March 2014

FOOD ENGINEERING VOLUME - I

By Pranav Kaushik

Food Sciences Blog Publications

About Page

“Food Engineering Volume - I” Ebook stands as 3rd Ebook in Food Sciences Blog Ebook Series, after “Food Product Development” and “Introduction To High Pressure Processing Of Foods” ebook publications.

I dedicate this ebook to every researcher working in the field of Food Science & Technology.

This ebook can be used as an introductory material to learn food engineering concepts.

This book covers Basic concepts and scope of food engineering. Roles are a food engineer are briefly explained here. This ebook mainly discusses the principles of food engineering.

Different categories of food properties; unit operations and unit processes; mass, momentum and energy balances; importance of transport phenomena and calculus; design and optimization are covered in this ebook.

Future volumes of food engineering will cover the topics – Transport Phenomena, Food Processing Plant Design, Engineering Properties of Food and Application of Food Engineering.

Thanks for your support

Pranav Kaushik

Contents

01. Introduction ......... 03

02. Variations & Definitions ......... 03

03. Scope of Food Engineering ......... 06

04. Roles of a Food Engineer ......... 08

05. Principles of Food Engineering ......... 09

06. Food Properties ......... 10

07. Unit Operations & Unit Processes ......... 13

08. Mass, Energy & Momentum Balances ......... 15

09. Importance of Transport Phenomena ......... 17

10. Advanced Engineering Mathematics ......... 18

11. Design & Optimization ......... 19

12. Conclusion ......... 20

13. References ......... 20

Introduction

The term ‘Food Engineering’ gives us a clear idea that it involves food and engineering concepts.

A branch of food science and technology which involves in agriculture, food science, microbiology, chemistry, physics and engineering.

“Food Engineering” is an inter-disciplinary research area based on physical, chemical and mathematical fundamental principles (microbiology and biochemistry are also considered).

Agricultural Engineering, Chemical Engineering, Mechanical Engineering are like ancestors of Food Engineering as the later area what we see today emerged only due to the advanced research done in former areas during the last 100 years.

Variations & Definitions

Food Engineering is also called as Food Process Engineering as this area involves lot of processes/processing which convert raw food materials into food products.

Although the word ‘Process’ holds significance in the term ‘Food Process Engineering’ as conversion of food from native form into a market-available final product involves 80-100% processing; food process engineering and food engineering are same.

People use general terms like Food Process Engineering, Food Product Engineering and Food Product Development think that all these notations are same but when we zoom into each of these areas, they are different.

Product Engineering – Designing, stabilizing, transforming and creating ingredients and/or products using ‘Unit Operations’.

Process Engineering - Science, Technology and Engineering used to standardize ‘Unit Processes and Unit Operations’ in order to produce new products.

Product Development – Complete process of bringing a new product into the market; right from analyzing the scope till the final step-marketing.

Processing - Set of interrelated tasks that transform inputs into outputs.

When it comes to Food Science and Technology, incorporating “Food” into above statements;

Food Product Engineering – Product Engineering of Food:

Designing, stabilizing, transforming and creating food ingredients, edible micro-structures and products using ‘Unit Operations’.

Food Process Engineering – Process Engineering of Food:

Food Science, Technology and Engineering used to standardize ‘Unit Processes and Unit Operations’ in order to produce new food products.

Food Product Development – Product Development of Food:

Complete process of bringing a new food product into the market; right from analyzing the scope till the final step-marketing.

Food Processing – Processing of Food:

Transformation of raw food ingredients/materials into final food products.

Aren’t they different ???

Yes, they are.

In fact, they are related to each other. In few cases, one is sub-set of other etc.,

Ex: Food Process Engineering deals only with engineering aspects of Food Processing. There are other aspects like Biology concepts, Harvesting/Post-Harvesting Processes, etc., too which are considered during Food Processing.

Thus, we can say Food Process Engineering is a sub-set of Food Processing.

