Browsing by Author "Hii, C.L."

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    Modeling using a new thin layer drying model and product quality of cocoa
    (2009) Hii, C.L.; Law, C.L.; Cloke, M.
    A new semi-theoretical thin layer model for modeling the air drying of cocoa beans with overnight tempering at ambient temperature was developed. The new model was a combination of the Page and twoterm drying model. Results showed that the new model was found best described the drying process under the conditions tested (60, 70 and 80 C). Effective diffusivities were found between 7.46 10 11 and 1.87 10 10 m2/s. The Arrhenius constant and activation energy were estimated at 8.43 10 4 m2/s and 44.92 KJ/mol, respectively. Analyses of pH and cut test for bean quality showed that beans dried at 60 C had lower acidity and good flavour quality as compared to other drying treatments
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    Thin layer drying kinetics of cocoa and dried product quality
    (2009) Hii, C.L.; Law, C.L.; Cloke, M.
    Studies were carried out to investigate the cocoa drying kinetics and compare the quality of the dried beans produced from sun and artificial hot air drying. Currently, these are the methods commonly used by cocoa farmers and plantations to dry cocoa beans. Drying trials were conducted in thin layer using natural sun light and by hot air inside an airventilated oven at air temperatures of 60 C, 70 C and 80 C. Comparison was also made against freeze-dried cocoa beans for quality assessment. The quality attributes assessed were colour (L*, a*, b* and hue angle), texture (hardness and fracturability) and polyphenol content (total polyphenols, epicatechin and catechin contents). Theoretical modelling was performed on the drying kinetics using Fick’s law of diffusion and to determine the effective diffusivity values. Reasonable values were obtained for the coefficient of determination (R2) between the experimental and predicted moisture ratio data (range 0.9845– 0.9976). Effective diffusivity values were found within the range reported in literatures (range 1.61 10 10m2 s 1–8.01 10 11m2 s 1). Quality assessment showed significant differences ( p < 0.05) among the sun dried, freeze-dried and oven dried samples in texture, colour and polyphenol content.