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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
Thermal Food Engineering Operations Presenting cutting-edge information on new and emerging food engineering processes, Thermal Food Engineering Operations, the first volume in the new series, "Bioprocessing in Food Science," is an essential reference on the modeling, quality, safety, and technologies associated with food processing operations today. As the demand for healthy food increases in the current global scenario, manufacturers are searching for new possibilities for occupying a greater share in the rapidly changing food market. Compiled reports and updated knowledge on thermal processing of food products are imperative for commercial enterprises and manufacturing units. In the current scenario, academia, researchers, and food industries are working in a scattered manner and different technologies developed at each level are not compiled to implement for the benefits of different stakeholders. However, advancements in bioprocesses are required at all levels for the betterment of food industries and consumers. This series of groundbreaking edited volumes will be a comprehensive compilation of all the research that has been carried out so far, their practical applications, and the future scope of research and development in the food bioprocessing industry. This first volume includes all the conventional and novel thermal technologies based on conduction, convection, and radiation principles and covers the basics of microbial inactivation with heat treatments, aseptic processing, retorting, drying, dehydration, combined high-pressure thermal treatments, and safety and quality concerns in food processing. Before studying the novel non-thermal processes and the concept of minimal processing, comprehensive knowledge about the conventional thermal technologies is desired along with benefits, constraints, equipment, and implementation of these technologies. Whether for the engineer, scientist, or student, this series is a must-have for any library. This outstanding new volume: * Discusses food safety and quality and thermal processing, laying the groundwork for further study and research * Provides case studies of solid-liquid and supercritical fluid extraction * Explores pasteurization, ohmic heating, irradiation, and more * Presents cutting-edge information on new and emerging food engineering processes Audience: Process and chemical engineers, chemists, engineers in other disciplines, managers, researchers, scientists, students, and teachers working in the field of food engineering and processing
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Table of Contents
Cover
Title Page
Copyright
Preface
1 Novel Thermal Technologies: Trends and Prospects
1.1 Introduction
1.2 Novel Thermal Technologies: Current Status and Trends
1.3 Types of Thermal Technologies
1.4 Future Perspective of Novel Thermal Technologies
1.5 Conclusion
References
2 Microbial Inactivation with Heat Treatments
2.1 Introduction
2.2 Innovate Thermal Techniques for Food Reservation
2.3 Inactivation Mechanism of Targeted Microorganism
2.4 Environmental Stress Adaption
2.5 Resistance of Stress
2.6 Various Techniques for Thermal Inactivation
2.7 Forthcoming Movements of Thermal Practices in Food Industry
2.8 Conclusion
References
3 Blanching, Pasteurization and Sterilization: Principles and Applications
3.1 Introduction
3.2 Blanching: Principles & Mechanism
3.3 Pasteurization: Principles & Mechanism
3.4 Sterilization: Principles, Mechanism and Types of Sterilization
3.5 Conclusions
References
4 Aseptic Processing
4.1 Introduction
4.2 Aseptic Processing
4.3 Principle of Thermal Sterilization
4.4 Components of Aseptic Processing
4.5 Aseptic Packaging
4.6 Applications of Aseptic Processing and Packaging
4.7 Advantages of Aseptic Processing and Packaging
4.8 Challenges of Aseptic Processing and Packaging
4.9 Conclusion
References
5 Spray Drying: Principles and Applications
5.1 Introduction
5.2 Concentration of Feed Solution
5.3 Atomization of Concentrated Feed
5.4 Droplet-Hot Air Contact
5.5 Drying of Droplets
5.6 Particle Separation
5.7 Effect of Process Parameters on Product Quality
5.8 Classification of Spray Dryer
5.9 Morphological Characterization of Spray-Dried Particles
5.10 Application of Spray Drying for Foods
5.11 Wall Materials
5.12 Encapsulation of Probiotics
5.13 Encapsulation of Vitamins
5.14 Encapsulation of Flavours and Volatile Compounds
5.15 Conclusion and Perspectives
References
6 Solar Drying: Principles and Applications
6.1 Introduction
6.2 Principle of Solar Drying
6.3 Construction of Solar Dryer
6.4 Historical Classification of Solar Energy Drying Systems
6.5 Storing Solar Energy for Drying
6.6 Hybrid/Mixed Solar Drying System
6.7 Solar Greenhouse Dryer
6.8 Solar Drying Economy
6.9 New Applications Related to Solar Drying
References
7 Fluidized Bed Drying: Recent Developments and Applications
7.1 Introduction
7.2 Principle and Design Considerations of Fluidized Bed Dryer
7.3 Design Alterations for Improved Fluidization Capacity
7.4 Energy Consumption in Fluidized Bed Drying
7.5 Effect of Fluidized Bed Drying on the Quality
7.6 Applications of Fluidized Bed Drying
7.7 Concluding Remarks
References
8 Dehumidifier Assisted Drying: Recent Developments
8.1 Introduction
8.2 Absorbent Air Dryer
8.3 Heat Pump–Assisted Dehumidifier Dryer
8.4 Applications of Dehumidifier-Assisted Dryers in Agriculture and Food Processing
8.5 Concluding Remarks
References
9 Refractance Window Drying: Principles and Applications
9.1 Introduction
9.2 Refractance Window Drying System
9.3 Heat Transfer and Drying Kinetics
9.4 Effect of Process Parameters on Drying
9.5 Comparison of Refractance Window Dryer with Other Types of Dryers
9.6 Effect of Refractance Window Drying on Quality of Food Products
9.7 Applications of Refractance Window Drying in Food and Agriculture
9.8 Advantages and Limitations of Refractance Window Dryer
9.9 Recent Developments in Refractance Window Drying
9.10 Conclusion and Future Prospects
References
10 Ohmic Heating: Principles and Applications
10.1 Introduction
10.2 Basic Principles
10.3 Process Parameters
10.4 Equipment Design
10.5 Application
10.6 Effect of Ohmic Heating on Quality Characteristics of Food Products
10.7 Advantages of Ohmic Heating
10.8 Disadvantages of Ohmic Heating
10.9 Conclusions
References
11 Microwave Food Processing: Principles and Applications
11.1 Introduction
11.2 Principles of Microwave Heating
11.3 Applications
References
12 Infrared Radiation: Principles and Applications in Food Processing
12.1 Introduction
12.2 Mechanism of Heat Transfer
12.3 Factors Affecting the Absorption of Energy
12.4 Applications of IR in Food Processing
12.5 IR-Assisted Hybrid Drying Technologies
12.6 Conclusion
References
13 Radiofrequency Heating
13.1 Introduction
13.2 History of RF Heating
13.3 Principles and Equipment
13.4 Applications in Food Processing
13.5 Technological Constraints, Health Hazards, and Safety Aspects
13.6 Commercialization Aspects and Future Trends
13.7 Conclusions
References
14 Quality, Food Safety and Role of Technology in Food Industry
14.1 Introduction
14.2 Future Trends in Quality and Food Safety
14.3 Conclusion
References
Index
Also of Interest
Wiley End User License Agreement
List of Table
Chapter 1
Table 1.1 Applications of Infrared heating: [1].
