真空干燥雪莲果粉玻璃化转变温度与贮藏稳定性研究

Glass Transition Temperature and Storage Stability of Vacuum-dried Yacon Powder

采用差示扫描量热法测定了真空干燥雪莲果粉(YP)和按总固形物质量比为1∶1添加麦芽糊精的雪莲果粉(YP-MD)玻璃化转变温度T g,分别采用GAB模型和Gordon-Taylor方程拟合水分吸附和T g数据,构建YP和YP-MD的状态图,探讨添加麦芽糊精(MD)对雪莲果粉临界水分活度和临界含水率的影响。结果表明,雪莲果粉的T g随着含水率升高而降低,YP的湿基含水率由5.95%增加至30.88%时,T g由15.8℃降低至-72.6℃;YP-MD的湿基含水率由5.11%增加至27.66%时,T g由30.5℃降低至-53.5℃。添加MD显著增加了雪莲果粉的T g。温度25℃时,YP和YP-MD的临界干基含水率为0.0455 g/g和0.0723 g/g,临界水分活度为0.12和0.27。因此,添加MD能显著增加雪莲果粉的临界含水率和临界水分活度,从而提高雪莲果粉的贮藏稳定性。

Differential scanning calorimetry was used to determine the glass transition temperature （T8） of vacuum-dried yacon powder with （yacon： mahodextrin total solid mass ratio of 1：1 ） and without addition of mahodextrin （MD）. GAB model and Gordon - Taylor equation were fitted to the sorption isotherms and Tg data, respectively. The state diagram was constructed to clarify the effect of MD on the critical water activity （CWA） and critical water content （CWC） of YP and YP - MD. The results showed that T8 decreased with increasing water content. Tg decreased from 15.8℃ to -72.6℃ as water content of YP increased from 5.95% to 30.88%. Tg decreased from 30.5℃ to - 53.5℃ as water content of YP-MD increased from 5.11% to 27.66%. Addition of MD significantly increased the Tg of yacon powders. At temperature of 25℃ , the CWC and CWA of YP and YP - MD were 0. 045 5 g/g, 0. 12, and 0. 072 3 g/g, 0.27, respectively. Therefore, the addition of MD could significantly increase the CWC and CWA, and then improved the storage stability of yacon powder.