花生壳/仁的吸附等温线与热力学特性  

Moisture Adsorption Isotherms and Thermodynamic Properties of Peanut Shell and Kernel

作　　者：赵亚[1] 张平平[1] 石启龙[1] ZHAO Ya;ZHANG Pingping;SHI Qilong(School of Agricultural Engineering and Food Science, Shandong University of Technology, Zibo 255000, China)

机构地区：[1]山东理工大学农业工程与食品科学学院,山东淄博255000

出　　处：《食品科学》2017年第7期55-62,共8页Food Science

基　　金：国家自然科学基金面上项目(31171708)

摘　　要：为了解花生壳与花生仁的含水率、水分活度(a_w)与温度的关系,提高花生的贮藏稳定性。研究花生壳与花生仁在10、20、30℃时的吸附等温线;探讨花生壳与花生仁的净等量吸附热(q_(st))、微分熵(S_d)、扩张压力、积分熵、积分焓、熵-焓互补、玻璃化转变温度(T_g)等热力学特性。结果表明,花生壳与花生仁的水分吸附呈Ⅲ型等温线。温度一定时,花生壳与花生仁的干基含水率随a_w增加而增加。描述花生壳与花生仁吸附特性的最适模型为GAB模型。花生壳与花生仁的q_(st)与S_d均随含水率增加而降低。扩张压力随a_w增加而升高,但随温度升高而降低。积分焓随含水率增加而降低,而积分熵随含水率增加而升高。花生壳的q_(st)和S_d均高于花生仁,而同一温度条件下花生仁的扩张压力高于花生壳。含水率相同时,花生仁积分焓低于花生壳,而花生仁的积分熵则高于花生壳。花生壳与花生仁水分吸附过程均为焓驱动、自发过程。花生壳与花生仁的T_g随含水率增加而降低,相同含水率时,花生壳的T_g值高于花生仁。根据状态图得到温度为10℃时,花生壳与花生仁的临界水分活度与临界含水率分别为0.80、0.175 4 g/g与0.68、0.095 5 g/g。研究结果可为花生干制工艺及其干制品贮藏稳定性提供理论依据。In order to reveal the relationships between temperature and moisture content and water activity(aw)of peanut shell(PS)and peanut kernel(PK)and thus to improve the storage stability of peanut,the moisture adsorption isotherms of PS and PK were investigated at10,20and30℃by the static weighing method.Thermodynamic properties such as net isosteric heat of sorption(qst),differential entropy(Sd),spreading pressure,integral entropy,integral enthalpy,enthalpyentropy compensation,and glass transition temperature(Tg)of PS and PK were also discussed.The results showed that the water adsorption of PK and PS followed a typical typeⅢisotherm behavior,and the water contents of PK and PS increased with increasing aw.The GAB model showed the best fit with the experimental data.The qst and Sd of PS and PK decreased with increasing moisture content.The spreading pressure increased with increasing aw,and decreased with increasing temperature.The integral enthalpy decreased with increasing moisture content,whereas reverse trend was observed for the integral entropy.Both qst and Sd of PS were higher than those of PK,while the spreading pressure of PK at the same temperature was higher than that of PS.At the same moisture content,the integral enthalpy of PK was lower than that of PS,whereas integral entropy of PK was higher than that of PS.The water adsorption processes of PS and PK were both a spontaneous process driven by enthalpy and Tg of PS and PK decreased with increasing water content,with the former being higher than the latter at the same water content.According to the state diagram,at10℃,critical water activity and critical water content were0.80and0.1754g/g for PS and0.68and0.0955g/g for PK,respectively.These results can provide a theoretical basis for peanut drying and improved storage stability of dehydrated peanut.

关 键 词：花生 吸附等温线 热力学性质 玻璃化转变温度 状态图 

分 类 号：TS255.1[轻工技术与工程—农产品加工及贮藏工程]