FSTC 311
FOOD PROCESSING
Current Events & Unit Operations
Dr. Peter S. Murano
Associate Professor
Department of Nutrition and Food Science
Texas A&M University
138 Cater-Mattil
2253 TAMU, College Station, TX 77843-2253
Phone: 979-862-7955
E-mail: psmurano@tamu.edu
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OUTLINE of TOPICS
A. Food Processing – definition and basics
B. Principles of Food Processing
C. Processing Industry Trends 2015
D . Unit Operations and Process Engineering
E. Heat Transfer Unit Operation
F. Fourier’s Law and thermal Conductivity
G. Heat Exchanger Equipment
H. Laws of Mass and Energy Conservation
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FOOD PROCESSING
is the conversion of raw food materials / ingredients
into typically packaged, more stable, consumable forms
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An interesting comment… what do you make of it?
“we have never seen food
consumers as confused as
they are today”
Indra Nooyi, CEO of PepsiCo
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WHY are foods processed
and what are
the general PRINCIPLES
of food processing?
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MURANO EXPLORING FOOD SCIENCE AND TECHNOLOGY © 2013
Can you SPOT the foods that are processed?
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5 Food Processing Industry Trends for 2015
Source: Food Manufacturing
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1. Innovative Solutions to Drive Down Costs
2. Energy Efficiency
3. Healthier, Natural Foods
4. A Refrigeration Strategy
5. CHINA: A Potential Growth Vehicle
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1. Innovative Solutions to Drive Down Costs
With the advent of the Internet and pricing transparency for
consumers, pressures are rising for food manufacturers to be
low cost. They are trying to find ways to drive more value,
and are looking for:
- Innovations that can help maintain profitability
- New products to bring to market
- Modifications to product categories
Food manufacturers are also on the hunt for more costeffective means of manufacturing, standardizing equipment,
and exploring automation to minimize labor costs.
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Food manufacturers can move towards innovation and the
standardization of certain product categories to drive down their
own costs. Food processors can rethink their manufacturing
strategies, optimizing what makes sense and developing a new
cost model. In the long run, they need to have the flexibility to
run products with higher margins.
Companies are trying to get
improved visibility into the
true cost of manufacturing
their products.
Whereas before they may have looked at the profitability of a
plant, they’re now diving deeper, examining the profitability of a
product category, manufacturing line or even a particular stock
keeping unit (SKU).
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WHAT WOULD YOUR DECISION BE …
Suppose your company produces several low-margin
products, along with ones that have high margins.
The management team examines last year’s profits and
losses and decides something must be done about the
low margin category:
What would you do?
1. Take steps to cut production costs
2. raise prices
3. discontinue offering the low margin products
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Consider the information on the next slide…
While it is focused on NANOTECHNOLOGY,
a new technology that can be applied to
food processing, it also clearly depicts the
centrality of food processing in the food
production chain “from farm to fork”.
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Recall that the first food processing industry trend
that we are discussing dealt with INNOVATION.
Studies of innovation show that there is a translation
of promising “technoscience” into products in society.
The concept frequently used to describe a consecutive
“up-valuing” of a material or technological device is
the value chain model.
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What is meant by a “value chain”?
It is the series of activities required to produce and
deliver a product or service.
The chain encompasses raw materials that create
products to the ultimate consumption of the finished
products.
Layers in a value chain have been described in terms
of a sequence, comprising: suppliers, manufacturers,
distributors, and consumers.
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What is this diagram telling us?
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What is this diagram telling us?
1. The VALUE CHAIN involves SUPPLIERS, BUSINESSES, CONSUMERS
2. SUPPLIERS provide or input materials to BUSINESSES
3. From these, BUSINESSES generate PRODUCTS for CONSUMERS
In order for this CHAIN to function repeatedly and successfully,
1. BUSINESSES provide PAYMENTS to SUPPLIERS so that they can
make their products
2. CONSUMERS provide PAYMENTS to BUSINESSES in order to buy
these products
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2. Energy Efficiency
The trend toward energy efficiency is driven in large part by an
increase in consumers who are concerned with the environment
and what they’re putting into their bodies.
