| 费颖昌,穆宏磊,陈杭君,牛犇,刘瑞玲,郜海燕.山核桃吸附-解吸等温线及平衡水分研究[J].保鲜与加工,2023,23(12):18~29 |
| 山核桃吸附-解吸等温线及平衡水分研究 |
| Determination of Water Adsorption-Desorption Isotherm and Moisture Balance in Pecan |
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| DOI： |
| 中文关键词: 山核桃 吸附-解吸等温线 热力学性质 安全贮藏 低场核磁 |
| 英文关键词:pecan adsorption-desorption isotherm thermodynamic properties safe storage low field nuclear magnetic resonance |
| 基金项目:国家重点研发计划课题项目（2021YFD2100502）；浙江省农业科学院地方科技合作项目（CA202107）；浙江省“高层次人才特殊支持计划”科技创新领军人才项目（2022R52025） |
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| 中文摘要: |
| 以带壳山核桃和山核桃仁为试材，采用静态称量法测定带壳山核桃和山核桃仁在25、35、45 ℃的吸附-解吸等温线，并采用等温线数学模型进行拟合，测定其热力学参数。采用低场核磁研究不同水分活度下带壳山核桃和山核桃仁中的水分结合状态。结果表明：带壳山核桃和山核桃仁的吸附与解吸等温线属于Ⅱ型，GAB模型拟合精度最高。带壳山核桃和山核桃仁的净等量吸附热、微分熵和积分焓均随含水率的增加而降低，积分熵随含水率的增加而上升，扩张压力随水分活度的增大而上升，并随温度的上升而下降。带壳山核桃的净等量吸附热、微分熵和积分焓均大于山核桃仁，而积分熵则相反。因此，带壳山核桃的贮藏稳定性较高，而山核桃仁易于干燥。根据安全水分活度可以得出带壳山核桃和山核桃仁的安全贮藏含水率分别为7.38%和5.61%。此外，根据解吸过程净等量吸附热可以得出，带壳山核桃和山核桃仁含水率分别低于14%和12%时需提供更多的热量以维持脱水速率。低场核磁结果表明，在高水分活度下，水分子主要以自由水和不易流动水状态存在，在低水分活度下，水分子主要以结合水状态存在。 |
| 英文摘要: |
| Adsorption-desorption isotherms and thermodynamic properties of solid substrates are the crucial factors for optimizing drying and storage conditions. The adsorption-desorption isotherms of pecan in shell and pecan kernel at 25 ℃, 35 ℃ and 45 ℃ were investigated by static weighing method and fitted with mathematical models. Net isosteric heat of sorption (qst), differential entropy (ΔSd), spreading pressure (Φ), integral enthalpy (ΔHin) and integral entropy (ΔSin) were measured. The moisture bound state of pecan in shell and pecan kernel under different water activity (aw) was determined by LF-NMR. The result showed that the adsorption-desorption isotherms of pecan in shell and pecan kernel followed a type Ⅱ, and the best fitting model was GAB model. The qst, ΔS and ΔHin of pecan in shell and pecan kernel decreased with increase of moisture content, while the ΔSin increased with the increase of moisture content. The Φ increased with the increase of aw and decreased with the increase of temperature. The qst, ΔS and ΔHin of pecan in shell were higher than that of pecan kernel, while the ΔSin was opposite. Therefore, pecan in shell was easy to store andpecan kernel was easy to dry. According to the safe aw, the safe storage moisture content of pecan in shell and pecan kernel were 7.38% and 5.61%, respectively. In addition, in accordance with the qst of desorption, more energy was needed to maintain the dehydration rate when the water content of pecan in shell and pecan kernel was less than 14% and 12%, respectively. Moisture existed as free water and semi-bound water in high aw and was dominant by bound water inversely, verified by low field nuclear magnetic resonance. |
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