Handbook of Food Process Design docx

Keklik Introduction 1166 Advanced Levels of Process Design for Complicated Systems 1178 References 1184 40 High-Voltage Food Processing Technology: Theory, Processing Paul Takhistov Int

Edited by

Jasim Ahmed, PhD

Kuwait Institute for Scientifi c Research

Safat, Kuwait

Mohammad Shafi ur Rahman, PhD

Sultan Qaboos University

Muscat, Sultanate of Oman

A John Wiley & Sons, Ltd., Publication

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Library of Congress Cataloging-in-Publication Data

Handbook of food process design / edited by Jasim Ahmed, M.Shafiur Rahman.

p cm.

Includes bibliographical references and index.

ISBN-13: 978-1-4443-3011-3 (hardback)

ISBN-10: 1-4443-3011-X (hardback)

1 Food processing plants–Design and construction 2 Food processing machinery.

3 Food industry and trade I Rahman, Shafiur

TH4526.H36 2011

664'.02–dc23

2011022689

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Preface xix

Mohammad Shafi ur Rahman

Introduction 1

References 16

Mohammad Shafi ur Rahman and Jasim Ahmed

Introduction 18

E Özgül Evranuz and Meral Kılıç-Akyılmaz

Introduction 39

Examples of Material Balance Calculations with and without

Santanu Basu and Pinaki Bhattacharya

Introduction 74

References 111

Jasim Ahmed, Kirk Dolan and Dharmendra Mishra

Introduction 113

Conclusions 158References 159

7 Thermal Food Processing Optimization: Single and Multi-objective

Ricardo Simpson and Alik Abakarov

Introduction 167

Single-objective Optimization of Thermal Food Processing 171

References 185

Weibiao Zhou and Nantawan Therdthai

Introduction 190

Measurements and Sensors in Food Process Control Systems 192

Recently Developed Measurement Techniques for Food Processes 201Summary 207References 207

Kazi Bayzid Kabir and M.A.A Shoukat Choudhury

Introduction 211

Current Practice and Future Trends in Food Process Automation 233Conclusions 236References 236

10 Use of Various Computational Tools and gPROMS for Modelling

I.M Mujtaba

Introduction 239

Model-based Techniques in Food Processing: Simulation, Optimisation

Conclusions 253References 254

Jasim Ahmed and Rajib Ul Alam Uzzal

Introduction 262

Gary Tucker

Introduction 335

References 361

Ricardo Simpson, Helena Núñez and Sergio Almonacid

Introduction 362Importance of Microorganisms in Sterilization and Pasteurization 363

Quality Evaluation 373

Acknowledgments 379References 379

Mohd Kaleem Khan

Introduction 381Refrigeration 382

References 428

Mohammad Shafi ur Rahman

Introduction 430Chilling 430Freezing 433Thawing 452Nomenclature 453References 455

Tarif Ali Adib

Introduction 460

Single-effect Evaporator and Design Calculations for Evaporators 463

Gianpaolo Ruocco and Maria Valeria De Bonis

Introduction 489

Food Processing and Control of Heating/Drying Treatments 499Conclusions 505Nomenclature 506References 508

