Quality improvement of freeze‐dried carrots as affected by sugar‐osmotic and hot‐air pre‐treatments

Abstract

To improve the visual-sensory and nutritional quality of freeze-dried carrots (FDC), the effects of sugar-osmotic dehydration (SO, 40°Brix, 3 h) and hot-air pre-drying (HAPD, 80°C, 10 min) on the FDC quality were investigated. Overall, SO&HAPD significantly improved the redness (8.26% - 11.67%), yellowness (1.24% - 5.82%) and ABTS radical scavenging activity (1.40% - 16.00%) of FDC. FDC pre-treated by sucrose showed the highest a* value (33.31), which was related to the β-carotene content. The influence order of independent variables on the redness was ABTS radical scavenging activity > total sugar content > β-carotene content. As for the carotenoid retention, the sample only treated by HAPD had the highest contents of β-carotene (119.97 μg/g) and α-carotene (93.73 μg/g). These results indicated that SO&HAPD and HAPD were effective pre-treatments for improving the color and carotenoid contents of FDC, respectively. This work provides an experimental-theoretical basis for the quality enhancement of carrot products.