مطالعه انتقال حرارت طي پاستوريزاسيون حرارتي تخم مرغ

چكيده انگليسي :

Study of Heat Transfer during Thermal Pasteurization of Egg Behzad Abasnezhad b abasnezhad@ag iut ac ir September Department of Food Science and Technology Isfahan University of Technology Isfahan Iran Degree M Sc Language Farsi Mohammad Shahedi Prof Supervisor shahedim@cc iut ac ir Nasser Hamdami Assist Prof Supervisor hamdami@cc iut ac ir Abstract Eggs are consumed all over the world and they have been recognized as a highly nutritive food Intact fresh clean shell eggs and derived egg products health food using raw eggs salads sauces ice cream and mayonnaise can get spoiled easily and may also contain Salmonella enteritidis bacteria which can be a major cause of food borne illnesses Pasteurization of eggs has been proposed as a possible way to eliminate foodborne illness related salmonellae from raw eggs In this study chemical composition of egg white and yolk were determined then thermophysical properties of egg white and yolk were studied at range of temperatures from C to C Three predictive models of the effective thermal conductivity during thermal process were developed Krischer parallel and series models The effective thermal conductivity of egg white predicted by Krischer model f and for egg yolk parallel model were in good agreement with the experimental data Data from differential scanning calorimeter DSC showed that denaturation of white protein start at C Surface heat transfer coffecient measured by transient temperature method in a three pasteurization temperature and C Surface heat transfer coffecient increased with increasing of temperature Density decreased during thermal process and was correlated by polynomial model A knowledge of rheological properties is important in processing handling process design product development and quality control The flow curves and time dependent flow properties of the liquid egg yolk and white were assessed at different temperatures of pasteurization and C and ambient temperature C by using concentric cylinder viscometer The shear rate range was to s for liquid egg white and to s for liquid egg yolk Rheological behavior was pseudoplastic and showed thixotropic behavior Forward and backward measurements of the flow curves were modeled and yolk fitted by the power law model and Herschel Bulkley model well described egg white experimental data The consistency behavior indexes apparent viscosity and yield stress dependent on temperature were expressed by an Arrhenius type equation The value obtained from C value of the three point system and area of the hysteresis loop showed the thixotropy and confirm that time dependency behavior decreased with increasing temperature To develop three dimensional numerical model governing partial differential equations of heat transfer equations using heat conduction mechanisms in the intact egg based on finite element method was solved by COMSOL multiphysics The model confirmed by comparing results predicted by the model with the measured data during thermal pasteurization of egg The developed model was able to predict temperature profiles the cold spot and intensity of heat treatment in egg at different pasteurization temperatures The air cell acted as insulation and when air cell increased heat transfer rate decreased and cold spot location changed PDF created with pdfFactory trial version www pdffactory com

عباس نژاد، بهزاد

مطالعه انتقال حرارت طي پاستوريزاسيون حرارتي تخم مرغ

خصوصيات ترموفيزيكي , سالمونلااينتريديس , كالريمتري اسكني تفرقي , مدل سازي عددي