مدل سازي رياضي فرايند حرارتي كنسرو زيتون سبز

چكيده انگليسي :

Mathematical modelling the thermal processing of canned green ripe olives Nafiseh Jahanbakhshian njahanbakhshian@yahoo com February Department of Food Science and Technology Isfahan University of Technology Isfahan Iran Degree M Sc Language FarsiNasser Hamdami hamdami@ut ac irAbstractSterilization of foods in cans has been well studied both experimentally and theoretically butlittle work has been done on sterilization of food contain large particles in a fluid Since many ofcanned foods belong to this group we decided to focus on their sterilization This work presentsa global approach aiming at the characterization of the thermophysical properties and at thesimulation of the coupled heat and mass transfers during thermal processing The green ripeolive was selected as the model product in this study At the first part of this study the quality factors firmness color and antioxidant activity thethermophysical properties of green olives Conservalea cv were determined after thermalprocessing at and C for selected times and in a vertical cylindricalcan cm high and cm in diameter Penetration test was used for firmness measurementusing Instron Color L a and b and anthioxidant activity of samples were evaluated with imageprocessing method and with Sousa method absorption of DPPH in nm respectively Thermal softening of olives follows from a first order kinetic reaction Green a and yellow b color changes of olives surface follow from a first order reaction while their lightness L followsfrom a zero order reaction The kinetic temperature dependence of these reactions was modeledby the Arrhenius equation Thermal conductivity was modelled by the parallel model At the second and main part of the study the modelling of the coupled heat and mass transfershas been applied to a cylinder geometry using the finite elements method Mathematicalsimulation is helpful in designing new or in improving existing processing systems or for theiroperation control The two dimensional equations of mass momentum and energy conservationare solved using FEMLAB software The meshes used were triangular elements where of them were in boundaries The fluid was assumed to have constant properties except forthe viscosity temperature dependent and density Boussinesq approximation The predictedprofiles of temperature were validated by comparison with the experiment The comparisoncriteria used to evaluate goodness of fit namely the coefficient of correlation r and the rootmean square error RMSE The liquid flows upwards in a thin boundary layer and flowsdownwards in the interstice between the olives The results showed that the natural convectionmeans to be displaced the Slowest Heating Zone SHZ towards the bottom of the can andeventually stay in a region that is about of the can height from the bottom The heattransfer by the fluid flow in can was very important in these products food products containlarge particles in a fluid This result could explain rapid heating of this type of canned foods The inactivation time for heat resistant fungus Monascus rubber during thermal processing ofgreen olives Conservolea cv at C was second based on SHZ A comparison betweenheat transfers by conduction with conduction convection showed that the rate of heat transferin conduction convection is much more than conduction Also the SHZ in conduction incontrast with conduction convection is displaced towards the top of the can Keywords Pasteurization Thermal processing Heat and mass transfer Simulation greenripe olive Thermophysical properties

جهان بخشيان، نفيسه

مدل سازي رياضي فرايند حرارتي كنسرو زيتون سبز

انتقال حرارت و جرم , خواص ترموفيزيكي