Ultra High Temperature Processing of Food Products

Brief Information about ultra high temperature processing of food products.

1. ULTRA HIGH TEMPERATURE PROCESSING
Of Food Products
Prepared by:-
Sourabh Bhartia
B.Sc. & M.Sc.
(Food Processing & Technology)
UTD, AVVV, BSP (C.G.)
[email protected]
www.linkedin.com/in/sourabh-bhartia

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CONTENTS
WHAT IS UHT PROCESSING ?_________________ 1
PURPOSE OF UHT PROCESSING_______________2
METHODS OF UHT PROCESSING______________4
DIRECT HEATING SYSTEMS__________________ 5
INJECTION, INFUSION & ELECTRIC HEATING_6
INDIRECT HEATING SYSTEMS________________7
PLATE HEAT EXCHANGER___________________ 8
TUBULAR HEAT EXCHANGER________________10
SCRAPED SURFACE HEAT EXCHANGER ______11
ADVANTAGES & DISADVANTAGES____________13
BIBLIOGRAPHY_____________________________ 14

3. Liquid foods Foods with solid
particles
Foods with larger
particles
Milk
Fruit Juice
Beer
Wine
Baby Foods
Tomato Products
Vegetable Soups
Stews
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ULTRA HIGH TEMPERATURE (UHT) PROCESSING

Higher processing temperatures for a shorter time are possible if the product is sterilized before is
filled into a pre-sterilized containers in a sterile atmosphere.
Continuous flow of heat at a temperature of 135⁰C for a very short time of 2to5 seconds destruct
almost all the microorganisms and spores present in the food.
This forms the basis of UHT processing (also termed as aseptic processing)

Residential time varies with respect to the products:

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PURPOSE OF UHT PROCESSING


To achieve a longer shelf life.
To kill all heat resistant spore forming bacteria in milk,
For e.g., Bacillus Licheniformis, Bacillus Subtilus;
To inactivate enzymes (Ultra High temperature
processing/High Temperature for Short Time through
High Hydrostatic Pressure), For e.g., to inactivate
pectinol and filtragol used in processing of beverages;
For inactivation of yeasts, For e.g., Saccharomyces
cerevisiae in beer;
To increase the sugar concentration in candy
processing.
Candy Processing Thermometer

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PARAMETERS OF CANDY PREPARATION THROUGH UHT PROCESSING
STAGE TEMPERATURE SUGAR CONCENTRATION
thread (e.g., syrup) 110 to 112 °C (230 to 234 °F) 80%
soft ball (e.g., fudge) 112 to 116 °C (234 to 241 °F) 85%
firm ball (e.g., soft caramel candy) 118 to 120 °C (244 to 248 °F) 87%
hard ball (e.g., nougat) 121 to 130 °C (250 to 266 °F) 90%
soft crack (e.g., salt water taffy) 132 to 143 °C (270 to 289 °F) 95%
hard crack (e.g., toffee) 146 to 154 °C (295 to 309 °F) 99%
clear liquid 160 °C (320 °F) 100%
brown liquid (e.g., liquid caramel) 170 °C (338 °F) 100%
burnt sugar 177 °C (351 °F) 100%

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METHODS OF UHT PROCESSING

There are 2 methods to perform a UHT processing:
DIRECT HEATING
INDIRECT HEATING

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DIRECT HEATING SYSTEMS

The high temperature steam is directly applied to the food material under strict controlled conditions.
Processing temperature of 140⁰C is quickly reached and hold it for 4 seconds.
The temperature is reduced by flash cooling in a vacuum vessel.
The short time process will not affect the nutritional qualities

There are 3 types of direct heating systems:-
INJECTION
INFUSION
ELECTRIC HEATING

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1.Injection:-
High pressure steam is directly applied into the food product by steam injector which raises the
temperature rapidly;
Then the food product is flash cooled in a vacuum;
Since this method is energy intensive and cause flavor damage, this method is suitable for limited
kind of food products.
2.Infusion:-
The product is pumped through a distributing nozzle into a chamber of steam with high pressure.
More surface area of the food product is exposed to steam in this system.
Immediately after processing, flash cooling is applied to the food product in a vacuum chamber.
Infusion method is an instant heating and cooling process.
Localized over heating is not applicable and highly suitable for low and high viscous food
products
3.Electric heating:-
Electric current is directly passing through the food products.
This system is applicable for liquid foods and particulate foods
Electrical resistance for liquid foods and solid creates problems in this system

