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Abstract

The drying behavior of the dashecn leaf under natural convection conditions at temperatures ranging from 40-70<>C was studied in an attempt to develop a dehydrated product from this popular vegetable often used in soups and commonly called - 'callaioo.' The effects of various pretreatments on the drying behavioral of the vegetable at 60°C were also studied, viz. steam blanching (96°C for 6 min ), water blanching (near boiling for 10s) and blanching in 0.06% magnesium carbonate at near boiling for 10 s prior to immersion in a mixed chemical bath consisting mainly of 20% sucrose, for 4 h at 21°C. Two falling rate periods of drying were observed for dashecn leaves dried at 40-70°C. However, a single falling rate period of drying was found for the water and magnesium carbonate blanched-infused vegetable at 60°C. Although drying rates markedly increased with increasing drying temperature, drying at high temperatures particularly at 60°C and 70°C resulted in a deleterious color change from green, typical of the fresh vegetable, to an unattractive olive-brown or brown discoloration. Steam blanching appeared to have no significant effect on the drying rate of the dasheen leaf compared to fresh leaves while for the water blanched vegetable, the drying rate was reduced by 50%. Compared to water blanching, alkali blanching was found to have no significant effect on the drying rate of the dasheen leaf. Blanching in water or alkali resulted in a superior dehydrated product which, unlike the steam blanched vegetable, showed minimal loss of green color.

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