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Thermal Food Engineering Operations

Scrivener Publishing

100 Cummings Center, Suite 541J Beverly, MA 01915-6106

Bioprocessing in Food Science

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

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Thermal Food Engineering Operations

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

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Library of Congress Cataloging-in-Publication Data

ISBN 9781119775591

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Cover design by Russell Richardson

Set in size of 11pt and Minion Pro by Manila Typesetting Company, Makati, Philippines

Printed in the USA

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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.

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.

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.

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