By M . SHIVA KUMAR ( 04AG1008 ) Under the guidance of PROF. SURESH PRASAD
ABSTRACT
• The use of microwaves in the food industry is attributed to the lower time needed to increase the temperature of foodstuffs compared to the traditional heating methods.
•However, the heating is not uniform and the products show hot and cold spots.
• In order to analyze the behaviour of foods heated by microwave oven, a mathematical method was developed solving the unsteady state heat transfer differential equations.. • It takes into account variable thermal and electromagnetic properties.
•The numerical solution was developed using an implicit finite difference method in one dimensional system (slab).
• It allows predicting temperature profiles. • The model will later be validated with experiments and data on apple fruit.
ADVANTAGES OF MICROWAVE HEATING
• Does not involve a conduction or convection medium • Food material is heated directly due to agitation of the polar molecules contained – namely water • Reduced drying time • Improved final quality of the dried products • Better rehydration
DRAWBACKS OF MICROWAVE HEATING
• Inherent non-uniformity of the electromagnetic field within a Microwave cavity. • Excessive temperatures along the edges and corners of products may lead to overheating and irreversible drying-out resulting in possible scorching and development of off-flavors.
• Final product temperature in MW drying is difficult to control, compared to that in hot-air drying in which product temperature never rises beyond air temperature. • Limited amount of water is available during the final stages of drying processes, hence the material temperature can easily rise to a level that causes scorching
TEMPERATURE PROFILE PREDICTION
A mathematical model is proposed to predict temperatures during microwave food heating, taking into account thermal and dielectric properties of the food material
Bibliography: • Y. Soysal, S. Oztekin and O. Eren. Microwave Drying of Parsley: Modelling, Kinetics, and Energy Aspects Biosystem Engineering Journal .Volume 93, Issue 4, April 2006, Pages 403-413 • M. E. C. Oliveira and A. S. Franca . Microwave heating of foodstuffs. Journal of Food Engineering .Volume 53, Issue 4, August 2002, Pages 347-359 • Ashim K.Datta, Ramaswamy C.Anantheswaran (2002), Handbook of Microwave Technology for Food Applications • Metaxas, A.C. and Meredtith, R.J.1983. Industrial Microwave Heating. Peter Peregrinus Ltd., Herts England • • • • L.A. Campañone and N.E. Zaritzky. Mathematical analysis of microwave heating process .Journal of Food Engineering .Volume 69, Issue 3, August 2005, Pages 359-368 James M. Hill and Timothy R. Marchant . Modelling microwave heating. Applied Mathematical Modelling Journal .Volume 20, Issue 1, January 1996, Pages 3-15 Y. E. Lin,R. C. Anantheswaranat & V. M. Purib(1995). Finite Element Analysis of Microwave Heating of Solid Food. Joumal of Food Engineering. Volume 25 . Pages 85-112 Henk H.J. Van Remmen, Carina T. Ponne, Herry H. Nijhuis, Paul V. Bartels, and Piet J.A.M. Kerkhof (1996) .Microwave Heating Distributions in Slabs, Spheres and Cylinders with Relation to Food Processing. Journal of Food Science.Volume 61, No. 6, 1996. Pages 1105-111 O. Siphaioglu and S.A. Barringer (2003) (2003).Dielectric Properties of Vegetables and Fruits as a Function of Temperature, Ash, and Moisture Content. Journal of Food Science. Volume 68. Pages - 234 – 239. • • •