When food companies reduce energy consumption, it appeals not
only to consumers for environmental reasons, but drives costs
down, as well.
Thus, by reducing energy consumption, food manufacturers are
reducing costs and increasing margins.
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3. Healthier, Natural Foods
Consumers have become more aware
of what they’re eating; there’s been
increasing interest in organic and
natural foods.
From a manufacturing standpoint, this presents more challenges in
terms of equipment types and how materials are processed. The
formulations and handling can be different for such products,
impacting how lines are set up and operated.
If a bakery is gluten free, for example, the processing is entirely
different than if you were to use standard ingredients due to
concerns over ingredient separation and cross contamination.
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3. Healthier, Natural Foods
CHALLENGE:
Many
consumers do
From:
http://windowstorussia.com/in-russia-it-is-easy-to-eat-healthy.html
NOT equate
“healthy foods”
with
“processed foods”
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Does packaging impact consumer perception of organic foods?
(packaging is a unit operation)
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Consumer Perceptions Of Processed Foods
Some consumers feel that:
- “processed foods are less healthy”
- “processed foods are junk food”
- “processed foods have too many added chemicals
+ fat, sugar, and/or salt; artificial flavors/colors
On the other hand, some consumers are aware that
through food processing/food technology,
- “such foods offer enhanced shelf-life and safety”
- “such foods meet sustainability goals for global needs”
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Consumer Perceptions Of Processed Foods
March 28, 2010
Consumers (43%) have a negative attitude toward processed foods, according to
a study conducted by the International Food Information Council (IFIC). The
study, which interviewed 1,500 adults in the U.S. who are the primary grocery
shopper in their household, found that negative perceptions are deeply rooted
and cross all demographics.
Source Information from this survey accessed from:
http://www.foodnutritionscience.com/articles/consumer-perceptions-about-processed-foods/
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Consumer Perceptions Of Processed Foods
Researchers discovered that both the obesity
epidemic and the move toward local and
organic alternatives are driving forces in this
attitude shift,
and
growing concerns about the healthfulness of
processed foods are leading to the de-selection
of some of these foods in certain food and beverage
categories.
“Processed Food… Nooo!”
The term “processed foods” itself also carries
with it a negative perception.
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Consumer Perceptions Of Processed Foods
While consumers’ general attitudes toward processed foods
are negative, there is recognition of the significant role
processed foods play in their everyday diets.
In addition, some types of processed foods have more
negative views associated with them than others. For
example, sodium, trans fats and high fructose corn syrup are
poorly perceived.
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Consumer Perceptions Of Processed Foods
Nearly all consumers eat both fresh and processed foods, and two-thirds of those
interviewed consume some organic foods. However, one-third of consumers plan
to reduce their consumption of processed foods in the next six months or say
they have recently done so.
Some of the most mentioned processed foods consumers say they eat include
cheese, canned soup, frozen meals, soda, lunch meats, chips and cereal.
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Consumer Perceptions Of Processed Foods
Foods identified as “fast” foods or “junk” foods top the deselection list, but virtually all categories of processed foods
receive a mention.
The majority of consumers (80%) are in the process of changing
how they eat, and of those, 48% are doing so for improved
health and nutrition. Thirteen percent cited the economy.
Consumers in this study acknowledged the positive aspects of
processed foods, like convenience, value and consistency, and
they do seem to understand that it is unrealistic to buy solely
fresh, local and organic foods – especially during tough economic
times.
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Consumer Perceptions Of Processed Foods
“We know that weight is tied to both diet and exercise,
but processed foods have been the primary target,
mostly due to negative information that isn’t always
science-based being perpetuated in the media,” says
Lindsey Loving, Senior Director, Food Ingredient &
Technology Communications for IFIC.
