| Summary: | In recent years, many dried fruit products have been developed in response to a strong demand by the customer. This type of fruit has a different composition and hence different moisture diffusivity (D). During drying, Fick's Law of diffusion, which describes the movement of liquid water was used to calculate this diffusivity. However diffusivity has strong effects on the material drying characteristics and these must be determined. In this paper, Fick's Law of diffusion with different kinds of boundary conditions was solve using separation of variable (SOV). In order to get the value of D, results obtained using SOV will be compared with the results from the drying of belimbi at temperature of 40°C, 50°C and 60°C. Although the results show that variation in the values of diffusivity for different temperatures is relatively small, but the variation in the total time required for drying is significantly bigger: between 3-7 hours. Its shown that diffusivity is an important measurement and should be considered in the modeling of the drying process. The chemical properties of belimbi slices in terms of Vitamin C, total ash and antioxidant activity with different air temperatures and pretreatment were also investigated. Higher drying temperatures gives less drying time, a lower Vitamin C and antioxidant activity but a greater total of ash, whilst pre-treatment can increased Vitamin C and antioxidant activity. The results show that pre-treatment and the drying temperature are important variables to improve mass and heat transfer, as well as the belimbi chemical properties. © Published under licence by IOP Publishing Ltd.
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