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Summary The influence of different osmotic solution pretreatments (sucrose and glucose with concentration of 45%) on desorption isotherms and glass transition temperatures (Tg) of mango was investigated. The Peleg model satisfactorily described the relationship between water activity (aw) and moisture content of all samples (0.992 < r2<0.997). The equilibrium moisture content of mangoes osmotically pretreated in sucrose was higher than that of samples pretreated in glucose. Differential scanning calorimetry was used to measure the Tg of samples equilibrated with different aw (0.12–0.75). The dependence of Tg on moisture content was adequately fitted by Gordon–Taylor model (0.946 < r2<0.949). The osmo‐dehydrated mangoes showed lower Tg than fresh samples at the same moisture content. Additionally, the samples osmotically pretreated in glucose showed the lowest Tg value.

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In order to obtain the optimal technological parameters of lettuce vacuum osmotic dehydration, the effects of osmotic temperature, slice thickness, sucrose concentration, and vacuum degree on the vacuum osmotic dehydration were explored. The lettuce water loss rate and solid gain rate decreased with the increase of slice thickness and vacuum degree, and increased with the increase of sucrose concentration and osmotic temperature. Response surface methodology was applied to analyze the infl uence of the four infl uential factors on the evaluated parameters and the optimization of lettuce vacuum osmotic dehydration was studied. The results indicated that, within the experimental scope, the optimized technological parameters of lettuce vacuum osmotic dehydration are the temperature of 28 o C, the slice thickness of 2 mm, sucrose concentration of 47%, the vacuum degree of 22 kPa, and the water loss rate and solid gain rate are 72.16% and 11.82%, respectively.

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