Processed Foods
“Another issue is the use of certain ingredients in
processed foods. There is a lot of misinformation out
there about the purpose, function, and safety of many
ingredients in processed foods, which creates
uncertainty and fear.”
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4. A Refrigeration Strategy
Another area that’s been generating a lot of interest is refrigeration
compliance.
Companies want to take an active role in developing a refrigeration
strategy for 2015, driven by Occupation Safety and Health
Administration (OSHA) mandates.
Due to its damage to the atmosphere,
food manufacturers must phase out
R-22 refrigerants and move toward
natural options such as CO2 by the
year 2020.
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The 1987 Montreal Protocol established a schedule for the phaseout
of HCFCs (hydrochlorofluorocarbons), which contain ozone-destroying
chlorine. Refrigerants of this type are called R-22.
The Montreal Protocol as amended is carried out in the U.S. through
Title VI of the Clean Air Act implemented by EPA.
According to the EPA, releases of R-22
into the environment, such as those
from leaks, contribute to ozone depletion.
In addition, R-22 is a greenhouse gas and the manufacture of R-22
results in a by-product (HFC-23) that contributes significantly to
global warming.
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At present, food manufacturers are making plans for the shift.
There are new technologies and developments emerging around
refrigeration and distribution such as skid-mounted refrigeration
systems that embrace CO2
WHAT ABOUT AMMONIA?
Ammonia (NH3) is naturally occurring and
makes a fine refrigerant.
While ammonia is an environmentally friendly refrigerant,
industry clients are asking for ways they can reduce their
ammonia charge to below 10,000 pounds to reduce costs
associated with process safety management (PSM) compliance
re: ammonia system operating and maintenance.
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Regulations: Ammonia is classified as a hazardous chemical so
the federal government has mandated that it be subject to
Occupational Safety and Health Administration's (OSHA) Process
Safety Management Rules (PSM) as well as the Environmental
Protection Agency's Risk Management Program Rules (RPM).
State and local regulations must also be considered. Although a
PSM program is not required under 10,000 lbs of ammonia (in a
food processing facility), employers have a duty to protect
employees (as stated under OSHA and EPA's "General Duty"
clause), and ammonia detectors are required by law.
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5. China: A Potential Growth Vehicle
Due to the emergence of its middle class, large food and beverage
companies are now seeing China as a potential growth vehicle.
In addition there is the Chinese population’s growing awareness of
food safety concerns, including fears about contamination and
ingredients from Chinese companies.
$$$
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5. China: A Potential Growth Vehicle
Because U.S. companies have respected
reputations regarding food safety and
product quality, Chinese consumers are
willing to pay premiums for U.S. products.
Many multinational companies are now
capitalizing on this opportunity to move
into the Chinese market.
$$$
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UNIT OPERATIONS
and
PROCESS ENGINEERING
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MURANO EXPLORING FOOD SCIENCE AND TECHNOLOGY © 2013
The continuum of Unit Operations related to
RAW MATERIALS HANDLING
Reception
Cleaning
Sizing & Sorting
Peeling and Trimming
Size Reduction
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Which Unit Operation is shown here?
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Here is a BOWL CHOPPER
Which Unit Op is it used for?
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SIZE REDUCTION
um… size reduction
is a key operation in food processing
METHODS of SIZE REDUCTION
include chopping, cutting, slicing, and dicing:
(a) Large to medium (cheese and sliced fruit for canning)
(b) Medium to small (bacon, dice carrot, sliced beans)
(c) Small to granular (minced or shredded meat, flaked
nuts, and shredded vegetables
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SIZE REDUCTION
is accomplished via MILLS for dry foods (cereals, grains)
typically via compression and/or shear force application
Example: roller milling
Feed
Two or more steel rollers revolve towards
each other and pull particles of food
through the nip (the space between
rollers).
The main force is compression, but if the
rollers are rotated at different speeds,
there is and additional shear force exerted
on the food
Size of the nip is adjustable for different
foods
Product
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The study of process engineering is an attempt to combine all forms
of physical processing into a small number of basic operations, which
are called unit operations.