Jasim Ahmed, U.S Shivhare and Rajib Ul Alam Uzzal

Introduction 510

Conclusions 539Acknowledgment 539References 539

R.T Patil and Dattatreya M Kadam

Introduction 542

Acknowledgment 576

Websites 577

M.N.A Hawlader and K.A Jahangeer

Introduction 578

Summary 615Nomenclature 616References 618

22 Freeze-drying Process Design 621

John J Fitzpatrick

Introduction 648Crystallization 651

Process Design of Continuous Evaporative and Vacuum Evaporative

Crystallizers 672

References 680

Prabhat Kumar, K.P Sandeep and Josip Simunovic

Introduction 682

References 707

Kasiviswanathan Muthukumarappan and Chinnadurai Karunanithy

Introduction 710

Supercritical Fluid Extrusion 732

Conclusions 734References 735

Emmanuel Purlis

Introduction 743

Rohit Ruhal and Bijan Choudhury

Introduction 769

Basic Theoretical Principle, Membrane Operation Mode

Fouling of Membrane in Ultrafi ltration and Microfi ltration 784

Applications 784Conclusions 786References 787

Ferruh Erdogdu and T Koray Palazoglu

Introduction 789

Quality Attributes of Fried Products 793

References 830

Siddhartha Singha and Tapobrata Panda

Introduction 834

Mixing Equipment: Mode of Operation and Comparative Analysis 839

Capital and Operating Costs for Different-sized Equipment 866

References 868

Q Tuan Pham and Frank P Lucien

Introduction 871

Economics 911

Nomenclature 913References 915

M Reza Zareifard, Ali Esehaghbeygi and Amin Allah Masoumi

Introduction 919

Devices 936

References 961

Rod Chu

Introduction 967

Capital and Operating Costs for Different Sizes of Equipment 991

References 994

Tatiana Koutchma

Introduction 998

HHP Pasteurization 1004

References 1025

Francesco Marra

Introduction 1031Indirect Electroheating: Basic Information about MW and RF Heating 1032Empirical Data and Properties Needed for Designing MW

Equipment 1041

References 1052

Ilkay Sensoy

Introduction 1057Applications of Ohmic Heating and Moderate-Electric-Field Processing 1059

Nomenclature 1071References 1072

Federico Gómez Galindo and Pär Henriksson

Introduction 1078

Calculations, Monitoring and Optimization of Treatment Parameters 1093

References 1100

38 Process Design Involving Ultrasound 1107

Jordi Salazar, Antoni Turó, Juan A Chávez

and Miguel J García-Hernández

Ali Demirci and Nene M Keklik

Introduction 1166

Advanced Levels of Process Design for Complicated Systems 1178

References 1184

40 High-Voltage Food Processing Technology: Theory, Processing

Paul Takhistov

Introduction 1188Unifi ed Analysis of Electric-Field-Based Food

Pulsed Electric Fields in Food Processing and Preservation 1202

Mathematical Model of Continuous Operation (Esplugas et al., 2001) 1218

Process Calculations 1219Physical Properties of Food Products for PEF Processing 1219

References 1229

41 An Overview of Food Packaging: Material Selection and

Jasim Ahmed and Tanweer Alam

Introduction 1237

Conclusions 1276References 1276

Marcella Mastromatteo, Amalia Conte and Matteo Alessandro

Del Nobile

Introduction 1284

References 1332

Gurbuz Gunes and Celale Kirkin

Introduction 1340

Nomenclature 1361References 1362

44 Packaging for Processed Food and the Environment 1369

Eva Almenar, Muhammad Siddiq and Crispin Merkel

Introduction 1369

The Future: the Role of Consumers and the Food Industry in the

Acknowledgment 1397References 1398

45 Food Quality and Safety Assurance by Hazard Analysis and

Tomás Norton and Brijesh Tiwari

Introduction 1406Introduction to Hazard Analysis Critical Control Points (HACCP) 1408

References 1433

Gerard La Rooy

Introduction 1436

References 1470

Generally, a process is defi ned as a sequence of events that transforms the biological materials of food products, via biochemical changes, into stable forms with added

value This can create new products or modify existing ones Process design refers to the design of food processes and manufacturing methods, while plant design refers to

the design of the whole processing plant The processing of food is no longer as simple

or straightforward as in the past Food process design is an interdisciplinary science that is highly regarded by the food industry The architecture of food process engineer-ing is based on the solid foundations of chemical and mechanical engineering, together with the basics of microbiology, chemistry, nutrition, and economics Other related disciplines, including instrumentation, computer science and mathematics, complete the discipline Process design is the core of food engineering, and frequently begins with a concept and eventually ends in fabrication Many types of documentation are involved in the process to test theories, display results, and organize data

Today, the food industry is one of the largest manufacturing industries in the world and the signifi cant contribution of food engineers to the industry is well recognized

A professional food engineer should be well versed in the basic principles, processes,

fl ow diagrams, instrumentation and process control The Handbook of Food Process Design has been developed primarily for fulfi lling these expectations and is intended

to be used by students in undergraduate and graduate courses in food process ing/food technology/biochemical engineering, as well as by professionals working in the food industry It could also be used by graduates in other disciplines, such as chemical and/or mechanical engineering

The editors of this book have vast experience in teaching, research, and extension activities related to the food industry and have long realized the need for such a hand-book on process equipment design to fi ll the current gap in the basic and applied fi elds

of food engineering They have endeavoured to gather eminent academics and sionals from across the globe and have succeeded in securing their participation in this book All the contributors have diverse backgrounds, ranging from electronic engineering to food science

