Osmotic treatments on the cryoprotection of strawberry and kiwi fruit.

摘要

The effect of osmotic treatments with sucrose solutions of different concentrations (35, 45, 55 and 65°Brix), with and without applying a vacuum pulse (50 mbar for 5 min), on different properties related with quality of strawberry and kiwi fruit and on their cryoprotection during frozen stored was analysed. Osmotic dehydration kinetics and the equilibration process between samples and osmotic solution of different concentration have been studied. The effect of osmotic treatments on physicochemical, optical and mechanical properties and volatile fraction of the fruits, when samples reached a determined concentration level (20°Brix in the strawberry and 30°Brix in kiwi fruit) was studied. Likewise, their cryoprotectant effect in terms of the fruit properties preservation and sensory quality was also analysed.;Osmotic treatments implied changes in optical and mechanical properties of strawberry and kiwi fruit. Sample became more transparent and dark without relevant changes on hue colour. Turgor loss associated to dehydration induced changes in mechanical response. Process conditions did not affect notably these physical changes. Osmotic processing promoted volatile formation related to fruit aroma, depending on process conditions. Partial dehydration supposed a better preservation of optical and mechanical properties and drip loss in thawed fruits, with scarce influence of process conditions. In strawberry, pretreatments implied an improved final volatile profile. Sensory tests demonstrated the cryoprotectant effect of osmotic treatments on quality of frozen kiwi fruit.