Careful analysis shows that these complicated and differing processes
can be broken down into a small number of unit operations.
For example, consider heating of which innumerable instances occur
in every food industry. There are many reasons for heating and
cooling - for example, the baking of bread, the freezing of meat, the
tempering of oils.
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Because of the dependence of the unit operation
on a physical principle(s), quantitative relationships
in the form of mathematical equations can be
built to describe them.
Such equations can be used to follow what is
happening in the process, and to control/modify
the process if required.
In the food industry are fluid flow, heat transfer,
drying, evaporation, contact equilibrium
processes (which include distillation, extraction,
gas absorption, crystallization, and membrane
processes), mechanical separations (which include
filtration, centrifugation, sedimentation
and sieving), size reduction and mixing.
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Processing Unit Operations
can be classified accordingly:
1. Ambient-temperature processing
2. Processing by application of heat
3. Processing by the removal of heat
4. Post-processing operations
Source: Ruben Morawicki, Univesity of Arkansas
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1. Ambient-Temperature Processing
• Raw material preparation
–
–
–
–
Cleaning
Sorting
Grading
Peeling
• Size reduction
• Mixing
• Mechanical separations
– Membrane concentration
– Centrifugation
• Fermentation
• Irradiation
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Let’s briefly consider:
SORTING
-
Dimensional sorting
Sorting by weight
Optical devices
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Dimensional sorting
• Screens of various designs are used to
separate the food based on size
• There are two basic types:
– Fixed aperture screens, and
– Variable aperture screens
Flat-bed screen
http://www.eurositex.cz/en/prumyslova-sita/
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Sorting by weight
• Sorting by weight is a more precise separation
than dimensional sorting
• Equipment designed to handle the products at
sufficient speed is limited
https://www.youtube.com/watch?v=WF6hXpnuFVA
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OVERVIEW of OPTICAL SORTING
1. Product enters machine
2. Vibratory feeders meter product onto chute
3. Product accelerates and singulates
4. Product viewed and classified in midair
5. Product is accepted or rejected
http://www.satake-usa.com/principals-of-optical-sorting.html
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Optical sorters utilize reflected light to analyze products that have been singulated and
presented to the viewing area. This singulation can be achieved utilizing low-friction
inclined chutes or conveyor belts.
Specially designed optical filters narrow the reflected light into specific wavelengths that
accentuate the difference between the acceptable product and the product to be
rejected.
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2. Processing by Application of Heat
• Heat processing using steam or water
– Blanching
– Pasteurization
– Heat Sterilization
– Evaporation
– Extrusion
• Heat processing using hot air
– Dehydration
– Baking and roasting
• Heat processing using hot oils
– Frying
• Heating by irradiated energy
– Microwave and infrared radiation
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3. Processing by the Removal of
Heat
• Chilling and controlled-atmosphere storage
• Freezing
• Freeze drying and freeze concentration
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4. Post-Processing Operations
• Coating or enrobing
– Coating
– Battering and breading
– Seasoning
• Packaging
• Filling and sealing containers
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Let’s focus next on
MASS and ENERGY
Energy
E = mc 2
Matter
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Two very important laws which all unit operations obey are the laws
of conservation of mass and energy.
Conservation of Mass
The law of conservation of mass states that mass can
neither be created nor destroyed. Thus in a processing
plant, the total mass of material entering the plant
equals the total mass of material leaving the plant, less
any accumulation left in the plant.
If there is no accumulation, then the simple rule holds
that "what goes in must come out". Similarly all material
entering a unit operation must in due course leave.
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For example, if milk is being fed into a
centrifuge to separate it into skim milk
and cream, under the law of conservation
of mass the total number of kilograms of
material (milk) entering the centrifuge per
minute must equal the total number of
kilograms of material (skim milk and
cream) that leave the
centrifuge per minute.