The book contains 46 chapters in two volumes, with chapters grouped according to their similar subject matter Chapters 1 – 12 are devoted to the basic principles, starting with units and dimensions, moving on to thermodynamics and reaction kinetics per-taining to foods, and followed by sensors and instrumentation involved in process automation The handbook is well balanced by its coverage of unit operations involved

in conventional and novel processing technologies to be used by the food industry

Each chapter is intended to provide concise up - to - date descriptions of fundamentals, applications, solved problems, and methods of cost analysis Chapters 13 – 18 cover heating and cooling systems used in food processing, including pasteurization, steri-lization, refrigeration, and freezing Drying is considered one of the most successful unit operations used in the food industry Process design related to the drying of food materials is covered in Chapters 19 – 22

Some important process designs, such as crystallization, extrusion, aseptic ing, baking, and frying, are well discussed in Chapters 23 – 28 Chapters 29 – 32 cover mechanical operations related to food process industries, including mixing/agitation, size reduction, and extraction and leaching processes Chapters 33 – 40 focus on novel process designs, including pulsed light, ultrasound, ohmic heating, pulsed electric

process-fi eld, high pressure, and irradiation Food packaging is discussed in Chapters 41 – 44 , while quality systems and cost analysis are covered in Chapters 45 and 46

The editors are confi dent that this handbook will prove to be interesting, tive, and enlightening to readers in the fi eld They would appreciate receiving new information and comments to assist in future development of the next edition

Jasim Ahmed Mohammad Shafi ur Rahman

We would like to thank Almighty Allah for giving us life and the opportunity to gain knowledge to write this important book We wish to express our sincere gratitude to the Sultan Qaboos University, Polymer Source Inc and Kuwait Institute for Scientifi c Research for providing the opportunity and facilities to execute such an exciting project, and for supporting us in research and other intellectual activities around the globe

We sincerely acknowledge the sacrifi ces made by our parents during our early cation Appreciation is due to all our teachers in the course of our careers Special thanks to our colleagues and other research team members for their support and encouragement We are grateful to our contributors for their wonderful cooperation and, fi nally, we are indebted to our families for their continued support and patience throughout the project

Jasim Ahmed

Jasim Ahmed, Research Scientist, at Kuwait Institute for Scientifi c Research, Kuwait,

is the author or co - author of over 150 technical articles including 95 refereed journal papers, 40 conference papers, 18 book chapters, 20 popular articles, and 4 books He

has edited several books including Novel Food Processing: Effects on Rheological and Functional Properties and Starch - based Polymeric Materials and Nanocomposites: Starch Chemistry, Processing and Applications published by CRC Press, Boca Raton,

Florida, and Handbook of Vegetables and Vegetables Processing and Handbook of Tropical and Subtropical Fruits Processing and Packaging published by Wiley - Blackwell, NJ

Dr Ahmed has served as an editor of the International Journal of Food Properties

for more than 5 years Furthermore, he has served as special editor for a number of other journals He is also associated with the editorial boards of three international journals In 2010, he was invited to serve as a sub - panel member for the Food Processing and Packaging Section of the Institute of Food Technology (IFT), Chicago, USA

Dr Ahmed is a professional member of the Institute of Food Technology (IFT) and

a life member of the Association of Food Scientists and Technologists (AFST), India

He has been involved in many professional activities, such as organizing international conferences, industrial training and workshops He received the BTech (Food and Biochemical Engineering) in 1991 and MTech (Food and Biochemical Engineering) in

1993 from Jadavpur University, Kolkata, India, and PhD in Food Technology in 2000 from GND University, India He worked as Visiting Professor and Research Director

at McGill University, and Polymer Source Inc., Montreal, Canada, before moving to Kuwait

Dr Ahmed was awarded a gold medal by Jadavpur University, India for securing the top position in the M.Tech degree He has received several grants from various funding agencies to carry out his research during his academic career He received a best reviewers ’ award by Elsevier in the area of food engineering in 2009

Dr Ahmed has been involved in food processing teaching, research and industry over

18 years and has proved himself an active scientist in the area of food engineering He has worked on food product development, food rheology and structure, novel food processing and the thermal behaviors of foods His current research focus is on biopolymer and starch - based nanocomposites Dr Ahmed ’ s work has been well recog-nized globally: there are more than 1000 citations of his work and his h - index is 20