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INDIRECT HEATING SYSTEMS
A partition placed between food product and Steam/Refrigerant where the partition acts as a
heating or cooling medium.
The heating medium pass through one side of partition and food product pass through the other
side of partition through the partition plate where heat is transferred.
The similar process occurs during cooling also.
In this method there is no direct contact between the food product and the heating medium
Flow rate of the product, physical properties of the food material, residential time and cleaning
are the important parameter to be considered before processing
There are 3 types of direct heating systems:-
PLATE HEAT EXCHANGER
TUBULAR HEAT EXCHANGER
SCRAPED SURFACE HEAT EXCHANGER

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PLATE HEAT EXCHANGER
Plate heat exchangers are originally developed for the pasteurization of milk, plate heat exchangers
are now used for a vast variety of heating, cooling and evaporation applications in the food industry.
They consist of a stack of corrugated thin metal plates, pressed together so as to form two
continuous flow channels for the fluids exchanging heat. Gaskets are placed between the plates to
prevent leakage.
Advantages of the plate heat exchangers:
Flexibility: the capacity can be increased or decreased by adding or removing plates.
Sanitation: by opening the stack, both sides of the entire exchange area are made accessible for
cleaning and inspection.
High heat transfer coefficient, due to increased turbulence in the narrow flow channel
Compactness: high exchange surface to volume ratio.
Disadvantages of the plate heat exchangers:
The narrow size of the flow channels results in high pressure drop and limits its use to low viscosity
fluids not containing large suspended particles.
The need for gaskets is also a disadvantage.

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LABELLED FIGURE OF A PLATE HEAT EXCHANGER

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TUBULAR HEAT EXCHANGER
The simplest representative of this group consists of a pair of concentric tubes.
For ease of cleaning, the food product usually flows in the inner tube and the heating or cooling
medium in the outer annular space.
Heating or cooling medium out
Heating or cooling medium in
Food product out
Food product in
BASIC STRUCTURE OF A TUBULAR HEAT EXCHANGER

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SCRAPED SURFACE HEAT EXCHANGER
They consist of a jacketed cylinder equipped with a central
rotating dasher with scraping blades.
They can be horizontal or vertical.
The product is fed into the cylinder.
The rapidly (600–700 rpm) rotating dasher spreads, scrapes and
moves the product as a film over the wall.
The heating or cooling fluid is fed into the jacket.
Scraped surface heat exchangers are used for heating and
cooling highly viscous fluids and for slush-freezing.
Continuous ice cream freezers and slush freezers are,
essentially, scraped surface heat exchangers with a refrigerant
evaporating in the jacket.
The scraped surface exchanger is an expensive piece of
equipment, both in price and in operating cost (moving parts).

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LABELLED FIGURE OF A SCRAPED SURFACE HEAT EXCHANGER
Product inlet
Outlet (inner jacket) Inlet (inner jacket)
Inlet (outer jacket)
Outlet (outer jacket)
Product outlet

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ADVANTAGES OF UHT PROCESSING

High Quality: The D & Z values are higher for quality factors than microorganisms. The
reduction in process time due to high temperature (UHTST) & the minimal come up & cool
down time leads to a higher quality product.
Longer shelf life: Greater than 6 months
Packaging Size: Processing conditions are independent of container size, thus allowing for
the filling of large containers for food service or sale to food manufacturers.

DISADVANTAGES OF UHT PROCESSING

Sterility: Complexity of equipment and plant are needed to maintain sterile atmosphere
between processing & packaging (packaging materials, pipe work, tanks, pumps) therefore,
this process needs higher skilled operators.
Other sterilization required: As process equipment, containers, lids, aseptic tunnel
Particle size: With larger particulates there is a danger of overcooking of surfaces and need
to transport material; both limits particle size.

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BIBLIOGRAPHY
Food process engineering & technology, ZEKI BERK

Food processing technology: Principles & Practices, P.J.FELLOWS

Improving the thermal processing of foods, PHILIP RICHARDSON

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THANKYOU