Simultaneous Mass Transfer Processes Research Articles

A Review on Osmotic Dehydration of Fruits and Vegetables: An Integrated Approach

AbstractOsmotic dehydration is a simultaneous mass transfer process which mainly promotes the flow of water molecules from the food to osmo‐active solution and some migration of solutes from the solution into the food, thus maintaining good organoleptic and functional properties in the finished product. This paper presents mechanism of osmotic dehydration and recent developments regarding the factors affecting osmotic dehydration process viz., pretreatment factors (blanching, coating, ultrasound treatment, high pressure processing, pulsed electric field effect, etc.), product‐related factors and osmotic solution related factors (temperature of osmotic solution, concentration of osmotic agent, type of osmotic agent, agitation/stirring process during osmotic process, osmotic solution and food mass ratio). The details on mathematical modeling of mass transfer during osmotic dehydration of foods and benefits of osmotic dehydration which includes energy saving methods and quality of final product are reviewed.Practical ApplicationOsmosis is a physical phenomenon that has been extensively studied in various disciplines of science and engineering. Osmotic dehydration has diverse applications in fruits and vegetables. Thus it can be used to decrease the post harvest losses. Being a simple process, it facilitates processing of fruits and vegetables with retention of initial fruit characteristics viz., colour, aroma, texture and nutritional composition. Since no preservative was used, it does not adversely affect the human body. This process could be used on small scale for development of self‐entrepreneurs and home scale industries. The mathematical models can be used for understanding the mass transfer phenomenon during the process. The economic interest relates to the reduced energy consumption as compared to conventional drying. This review serves to provide an updated status on osmotic dehydration and its research gap which is useful for academics, research purpose and processing industries.

Modeling Mass Transfer Processes in Soil Columns with Pore‐Scale Heterogeneity

AbstractRemoval of dissolved organic compounds from natural porous media is rate limited by multiple, simultaneous mass transfer processes, including slow diffusion from immobile zones of varying sizes and shapes, and rate‐limited sorption. We examined the variability in mass transfer rates and quantified the effects of multiple, simultaneous mass transfer processes on unsaturated column experiments using a diffusion model with a statistical distribution of diffusion rate coefficients. We examined the validity of conventional first‐order mass transfer and diffusion models to represent mass transfer in subsurface systems and compared this with a diffusion model with a lognormal distribution of diffusion rate coefficients. The main conclusions of our work are: (i) even in relatively homogeneous porous media, extreme variability (exceeding four orders of magnitude) in diffusion rate coefficients (Da/a2) must be invoked to represent mass transfer in the experiments we examined; (ii) models using a lognormal distribution of diffusion rate coefficients, while employing only one more mass transfer parameter than conventional models, generally represent mass transfer much better; (iii) single‐rate‐coefficient models (either first‐order or diffusion) very poorly represent mass transfer in all experiments examined, although some of this failure is attributed to our use of a linear isotherm; (iv) models with two diffusion rate coefficients, although containing twice as many estimated parameters, also offer poor representations of mass transfer.