Mohammad Shafi ur Rahman

Mohammad Shafi ur Rahman, Professor at the Sultan Qaboos University, Sultanate of Oman, is the author or co - author of over 250 technical articles including 90 refereed journal papers, 87 conference papers, 58 book chapters, 34 reports, 12 popular articles, and seven books He is the author of the internationally acclaimed and award - wining

Food Properties Handbook , published by CRC Press, Boca Raton, Florida, which was

one of CRC ’ s bestsellers in 2002 The second edition is now released under his

editor-ship He was also the editor of the popular book Handbook of Food Preservation

published by CRC Press, Boca Raton, Florida The fi rst edition was one of CRC ’ s bestsellers in 2003, and the second edition is now on the market He was invited to

serve as one of the associate editors for the Handbook of Food Science, Engineering and Technology , and as one of the editors for the Handbook of Food and Bioprocess Modeling Techniques published by CRC Press

Professor Rahman initiated the International Journal of Food Properties (published

by Marcel Dekker) and has served as the founding editor for more than 10 years He also serves on the editorial boards of eight international journals He is a member on the Food Engineering Series Editorial Board of Springer Science, New York, and serves

as a section editor for the Sultan Qaboos University Journal of Agricultural Sciences

In 1998 he was invited to serve as a Food Science Adviser for the International Foundation for Science (IFS) in Sweden

Professor Rahman is a professional member of the New Zealand Institute of Food Science and Technology and the Institute of Food Technologists, a member of the American Society of Agricultural Engineers and the American Institute of Chemical Engineers, and Member of the Executive Committee of the International Society of Food Engineering (ISFE) He has been involved in many professional activities, such

as organizing international conferences, training workshops and other extension ities related to the food industry He has been a keynote/plenary speaker at many international conferences He received the BSc Eng (Chemical) in 1983 and MSc Eng (Chemical) in 1984 from Bangladesh University of Engineering and Technology, Dhaka, MSc in food engineering in 1985 from Leeds University, England, and PhD in food engineering in 1992 from the University of New South Wales, Sydney, Australia Professor Rahman has received numerous awards and fellowships in recognition of his research and teaching achievements, including the HortResearch Chairman ’ s Award, the Bilateral Research Activities Program (BRAP) Award, CAMS Outstanding Researcher Award 2003, SQU Distinction in Research Award 2008, and the British Council Fellowship In 2008 Professor Rahman ranked among the top fi ve leading scientists and engineers of 57 OIC member states in the agroscience discipline Professor Rahman is an eminent scientist and academic in the area of food process-ing He is recognized for his signifi cant contributions to the basic and applied knowl-edge of food properties related to food structure, engineering properties and food stability His total SCOPUS citation is more than 1200 and his h - index is 20, which indicates the high impact of his research in the international scientifi c community

Mohammad Shafi ur Rahman, PhD

Technical University of Madrid, Higher Technical School of Agricultural

Engineering, Madrid, Spain

Rajib Ul Alam Uzzal, PhD

Powertrain Control Engineer

Chrysler Technical Center

Chrysler Drive, Auburn Hills, Michigan, USA

email: rajiboic@gmail.com

Tanweer Alam, PhD

Associate Professor (Joint Director)

Indian Institute of Packaging, Mumbai, India

email: amtanweer@rediffmail.com

Department of Food Engineering

National Institute of Food Technology, Entrepreneurship and Management, Kundli, Haryana, India

Sensor Systems Group, Department of Electronic Engineering, Universitat

Polit è cnica de Catalunya, Barcelona, Spain

M.A.A Shoukat Choudhury, PhD

Maria Valeria De Bonis, PhD

Post - doctoral teaching assistant

CFDfood - DITEC, Universit à degli Studi della Basilicata, Potenza, Italy

Department of Agricultural and Biological Engineering, Pennsylvania State

University, University Park, Pennsylvania, USA

Ferruh Erdogdu, PhD

Professor of Food Process Engineering

Department of Food Engineering, University of Mersin, Mersin, Turkey

Professor of Food Process Engineering

Food Engineering Department; Faculty of Chemical & Metallurgical Engineering; Istanbul Technical University, Maslak, İ stanbul, Turkey

Sensor Systems Group, Department of Electronic Engineering, Universitat

Polit è cnica de Catalunya, Barcelona, Spain

M.N.A Hawlader, PhD

Professor

Department of Mechanical Engineering, Faculty of Engineering

International Islamic University Malaysia, Jalan Gombak, Kuala Lumpur, Malaysia email: mehawlader@iium.edi.my

