干制“储良”龙眼吸附等温线与热力学特性研究  

Adsorption isotherms and thermodynamic characteristics of dried ’Chuliang’ longan

作　　者：马兴灶 连海山 吕莹 郑丹娜 MA Xingzao;LIAN Haishan;L Ying;ZHENG Danna(School of Mechatronic Engineering, Lingnan Normal University, Zhanjiang 524048, China)

机构地区：[1]岭南师范学院机电工程学院

出　　处：《食品与发酵工业》2019年第19期98-103,共6页Food and Fermentation Industries

基　　金：国家自然科学青年基金项目(51705228);广东省教育厅青年创新人才类项目(2017KQNCX123);湛江市科技专项(2017A03013);岭南师范学院人才专项(ZL1806)

摘　　要：为考察干制“储良”龙眼含水率与水分活度、贮藏温度之间的关系,以及探讨净等量吸附热、焓变、熵变和自由能等热力学特性,采用静态称重法,测定干制“储良”龙眼在20、30、40 ℃和水分活度为0.113~0.946条件下的吸附平衡含水率,并绘制其吸附等温线。采用6种常用的农产品吸附模型,对实验结果进行拟合分析。结果表明,干制“储良”龙眼的水分吸附呈Ⅲ型等温线,Halsey模型是描述吸附等温线的最适模型。热力学特性结果表明,净等量吸附热随含水率的升高而降低,当平衡含水率 M e大于30%d.b.(干基)时趋近于0;净等量吸附热与焓变相等,其范围为0.2~467.69 kJ/mol;熵变随含水率的增加而降低,但温度对其影响不显著;干制“储良”龙眼的水分吸附过程可用焓-熵互补理论解释,此过程是焓驱动过程。研究结果可为“储良”龙眼的加工、包装和安全贮藏提供参考。In order to investigate the effects of water activity and storage temperature on moisture content, and to explore the thermodynamic characteristics of net adsorption heat, enthalpy, entropy and free energy of dried ‘Chuliang’ longan. The static weighing method was used to determine equilibrium moisture content of dried ‘Chuliang’ longan at 20, 30, and 40 ℃ with a range of water activities from 0.113 to 0.946. The adsorption isotherms were plotted and the experimental results were fitted by 6 commonly-used agricultural products adsorption models. The results showed that the moisture adsorption isotherm of dried ‘Chuliang’ longan was type III and the Halsey model was most suitable for describing adsorption isotherm. In addition, the net adsorption heat decreased with the increase of moisture content and approached to zero as equilibrium moisture content was higher than 30%d.b.(dry basis). The net adsorption heat was equal to the enthalpy changes, which ranged from 0.2 kJ/mol to 467.69 kJ/mol. Changes of entropy values decreased with the increase of moisture content, while temperature showed no significant effect. The water adsorption process of dried ‘Chuliang’ longan could be explained by enthalpy-entropy complementarity theory, which was driven by enthalpy. The results provide a reference for the processing, packaging and safe storage of ‘Chuliang’ longan.

关 键 词：龙眼 贮藏 吸附等温线 热力学特性 平衡含水率 

分 类 号：TS255.3[轻工技术与工程—农产品加工及贮藏工程]