为研究不同预处理对赛买提杏片热风干燥特性及水分迁移规律的影响,以切分去核的赛买提杏片为原料,在消除酶促褐变的基础上,经4种预处理(热水漂烫、蒸汽漂烫、微波处理及硫处理),探究3个温度(40,50,60 ℃)下的干燥特性、水分有效扩散系数及活化能,并建立干燥动力学模型,研究模型参数与干燥温度间的关系.结合低场核磁共振(LF-NMR)和成像技术(MRI),通过横向弛豫时间和成像伪彩图的变化阐明干燥过程中杏片内部水分迁移规律.结果表明:与40℃相比,经4种预处理的杏片干燥耗时分别缩短41.67％,36.36％,53.85％,50.00％.Deff随着温度的升高而增大,主要在5.9637× 10-7～1.3530×10-6m2/s范围.基于干燥动力学进行模型拟合,漂烫及微波等热处理的最适模型均为Wang and Singh模型,R2分别为0.9929,0.9955,0.9942,而非热预处理的硫处理最适模型为Page模型(R2=0.9967).LF-NMR试验表明干燥前期主要由表面汽化为主,杏片中自由水最先被脱除,干燥后期由内部扩散控制,部分自由水转化为不易流动水和结合水,水分扩散速率降低.护色预处理结合热风干燥对杏片干燥特性及水分迁移均有一定影响.方差分析显示,4种护色处理方式在各温度干燥时Deff无显著差异(P＞0.05),干燥温度对干燥过程中的水分扩散起决定性作用.结合低场核磁共振技术可知,微波和硫处理组杏片至干燥结束,在干燥温度50℃和60℃,干燥时间相较于漂烫处理组可缩短4 h.
Effects of Pretreatment on Hot Air Drying Characteristics and Water Migration of Saimaiti Apricot Slices
To study the drying characteristics and water migration of Saimaiti apricot slices after different pretreatment during hot air drying.Samaiti apricot slices was used as raw material,the drying characteristics,effective diffusion coef-ficient and activation energy of water were investigated at three temperatures(40,50℃ and 60℃)after four kinds of pretreatment(hot water blanching,steam blanching,microwave treatment and sulfur treatment)on the basis of eliminat-ing enzymatic browning,and the drying kinetics model was established.The relationship between model parameters and drying temperature was studied.Further combining with low field nuclear magnetic resonance(LF-NMR)and magnetic resonance imaging(MRI),the lateral relaxation time and pseudo-color images were used to elucidate the water migration in apricot slices during drying.Results showed that the drying time of apricot slices compared with 40℃ was shortened by 41.67％ ,36.36％ ,53.85％ and 50.00％ ,respectively.Deff increased with the increase of temperature,mainly in the range of 5.9637×10 m2/s to 1.3530×10 6 m2/s.For model fitting based on drying kinetics,Wang and Singh model was the most suitable model for blanching and microwave heat treatment,with R2 of 0.9929,0.9955 and 0.9942,respectively,while Page model was the most suitable model for sulfur treatment without thermal pretreatment(R2=0.9967).The results of LF-NMR experiment showed that the surface vaporization was the main factor in the early drying stage,and the free water was the first to be removed.In the late drying stage,the water diffusion was controlled by internal diffusion,and part of the free water was converted into immobilized water and bound water,and the water diffusion rate decreased.Color protection pretreatment combined with hot air drying had certain effects on drying characteristics and water migra-tion of apricot slices.Analysis of variance showed that there was no significant difference in Deff of the four color protec-tion treatments at different temperatures(P＞0.05),and the drying temperature played a decisive role in the water diffu-sion during drying.Combined with low-field NMR technology,the drying time of apricot slices in microwave and sulfur treatment group could be shortened by 4 h at 50 ℃ and 60℃ compared with that in blanching treatment group.
万方数据
维普