P ä r Henriksson

Managing Director

Arc Aroma Pure AB, Lund, Sweden

email: info@arcaromapure.se

K.A Jahangeer, MEng, MIES

Professional Offi cer (Academic Research)

Department of Mechanical Engineering, National University of Singapore, Singapore email: mpejkah@nus.edu.sg

Kazi Bayzid Kabir, PhD

Agricultural and Biosystems Engineering Department, South Dakota State

University, Brookings, South Dakota, USA

Gerard La Rooy, Dip Mgt, MBA (Otago)

Round Earth Business Process Improvement, Havelock North, New Zealand

Marcella Mastromatteo, PhD

Post - doc

Istituto per la Ricerca e le Applicazioni Biotecnologiche per la Sicurezza e la

Valorizzazione dei Prodotti Tipici e di Qualit à – BIOAGROMED, Foggia, Italy email: ma.mastromatteo@unifg.it

Thermal Process Expert

Nestle Nutrition, Fremont, Michigan, USA

Agricultural and Biosystems Engineering Department, South Dakota State

University, Brookings, South Dakota, USA

email: Kas.Muthukum@sdstate.edu

Tom á s Norton, PhD

Senior Lecturer

Harper Adams University College, Newport, Shropshire, UK

email: tnorton@harper - adams.ac.uk

Tapobrata Panda, PhD

Professor

Biochemical Engineering Laboratory, Indian Institute of Technology Madras,

Chennai, Tamilnadu, India

Centro de Investigaci ó n y Desarrollo en Criotecnolog í a de Alimentos

(CIDCA – CONICET La Plata), Facultad de Ciencias Exactas, UNLP, La Plata, Argentina

Sensor Systems Group, Department of Electronic Engineering, Universitat

Polit è cnica de Catalunya, Barcelona, Spain

email: ricardo.simpson@usm.cl

Josip Simunovic, PhD

Research Associate Professor

Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina, USA

email: josip_simunovic@ncsu.edu

Siddhartha Singha, MTech

Research Scholar

Biochemical Engineering Laboratory, Indian Institute of Technology Madras,

Chennai, Tamilnadu, India

Department of Product Development, Faculty of Agro - Industry, Kasetsart

University, Bangkok, Thailand

Head of Baking and Cereals Processing

Campden BRI, Chipping Campden, UK

email: g.tucker@campden.co.uk

Antoni Tur ó , PhD

Associate Professor

Sensor Systems Group, Department of Electronic Engineering, Universitat

Polit è cnica de Catalunya, Barcelona, Spain

email: antoni.turo@upc.edu

M Reza Zareifard, PhD

Food Engineering Researcher

Agriculture and Agri - Food Canada, Food Research and Development Centre, Ste Hyacinthe, Quebec, Canada

Food Preservation and Processing Methods

Mohammad Shafi ur Rahman

1

Introduction

Innovation, sustainability and safety have become the main foci of the modern food industry Food preservation involves the actions taken to maintain foods with the desired properties or nature for a desired time frame (Rahman, 2007 ) For example, a fresh sandwich has a shelf - life of about 1 day, whereas canned vegetables have a shelf - life of at least 1 year First it is important to identify the properties or characteristics one wants to preserve A property may be important in one product but detrimental

in others For example, collapse and pore formation occurs during the drying of foods, and this can be desirable or undesirable depending on the desired quality of the dried product Two illustrations will suffi ce: fi rstly, crust formation is desirable for long bowl life in the case of breakfast cereal ingredients, whereas quick rehydration is necessary (i.e no crust and open pores) for instant soup ingredients; and secondly, consumers expect apple juice to be clear whereas orange juice can be cloudy In the case of preservation and safety we want to eliminate pathogenic and spoilage bacteria, whereas in the case of yoghurt we want to preserve the benefi cial lactic acid bacteria

The preservation and processing of food is not as simple or straightforward as it was

in the past: it is now progressing from an art to a highly interdisciplinary science A

Handbook of Food Process Design, First Edition Edited by Jasim Ahmed and Mohammad Shafi ur Rahman.