Chemical Engineering Vs Mechanical Engineering – Food Process Industry

Food Process engineering is an integration of Agricultural Engineering, Chemical Engineering and Mechanical Engineering.

I often wondered that the principles used in Food Process Engineering are different from Mechanical Engineering or from Chemical Engineering.

Basic fundamentals are same. Applications differ in both fields.

Mechanical Engineering and Chemical Engineering both overlap with Food Process Engineering.

Only the names are different. Below are the areas common in both fields.

Chemical Engineering Thermodynamics | Mechanical Thermodynamics

Chemical Engineering Fluid Mechanics | Mechanical Fluid Mechanics

Chemical Engineering Transport Phenomena | Mechanical Transport Phenomena

Chemical Engineering Design | Mechanical Engineering Design

Chemical Engineering Heat Transfer | Mechanical Engineering Heat Transfer

The principles related to Fluid Mechanics or Heat or Mass Transfer; they are all same in all these 3 fields – chemical, mechanical and food engineering.

Final Outputs – Efficiency and Yield are important for both mechanical and chemical processes.

Mechanical Industries and Chemical Companies operate the Unit Operations similarly.

Only one difference exists, when mechanical and chemical processes are compared.

Chemical processes are involved in the preparation of Pharmaceuticals, Proteins, Food Ingredients, Food Micro-structures, New Food Products etc.,

All these final products should be pure and safe for consumer use.

“Product Quality” is a very very critical parameter to be considered by Chemical Industries.

A small trace of contamination or harmful toxin or impurity can be fatal to consumers.

Chemical processes should be strictly monitored in Pharmaceutical industries, Food industries and Chemical Industries.

Doesn’t mean that end products of mechanical industries should contain impurities, but pharma or food products are more crucial than mechanical products.

There is No doubt that Mechanical processes give maximum yield and very efficient. Also, accuracy is required.

Hope you understood the difference in both the fields.

Scope of Food Engineering

Food (Process) Engineering primarily involves various unit operations and chemical reaction processes which convert raw materials into final food products.

This area of food science and technology involves basic biological, physical and chemical principles and advanced engineering mathematical principles.

The whole stuff is to produce end products which are

1. Safe and best in quality

2. Convenient and ready to eat

3. Nutritious and healthy

4. Affordable and available in plenty

Food Engineering also deals with design of food-processing equipment for maximum product yield as well as for sanitation/cleaning purposes.

Sanitation also plays a crucial role because chemical, physical and microbiological hazards can be harmful to consumers.

Area-wise Scope:

1. Food Processing Technology

2. Food Machinery and Equipment

3. Food Packaging Technology

4. Food Ingredient Technology

5. Food Manufacturing Processes

6. Instrumentation Control

7. Food Product Development

8. Food Quality control

All the above areas are linked with Food Engineering principles. Food engineers can work in one or combination of more than one areas.

Industrial Sectors:

The below sectors of Food industry utilize engineering principles for the preparation of food products.

1. Bakery – Bread, Snack, flour-related

2. Confectionery – Chocolate, biscuit, sweets

3. Breweries – Tea, Coffee, Wine and other beverages

4. Dairy – Milk, Yogurt, Cheese, Ice cream

5. Fruit, Vegetable – Jam, Jelly, Pickle, ready-to-eat

6. Ingredient – Colors, Flavors, Spices, Oils, Enzymes, Additives

Roles of a Food Engineer

Food Engineering deals with the application of Engineering Principles on Food.

Most importantly; Food Quality, Food Safety and Engineering economics are crucial !!!

It is something like your newly developed food products cannot be accepted by people which are

1. poor in quality,

2. not safe to consume or

3. very very costly

And Quality, Safety and Economics are something very difficult to be optimized, not impossible though.

What are the roles of a food engineer ???

Food Engineers aim @

1. Production of high-quality, safe and nutritious food products Everyone needs quality and nutrition in the food products purchased.

2. Focus on minimizing the spoilage and increasing the shelf-life of food products

People expect food products to exist safe for longer periods.