Table 1.2 List of some techniques combined with microwave technology.
Chapter 2
Table 2.1 Application of thermal techniques in food industry.
Chapter 3
Table 3.1 Application of different blanching methods for processing of agricultu...
Table 3.2 Advantages and disadvantages of different blanching methods.
Table 3.3 Application of novel thermal pasteurization techniques for the process...
Table 3.4 Sterilization methods and their application in food.
Chapter 4
Table 4.1 History of aseptic processing and packaging.
Table 4.2 D value for acidic and non-acidic foods.
Table 4.3 Methods for the sterilization/decontamination of the packaging materia...
Table 4.4 Methods for sterilization/decontamination of packaging materials.
Table 4.5 Types of food processed and packed under UHT/Aseptic Condition [14].
Chapter 5
Table 5.1 Application of spray drying for encapsulation of various bio-active co...
Chapter 7
Table 7.1 Typical air velocity needed for fluidization of different sized partic...
Table 7.2 Comparison of fluidized beds, spouted beds and spout fluidized beds.
Table 7.3 Application of fluidized bed drying in different drying studies.
Chapter 9
Table 9.1 Energy consumption of refractance window in comparison with other drye...
Table 9.2 Energy efficiency of refractance dryer when compared to other dryers [...
Table 9.3 Color measurements of asparagus dried using five drying techniques [8]...
Table 9.4 Color analysis for mammee apple pulp after drying using RW drying tech...
Table 9.5 Carotene loss for the different drying methods [12, 17].
Chapter 10
Table 10.1 Application and effects of ohmic heating on quality attributes of dif...
Table 10.2 Effect of ohmic heating on viablity of microorganisms in different fo...
Chapter 11
Table 11.1 Form factor b and internal electric field for some simple geometrical...
Chapter 12
Table 12.1 Emissivity of different materials.
Table 12.2 Performance characteristics of infrared emitters.
Table 12.3 The depth of penetration of near-infrared rays into some food product...
Chapter 13
Table 13.1 Comparison of RF heating with conventional and other electromagnetic ...
Table 13.2 Application of radiofrequency for disinfestations, thawing, drying an...
Table 13.3 Applications of radiofrequency in industrial application for bacteria...
Chapter 14
Table 14.1 Regional effects of food quality and safety (Source: WHO).
Table 14.2 Region-wise average annual growth rate of consumer spending on eating...
Table 14.3 Ranking of countries with largest food and beverages market (Source: ...
Table 14.4 Comparison of targeted and non-targeted analyses.
Table 14.5 Food security score of select countries (Source: Economist Intelligen...
Table 14.6 Codex timelines (Source: FAO).
Table 14.7 List of food safety standards implemented across the global food indu...
List of Figures
Chapter 1
Figure 1.1 Illustration of radiofrequency heating [25].
Figure 1.2 Circuit diagram of static (batch type) resistance heating process [46...
Chapter 3
Figure 3.1 Combined Infrared and hot air system [56].
Figure 3.2 Microwave-assisted thermal pasteurization system [145].
Figure 3.3 Diagram showing components of microwave-assisted thermal sterilizatio...
Chapter 4
Figure 4.1 Aseptic processing and packaging system.
Figure 4.2 Death rate curve for microbial population [3].
Figure 4.3 z values at different temperatures and D values [3].
Figure 4.4 (a) Plate heat exchanger, (b) shell and tube heat exchanger, (c) scra...
Figure 4.5 (a) Steam Injection system, (b-1) Steam Infusion Vaction
™
PumpIn tank...
Figure 4.6 UHT process with heating by direct steam injection combined with plat...
Chapter 5
Figure 5.1 Schematic diagram of the droplet drying process.
Figure 5.2 Schematic diagram of a spray dryer and drying process.
Figure 5.3 Classification of spray dryer.
Figure 5.4 Different morphologies due to bubble inflation during spray drying.
Chapter 6
Figure 6.1 Photograph of solar collector and dryer [35].
Figure 6.2 Schematic diagram of the components of the integrated solar dryer sys...
Figure 6.3 The forced convective solar dryer implemented in Marrakech [44].
Figure 6.4 Schematic diagram of the new mixed solar dryer [47].
Figure 6.5 Experimental setup of solar PV operated the greenhouse dryer for dryi...
Figure 6.6 Dryers and drying modes and classification.
Chapter 7
Figure 7.1 A typical fluidized bed dryer.
Figure 7.2 (a) Continuous plug flow and (b) Continuous well-mixed fluidized bed ...
Figure 7.3 (a) A Conventional SBD, (b) a typical spouted bed dryer with draft tu...
Figure 7.4 Different configuration of spout fluidized bed dryer: (a) pseudo 2D (...
Figure 7.5 Microwave-assisted [29].
Figure 7.6 FIR-assisted FBD [29].
Figure 7.7 Heat pump–assisted FBD; reprint from [33].
Figure 7.8 Solar-assisted FBD; reprint from [36].
Figure 7.9 Different view of a typical vibrated FBD; courtesy of [38].
Figure 7.10 A typical agitated FBD [38].
Figure 7.11 (a) Side view and (b) top view of a typical centrifugal fluidized be...
Chapter 8
Figure 8.1 Dispersive adhesion.
Figure 8.2 Desiccant drying motor, source: [17].
Figure 8.3 Desiccant food drying system with temperature and airflow control 1. ...
