Functional properties of carrot slices as affected by blanching in trehalose solutions and frozen storage.

Frozen vegetables represent high added value and convenience. Blanching is a thermal pre-treatment usually applied for stabilizing vegetable products to be stored in frozen conditions. However, this process may induce negative effects on the quality of frozen vegetables by impairing their mechanical, sensory and functional characteristics. The use of thermo- and cryo-protective solutes as trehalose during blanching could positively affect the quality of the final products by reducing the thermal damages induced by the pretreatment and subsequent freezing and frozen storage. The aim of this work was thus to evaluate the effect of trehalose and storage temperature on quality attributes and functional properties of blanched and frozen carrots. Sliced carrots (1 cm) were blanched for 10 min at two temperatures (75 and 90°C), in water (control) and in 4 and 10% w/w trehalose solutions. Samples were frozen at -40°C and stored at -18 and -40°C up to 12 months of storage. The following determinations were carried: texture analysis (recovered energy), total carotenoids, total polyphenols content and radical scavenging activity of both the carotenoid and polyphenolic fractions. Blanching generally caused a significant decrease of the functional compounds under investigation with major effect on the polyphenolic fraction; despite this decrease, the antiradical activity of the phenolic compounds was not impaired by the blanching treatment and was not affected by the presence of threalose. On the contrary, the antiradical activity of carotenoids resulted to be impaired by the blanching treatment even though samples blanched in trehalose solutions resulted to exert higher antioxidant activity. Freezing and frozen storage dramatically affected the mechanical properties of sliced carrots. At both the storage temperatures, the use of trehalose exerted some positive effect on carrots texture. From the functional point of view, both the storage temperature and the use of trehalose affected the antiradical properties and the effect differed as a function of the different pre-treatment applied.