3. Making the processes more efficient and products more economical

More efficiency => More yield => More profits

More Economical => Cheaper products – More preferred by consumers

4. Reduction of food waste and utilizing energy waste from processing industries

Food Wastage => Affects environment => Global warming, sanitary problems etc.,

Now think how Crucial will be the roles of Food Engineers in Food Industry !!!

Principles of Food Engineering

Food Engineering deals with food manufacturing processes, design and optimization of these unit operations.

Food Engineering is based on the below principles:

1. Food Properties

2. Unit Operations & Unit Processes

3. Mass/Energy Balances

4. Advanced Engineering Mathematics

5. Design and Optimization

Food Properties

Studying the properties of food materials/molecules forms the first and important part of food engineering principles.

Rheological, Optical, Mechanical, Chemical, Thermal, Mass-transfer, Sensory and Electrical properties of food should be properly understood before proceeding to engineering process calculations and material balances.

Food Properties are classified into 8 types

In order to understand the unit operations involved in food manufacturing, one needs to know about the different diverse properties of food molecules.

Properties of food are briefly explained below.

1. Rheological

Rheological properties of food help in understanding the complex structure of foods.

Newtonian and Non-Newtonian fluids are studied based on the viscosity values.

Rheometers and viscometers are the instruments used in the study of rheological properties.

2. Optical

Famous optical properties include Color, Refractive index, colorimetric properties like reflectance, transmittance.

Color is the primary optical property which plays crucial role in consumer acceptance of food products.

Refraction index value can be used to study the structural aspects of food.

Colorimetric properties along with the wavelength values are used to determine the concentration of food samples in spectrophotometer.

3. Mechanical

Mechanical properties include density, shape, particle size, porosity, surface roughness, cellularity, specific gravity, surface tension, elastic modulus, shear, etc.,

In order to study the material science of food particles, one need to know about material properties like elastic modulus, surface tension, specific gravity, density etc.,

Structural and Geometric properties like size, shape, porosity, etc., determine the structural aspects of molecules.

4. Chemical

Chemical and biochemical properties are crucial during the transformations or reaction steps.

Rate constant values for different order of reactions are used to calculate the concentration of reactants or products.

5. Thermal

Specific volume, specific heat, thermal conductivity, boiling point elevation, freezing point depression are thermal properties studied in transport phenomena.

They characterize the heat transfer mechanisms in different unit operations like refrigerators, heat exchangers, evaporators etc.,

Specific heat, thermal conductivity explain about the heat energy flow rate. Where as thermal diffusivity says about the speed of heat in a 3 dimensional plane.

6. Mass-transfer

Diffusivity, permeability and other mass transfer properties are used to study the transformation process of food reactants to products.

7. Sensory

May it be color or flavor; texture or hardness; sensory properties play vital role in producing desired foods.

8. Electrical

Electrical conductivity, permittivity are used to study the food processing mechanism in Pulsed Electric fields, Ohmic heating and Microwave Processing.

Conductivity is a mandatory property which need to be studied for Process design.

Unit Operations & Unit Processes

A process requires many unit operations and unit processes to obtain the desired product from the starting materials or feedstocks.

Process = Sum (Unit Operations + Unit Processes)

Engineering unit operations and engineering unit processes form the main principles of all kinds of food-processing industries and are the foundations for designing food-processing plants and equipments.

Unit Operations mean the units which depends solely on physical principles.

Suppose consider membrane filter where products are separated based on membrane pore size. (Size – Physical property)

Unit Operations are large operating units based on physical principles. These are operated in series or parallel to achieve the desired results.

Examples: Separation, Filtration, Evaporation, Homogenization, Freezing, etc.,

Process Engineering Unit Operations are categorized into 5 groups:

1. Thermodynamic processes – Refrigeration, Liquefaction

2. Mechanical processes – Crushing, Homogenization

3. Fluid flow processes – Filtration, Fluidization, Fluid transport

4. Heat Transfer processes – Evaporation, Heat exchangers

5. Mass Transfer processes – Distillation, Extraction, Drying

Unit Processes mean Chemical Processes which involve chemical reactions. Polymerization, Fermentation, Isomerization etc., come under this category.

