The convective drying of grape seeds: Effect of shrinkage on heat and mass transfer

Abstract

Detailed knowledge of thermal, hydric and mechanical phenomena within a product during drying helps decrease energy costs by reducing the exposure time and improve product quality by respecting the severe standards requirements. In this context, we simulate the spatiotemporal behavior of a highly deformable product saturated with water during convective drying. The numerical simulation of heat and mass transfer states consists of solving the full conductive solid phase conservation equation, the convecto‐diffusive conservation equation of the liquid water together with the energy equation. These equations are coupled by the solid phase contraction rate due to water removal, which represents the shrinkage. The thermo‐physical properties of the considered product, grape in our case, were determined from characterization experiments. Measurement series were carried out in a laboratory‐drying loop and the obtained numerical results are found to be in good agreement with the experimental ones. The simulation allows the monitoring of the time evolution of temperature and humidity inside the product for different drying conditions. At 20% relative humidity of drying air, the ideal temperature was found to be 55 °C and not 60 °C, which minimizes the cost of drying and conserves better the structure of the product. The simulation results of a deformable product can be extended to deformable foodstuffs to minimize the exposure time needed for predefined final water content. Practical applications The research of optimization of drying process of grapes led to the finding of the corresponding temperature and relative humidity of convective drying air. A proposed simulation model which takes the shrinkage of this product into account describes its behavior, gives the exposure time needed for predefined final water content. The model can be extended to other deformable products.

Mathematical modeling and effect of drying temperature on physicochemical properties of new commercial grape “Kyoho” seeds

“…Therefore, recent developments in the field of food engineering have led to a renewed interest in the application of drying techniques (of grape residue utilization) to extend the shelf‐life of grape seeds for application in novel food product development. Several attempts have been made on various drying techniques of grape seeds including sun drying (Doymaz, ), supercritical fluid extraction (Prado et al, ), and convective drying (Azzouz, Hermassi, Chouikh, Guizani, & Belghith, ), but the drying methods and conditions have a great effect on physicochemical properties and quality changes of grape seeds. For example, a recent study investigated by Wang et al () reported that drying is directly associated with a change in the physicochemical and biological properties of food materials.…”

“…Several attempts have been made on various drying techniques of grape seeds including sun drying (Doymaz, 2012), supercritical fluid extraction (Prado et al, 2012), and convective drying (Azzouz, Hermassi, Chouikh, Guizani, & Belghith, 2017), but the drying methods and conditions have a great effect on physicochemical properties and quality changes of grape seeds. For example, a recent study investigated by Wang et al (2016) reported that drying is directly associated with a change in the physicochemical and biological properties of food materials.…”

Soybean drying as a moving boundary problem: Shrinkage and moisture kinetics prediction

“…This phenomenon may also be observed in mass diffusion processes in polymers or porous solids, in which diffusion is the chief controller for the movement of the solid phase (Barry & Caunce, 2008). Examples of the mathematical modeling of the drying of food and biological products, which consider shrinkage throughout the process, include the drying of grape seeds (Azzouz, Hermassi, Chouikh, Guizani, & Belghith, 2018), drying of coffee berries (Sampaio, Afonso, & Novo, 2003), drying of cylindrical slices of banana (Saha, Bucknall, Arcot, & Driscoll, 2018), drying of kiwi with hot air and microwaves (Maskan, 2001), shrinkage in biomass pyrolysis (Babu & Chaurasia, 2004; Hagge & Bryden, 2002), drying of longan fruit (Apinyavisit, Nathakaranakule, & Mittal, 2018), and drying of potatoes in a cylindrical shape (Dhalsamant, Tripathy, & Shrivastava, 2017). Although such works agree that the consideration of shrinkage provides more significant parameters and more realistic descriptions of the drying process, none of them propose models with moving boundaries.…”

Mathematical model for mint drying kinetics prediction by freeze‐drying process: Gene expression programming

“…The development of a mathematical model for the freeze‐drying process is crucial for design engineers to select the appropriate drying conditions that meet the desired operating parameters (Avhad & Marchetti, ). There have been various studies on the modeling of food drying; such as development a model using regression analysis for rehydration kinetics in freeze‐drying of tomatoes (Lopez‐Quiroga, Prosapio, Fryer, Norton, & Bakalis, ), simulation of the spatiotemporal behavior of grapes during convective drying (Azzouz, Hermassi, Chouikh, Guizani, & Belghith, ), prediction of freeze‐dried mushrooms behavior using artificial neural network model (Tarafdar, Shahi, & Singh, ). However, there are not enough studies as yet based on the GEP approach.…”