Effect of blanching and osmotic pre-treatment on drying kinetics, shrinkage and rehydration of chayote (Sechium edule) during convective drying

Abstract

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 (R2= 0.9993) and brine-treated (R2= 0.9991) chayote while Midilli et al. model best described the blanched chayote (R2= 0.9970). Effective moisture diffusivities ranged from 1.09 x 10-8 m2s-1 and 1.30 x 10-8m2s-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