The law of conservation of mass applies also to each component in the starting
material. For example, consider the butter fat in the milk entering the centrifuge.
The weight of butter fat entering the centrifuge per minute must be equal to the
weight of butter fat leaving the centrifuge per minute.
A similar relationship will hold for the other components: the milk proteins casein and
whey, the milk sugar lactose, and so on.
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Conservation of Energy
The law of conservation of energy states that energy can neither be
created nor destroyed. The total energy in the materials entering the
processing plant, plus the energy added in the plant, must equal the total
energy leaving the plant.
This is a more complex concept than the conservation of mass, as energy can
take various forms such as kinetic energy, potential energy, heat energy,
chemical energy, electrical energy and so on.
During processing, some of these forms of energy can be converted from one
to another. Mechanical energy in a fluid can be converted through friction into
heat energy. Chemical energy in food is converted by the human body into
mechanical energy.
Note that it is the sum total of all these forms of energy that is conserved.
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Conservation of Energy
For example, consider the pasteurizing process for milk, in which
milk is pumped through a heat exchanger and is first heated and
then cooled.
The energy can be considered either over the whole processing
plant or only as it affects the milk.
For total plant energy, the balance must include: the conversion in
the pump of electrical energy to kinetic and heat energy, the
kinetic and potential energies of the milk entering and leaving the
plant and the various kinds of energy in the heating and cooling
sections, as well as the exiting heat, kinetic and potential energies.
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To the food technologist, the energies affecting the product are
the most important.
In the case of the pasteurizer, the energy affecting the product is
the heat energy in the milk.
Heat energy is added to the milk by the pump and by the hot
water passing through the heat exchanger.
Cooling water then removes part of the heat energy and some of
the heat energy is also lost to the surroundings.
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Conservation of Energy
The heat energy leaving in the milk must equal the heat
energy in the milk entering the pasteurizer plus or
minus any heat added or taken away in the processing
plant.
Heat energy leaving in milk =
initial heat energy . . .
+ heat energy added by pump
+ heat energy added in heating section
- heat energy taken out in cooling section
- heat energy lost to surroundings
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From these laws of conservation of mass and
energy, a balance sheet for materials and for
energy can be drawn up at all times for a
unit operation.
These are called material balances and
energy balances.
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Using a material balance and an energy balance, a food engineering process can be
viewed overall or as a series of units. So we back to the notion of the unit operation.
The unit operation can be represented by a box as shown below:
Unit Operations in Food Processing. Copyright © 1983, R. L. Earle. :: Published by NZIFST (Inc.)
Into the box go the raw materials and energy, out of the box come the desired
products, by-products, wastes and energy. The equipment within the box will
enable the required changes to be made with as little waste of materials and energy
as possible. In other words, the desired products are required to be maximized and
the undesired by-products and wastes minimized. Control over the process is
exercised by regulating the flow of energy, or of materials, or of both.
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In process engineering, the prime considerations are the extent
of the heating or cooling that is required and the conditions under
which this must be accomplished. This specific physical process is
the unit operation called heat transfer or heat exchange.
Heat transfer is a unit operation wherein the fundamental physical
principle underlying it is that heat energy will be transferred
spontaneously from hotter to colder entities.
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Deep-fat frying is one of the oldest unit operations used worldwide. It produces food
products with a unique flavor and texture unlike any other technique. This is one of the
many unit operations you will learn in this class. The mechanisms involved in the heat
and mass transfer of deep-fat frying is very complex. They include heat transfer by
convection and conduction; mass transfer by diffusion, convection, and capillary
pressure. In addition, structural changes occur resulting in a crunchy porous network
characteristic of fried foods. Oil absorption is the least understood transport
phenomenon in this process.
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Let’s take some time now
to focus on the
HEAT TRANSFER
unit operation
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WHAT IS HEAT TRANSFER?
