玉米吸湿特性及其等温线类型研究

The Hygroscopic Properties and Sorption Isotherm Classification of Sixteen Chinese Shelled-Corn Varieties

对测定的我国16个玉米品种的水分吸着等温线数据,采用9个水分吸着方程进行拟合,并根据修正4-参数Guggenheim-Anderson-de Boer方程(4-MGAB)派生的指标划分等温线类型。结果表明,CAE、修正Chung-Pfost(MCPE)、Strohman-Yoerger(STYE)、Brunauer-Emmett-Teller(BET)、3-MGAB、4-MGAB、修正Henderson(MHE)及修正的Oswin(MOE)方程均适合拟合测定的玉米水分吸着等温线,而Modi-fied Halsey(MHAE)不适合。MCPE和CAE被认为是玉米较佳水分吸着方程,方程参数MCPE的C1和C2、CAE的b1在不同玉米品种之间、黄玉米和白玉米之间差异不明显。但是,同一玉米品种吸附等温线的方程参数不同于解吸等温线的对应方程参数。另外,根据D10、Rfi、awn、X4指标判断玉米水分吸着等温线类型,16个玉米品种的吸附和解吸等温线均属于S型等温线(Ⅱ)。结果表明玉米水分吸附与解吸的MCPE和CAE方程参数可用于玉米收获后干燥及储藏通风操作。

Equilibrium moisture content （EMC） data for shelled corn of sixteen Chinese varieties were obtained by a static gravimetric method at equilibrium relative humidity （ERH） ranging from 11% to 96% and five tempera- tures of 10, 20, 25, 30, and 35℃. Seven models, namely CAE, Modified Chung - Pfost （ MCPE）, Strohman - Yoerger （ STYE）, Brunauer - Emmett - Teller （BET） , Modified 3 - parameter Guggenheim - Anderson - de Boer equation （ 3 - MGAB ） , 4 - MGAB, Modified Henderson （MHE） , and Modified Oswin （MOE） all fitted well the data, but Modified Halsey （MHAE） did not fit. Both MCPE and CAE were judged as the better moisture sorption equations for shelled corn. Each parameter in MCPE or CAE was similar between yellow and white corn, and insignificant among corn varieties, suggesting the similar hygroscopic properties among corn varieties. However, the parameters C1 and C2 in MCPE and b1 in CAE were significantly different between adsorption and desorption, indicating a hysteresis between desorption and adsorption, thus the desorptive and adsorptive CAE were dividually given. The basic characteristics of shelled corn sorption isotherms were decided by the parameters such as D10, Rfi, awn, and X4. All desorption and adsorption isotherms of sixteen corn varieties belonged to Brunauer＇ s type II sorption isotherm. It was concluded that the parameters of MCPE and CAE for shelled corn adsorption and desorption could be widely used for grain drying and aeration during storage.