Figure 8.4 Flowchart of control algorithm, source: [17].
Figure 8.5 Humidity and temperature variation with no temperature and airflow co...
Figure 8.6 Humidity and temperature change with respect to time under controlled...
Figure 8.7 Schematic illustration of heat pump dehumidifier dryer, source: [26].
Figure 8.8 Mollier chart representing thermodynamic cycle for the air stream, so...
Chapter 9
Figure 9.1 Schematic drawing of refractance window dryer. Adapted from reference...
Plate 9.1 Refractance window dryer. Adapted from MCD Technologies Inc.
Figure 9.2 (a-d) Illustration of the principle of operation of refractance windo...
Figure 9.3 Drying kinetics (a) water-plastic-air represents the dryer without th...
Figure 9.4 Typical temperature profiles in a refractance. Adapted from reference...
Plate 9.2 Comparison of color preservation on potato and carrot flakes by RW dry...
Figure 9.5 Layout of a refractance window evaporator. Adapted from reference [45...
Chapter 10
Figure 10.1 Schematic diagram of the principle of ohmic heating.
Figure 10.2 Different electrode configurations: (a) Batch, (b) Transverse, (c) C...
Chapter 11
Figure 11.1 Propagation of a plane EM wave in a lossy material.
Figure 11.2 (a) Variation of dielectric permittivity of an isolated water molecu...
Figure 11.3 Variation of the dielectric properties of two varieties of onions as...
Chapter 12
Figure 12.1 Electromagnetic spectrum.
Figure 12.2 Artificial source of IR radiations.
Figure 12.3 Factors associated with the extent of IR energy absorbed from total ...
Chapter 13
Figure 13.1 Schematic circuit diagram of arrangement for dielectric heating of f...
Chapter 14
Figure 14.1 Contributors to food quality.
Figure 14.2 Per capita GDP of 2019 versus food quality and safety rating of sele...
Figure 14.3 Rice mixed with plastic [(1) As seen by naked eye (2) As captured by...
Figure 14.4 Expected growth of AI in food and beverages market during 2019–24. (...
Guide
Cover
Table of Contents
Title Page
Copyright
Preface
Begin Reading
Index
Also of Interest
Wiley End User License Agreement
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Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106
Bioprocessing in Food Science
Series Editor: Anil Panghal, PhD
Scope: Bioprocessing in Food Science will comprise a series of volumes covering the entirety of food science, unit operations in food processing, nutrition, food chemistry, microbiology, biotechnology, physics and engineering during harvesting, processing, packaging, food safety, and storage and supply chain of food. The main objectives of this series are to disseminate knowledge pertaining to recent technologies developed in the field of food science and food process engineering to students, researchers and industry people. This will enable them to make crucial decisions regarding adoption, implementation, economics and constraints of the different technologies.
As the demand of healthy food is increasing in the current global scenario, so manufacturers are searching for new possibilities for occupying a major share in a rapidly changing food market. Compiled reports and knowledge on bioprocessing and food products is a must for industry people. In the current scenario, academia, researchers and food industries are working in a scattered manner and different technologies developed at each level are not implemented for the benefits of different stake holders. However, the advancements in bioprocesses are required at all levels for betterment of food industries and consumers.
The volumes in this series will be comprehensive compilations of all the research that has been carried out so far, their practical applications and the future scope of research and development in the food bioprocessing industry. The novel technologies employed for processing different types of foods, encompassing the background, principles, classification, applications, equipment, effect on foods, legislative issue, technology implementation, constraints, and food and human safety concerns will be covered in this series in an orderly fashion. These volumes will comprehensively meet the knowledge requirements for the curriculum of undergraduate, postgraduate and research students for learning the concepts of bioprocessing in food engineering. Undergraduate, post graduate students and academicians, researchers in academics and in the industry, large- and small-scale manufacturers, national research laboratories, all working in the field of food science, agriprocessing and food biotechnology will benefit.
Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])
Thermal Food Engineering Operations
Edited by
Nitin Kumar
Anil Panghal
and
M. K. Garg
This edition first published 2022 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA© 2022 Scrivener Publishing LLCFor more information about Scrivener publications please visit www.scrivenerpublishing.com.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions.
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Library of Congress Cataloging-in-Publication Data
ISBN 9781119775591
Cover image: Wikimedia Commons and the editorsCover design by Russell Richardson
Set in size of 11pt and Minion Pro by Manila Typesetting Company, Makati, Philippines
Printed in the USA
10 9 8 7 6 5 4 3 2 1
Preface
Thermal processing is a significant component of the undergraduate and postgraduate degrees in agriculture engineering, food engineering and food science technology throughout the world. Thermal food engineering operations are considered one of the core competencies for these programs and in industries as well. Researchers will be able to use the information as a guide in establishing the direction of future research on thermophysical properties and food processing. The audience for this volume will be the student preparing for a career as a food engineer, practicing engineers in the food and related industries, and scientists and technologists seeking information about processes and the information needed in design and development of thermal food engineering processes and operations. Simultaneously, improving food quality and food safety are continue to be critical issues during thermal processing. So, quality, food safety and role of technology in food industry are discussed to cover these areas of food industry.
A great variety of topics is covered, with the emphasis on the most recent development in thermal operations in food industry. The chapters presented in this volume throw light on a number of research subjects that have provided critical information on different thermal processes, their impact on different food components, and their feasibility in food industry. Each chapter also provides background information of the changes in different thermal operations which changed drastically over the years. The authors emphasis on newer thermal technologies which are making a great impact on the industry and the resulting finished products. The adoption of modern technology has increased efficiency and productivity within the factory. Most importantly, utilizing the newer thermal operations has greatly improved product quality. All chapters are supported with a wealth of useful references that should prove to be an invaluable source for the reader. Self-explanatory illustrations and tables have been incorporated in each chapter complimentary to the main text.
Thanks are due to all authors for contributing their knowledgeable chapters in this volume and helping us to complete the book. We also thank the authorities of Chaudhary Charan Singh Haryana Agricultural University, Hisar for their help and support. Finally, we also express indebtedness and thankfulness to Scrivener Publishing and Wiley team for their unfailing guidance and helpful assistance.
