of quality control. Te increased linearly (r2=0.95) with Tg, which appeared to be a good reference temperature for studying expansion behavior. Te was about 20~100℃ higher than Tg. The expansion appeared to occur at rubbery state. The Tg of binary-mixture pellet (rice flour, water) can be estimated by using Gordon-Taylor equation. The method to estimate Tg for ternary-mixture pellet ( rice flour, dextrin, water) has also been discussed. Heating method affected the temperature rising rate and water loss rate, which were important factors affecting the expansion of pellet. High temperature rising rate softened the pellet that can be expanded by the pressure exerted by water vapor. Low temperature rising was not able to generate flexible material resulted in burned out of the pellet. The established of phase diagram would be helpful to understand the roles of Tg, Te and heating method on expansion of pellet.