Effect of different drying pretreatments of carrot discards on quality characteristics of obtained powder upon storage

Dehydration of fruits and vegetables is carried out for developing new products and long-term storing purposes. There are numerous detrimental reactions taking places while drying techniques, which can be eliminated by applying suitable pretreatment methods. In this study, effect of different pretreatments i.e. hot water blanching with citric acid (pH=4.5), cold water blanching with citric acid, hot water blanching and a control sample (with no pretreatment) were investigated on some quality characteristics of dries carrots . Carrot discards were dried in a cabin dryer at 85 °C with a hot air speed of 1 m/s until 2% final moisture and then powdered. Carrot powder stored for 3 months at ambient temperature of 25 °C. Fibre, ash and moisture content of obtained powders were measured. Phenolic compounds, vitamin C and carotenoids in stored carrot powders were measured in time intervals of 1, 45 and 90 days. Results showed that blanching led to a significant (p<0.05) increase carotenoid content of dried carrots due to the inactivation of pigment degrading enzymes in carrot. Hot water blanching increased phenolic compounds and decreased vitamin C content of dried carrots. However, hot water blanching with citric acid restricted vitamin C destruction process. Carotenoid and phenolic contents of carrot powder significantly (p<0.05) decreased upon storing times. However, blanching pretreatments compared to cold citric acid pretreatment and control diminished such decreasing trend. Concluding, results indicated that blanching pretreatment prior to dehydration of carrot can maintain carotenoids and phenolic compounds of obtained powder.