Enhancing the retention of -carotene and vitamin C in dried mango using alternative blanching processes

Abstract

The effects of microwave (MW) dry blanching of mango in comparison with conventional water blanching and blanching in closed plastic bags prior to hot air drying (70°C) were evaluated on the retention of vitamin C and β-carotene and on the activity of polyphenol oxidase (PPO) and ascorbic acid oxidase (AAO) enzymes. Blanching conditions for MW and water blanching were 2 min at 90°C high temperature and short time (HTST) or for 10 min at 70°C low temperature and low time (LTLT). PPO was completely inactivated by the blanching treatments, while low AAO activity remained. High retentions (~100%) of vitamin C were found in dried mango after blanching treatments HTST with MW and blanching in closed plastic bags, while lower retention was observed after LTLT with MW (81.8 ± 4.5%), and conventional water blanching 86.7 ± 2.6% (HTST) and 78.6 ± 2.5% (LTLT). Blanching resulted in partial oxidation of L-AA into dehydroascorbic acid (DHAA). Lower retention of all-trans-β-carotene was obtained in MW and HTST water blanched dried mango (82 to 90%) compared with LTLT water blanched dried mango (~100%). In all dried blanched mango samples the levels of 13-cis-β-carotene isomer increased. A slight darkening of colour was observed only in conventional blanched mango samples.