مدل سازي انتقال جرم و حرارت طي سرخ كردن خلال سيب زميني

چكيده انگليسي :

81Heat and Mass Transfer Modeling in Potato Strip during Deep Frying Iman Berarnejad Bariki i berarnejad@ag iut ac ir March 3 2015 Department of Food Science and Technology Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Naser Hamdami hamdami@cc iut ac irAbstractFrench fries are one of the most famous potato products that are mainly produced by deep frying Deep fat frying is referred to immersion of food in hot edible oil at temperature higher than water boiling point This process is preferred due to its unique organoleptic characteristics and low cost at large scaleproduction Modeling of frying process is necessary for design and optimization Many studies in therecent years have followed the goal of developing the mathematical models describing heat moisture andfat transfers during deep fat frying process The aim of this study is determination of moisture and heattransfer coefficients and modeling the moisture and heat transfer for blanched and pre dried French friesduring deep fat frying Firstly potatoes of Agria variety were cut into strips with dimension of 0 8 0 8 cm after being washed and peeled The potato strips were blanched at 70 C adjusted distilled waterfor 10 minutes Then pre dried at shelf dryer at hot air velocity 1m s with temperature of 70 0 5 C untilbeing achieved to humidity of 75 wet basis To measure temperature profile two thermocouple wereinserted at both surface and center of strip and were fried with 4 other strips at oil with temperature 160 175 and 190 C for 5 minutes Heat transfer coefficient at surface was done determined by measuringtemperature at unsteady state Newton law with two different methods So Aluminum strip alone andwith 4 other potato strips putted at oil The results showed that heat transfer coefficient amounts at surfacein temperature range of 160 190 C were 182 221 W m2 C and 383 658 W m2 C respectively Heattransfer coefficient at surface was a time dependent parameter that achieved maximum during frying Also this maximum amount enhance with oil temperature increasing Moisture transfer coefficient andmoisture content of potato strip were also determined during differential frying times Results showed thatmoisture transfer coefficient at surface and moisture diffusion in temperature range of 160 190 C is2 28 10 5 3 96 10 5 m s and 0 90 10 8 1 43 10 8 m2 s respectively Also the temperature dependence ofmoisture transfer coefficient and moisture diffusion coefficient were described by Arrhenus equatioan Inorder to model moisture and heat transfer during frying a numerical model with three part of crust coreand interface were developed based on Fick law and Fourier law solution using MATLAB softwareseparately It was assumed that thermo physical properties of crust and core were different and theoutcome of output and input heat at interface is consumed for water evaporation Finally to verify thedeveloped model the temperature and moisture contents profile of potato strip were determined andcompared with predicted values by model The obtained good correlation between predicted profiles andmeasured values revealed that developed model is sufficiently reliable Keywords Heat Transfer Moisture Transfer Crust French Fries Frying Potato Modeling

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مدل سازي انتقال جرم و حرارت طي سرخ كردن خلال سيب زميني

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