Unit Processes involve in chemical transformations which are primarily based on chemical principles.

Fermenter or biochemical reactor, Baking unit, Sterilizer can be perfect examples for unit processes.

Understanding the mechanism of each unit process and unit operation clearly, helps in working on material balances and proper construction/design of mathematical solutions for complete processing plant.

Engineering Chemical Processes are classified into different types.

Some of them are:

1. Fermentation – Curd/yogurt, wine

2. Hydrogenation – Hydrogenation of vegetable oils

3. Hydrolysis – Vegetable Protein hydrolysis

4. Dehydration – Powders such as milk powders, flours

5. Esterification – Trans-esterification of lipids

6. Polymerization – Packaging material

7. Catalysis – Magarine (nickel), corn syrup (glucose-isomerase)

Mass, Energy & Momentum Balances

Once the food properties are studied and unit operations/chemical processes are identified, material balances need to be worked out.

Material balances include mass balance and energy balance in single unit processes as well as multiple unit processes.

Mass balance is based on Law of Conversation of Mass which states that the mass of closed system should remain constant over time. Even if any chemical, nuclear reaction or radio-active decay occurs, mass of the system is conversed within the system.

Energy balance is based on Law of Conversation of Energy. This states that the total energy within an isolated system cannot be changed.

Let us consider an example of unit operation where mass-transfer is happening as well as thermal energy is involved.

Now for mass-transfer phenomena; all possible cases of diffusion/ conduction/convection/radiation are considered to give out mass balance equation.

Input = Output, in a steady state

For unsteady state situations, some amount of mass is gathered within the unit. This is termed as accumulation.

Considering the above case, mass balance is given as Mass accumulation = Total Input mass flow – Total Output mass flow

Energy balance equation is given asEnergy accumulation/Power = Total Input energy flow – Total Output energy flow

If suppose, any of the mechanical properties are changing (in specific – fluid mechanics related), then they should also be considered.

Considering energy generation and depletion cases, over all equation for energy balance is given by

Input + Generation = Output + Accumulation + Consumption

Momentum Balance:

Apart from Mass and Energy; there is one more quantity called Momentum which is considered for over all balance within the system.

Dynamics of a process cannot be understood with Momentum changes occurring in the system because force (Dynamic quantity) is the rate of change of momentum.

Drag, thrust, pressure, torque, stress over a definite area are all relational to the concept of force or rate of change of momentum.

To understand

– drag/thrust which increases/decreases the velocity of the object,

– torque which produces changes in rotational speed of the object,

– stress(pressure) which causes deformation/flow in solids/fluids

one needs to study about momentum changes and derive overall equations for momentum rate balance for each distinct case.

Momentum Balance is based on Conversation of Momentum (Linear as well as Angular) which states total momentum is constant within a closed system.

Importance of Transport PhenomenaTransport phenomena deals with the fundamental principles of heat, momentum and mass transport.

Using the conservation laws of mass, momentum and energy; overall balance equations are designed and these primary equations are used to calculate relevant profiles like velocity, heat and mass.

In fluid mechanics, overall momentum balance equation can be used to determine the velocity profiles for different applications (falling film, slab, annulus, sphere)

Similarly, overall energy balance equation is used to determine heat and temperature profiles for geometric cases like cylinder, sphere, rectangular slab etc.,

Overall mass balance equation gives the concentration profiles and mass flow rate value for different chemical- homogenous and heterogeneous reactions.

Each transport phenomenon is an attempt to move the system towards equilibrium.

Heat – Thermal Equilibrium Momentum – Mechanical Equilibrium Mass – Chemical Equilibrium

Fluid dynamics deals with the empirical and non-empirical laws derived from flow measurement and modeling of velocity, pressure, density and temperature profiles with respect to variables -space and time.

