Effective Moisture Diffusivity and Rehydration Characteristics of Osmo-air Dehydrated Tomato

Abstract

The aim of this study was to investigate the effect of osmotic dehydration on effective moisture diffusivity and rehydration characteristics of osmo-air dehydrated tomato. Sliced tomato samples of Hausa variety of uniform 10 mm thickness were deseeded, blanched at 90^oC and immersed in an honey and sugar hypertonic solution under different levels of osmotic concentrations of 20, 30, 40, 50 and 60^oBx, temperature of 10, 20, 30, 40 and 50^oC and duration of 10, 20, 30, 40, and 50 min. Samples were dried in a hot-air cabinet dryer at 65^oC for 10 hours to reach an equilibrium moisture content of 3-5%, which is considered safe for long term storage. The experiment was designed using central composite design (CCD) of response surface methodology (RSM) of Design expert software version 6.0.6. Statistical analysis and regression models were done using the software at p≤0.05 significance level. Results showed that effective moisture diffusivity (EMD) and rehydration ratio (RR) of Hausa variety of tomato for all samples were between 1.40 x 10^-9 to 4.19 x 10^-8 m²/s and 0.60 – 2.00 respectively. The maximum values EMD and RR of 3.42 x 10^-8 m²/s and 1.81 were achieved at osmotic concentration of 20^oBx, osmotic duration of 42 mins and osmotic temperature of 50^oC respectively, through optimization with  desirability of 83.6%. This would aid faster drying rate thereby preserving more of foods quality parameters, reducing energy consumption and saving time.