Kinetics of apparent mass diffusivities on osmotic dehydration of carrots.

摘要

Osmotic drying of carrots was investigated. Effects of 3 concn. of sugar solution (50, 55 or 60%) and 3 temp. (30, 40 or 50 degrees C) were examined. Apparent mass diffusivities of water from carrot samples to sugar solution and that of sugar solutes from sugar solution to carrot samples were estimated following Fick's second law. Kinetic parameters (activation energy (Ea) and Arrhenius constant (Do)) for both the water and the solute diffusion processes were evaluated by fitting the apparent mass diffusivities data to an Arrhenius model. Ea and Do, as functions of concn. of sugar solution were developed and fitted to an Arrhenius model. The ultimate form of Arrhenius model, showing apparent mass diffusivities as a function of temp. and sugar solution concn. was developed. With increases in sugar concn., the apparent mass diffusivities of water increased and that of solute decreased. Drying efficiency increased with increase in sugar solution concn. but decreased with increases in temp. The optimum drying efficiency was achieved at 30 degrees C and using a 60% sugar solution. It is suggested that the apparent moisture and solute diffusivities can be predicted from the developed models with given temp. and osmotic solution concn.