Changes in mechanical properties throughout osmotic processes: Cryoprotectant effect

Abstract In osmotic dehydration of fruits, physical and chemical changes occurring throughout the process provoke changes in the product texture and appearance to a different degree depending on the process conditions and product characteristics. Nevertheless, water content reduction and sugar gain have been observed to have some cryoprotectant effects on colour and texture in several fruits. In this work, the specific influence of osmotic treatments with sucrose solutions at 30°C on mechanical properties of mango, kiwi and strawberry are discussed. The combined effect of blanching and vacuum impregnation is analysed in mango. The influence of osmotic solution concentration and vacuum impregnation on kiwi fruit is discussed and the effect of osmotic dehydration, as compared with air drying is analysed in strawberry. In all cases, changes in mechanical properties of fresh and pre-dehydrated fruits due to freezing–thawing are compared in order to quantify the cryoprotectant effect of the osmotic treatment.