Nitin KumarAnil PanghalM.K. Garg
1Novel Thermal Technologies: Trends and Prospects
Amrita Preetam1*, Vipasha1, Sushree Titikshya1, Vivek Kumar1, K.K. Pant2 and S. N. Naik1
1Centre for Rural Development and Technology, IIT Delhi, Delhi, India
2Department of Chemical Engineering, IIT Delhi, Delhi, India
Abstract
Heating is possibly the most traditional way of processing foods. The technologies involved in heating have been continuously developing for the past many years as per consumer need, satisfaction and demand. Techniques such as dielectric heating, ohmic heating, and infrared heating are evolving and can substitute for the conventional heating methods for improving quality and shelf life, and providing a faster production rate. The conventional technologies are primarily based on convective, conductive, and radiative heat transfer. But the new novel thermal methods are mainly relying on the electromagnetic field or electrical conductivity and are having cleaner environmental impacts such as energy saving, water savings, improved efficiencies, fewer emissions, and eventually decreasing dependency on non-renewable resources. The chapter discusses novel thermal technologies. Definitions, basic principles, environmental impacts, current trends, and future perspectives are described along with the mechanism and advantages of the novel thermal technologies. The novel thermal technologies are continuously emerging and evolving as per consumer requirements and need.
Keywords: Novel thermal technologies, infrared heating, ohmic heating, microwave heating, radiofrequency heating
1.1 Introduction
The primary goal for food processors is quality and safety assurance. To ensure microbiological food safety, the use of heat by thermal operation involving drying, sterilization, evaporation, and other methods are common practices. The conventional heating methods rely on principles such as convection, radiation, and conduction [36] that primarily rely on heat generation exterior of the product to be warmed up. But there are limitations attached to it. These conventional ways of processing, due to the decrease in efficiency of heat transfer, by excessive heating because of time reach the thermal center of foods for conducting sufficient heat or losses because of the heat on the surface of equipment and installation. Some of these problems can be resolved by technical solutions such as heat recycling or advanced designing and installation methods but at high expense.
Therefore research has been made for raising the quality and safety and economic aspects of food through technological development. The novel thermal technologies in which the main processing factor is temperature change as the main parameter responsible for food processing can be considered as the promising alternative in food processing as compared to the traditional process. Unlike traditional technologies, novel thermal technologies are based on electromagnet field (EMI) or electric conductivity. Novel thermal technologies are based on the heat generations directly inside the food. The novel thermal technologies have successfully helped in enhancing the effectiveness of heat processing along with ensuring food safety and maintaining nutritional food properties. Infrared heating has also evolved for the processing of food. The thermal technologies involve the equipment plotted to heat the food to process it, whereas in non-thermal techniques the food is virtually processed without the involvement of food. The general definition of common technologies involved in novel thermal techniques and their basic differences are discussed below.
Ohmic heating is also called Joule heating, electrical residence heating. It is a method of heating the food by the passage of an electric current, so heat is generated due to the electrical current. It is a direct method, as the heat energy is directly dissipated into the food. It is primarily used to preserve food. Electric energy is dissipated into heat, which results in quick and uniform heating followed by maintaining the nutritional value and color. The key variable in electrical conductivity is designing of an effective ohmic meter. Ohmic heating uses a normal electrical supply frequency which is of 50-60Hz. Ohmic heating instantly penetrates directly into the food. The applications of ohmic heating include UHT sterilization, pasteurization, and others.
Dielectric heating is another novel process that provides volumetric heating, for uniform sterilization or preserving of food. It is also a direct method and is based on the process of heating the material by causing dielectric motion in its molecule using alternating electric fields, microwave electromagnetic radiation, or radio wave. The intensity of the electric field and the dielectric properties of the product regulate the volumetric power and absorption and the rate of heat generation. Both microwave heating and radiofrequency belong to this category and follow the principle of dielectric heating. The depth of penetration is directly related to frequency in the case of dielectric heating. The thermal conductivity is not so important in dielectric heating. The few application of microwave and radiofrequency are in freeze-drying, baking, sterilization, rendering, frying, and many others.
Infrared heating is mainly utilized to modify the eating characteristics of food by varying its color, texture, flavor, and odor. Radiant heat is less managed and has a broader range of frequencies. The thermal conductivity is a limiting factor in infrared heating. It acts as an indirect method of heating. Infrared is simply absorbed and converted into heat. It has limited penetration depth in food. It has several advantages over conventional methods such as decreased heating time, reduce quality loss, and uniform heating, versatility, easy to operate and compact equipment, and many others. It also has a vast area of application includes drying, frying, baking, cooking, freeze-drying, pasteurization, sterilization, blanching, and many others.
The other technique is non-thermal heating technologies which are based on pulsed light, pulsed electric fields, ultrasound, and gamma radiation, and others, where the temperature may change also but is not the prime parameter for food processing. The purpose of this chapter is to deliver a general outlook of novel thermal technologies in the food processing sector along with their environmental impact, current trends, and future perspective.
1.2 Novel Thermal Technologies: Current Status and Trends
The most common approach for food processing in the last 50 years is thermal processing because a huge amount of microorganisms are removed at elevated temperatures by killing them. Thermal processing protects food by pasteurization, hot air drying, and others, induces variations to improve food quality by baking, blanching, roasting, frying, and cooking. Time and temperature used are the key variable depending on the application used. In the case of thermal processing, sometimes the high temperature may lead to loss of nutrients or bioactive compounds which results in low-processed food and low-grade food.
So in such a situation, novel thermal techniques or with the combination of traditional technologies are used to modify the quality and shelf life while decreasing the change in sensory properties. The food industry is continuously developing in order to fulfill customer demand for food nutrition, natural flavors, food quality, and taste. Innovation and research are continuously growing all over the world to maintain and improve standards. Currently, consumers demand food with the least or no chemical additives and should be minimally processed [37]. These developing technologies are called ‘novel’ technologies because they are successfully fulfilling the needs of consumers and are an improvement of conventional technologies. Depending upon the principle used, it can be thermal or non-thermal. Techniques such as microwave, ultrasound, and pulsed electric field can be an alternative proved by many researchers to develop nutritious and safe food [10, 15, 16]. Such techniques are being used broadly by many innovative food companies [6]. As compared to traditional technologies these new emerging technologies have many benefits over traditional techniques such as more heat and mass transfer, improved product quality, short process and residence time, better functionality, enhanced preservation, and others. The processing of the food is important for taste, nutritional content, texture, and appearance [36]. The benefits of novel processing technologies over traditional techniques are improved functional characteristics and retention of sensory attributes by using the promising next-generation food [62]. The development, research, and large-scale set-up of these novel technologies are taking place internationally. It is evident from the number of publications on the benefits of novel thermal technologies in food processing in various food and agriculture processing research journals [51].
