Combined effect of trehalose and storage temperature on mechanical and functional properties of blanched and frozen carrot slices

INTRODUCTION Frozen vegetables represent high added value and convenience. Nevertheless, damages induced on raw matrices by processing may, however, limit their technological, sensory and nutritional characteristics.The use of solutes with thermoprotective and cryoprotective properties may improve the quality of the final products. The aim of this work was thus to evaluate the effect of trehalose and storage temperature on mechanical and functional properties of blanched and frozen carrots. METHODOLOGY 1 cm-thick sliced carrots were blanched (80°C, 10 min) in water (control), and in 1 and 4%w/w trehalose solutions and then frozen at different temperatures (-18, -40 and -80°C) and stored at the same temperature conditions up to 60 days. The following determinations were carried out: water gain/water loss, texture measurements (shear test), total carotenoids content and radical scavenging activity. RESULTS AND DISCUSSION Carrots mechanical properties and carotenoids content resulted to be affected mostly by the blanching treatment rather than the trehalose concentration. Despite the decrease in carotenoids upon blanching, the antiradical activity of the blanched samples was not significantly different in comparison to the fresh one. At all storage temperatures and for all the differently blanched samples a significant decrease of hardness was shown in the first 15 days of storage; longer storage time did not exert any further meaningful effect. At all storage temperature an increase of b-carotenoids content in all the samples occurred (ranking: trehalose 1% > Trehalose 4% > Control > Fresh); the antiradical activity showed an increase over storage time in the control and in the samples blanched in 1% trehalose solutions. CONCLUSIONS Trehalose showed under the tested conditions a limited effect in limiting physical damages of frozen carrots. However, b-carotenoids content and the antiradical activity in blanched frozen carrots seems to be related to a thermoprotective and cryoprotective effect in the vegetable tissue.