Effect of Blanching and Osmotic Pre-treatmenton Drying Kinetics, Shrinkage and Rehydrationof Chayote (Sechium edule) duringConvective Drying

摘要

Aims: The influence of brine pretreatment and blanching on drying kinetics, area shrinkage and rehydration of oven-dried chayote slices was investigated.Study Design: Completely Randomized Block Design.Place and Duration of Study: Food Processing and Engineering Division of the Food Research Institute between January 2012 and February 2013.Methodology: Chayote slices (4±1 mm thick) were blanched in hot water at 80oC or osmo-dehydrated in 10% brine for 3 min, or left untreated as control and subsequently dried at 65oC. Shrinkage of dried samples, rehydration ratio and effective diffusivity of samples were determined. Experimental drying data was fitted by non-linear regression to 10 selected thin layer drying models.Results: Modified Henderson and Pabis model gave the best fit for untreated chayote (R~(2)= 0.9993) and brine-treated (R~(2)= 0.9991) chayote while Midilli et al. model best described the blanched chayote (R~(2)= 0.9970). Effective moisture diffusivities ranged from 1.09 x 10~(-8) m~(2)s~(-1) and 1.30 x 10~(-8)m~(2)s~(-1), rehydration ratios over a period of 270 min decreased from blanched > control > brine-treated while shrinkage was highest in blanched samples and lowest in brine-treated samples.Conclusion: Blanching and osmo-dehydration in brine pre-treatment prior to oven-drying affect the drying kinetics, shrinkage and rehydration parameters of chayote slices.