Correction of moisture and sucrose effective diffusivities for shrinkage during osmotic dehydration of apple in sucrose solution

• Consideration of shrinkage in the estimation of diffusivity in osmotic dehydration.
• Using the modified form of Fick's second law of diffusion.
• Experimental investigation on slab shape samples of apple.
• Prediction of water loss and solid gain at equilibrium condition.
• Correlation of moisture and sucrose effective diffusivities in apple.

Shrinkage, moisture and sucrose effective diffusivities were correlated for infinite slab shape samples of apple during osmotic dehydration in sucrose solution. Experiments were carried out in the sucrose solutions of different concentrations (30%, 40% and 50%) and temperatures (30 °C, 40 °C and 50 °C). The two parameter model, developed by Azuara et al. (1992), was used to predict water loss and solid gain at equilibrium condition. Moisture and sucrose diffusivities were estimated by fitting the experimental moisture loss and solid gain data to the modified form of Fick's second law of diffusion, considering the shrinkage of the apples during osmotic dehydration. Results showed that the volume of the samples decreased linearly with water loss (WL) and weight reduction (WR). For above conditions of osmotic dehydration, effective diffusivities without considering the shrinkage were found to be in the range of 1.36 × 10−10 m2/s–2.00 × 10−10 m2/s, and those with considering the shrinkage were in the range of 0.87 × 10−10 m2/s–1.27 × 10−10 m2/s. The values of the effective diffusivities estimated by considering the shrinkage were smaller than those without considering this phenomenon.