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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 KumarAnil PanghalM.K. Garg
1
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 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
