Effect of selected pretreatments prior to drying on physical quality attributes of dried mango chips
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This study investigated the effect of pretreatments namely citric acid, lemon juice and blanching on the physical attributes of dried chips from two popular commercial mango varieties grown in Kenya viz ‘Apple’ and ‘Ngowe’. The pretreated mango chips were either subjected to a convective dryer or solar drying. Moisture content, extent of dryness, rehydration characteristics, water activity and color retention were determined to establish the effect of the pretreatments before drying on physical quality attributes of dried mango chips. Moisture content, water activity and color were determined using standard procedures. Equilibrium relative humidity was estimated using Drycard™. Results obtained indicated that optimal drying was achieved with dryer temperatures of 50 °C and 65 °C for 10 and 7 h respectively that reduced moisture content to ~ 11% and water activity to below 0.65 (sufficient for inhibited spoilage). The best color parameters and rehydration characteristics were observed with 1% citric acid and 0.5 v/v lemon acid pretreated samples. Blanched as well as control (untreated) samples showed relatively poor color retention in relation to flesh mango chips and had the least rehydration ratio (1.65 ± 0.01) and coefficient of rehydration (0.33 ± 0.1). As pretreatments before drying affect physical parameters of dried mango chips, the best choice of pretreatments should be made to produce high quality end products. Citric acid and lemon juice pretreatments before drying at 50 °C and 65 °C had the optimal outcome and produced the best physical quality parameters.
KeywordsFruits Drying Equilibrium relative humidity Moisture content Dehydration Mango
The authors wish to acknowledge the financial assistance by the Rockefeller Foundation supported Postharvest project through the University of Nairobi and the German Academic Exchange Service [DAAD (Personal Ref. No: 91636877)].
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