Modelling for moisture variation during osmo-concentration in apple and pineapple

A mathematical model for prediction of moisture content in apple and pineapple during osmo-concentration was developed using both water loss and sugar gain as input variables. The model predicts theoretical maximum water loss from osmotic pressure equilibrium considerations. Using water diffusivity and `sugar-water diffusion quotient' as the primary variables, sugar diffusivity, sugar gain, water loss and moisture contents could be predicted at different temperatures (30, 40 and 50 °C) and concentrations (50, 60 and 70°Bx) of sucrose solution. Theoretical maximum water loss was found to vary between 0.69-0.81 kg water kg slice−1 for apple and 0.64-0.77 kg water kg slice−1 for pineapple. Predicted values of water diffusivity varied between 0.78-3.46 × 10−10 m2 s−1 for apple and 1.90-4.35 × 10−10 m2 s−1 for pineapple. The average value of `sugar-water diffusion quotient' was found to be 3.53 ± 0.652 and 4.07 ± 0.776 for apple and pineapple, respectively. The actual and predicted values of moisture contents in the two fruits were found to have good agreement with a relative deviation percent below 10%.