Ohmic heating

ANKITA GARG BTFT/2007/103

Ohmic heating is also called electrical resistance heating, Joule heating, or electro-heating.

In OH product is heated up to 140 °C in less than 90 sec & then cooled to an ambient temperature.

Introduction

Ohmic heating is an advanced thermal processing method where electric is current passed through foods to heat them.

Advent of ohmic heating

Conventional method of thermal treatment

to inactivate microbes & enzymes affect its sensory & nutritional values.

Heat sensitive material food

component are damaged by

localized over-heating.

Color, taste, aroma, texture and flavor are

affected.

Ohmic heating is a potential alternative to conventional method.

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In 1993,FDA approve OH for the processing of low acid good at ambient temperature.

Important dates

In OH alternating current (AC) pass through the food to create heat due to electrical resistance within the food.

Acc to Ohm’s law, when electric current flows through a material, heat is generated.

W=I2R Where W is power, I is current

and R is the resistance.

BASIC PRINCIPLE

ELECTRODE

FREQUENCY

WAVE- FORM

Electrode present Unrestricted of Frequency Unrestricted of Waveform

OHMIC HEATING IS DISTINGUISHED FROM OTHER

ELECTRICAL HEATING METHODS

EQUIPMENT

The best known OH system is APV ohmic heating column, where electrodes are in direct contact of food, which is transported in a vertical concentric tube.

Inside of tube is lined with high temperature and electrically inert plastic material.

Electrodes are constructed of noble metal-coated titanium to avoid electrochemical reaction and dissolution of metal ion in food.

Experimental Design:-

The most critical property for the applicability of OH is Electrical conductivity.

Electrical conductivity is a measure of a material's ability to conduct an electric current.

It varies with temperature, solid content and starch among others.

Electrical conductivity (σ ) is related with Resistance as R=L/(A σ)

Rate of heating is directly proportional to the square of the electric field strength and the electrical conductivity of the product.

Foods containing dissolved ionic salts that conduct electricity are suitable for ohmic heating.

Fats, sugars and syrups are not suitable for this type of processing.

Concentrated high viscosity ,proteinacious food products.

PasteurizationSterilization

Shelf stable milkHigh acid food

BlanchingFruit peelingExtraction of juice

Vegetable,

fruits, meat, poultry,

fish.Ready to

serve meals

•Soups, milk, custard ,dairy desserts, fruit juices, fruit chunks,• Recipe dishes such as ready meals sauces, chowders and ragouts.

Applications

Tomato paste, cheese spreads, baby food, & liquid egg.

• Dairy product• Tomato based sauce

Juice from fruits like apple, • Sucrose from sugar beet,• Soymilk from soybean.

Advantages

Heat sensitive material of foods are not damaged by localized over-heating.

Taste, aroma, and nutritional

value are preserved

Heating take place volumetrically ,with no temperature gradient within the product.

Reducing risks of fouling result in minimal mechanical damage & better nutrients & vitamin retention.

High energy efficiency because 90% electrical energy is converted into heat.

Ability to increase temperature & decrease holding time in process enhance product shelf life.

Easy process control with instant switch-on and shutdown.

Reduced maintenance cost ,as there are no moving parts.Ohmic heating is environmentally friendly.

DISADVANTAGE

Electrode material is inert and may release metal ion into the conducting solution and eventually to the food.

Ensuring that the electrode material is isolated from the food is also a problem of Ohmic heating.

Food components of different electrical conductivities heat at different rates.

Packaging involved

After application of Ohmic heating products are cooled down & then packed in a similar way as in conventional aseptic packaging.

Prominence of Ohmic Heating

Currently, at least 18 OH systems are operational in Europe, Japan & USA.It is in commercial use in Europe , Japan, & USA for:Aseptic processing of high added value ready meals, stored at ambient temperature.Pasteurization of particulate foods for hot filling.Pre heating of products before canning.

The most successful of these system have been for the processing of whole strawberries and other fruits for in Japan, & low acid ready to eat meals in USA.

Currently there are two successful manufacturer of OH equipment:•APV Bakers Ltd (UK & USA)•Crawley(USA)

Futures Prospect

There is a great expectations for this aseptic technology may be on the brink of realization.

OH has good prospects for being used in Dairy industry.

It can be used as an alternative to thermal pasteurization.

“We're changing the world with technology.”

By: Bill Gates

THANKS