食品科学

• 基础研究 • 上一篇    下一篇

糯米粉的水分等温解吸及孔特性

张 华1,2,赵学伟1,2,白艳红1,2,段瑞谦1   

  1. 1.郑州轻工业学院食品与生物工程学院,河南 郑州 450002;2.河南省食品生产与安全协同创新中心,河南 郑州 450002
  • 出版日期:2017-04-15 发布日期:2017-04-24

Water Desorption Isotherm and Pore Characteristics of Glutinous Rice Flour

ZHANG Hua1,2, ZHAO Xuewei1,2, BAI Yanhong1,2, DUAN Ruiqian1   

  1. 1. School of Food and Bioengineering, Zhengzhou University of Light Industry, Zhengzhou 450002, China;
    2. Henan Province Collaborative Innovation Center for Food Production and Safety, Zhengzhou 450002, China
  • Online:2017-04-15 Published:2017-04-24

摘要: 糯米粉的等温解吸特性一方面对分析其与周围环境之间的水分传递十分必要,另一方面,还可用于计算糯米粉内孔的特性,借此加深对水分吸附机理的了解。本实验采用静态称质量法在10、20、30 ℃条件下测定糯米粉在10 个水分活度解吸后的平衡水分含量,然后采用4 个等温吸附模型对实验结果进行拟合,并分析糯米粉的孔特性。研究结果表明:糯米粉中水分的解吸属于典型的Ⅱ型吸附;Lewicki模型最能描述同一温度条件下的等温解吸过程,而GDW模型能够同时描述温度和水分活度对平衡水分含量的影响。糯米粉中同时存在微孔和介孔;孔径分布为单态分布,仅在微孔区域出现一单峰,温度变化仅对该峰的峰值产生影响;微孔体积随温度降低而增大;糯米粉的吸附面具有分形特性,随温度降低吸附表面的多孔性增强,单位吸附面积增大,最终导致吸附能力增强。

关键词: 糯米粉, 解吸, 孔径, 孔径分布, 单位表面积, 微孔体积, 分形维数

Abstract: Water desorption isotherm of glutinous rice flour is necessary for understanding water transfer from it to environment. On the other hand, the isotherm data can be used to explore pore characteristics a solid matrix, which will allow a deeper understanding of water adsorption mechanism. Equilibrium water contents of glutinous rice flour were determined after conditioning to 10 different water activity levels at 10, 20 and 30 ℃ using a static gravimetric method. The obtained desorption data were fitted with four selected isotherm models, and were further mined to estimate pore properties of glutinous rice flour. Glutinous rice flour exhibited a typical type-Ⅱ adsorption isotherm. The Lewicki model performed best in predicting water desorption of glutinous rice flour at a constant temperature, while the GDW model could predict the moisture content as a function of water activity and temperature. The pores in glutinous rice flour included micropore and mesopore. Pore size distribution posed a single peak located in micropore zone whose value increased with the decrease in temperature. Consequently, micropore volume also increased as temperature decreased. The pore surface in glutinous rice flour was fractal in nature. The more porous surface structure and the larger specific surface area at lower temperature contributed to the increased adsorption capacity.

Key words: glutinous rice flour, desorption, pore size, pore size distribution, specific surface area, micropore volume, fractal dimension

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