Microwave: The most popular and extensive technology studied worldwide both domestically and industrially is microwave processing due to its various advantages such as easy operation, lower maintenance requirement, and cleaner environment [77]. But despite all the advantages, microwave is facing two main hurdles, i.e., irregular distribution of temperature within the food product and high cost of energy regarding this technique [6]. Furthermore, the set-up operated at 2450 MHz may give rise to serious boundary and surface overheating of the food to outstretch the desired elevated temperature in cold spots. For those cases, continuous microwave systems have been used to provide uniform temperatures for the heating of foods. Some authors have suggested fusion with water as the heating medium, pulsed microwave [24, 51]. The most common technology is microwave-assisted thermal sterilization system (MATS™) based on 915MHz single-mode cavities using a shallow bed with water food immersion; it penetrates deeper in food and water offers to reduce the edge heating. It got approval in 2009 by the Food and Drug Administration (FDA) [72].
Infrared heating: Proved by many researchers, Infrared heating (IRH) is an efficient process for the purification of pathogenic microorganisms in food. Many operational variables such as food temperature, size and kind of food materials, IR power intensity, IR power intensity, and others are necessary for microbial inactivation. At a commercial scale, IRH had been found as the replacement or substitute to decrease non-uniform temperature distribution which occurs in microwave heating [6]. Internationally, IRH is used for blanching, drying, baking, roasting, and peeling. At the industrial level IRH has considerable advantages such as a large heat delivery rate, no medium required, high energy efficiency, low environmental footprint, and others [39]. But because of less penetration depth, this technology is not successful at the commercial level; for example, it cannot be utilized in in-packaging food processing. The major successful large-scale (commercial) applications of IRH is drying of low-moisture foods (grains, pasta, tea, etc.), also the applications in baking (e.g., pizzas, biscuits, and others) and in the oven for roasting of cereals, coffee, etc.
Radiofrequency: Another thermal technology is Radiofrequency heating (RFH), used from the 1940s. Earlier applications were to warm bread, dry up and blanch vegetables and others. RFH has a greater industrial interest because of its unique properties such as deeper penetration due to its lesser frequencies, uniform electric field distribution, and longer wavelength. Major applications are in the food-drying sectors for pasta, snacks, and crackers and sterilization or pasteurization process, treatment of seeds and disinfection of product [19]. As compared to microwave heating, RF has the potential to reduce surface overheating and can also give better results at a commercial scale [81]. On a commercial scale, such as for treating bulk materials, sterilization of packaged foods is successful because they are simple to construct, have a more uniform heating pattern, and have greater penetration depth. Drawbacks of this technology include, at industrial scale, the design equipment is complicated, there is a high investment cost and technical issues such as dielectric failure and thermal runaway heating that can damage package and product [1]. Another common thermal technique is ohmic heating (OH) where internal heat generation takes place by passing a current into the materials.
Ohmic heating (OH): Compared to other technologies, ohmic heating has advantages such as larger temperature in particles than in liquid, decreased fouling, energy-efficient, uniform heating (achieved by thermal, physical, and rheological properties), and lower cost [64]. The drawbacks include the requirement of aseptic packing after OH heating, the possibility of corrosion, direct exposure of the electrode with food.
Major utilization of OH are blanching, sterilization, evaporation, dehydration, extraction, and evaporation. The basic procedure involved in OH of microbial inactivation is thermal harm and in some cases by electroporation. In comparison to traditional heating, OH heating can attain lesser heating times, can keep away from hot surfaces, and can decrease the temperature gradients.
Since the 1990s, OH is now utilized in developing countries and all over the world. Almost a hundred processing plants have been placed all over the world. The market is in the developing stage and evolving constantly. OH equipment is installed all over the world such as in Italy, France, Spain, Greece, and Mexico [54]. The application of OH is not much commercialized for solid food products. For liquids, viscous liquids, and pumpable multiphase products, the installed set-ups perform the sterilization and pasteurization of numerous food products with great characteristics with main applications in vegetables and fruit areas.
Overall, the major issue involved in commercialization of electromagnetic techniques for numerous food applications is the lack of heat uniformity, which has a major impact on key variables of food processing and safety. To avoid this downside, hybrid systems are proposed, i.e., the combination of traditional and volumetric heating [54, 63]. The hybrid system offers advantages such as safety, improved process efficiency, and product properties. Successful hybrid techniques are IR-convective drying, a combination of IRH, IR-heat pump drying, and microwave heating, and many others are still in progress because of the magnified energy throughput.
1.2.1 Environmental Impact of Novel Thermal Technologies
The emergence of novel thermal technologies and non-thermal processes in food processing industries is capable of producing high-quality and standardized products. Both of them are environmentally sound and efficient in nature as compared to conventional technologies. Here we will consider more on the environmental footprints of novel thermal technologies. The primary objective in the food industry is food safety which requires high energy consumption, but novel thermal technologies are successfully able to balance energy saving and energy consumption.
The high value of hygiene and safety of food requires large use of water in both hot and cold cycles in production which consequently increases the environmental footprint. Processes such as cooking, sterilization, drying, and pasteurization require various types of energy. Novel thermal technologies are promising, attractive, and efficient in nature. They are capable of providing improved quality and reduced environmental effects which will eventually reduce environmental footprints. Novel thermal technologies can reduce processing costs followed by improving and maintaining the value-added products. Overall the primary types of energy used based on conventional thermal processing techniques are fossil fuel and electricity, majorly utilized in refrigeration and mechanical power in pumps. A heat exchanger is commonly used in the pasteurization of beverages where the pathogens are killed when heated to a particular residence time. During thermal treatment, convection and conduction play a major role to transfer heat to the products. For viscous fluids, directing heating process is applied, e.g., steam injection and steam infusion are utilized for thermal treatments. In the food and beverages industry, regarding the distribution of energy in 2002, Denmark suggests that total consumption of energy (TJ/Year) is 135,200 including the amount of heating and power. Adapted from [58].
