مطالعه فرآيند آبگيري اسمزي ورقه هاي كيوي با اعمال پيش تيمار فراصوت و مدل سازي آن

چكيده انگليسي :

105 Study of Osmotic Dehydration of Kiwifruit Slices with Applying Ultrasound Pretreatment and its Modeling Mina Sadat Bargegol Email address ms bargegole@ag iut ac ir June 5 2016 Department of Biosystems Engineering College of Agriculture Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Morteza Sadeghi sadeghimor@cc iut ac ir AbstractKiwifruit Actinidia deliciosa is a fruit full of various vitamins Due to the short shelf life and fastdeterioration its storage and processing before consumption is of great importance Osmotic dehydrationprocess is one of preservation techniques for fruits which is mostly used as a pretreatment for subsequentprocesses such as drying In this process both water loss and solid gain phenomena occur simultaneously However the low rate of water loss in the process is one its drawbacks Applying pretreatments such asultrasound waves can help overcoming this problem In order to reach the optimum performance of eachprocess the control of the process is needed which in turn requires investigating on the mechanisms involvedin the process in detail and knowing how the effective parameters act on it In this regard adopting aphenomenological modeling approach can facilitate the study Moisture sorption isotherms are important toolsto determine changes in moisture content during storage of the food materials thermodynamic conditions aftermixing the products and making decisions pertaining to undesirable chemical and enzymatic reactions On theother hand determination of the glass transition temperature Tg as a powerful tool for understanding waterproperties in foods and control of the products shelf life is vitally important The objective of the presentstudy was applying osmotic dehydration process for kiwifruit slices in sucrose solution at concentrations of 30 40 and 50 Brix immersion durations of 0 5 10 20 30 60 and 120 min and indirect ultrasound pretreatmentat durations of 10 20 and 30 min After conducting the experiments the optimum treatment was determinedusing response surface methods RSM and genetic algorithms GA Through analytical modeling of osmoticdehydration process in axisymmetric cylindrical coordinates two dimensional approximation the coefficientsof moisture diffusion were obtained The effect of osmotic dehydration and ultrasound pretreatment on fruit stissue was examined by scanning electron microscopy SEM Moisture desorption isotherms for the fresh andoptimized treated samples were determined at temperature of 20 C Among well known models the mostappropriate one was selected based on the highest correlation coefficient and the lowest root mean square errorand mean relative error indices The results showed that applying the ultrasound waves before osmoticdehydration of the product enhanced the rate of water loss Moreover by increasing the immersion duration concentration of the osmotic solution and ultrasound pretreatment time water loss and solid gain increased Thebest model predicting the moisture desorption of the kiwifruit samples were GAB and Peleg models Thermalanalysis showed that the Tg values decreased with increasing moisture content The modeling of Tg showed thatthe best model for predicting the variations in Tg values of the fresh and optimized treated samples withequilibrium moisture content was Brostow et al model The obtained values of model parameters Gordon Taylor near other researchers parameters better Moreover in modeling of Tg as a function of water activity Ross model and Khalloufi et al model showed an acceptable agreement with the experimental data Key Words Glass transition temperature Moisture desorptionption isotherm Optimization Thermal analysis

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مطالعه فرآيند آبگيري اسمزي ورقه هاي كيوي با اعمال پيش تيمار فراصوت و مدل سازي آن

آناليز حرارتي , بهينه سازي , دماي گذار شيشه اي , هم دماي دفع رطوبت