A dynamic process in which heat is transferred spontaneously
from one material to another of lower temperature
PRINCIPLES OF HEAT TRANSFER
- The rate of transfer depends on the differences between the
materials; the greater the temperature difference, the GREATER
the rate of heat transfer
- The DRIVING FORCE in heat transfer is therefore the temperature
difference between the heat source and the receiving material
- An increase in temperature difference results in an increase in
the driving force, increasing the rate of heat transfer
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Mechanisms of heat transfer
H
E
A
T
T
R
A
N
S
F
E
R
Conduction
Convection
Radiation
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Mechanisms of heat transfer
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Two terms that you will come across
related to this topic in this food processing
course as well as food engineering courses:
THERMAL CONDUCTIVITY
A food material’s ability to transfer heat energy
THERMAL DIFFUSIVITY
The ratio of thermal conductivity to the “volumetric
heat capacity” of the food (the ratio of the food
material’s ability to transfer heat to its capacity to
store it
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HEAT TRANSFER APPLICATIONS
These are widespread in the food industry:
•
•
•
•
•
•
•
Milk and juice pasteurization
Fruit and vegetable refrigeration
Meat cold storage/freezing
Canned foods thermal sterilization
Evaporation
Distillation
Drying
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FOURIER’S LAW
The rate of heat flow (Q/t) through a uniform material
is proportional to the area A, the temperature change
(drop) ∆T, and inversely proportional to the length of
the path flow (x).
x
KA ∆T
Q
=
x
t
A = cross-sectional area
∆T = temp difference between ends
x = distance between ends
K = the material’s conductivity
Q
Q
AQ
Q
Q
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What is the basis of FOURIER’S LAW?
It has to do with a property of matter called
THERMAL CONDUCTIVITY (K value)
Heat always conducts from warmer objects to cooler
objects. The composition of a material effects its conduction
rate. If a copper rod and an iron rod are joined together end
to end, and the ends placed in heat sources, the heat will
conduct through the copper end more quickly than the iron
end because copper has a K value of 92, whereas, iron has a
K value of 11. The larger the K, the faster heat will conduct.
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What is a heat exchanger?
- Device for the transfer of heat between two fluids separated
by a partition
- Partition is a heat conducting solid (i.e. metal)
- Heat exchangers are extensively used in the food industry
-
Pasteurizer
Chilled water generator
Freezer
Evaporator
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Comparison of operating designs:
(1) Counterflow heat exchanger
(2) Parallel flow heat exchanger
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COUNTERFLOW HEAT EXCHANGER
Cold
Fluid
Hot
Fluid
Cold
Fluid
Featuring a CLOSED-TYPE DESIGN in which
fluid streams do not come in direct contact
with each other.
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PARALLEL FLOW HEAT EXCHANGER
Hot
Fluid
Cold
Fluid
The hot and cold fluid streams are separated
by a flat wall or plate.
Cold
Fluid
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Two Examples of Heat Exchange Equipment:
(1) Fluid Bed Dryer
(2) Spray Dryer
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Fluid bed technology is used for cooling, heating and drying of bulk solids food and
dairy materials. Fluid bed heat exchange takes place by passing a gas (commonly air)
through a perforated distributor plate which then flows through a layer (bed) of solids.
The air performs two functions. First, the air flows through the bed of solids at a velocity
sufficient to support the weight of the particles, which creates a fluidized state enabling
the particles to flow. Second, the air in the fluid bed serves to cool, heat or dry the
particles as it comes into direct contact with the solids material within the fluid bed
chamber.
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Example:
at input is wet
experimental cake batter
Collected at output:
spray-dried cake batter powdered mix
In a spray dryer, liquid or fine solid material in a slurry is sprayed in the form of a fine
droplet dispersion into a current of heated air. Air and solids may move in parallel or
counterflow.
Drying occurs very rapidly. The dryer body is large so that the particles can settle, as they dry,
without touching the walls on which they might otherwise stick. Commercial dryers can be
on the order of 10 m diameter and 20 m high.
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Thank You.
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