This concludes that major heat is used in frying, evaporation, drying, and heating for thermal processes. Until the present moment, this trend is still functioning. Novel thermal technologies such as radio frequency, ohmic heating, microwave, etc., for food processing being continuously evolving. These novel thermal technologies have reduced emissions, reliability, improved productivity, high product quality, energy saving, water saving and consequently have less impact on the environment; [45] investigated that for Orange juice and cookies manufacturing, radio frequency drying (RF) can range up to 0 to 73.8 TJ per year in terms of primary energy saving. The major kinds of gas emissions from food industries are linked to power and heat production particulate matter and gases such as SO2, CO2, NO, from combustion processes. The particulate matter and volatile organic compounds (VOCs) and other chemical emissions are from methods such as size reduction, heating, refrigeration system, and cooking methods.
Conventionally 33% of the overall energy consumed in food processing corresponds to the production of steam. The steam is commonly used in drying, concentrating liquids, cooking, sterilizing, etc., in the processing of food processes. The generation of steam used in food industries involves the utilization of boilers. To remove the dissolved solid from the boiler system a large quantity of water is periodically drained from the bottom, which is called a blow-down. Inadequate blow-down may lead to the gathering of dirt which reduces the heat transfer rates and increases the loss of energy. Irregular boiler maintenance can decrease the efficiency of the boiler up to 20-30%. The efficiency of a boiler is affected by losses of heat by convection and radiation [58]. Improper boiler maintenance can also emit large emissions of CO2 and loss of energy. [58] also mentions the losses that occurred of a boiler or steam generation system composed of: gases from the combustion of air, or incomplete combustion, radiation losses, boiler blow-down water, heat convection, and fouling of heat transfer surfaces from hot boiler surface. Many attempts have been made to evolve a sustainable sector for lowering the emission of gases, e.g., CO2 and enhance the energy efficiency of devices and methods using renewable energy is now the main concern for every method. Therefore, using electricity in food powering systems may show an environmental benefit as compared to conventional techniques used. Overall novel technologies are considered sustainable, once they reduce the consumption of boilers or steam generation systems and eventually decrease the waste-water, heat loss and increase energy-saving and water-saving as well. Furthermore, the electricity is produced by an eco-friendly source of renewable energy; after that these methods will efficiently contribute to decreasing the pollution, assisting them to protect the environment. [82] shows the balancing by ohmic heating decreased the extent of solid leaching irrespective of the dimensions of the product. It is concluded by [65], OH blanching offers benefit in aspects such as water-saving by maintaining the quality of the processed products. Novel thermal can efficiently accelerate the drying processes when related to traditionally heat pre-treated samples allowing exact control of the process temperature and eventually it can decrease costs of energy, reduce the gas consumption and lower combustion-related emissions [53].
So we can conclude that novel thermal technologies are one of the most novel techniques in food preservation processes. Novel thermal technologies are quite efficient in all aspects such as the efficiency of energy, saving of water, and reduced emissions. Most of the processes involved in novel thermal technologies are green and hence more environmentally friendly, having the least environmental impact as compared to conventional technologies.
1.2.2 The Objective of Thermal Processing
The major purpose of thermal processing is to maintain certain quality standards, to reduce enzymatic activities, reduce microbial activities to enhance its shelf life, increase digestibility, and maintain certain physical and chemical variations to ensure its characteristic and safety of food. The objective also includes adding values such as maintaining its texture, flavor, color, etc., and make varieties of new products; it should also be needed by the specific section of the population. Over the past several years, consumer demands have improved standard, convenient and varied food which required the modification and development in existing traditional process for the new food preservation technologies. For that, the new novel thermal technologies evolved. Novel thermal technologies are better not only in terms of their quality improvements of food and heating efficiency but also in other important aspects such as water-saving, energy-saving, and reduced emissions. Most of these technologies are green and have less environmental impact and improve the added value of foods.
1.2.3 Preservation Process
The basic definition of food indicates that food is the materials, formulated or processed which are consumed orally by living organisms for development, pleasure, needs, and fulfillment. The chemical composition of food includes majorly water, fats, lipids, and carbohydrates with less amount of minerals and compounds containing organics. The different categories of food are perishable, synthetic, non-perishable, fresh, medical food, harvested, manufactured, preserved, and others. The preservation of food majorly depends on the type of food required to be produced and formulated. Preservation of food is defined as maintaining its properties at the desired level for long as possible. Safety with sustainability and innovation are the major aspects and priorities to ensure the preservation of food. In the modern era, the preservation of and processing of food not only includes the safety of the foods but also maintains sustainable innovation, economic feasibility, customer satisfaction, nutritional aspects, absence of chemical preservative, and should be environmental sound [62].
Food preservation is necessary for ensuring desired quality level, consumer satisfaction, to maintain preservation length and also to focus on the group for whom the products are to be preserved [10]. The reason for preservation also includes to form the value-added products, provide modifications in diet, and most importantly to overcome the improper planning in agricultural sectors. Preservation loss not only results in minor deterioration of food but also results in the transformation of the food to a severely toxic state.
After a certain period of time, the quality and characteristics of food may get deteriorated and become undesirable for consumption so it becomes the prime factor to study the rate of variations of quality attributes which indicates its shelf life; this is a very important parameter to consider. The quality of products can rely on appearance, yield, eating characteristics, microbial characteristics, and the consumer’s overall experience. The deterioration of food depends upon mechanical, chemical, physical, and microbial reactions. The quality of the product was maintained at every stage of food production and overall processing chains such as manufacture, storage, distribution, and sale. Additionally, the need for preservation must depend on its purpose and use, and consider the population for whom the preservation is to be done as the nutritional requirement and food restriction apply differently to different sections of groups.
There are many measures for food preservation; inhibition, inactivation, and avoiding recontamination are the common ones. Each method contains several processes of preservation such as inhibition, which includes a decrease of oxygen, adding preservatives, control of pH, freezing, drying, surface coating, gas removal, fermentation, and many others. Inactivation includes irradiation, sterilization, extrusion, and others; avoiding contamination involves packaging, hygienic processing, aseptic processing, and others.