Mass transfer deals with diffusive and convective transport of chemical species and derivations of concentration & mass-flux profiles with respect to time and space.

Heat transfer deals with the derivation of temperature, heat flow rate and pressure profiles as functions of time and distance.

To derive these profiles for unit operations and unit processes in food processing plants; knowledge of transport phenomena is mandatory.

Hence, these transport processes hold significance in process engineering studies.

Advanced Engineering Mathematics

Mathematical equations are designed using the principles of applied statistics, integral and differential calculus.

Basic equations in mathematics are applied to specific cases like heat exchanger, membrane filter, evaporator, refrigerator.

Depending on mensuration parameters like length, area, height, radius, etc., and food properties like specific heat, thermal conductivity, diffusivity, convective heat transfer co-efficient, viscosity etc., the basic equations are integrated to get mathematical solutions for each unit operations existing in different modules or shapes.

Why Calculus?

Many food engineering problems are solved using (calculus) differential and integral equations.

It is very difficult to understand the mechanisms of mass, energy and momentum transfer on a large space and over a long time period.

Hence, the observations are done within a limiting system (time or volume) and using mathematical equations, extended to the whole system.

1. Considering differential balance and generating differential equations

2. Solving differential equations using analytical and numerical integration

This is an effective tool for modeling, simulation and understanding the system.

Consider a differential heat energy balance equation within an infinitely small time period (almost zero).

This equation can be integrated to whole system and solved to obtain temperature and heat flow rate profile functions using initial and boundary conditions for specific cases.

Design & Optimization

Designing a food processing plant on lab scale or pilot scale requires thorough knowledge on design parameters.

Design parameters are mainly based on the process to be followed.

Process includes process organization, materials flow, process automation, packaging, data collection, process equipment, waste disposal plan etc.,

Process also involves in instrumentation control for monitoring physical and chemical parameters like pressure, temperature, heat, pH, concentration, etc.,

Handlers such as conveyer belts, pneumatic conveying systems, elevators, of necessary need to be designed as part of processing plant.

This is not over yet. There are lot of things to be studied many times about the Facility (Location, Construction, Budget estimates, Clearances, etc.,)

Right from the selection of facility such as infrastructure, utilities, sanitation, access; till the flooring, process equipment handling, warehousing, waste water treatment; all facility factors should be considered.

Optimization is a fundamental task for process engineering industries.

Experimental design, estimation of parameters, development of model, process analysis, process design, statistical analysis, integration of process operations into manufacturing and distribution are the components observed for optimization of food-process engineering processes.

Along with engineering processes, parameters like temperature, pressure, pH, concentration, molar volume, humidity etc., are also optimized to ensure high yield of desired products.

Conclusion

Food Engineering deals with the food manufacturing processes – unit operations and chemical reactions, design and optimization of engineering processes.

Food Engineering involves the concepts of Process Calculations, Transport Phenomena–Fluid Mechanics, Heat transfer and Mass transfer, Chemical/ Biochemical Reaction Engineering and Process Design.

Definitions and Variations related to food engineering are explained. Scope and Principles of Food Engineering are covered and roles of food engineer are briefly listed.

This ebook has covered the basics of food engineering briefly. Future volumes of Food Engineering ebook will focus on Applications of Food Engineering, Unit Operations, Chemical Processes, Transport Phenomena, Designing a pilot plant, Optimization methods.

References

Books:

1. Unit Operations In Food Processing – R. L. Earle and M. D. Earle http://www.nzifst.org.nz/unitoperations/matlenerg2.htm

2. Introduction to Food Engineering – R Paul Singh and Dennis R Heldman

3. Food Process Engineering and Technology – Zeki Berk, Taylor : Elsevier

4. Transport Phenomena – R. B. Bird, Warren E. Stewart and Edwin N. Lightfoot

Other resources:

1. Food Engineering Design And Economics http://food.ege.edu.tr/files/designlecturenoteschp2.ppt

2. http://en.wikipedia.org/wiki/Transport_phenomena