© 2012 Blackwell Publishing Ltd Published 2012 by Blackwell Publishing Ltd.

number of new preservation techniques are being developed to satisfy the current demands of economic preservation and consumer satisfaction with regard to nutri-tional and sensory aspects, convenience, safety, absence of chemical preservatives, low price, and environmental safety The ultimate success of the food industry lies in the timely adoption and effi cient implementation of the emerging new technologies

to satisfy the present and future demands of consumers The preservation method is mainly based on the types of food that need to be prepared or formulated The factors that should be considered before selecting a preservation process include the desired quality of the product, the economics of the process, and the environmental impact

of the methods Food industry waste is now also of concern to both enforcement authorities and consumers Food waste is not only an economic loss, but also has an impact on the environment It is important to make every effort to minimize waste from the food industry, to set up effective recycling systems, and to implement suit-able systems for value - added products

Purpose of Food Preservation

The main reasons for food preservation are to overcome inappropriate planning in agriculture, to produce value - added products, and to provide variation in the diet (Rahman, 2007 ) The agricultural industry produces raw food materials in different sectors Inadequate management or improper planning in agricultural production can

be overcome by avoiding inappropriate areas, times, and amounts of raw food als as well as by increasing storage life using simple methods of preservation Value - added food products can provide better - quality foods in terms of improved nutritional, functional, convenience and sensory properties Consumer demand for healthier and more convenient foods also affects the way that food is preserved Eating should be pleasurable to the consumer, and not be boring People like to eat a wide variety of foods with different tastes and fl avors Variation in the diet is important, particularly

materi-in underdeveloped countries materi-in order to reduce reliance on a specifi c type of gramateri-in (i.e rice or wheat) In addition food preservation, storage and distribution are also important factors in achieving food security In food preservation, the important points that need to be considered are desired quality, desired shelf - life, and target consumers

the food becoming extremely hazardous to minor deterioration such as loss of color (Gould, 1989 )

Desired Shelf - life

One of the the most important factors to consider when preserving a food product is the length of time before it becomes unsuitable for consumption (i.e its shelf - life) Shelf - life is determined by the manufacturer and recommends the length of time that products can be stored during which the quality remains acceptable under specifi ed conditions of distribution, storage, and display A product that has passed its shelf - life might still be safe, but quality is no longer guaranteed The best - before date is shorter than the shelf - life by a good margin Hence, it is usually safe to consume a product after the best - before date, provided the product has been stored under the recom-mended conditions, but it may begin to lose its optimum fl avor and texture

In studying the shelf - life of foods, it is important to measure the rate of change of

a given quality attribute (Singh, 1994 ) Product quality can be defi ned using many factors, including appearance, yield, eating characteristics, and microbial characteris-tics, but ultimately the product must provide a pleasurable experience for the con-sumer (Sebranek, 1996 ) Loss of quality is very dependent on the food type and composition, formulation (for manufactured foods), packaging, and storage conditions (Gould, 1989 ) Loss of quality can be minimized at any stage and thus quality depends

on the overall control of the processing chain The required length of preservation depends on the purpose In many cases, very prolonged storage or shelf - life is not required, which simplifi es both transport and marketing of the foodstuff For example, prepared meals for lunch need a shelf - life of only one or even half a day In this case there is no point in ensuring preservation of the product for weeks or months In other cases very long shelf - lives up to 3 – 5 years may be required, for example foods for space travelers, and food storage during wars

Target Consumers

It is important to know for whom the preserved food is being produced Nutritional requirements and food restrictions apply to different population groups Food poison-ing can be fatal, especially in infants, pregnant women, the elderly, and those with depressed immune systems The legal aspects of food preservation are different in foods produced for human or animal consumption Thus, it is necessary to consider the group for whom the products are being manufactured

Food Preservation Methods

At present different methods of food preservation are available for the food industry Based on the mode of action, the major food preservation techniques can be

categorized as (i) slowing down or inhibiting chemical deterioration and microbial growth, (ii) directly inactivating bacteria, yeasts, molds, or enzymes, and (iii) avoiding recontamination before and after processing (Gould, 1989, 1995 ) A number of tech-niques or methods from the above categories are shown in Figure 1.1 In many cases

it would be very diffi cult to make a clear distinction between inhibition and tion Take, for example, preservation by drying and freezing Although the main purpose of freezing and drying is to control the growth of microorganisms during storage, there is also some destruction of microorganisms Freezing causes the appar-ent death of 10 – 60% of the viable microbial population and this gradually increases during storage The following sections summarize food preservation methods (reviewed

inactiva-by Rahman, 2007 )

