Ohmic Heating

Fig. 1Fig. 1 Principle of ohmic heatingPrinciple of ohmic heating

electric current is passed through foods heating electric current is passed through foods heating occurs in the form of occurs in the form of internal energy generationinternal energy generation within the material temperature rise throughout within the material temperature rise throughout its volumeits volumerapid and uniform heatingrapid and uniform heating

Principle of ohmic heatingPrinciple of ohmic heating

HIGH TEMPERATURE SHORT TIME (HTST) PROCESSES

THE CONCEPT OF OHMIC HEATING

– Based on the passage of alternating electrical current through a food product that serves as an electrical resistance.

– The electrical power introduced into the product is translated into heat.

– The electrical currents passed along or across the flowing fluid.

Fig. 2(d) Schematic drawing of ohmic cell for liquid sample

Fig. 3 Picture of Ohmic heating device

GENERATE HEAT IN SITU PASSAGE OF ELECTRIC CURRENT:

Electric resistance of material: heat by P= I2R A commercial process and some proposed

processes Need to model and control the system- study

stationary food mixtures

Microwave Heating• less time at lower cost• get more product

Heating system• Microwave penetrate a food and heating

extends with in the entire food material • Rate of heating is therefore more rapid

Ionic Polarization

• Electrical field is applied to food solution containing ions, and ion move at an accelerated pace due to their in herent charge the resulting collisions between the ions

Dipole Rotation

Polar molecule Such as waterMolecule have a random orientation when an electric field is applied the molecules orient themselves according to the polarity of the field

Penetration Depth of Microwave

Distribution of energy within a material is determined by α’ follow

2/1

2/

/ 1tan12

2

Penetration Depth of Microwave

Field penetration depth (Z)

2/1

2/ 1tan1(

2

2

Z

Application of Microwave

• Dehydration • Freeze drying• Processing of meat & meat product• Blanching• Thawing• Pasteurization and Sterilization

Induction Heating

– When an electrically conductive material is placed in a varying magnetic field

The Concept Of Induction Heating

Basic Induction Heating

Rapid heating rate 125 C /s

Induction Heating Application Systems

• coils within the bottom of the rice cooker create the magnetic field. When the inner nonstick aluminum cooking pan with stainless steel outer lining is placed into the rice cooker and the unit is activated, a magnetic field is generated to create instant heat.

Application

Induction Heating system Rice Cooker

Induction technology heats the entire nonstick inner pan for consistent.