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Thermal Food Engineering Operations
Scrivener Publishing
100 Cummings Center, Suite 541J Beverly, 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. e main objectives of this series are to disseminate knowledge pertaining to recent technologies developed in the eld of food science and food process engineering to students, researchers and industry people. is will enable them to make crucial decisions regarding adoption, implementation, economics and constraints of the di erent 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 di erent technologies developed at each level are not implemented for the bene ts of di erent stake holders. However, the advancements in bioprocesses are required at all levels for betterment of food industries and consumers.
e 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. e novel technologies employed for processing di erent types of foods, encompassing the background, principles, classi cation, applications, equipment, e ect on foods, legislative issue, technology implementation, constraints, and food and human safety concerns will be covered in this series in an orderly fashion. ese 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 smallscale manufacturers, national research laboratories, all working in the eld of food science, agriprocessing and food biotechnology will bene t.
Publishers at Scrivener
Martin Scrivener (martin@scrivenerpublishing.com)
Phillip Carmical (pcarmical@scrivenerpublishing.com)
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 LLC
For more information about Scrivener publications please visit www.scrivenerpublishing.com.
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Library of Congress Cataloging-in-Publication Data
ISBN 9781119775591
Cover image: Wikimedia Commons and the editors
Cover 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
3.1
3.2.1.2
4.4
4.3.2
5.4
5.6
5.8
5.8.1
5.8.2
5.8.3
6.4
6.5
6.6
6.7
6.8
8.3
8.2.1
9.5
9.6
8.2.3
8.2.3.2
Modiri
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9.7.2
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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.
Garg
Nitin Kumar Anil Panghal M.K.
Novel 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
*Corresponding author: amritapreetam92@gmail.com
Nitin Kumar, Anil Panghal and M. K. Garg (eds.) Thermal Food Engineering Operations, (1–44) © 2022 Scrivener Publishing LLC
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 nonthermal 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 lowprocessed 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 nonuniform 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.