Inhibition

Methods based on inhibition include those that rely on control of the environment (e.g temperature control), those that result from particular methods of processing (e.g microstructural control), and those that depend on the intrinsic properties of particular foods (e.g control by adjustment of water activity or pH) (Gould, 1995 ) The danger zone for microbial growth is considered to be between 5 and 60 ° C; thus food products

Figure 1.1 Major food preservation techniques (From Gould, 1989, 1995 )

Packaging Hygienic processing Hygienic storage Aseptic processing HACCP

GMP ISO 9000 TQM Risk analysis and management

Food Preservation Methods

chilled and stored at a temperature below 5 ° C is one of the most popular methods of food preservation

Use of Chemicals

The use of chemicals in foods is a well - known method of food preservation A wide variety of chemicals and additives are used in food preservation to control pH, as antimicrobial agents and antioxidants, and to provide food functionality as well as preservative action Some additives are entirely synthetic (not found in nature), such

as the phenolic antioxidant tertiary butylhydroquinone (TBHQ), while others are extracted from natural sources, such as vitamin E Irrespective of origin, food additives must accomplish some desired function in the food to which they are added, and they must be safe to consume under the intended conditions of use

Many legally permitted preservatives in foods are organic acids and esters, including sulfi tes, nitrites, acetic acid, citric acid, lactic acid, sorbic acid, benzoic acid, sodium diacetate, sodium benzoate, methylparaben, ethylparaben, propylparaben, and sodium

propionate (Silliker et al 1980 ) When a weak acid is dissolved in water, an

equilib-rium is established between undissociated acid molecules and charged anions, the proportion of undissociated acid increasing with lower pH The currently accepted theory of preservative action suggests inhibition via depression of internal pH Undissociated acid molecules are lipophilic and pass readily through the plasma mem-brane by diffusion In the cytoplasm (pH approximately 7.0), acid molecules dissociate into charged anions and protons These cannot pass across the lipid bilayer and accu-

mulate in the cytoplasm, thus lowering pH and inhibiting metabolism (Krebs et al

1983 ) There are several limitations to the value of organic acids as microbial tors in foods: they are usually ineffective when initial levels of microorganisms are high; many microorganisms use organic acids as metabolizable carbon sources; there

inhibi-is inherent variability in resinhibi-istance of individual strains; and the degree of resinhibi-istance

may also depend on the conditions (Silliker et al 1980 )

Nitrites and nitrates are used in many foods as preservatives and functional dients They are critical components in the curing of meat, and are known to be multifunctional food additives and potent antioxidants Many plants contain com-pounds that have some antimicrobial activity, collectively referred to as ‘ green chemi-cals ’ or ‘ biopreservatives ’ (Smid and Gorris, 1999 ) Interest in naturally occurring antimicrobial systems has expanded in recent years in response to consumers ’ require-ments for fresher, more natural additive - free foods (Gould, 1995 ) A range of herbs and spices are known to possess antibacterial activity as a consequence of their chemical composition Antimicrobial agents can occur in foods of both animal and vegetable origin Herbs and spices have been used for centuries by many cultures to improve the fl avor and aroma of foods Essential oils show antimicrobial properties, and are defi ned by Hargreaves as a group of odorous principles, soluble in alcohol and to a limited extent in water, consisting of a mixture of esters, aldehydes, ketones, and

ingre-terpenes They not only provide fl avor to the product, but also act as preservatives Scientifi c studies have identifi ed the active antimicrobial agents of many herbs and spices These include eugenol in cloves, allicin in garlic, cinnamic aldehyde and eugenol in cinnamon, allyl isothiocyanate in mustard, eugenol and thymol in sage, and isothymol and thymol in oregano (Mothershaw and Al - Ruzeiki, 2001 )

Rancidity is an objectionable defect in food quality Fats, oils or fatty foods are deemed rancid if signifi cant deterioration in sensory quality is perceived, particularly aroma or fl avor, but appearance and texture may also be affected Antioxidants are used to control oxidation in foods, and they also have health functionality by reducing the risk of cardiovascular disease and cancer, and slowing down the aging process The use of woodsmoke to preserve foods is nearly as old as open - air drying Although not primarily used to reduce the moisture content of food, the heat associated with the generation of smoke also gives a drying effect Smoking has been mainly used with meat and fi sh Smoking not only imparts desirable fl avor and color to some foods, but some of the compounds formed during smoking have a preservative effect (bactericidal and antioxidant)

