冻干草莓内部孔隙率的分布及其影响的实验研究  

Experimental study on porosity distribution and its eflect on freeze-dried strawberries

作　　者：肖鑫[1] 陶乐仁[1] 顾茜姣[1] 

机构地区：[1]上海理工大学低温技术与食品冷冻研究所,上海200093

出　　处：《食品与机械》2007年第2期66-69,共4页Food and Machinery

基　　金：上海市教委重点学科项目和上海市重点学科项目(项目编号:T0503)

摘　　要：冻干食品内部是多孔的疏松结构,针对不同预冻结速率和厚度的草莓,进行了冻干实验,采用微型CT扫描仪对冻干样品进行扫描和图像重构,计算得到了孔隙率。测量了冻干过程失水率,冻干后复水比,并且用二甲苯-二氯靛酚比色法测定了冻干前后抗坏血酸的值。结果表明:预冻结速率越快,孔隙率越小,且超速冻(速率大于10cm/h)的孔隙率基本维持在一恒值10%。物料厚度越大,升华干燥速率越慢,孔隙率越大,复水比越大。8mm切片抗坏血酸保持得最好,并且孔隙率越大,抗坏血酸保持率越低。Freeze-dried foods have porous structure. Micro-CT was used to scan freeze-dried strawberries at different pre-freezing rates and thicknesses, porosity was calculated with those reconstruction images. The dehydration ratios during freeze-drying and the rehydration ratios after freezedrying were measured. The content values of ascorbic acid（AA） were determined before and after freeze-drying using dimthylbenzene-two, six-dichlor indophenol＇s colorimetry method. The results showed that, the quicker tha pre-freezing rate, the smaller ths porosity. The porosity at ultra rapid frozen rate （10cm/h） is kept around 10%. When samples were thicker, sublimation rate was slower, porosity was higher, rehydration ratio was higher. 8mm slice could get the best AA retaining rate, and the higher the porosity, the worse the AA retaining rate.

关 键 词：冷冻干燥 草莓 预冻结速率 厚度 孔隙率 抗坏血酸 

分 类 号：TS255.1[轻工技术与工程—农产品加工及贮藏工程]