Thermal technology has been the backbone of food production and preservation for many years. In this technology, the temperature is assumed to be the major parameter for preservation and processing mechanism to make food commercially sterile, i.e., to get rid of pathogens and microorganisms which usually grow in the normal shelf life of the food product. Thermally processing the food provides real importance to the food by increasing and preserving its shelf life longer than the chilled food processing technologies.
In novel thermal technologies, preservation is done by the use of electricity. Various forms of electrical energy are utilized for food preservation such as ohmic heating, high intensity pulsed electric field, high-voltage arc discharge, microwave heating, and low electric field stimulation. Ohmic heating is the most common and is based on volumetric heating which prevents the overheating of food, provides uniform and quick heating; it depends on the principle that generation of heat in the food is an outcome of electrical residence when an electric current is moved through the food product. Furthermore, ohmic heating prevents thermal damage and promotes the efficiency of energy. Similarly, microwave heating is also very common and utilized in almost every household and the food industry but its low penetration depth of microwave into solid provides thermal non-uniformity. The other available methods utilizing electric energy are also very versatile, useful, and efficient for the preservation of food. The current electro heating can be used to produce to form new and up-to-date products with diversified functionality.
1.3 Types of Thermal Technologies
Thermal processings are perhaps most essential in the food sector which has been used for the past many years; it has been discovered to increase the quality and shelf life of food with heat treatments. Thermal processing is the heating of foods at a particular temperature for a specified period of time. There are several techniques available in thermal technologies such as radiofrequency heating, ohmic heating, blanching, drying, frying, chilling, infrared heating, freezing and microwave heating, and extrusion. Combined high-pressure thermal treatment of food is also a very efficient prospect for the processing and preservation of food. The most common among them are microwave heating, ohmic heating, combined microwave vacuum-drying, radiofrequency processing, and new hybrid drying technologies.
Hybrid technologies are the recent development in engineering in the operation and design of the dryers to attain dried products with desired characteristics. In hybrid technologies, the drying technologies are combined with the new drying techniques to achieve a new age drying process to reduce energy consumption and enhance product quality. New age drying technologies would be very helpful for the bioproducts in agricultural sectors for all economic, environmental, and product quality aspects. Instant infusion is another new process for the heat treatment of food, depending upon the product requirement providing mild pasteurization and sterilization. For effective and efficient pasteurization and sterilization, the following are the needs: rapid and small heating time, accurate, and small residence time at sterilizing temperature, and rapid cooling time.
For examining the food when it goes under thermal process, nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) can be used as they possess some unique properties for the same. Both of them can be used to investigate variation in the food during processing. Both of them are non-invasive and able to detect water mobility. NMR is the most versatile analytical technique used in modern times. It is capable of revealing complicated multivariate information inside the optically opaque and complex food matrix, also the thermal transformation in liquid, suspension, and gels regarding food samples. NMR and MRI are based on the magnetic properties of atomic nuclei and many elements have isotopes with such properties. Both of them are superior to any other instrumental methods because both are non-invasive, non-destructive, both measure volumes instead of surfaces, and are able to extract both physical and chemical information. By both techniques, it can extract knowledge about diffusion, flow, water distribution, and others. Furthermore, processes such as heating, freezing, hydration, dehydration, and salting can be detected and monitored non-invasively.
1.3.1 Infrared Heating
1.3.1.1 Principal and Mechanism
Infrared was discovered by William Herschel in the 1800s. Infrared depicted below red (infra: below); red is the longest wavelength of visible light. IR heating is the transmission of thermal energy in the form of electromagnetic waves. Wavelength between 0.7 and 1000 micrometer, wavelength larger than visible light but smaller than those of radio waves are the infrared waves. Three major types of infrared waves are [39]:
Short waves 0.76-2 μm (near IR waves), temperature above 1000°C
Medium waves: 2-4 μm (medium IR waves), when the temperature is above 400 - 1000°C
Long waves: 4-1000 μm (far IR waves), when the temperature is below 400°C
The working principle of infrared waves includes: IR energy is electromagnetic radiation emitted by hot objects (quartz lamb, quartz tubes, or metal body) by vibrations and rotation of molecules. When it is absorbed, the radiation provides up its energy to heat materials. An object is a “black-body”, if it absorbs (or emits) 100% of incident IR radiation. The quantity of heat emitted from a perfect radiator (blackbody) is expressed by Stefan-Boltzmann law equation:
Where Q is defined as the rate of heat emission, σSB is the Stefan-Boltzmann constant, T is defined as the absolute temperature, and A is defined as the surface area.
When radiant heaters and food products are not perfect absorbers, the Stefan-Boltzmann equation was modified and the concept of “grey body” was found:
Where ɛ defined as the emissivity of the grey body (ranging from 0 to 1).
This property changes with the wavelength of emitted radiation and temperature of the grey body.
The heating level depends on the absorbed energy, which then rely on the composition of food and the radiation frequency.
Mathematically, the transfer of heat rate to food is expressed as,
Where T1 depicts the temperature of the emitter and T2 depicts the temperature of the absorber. Heat transfer rate relies on:
Surface temperatures of heating and receiving bodies or materials,
Surface characteristics of both bodies or materials,
Shapes of the emitting and receiving materials.
Quantities indicate infrared radiations are the perfect source of energy for heating purposes. They indicate the factors such as larger heat transfer capacity, heat penetration directly into the product, no heating of surrounding air, and fast process control. A perfect balance required for optimal heating between the body and surface heating is attained with IR. The parameters that are important to control to achieve optimal heating results are radiator temperature, infrared penetration characteristics, radiator efficiency, and infrared reflection or absorption properties.
1.3.1.2 Advantages of IR Heating
There are several advantages of IR over traditional heating techniques: [1].
Instant heat: Electric IR system forms heat instantly so there is no need for heat build-up.
Reduced operating costs: The energy can reach 50%, depending upon the insulation, types of construction, and other factors. Furthermore, operations maintenance is limited to the cleaning of reflectors and heat source changing.
Clean and safe: Operating IR is a low-risk task and there is no production of by-products.
