Influence of sugar composition on water sorption isotherms and on glass transition in apricots

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• 作者：Nadia Djendoubi Mrad^a ; ^b ; ^c ; Catherine Bonazzi^a ; ^c ; Nourhè ; ne Boudhrioua^d ; ^{nourhene.boudhrioua@yahoo.fr} ; ^{nourhene.boudhrioua@fss.rnu.tn} ; Nabil Kechaou^b ; Francis Courtois^a
• 关键词：Sugar composition ; Glass transition ; Sorption isotherms ; Apricots
• 刊名：Journal of Food Engineering
• 出版年：2012
• 期刊代码：67_02608774
• 类别：abs
• 出版时间：July, 2012
• 卷：111
• 期：2
• 页码：403-411
• 文件大小：641 K

摘要

Desorption isotherms of fresh and osmotically treated (70%, 30 掳C) apricots have been measured at 30, 45 and 60 掳C by the static gravimetric method. A differential scanning calorimeter was used to determine the T_g of samples equilibrated with several water activities. The osmotic pretreatment affected the shape of the desorption isotherms because of biopolymer binding at low activities values and dissolution of sucrose at high activities values. At 45 掳C, isotherms of fresh and sucrose impregnated apricots are identical. At 60 掳C, sucrose impregnation depressed water activity, while at 30 掳C the opposite effect is observed. Evolution of moisture content at the first saturation layer expresses these effects of sucrose impregnation and temperature. Peleg model fitted the best experimental desorption isotherms of the fresh and osmotically treated apricots (0.990 猢?#xA0;r² 猢?#xA0;0.999, 0.005 猢?#xA0;S 猢?#xA0;0.045). A strong plasticizing effect of water on the T_g was found, with a great reduction in this value with increase in water activity.