Hydrogen ion concentration, measured as pH, is a controlling factor in regulating many chemical, biochemical, and microbiological reactions Foods with pH below 4.5 are considered low - risk foods, and need less severe heat treatment Microorganisms require water, nutrients, and appropriate temperature and pH levels for growth Below about pH 4.2 most food - poisoning microorganisms are well controlled, but microor-ganisms such as lactic acid bacteria and many species of yeast and molds grow at pH values well below this Many weak lipophilic organic acids act synergistically at low

pH to inhibit microbial growth Thus, propionic, sorbic, and benzoic acids are very useful food preservatives The effi cacy of acids depends to a large extent on their ability to equilibrate, in their undissociated forms, across the microbial cell membrane and, in doing so, interfere with the pH gradient that is normally maintained between the inside (cytoplasm) of the cell and the food matrix surrounding it In addition to weak lipophilic acids, other preservatives widely used in foods include esters of benzoic acid, which are effective at higher pH values than organic acids Inorganic acids such as sulfate and nitrite are most effective at reduced pH values, like organic acids While these preservatives are employed at low levels (hundreds to thousands of ppm), the acids used principally as acidulants are often employed at percentage levels (Booth and Kroll, 1989 )

The pH affects not only the growth of microorganisms, but also affects other ponents and processes, such as enzyme stability, gel formation, and stability of pro-teins and vitamins Antimicrobial enzymes also have current applications and further

com-future potential in the food industry Fuglsang et al (1995) pointed out that the

poten-tial of these enzymes in food preservation is still far from realized at present

Antibiotics can be medical or non - medical Non - medical antibiotics, such as natamycin and nisin, produced either by microbes or synthetically, inhibit microbes

at very low concentration Organisms present in food can become resistant to otics and colonize the gut of animals and humans Antibiotics used therapeutically

antibi-may then become ineffective Antibiotics are also used in growth enhancement and disease control in healthy animals However, the increasing incidence of antibiotic resistance is raising great concern and it is becoming a complicated issue

When a chemical is used in preservation, the main question concerns its safety, and

a risk – benefi t analysis should be carried out Antimicrobial agents or preservatives are diverse in nature, but legal, toxicological, marketing, and consumer considerations have created a trend such that the number of preservatives, and their concentration

in particular foods, are diminishing rather than increasing (Fuglsang et al 1995 )

Control of Water and Structure

Many physical modifi cations are made in ingredients or foods during preservation Such modifi cations can also improve the sensory, nutritional, and functional proper-ties of foods Changes experienced by foods during processing include glass formation, crystallization, caking, cracking, stickiness, oxidation, gelatinization, pore formation, and collapse Through precise knowledge and understanding of such modifi cations, one can develop safe high - quality foods for consumption (Rahman, 2007 )

The concepts of water activity, glass transition and state diagram are clearly reviewed

by Rahman (2006, 2009, 2010) In the 1950s scientists began to discover the existence

of a relationship between the water contained in a food and its relative tendency to spoil (Scott, 1953 ) It was observed that the active water could be much more impor-tant to the stability of a food than the total amount of water present Thus, it is pos-sible to develop generalized rules or limits for the stability of foods using water activity For example, there is a critical water activity level below which no microor-ganisms can grow Pathogenic bacteria cannot grow below a water activity of 0.85, whereas yeasts and molds are more tolerant to reduced water activity, but usually no growth occurs below a water activity of about 0.6 It has been widely accepted that the concept of water activity is a valuable tool for determining microbial stability (Chirife and Buera, 1996 ) A complete discussion of the microbial response to low water activity has been presented by Rahman (2009)

A food product is the most stable at its “ monolayer moisture ” content, which varies with the chemical composition, structure and environmental conditions, such as temperature The BET (Brunauer – Emmet – Teller) monolayer value can be determined from the well - known BET equation The BET - monolayer estimation is an effective method for estimating the amount of water molecules bound to specifi c polar sites in

a food matrix and it does not simply apply to the product surface A more detailed explanation of the BET - monolayer, including estimation and validity, was recently provided by Rahman and Al - Belushi (2006) In general the rule of the water activity concept is that food products are most stable at their “ BET - monolayer moisture ” content or “ BET - monolayer water activity ” and unstable above or below BET - monolayer In many other instances it has been shown that optimal water content for stability is not exactly the BET - monolayer The reason for this variation is due to the fact that the BET theory of adsorption was developed based on many simplifi ed