Zone control: The IR energy is absorbed only where it is directed and does not propagate. Other advantages of IR are as follows:
Quick heating rate
Shorter residence time
Uniform drying temperature
A high degree of process control
Higher thermal efficiency
Cleaner work environment
Alternate source of energy
The utilization of IR technique in the food sector is still developing; many attempts are continuously growing for the development of IR technologies and the future research is focusing on process control and equipment design development, expanding the areas of applications of IR heating and understanding the interaction between heating process and product characteristics.
1.3.1.3 Applications of IR Heating
There are wide applications for IR (infrared radiation) which include medical, paper industries dye, automobile, and others. Table 1.1 discusses the several application of IR heating [1]. In industrial applications, medium to long-range wavelengths seem to be beneficial, for all materials to be heated or dried give the largest absorption in the 3-10 mm region. Moreover, the applications in short waves are continuously evolving. Applications of IR are mostly within the area of food for drying and many other processes during the period from the 1950s to the 1970s from the Soviet Union, the United States, and the Eastern European countries. During the 1970s, much research was performed about industrial frying or meat products cooking and the utilization of near-infrared (NIR) techniques is initiated [28, 43]. In the 1970s and 1980s, several types of research were carried out to apply this technique in the sector of food, mostly at [Swedish Institute of Food and Biotechnology] and gained a set of knowledge. Recent work is experimental in nature and performed in Japan, Taiwan, and several other countries. Applications are mostly from areas such as dehydration, drying of vegetables, fish, rice, roasting of coffee, cocoa, and cereals, heating of floor, frying of meat, baking of pizza, biscuits, and bread, enzymes, and pathogens inactivation. Also, for thawing, blanching, sterilization, pasteurization of packing materials, and surface pasteurization, these techniques have been used.
The major effects on food involve the quick heating of food surfaces sealed in moisture and aroma compounds. Variation to components of food surfaces is equivalent to those that happen during baking.
1.3.2 Microwave Heating
1.3.2.1 Principal and Mechanism
With the increasing demand for healthy foods, there is a repeated effort given to enhance and optimize different processing techniques in food, to meet the expectations of consumers. With the advancement of emerging technologies, microwave energy has become an indispensable part of every household system. The use of microwave has expanded from heating and defrosting to thawing, blanching, sterilization, drying, etc., in food industries [20, 69]. Microwave is electromagnetic waves with a frequency which ranges from 300 Mhz to 300 GHz. Frequency of microwave used for domestic purposes is 2.45 GHz, whereas the frequency for industrial purposes is 915 MHz [8].
Table 1.1 Applications of Infrared heating: [1].
Industry
Methods
Agriculture
Incubation and warming
Bottling
Drying
Glass
Drying, curing the varnish or paint on back—mirrors and tempering layers
Medical-applications
Incubation and warming
Environmental chambers
Heating
Food
Toasting, cooking, food warming, drying, broiling, and melting
Pharmaceutical
Drying water from powder—tablets
Metal treatment
Preheating—aluminum; steel
Paper
Laminating Calendaring—rolls Adhesive—labelsDrying water from—towels
Paint
Primer, topcoat alkyd, acrylic—steel panels, Drying—bicycles, vehicles bodies, aluminiumbodies
Textiles
Moisture elimination—carpets Latex and PVC backingMoisture elimination from dyes
Plastics
Laminating Annealing FormingEmbossing
Microwave is a varying magnetic field that generates heat on interaction with, and absorption by, certain dielectric materials, and with the positioning of the direction of the electric field, the native thermal motion of the polarity molecule changes [26]. Water, the dominant polar molecule, consists of separated molecules of an oxygen atom with a negative charge and hydrogen atom with a positive charge which combinedly structure into an electric dipole. When these dipoles fluctuate swiftly back and forth from positive to negative in the direction of the electric field numerous times per second, these express reversals produce frictional heat. This implies that the polar molecules in food play a vital role in the heating performance of food in the microwave system. Due to this frictional rise in the temperature of the water, food components get heated up by convection and conduction. The loss factor dielectric constant of the food determines the depth of penetration of both microwaves and RF energy [49]. This also relies on the varying temperature and moisture concentration of the sample material plus the frequency of the electric field. Overall, with lesser frequency and loss factors, we get more depth of penetration. Energy distribution varies with food samples which also governs the depth of penetration of the microwave inside the food. As the food material to be heated in the microwave matches with the wavelength of the material, it becomes difficult to manage the heat uniformity of microwave heating which can be taken as a crucial constraint for industrial application of microwave heating. Thus, a central obligation for microwave energy application and microwave equipment in the food industry is the potential to accurately regulate heating uniformity. Microorganisms are not affected as a result of microwave radiation but are susceptible to the heat generated because of the radiation. Microwaves are likely to be a channel through ceramics, thermoplastics, and glass whereas they are absorbed by carbon and water; reflected by metals but conceivably transmitted using metal hollow tubes and on transiting amongst diverse materials get refracted like the visible light. Microwaves can also be focused on a beam [77].
The microwave energy is transferred to food through the contactless transmission of the wave. This system ensures the uniform heating of food samples during the operation. The equipment comprises a magnetron which is the generator, guide waves which are the aluminium tubes, and for a continuous operation, it has a tunnel attached with a conveyor or a metal compartment for batch operation. These chambers and tunnels are sealed by absorbers or traps to prevent the microwave from escaping and causing injury to the operator [11].
In the microwave system, the two oscillating perpendicular fields, i.e., electric and magnetic, act directly on the heating material, converting the part of absorbed energy to thermal energy. The interaction of the microwave radiation with chemically bound water present in the food material generates high pressure and temperature due to the absorption of the characteristic photonic energy of electromagnetic waves. This process causes moisture evaporation, resulting in pressure exertion on the plant material to cellular and subcellular level leading to swell up and rupture eventually [44].
Microwaves are defined by two mechanisms:
(a) Ionic polarisation: ions present in the solution, when suspended to the electric field, orient themselves, experiencing acceleration and an upsurged kinetic energy. When ions collide with each other it gets converted into heat. This frequent collision increases the density or the concentration of the solution which is also known as the ionic polarization effect [3], whereas in gases the collision becomes difficult due to the spacing between the molecules. In food material, cations are generated by the presence of salts of sodium, potassium, or calcium whilst chlorine produces anions.
