Advances in Cold Plasma Applications for Food Safety and Preservation

Daniela Bermudez-Aguirre

• Publisher: Academic Press
• Year: 2019
• Print ISBN:
  9780128149218
• eBook ISBN:
  9780128149225
• Topic: Tecnología e ingeniería
• Subtopic: Ciencia de los alimentos

Cold plasma is one of the newest technologies tested for food preservation. In the last decade, this novel approach has shown promising results as a disinfectant of food products and packaging materials. Cold plasma is also affordable, waterless, waste-free, and leaves no chemical residue on the product. This exciting new technology is covered thoroughly in Advances in Cold Plasma Applications for Food Preservation.The book presents the basic principles of cold plasma, examples of food products disinfected by cold plasma, and the challenges of using cold plasma to maximize microbial and spore inactivation. Some chapters are devoted to specific applications of the technology, such as the use of cold plasma for space missions. Insights about the required regulations for this technology are also discussed.Written and edited by experts in the field, Advances in Cold Plasma Applications for Food Preservation is aimed at academic researchers, food scientists, and government officials working on disinfection of food products. - Covers the basic principles of cold plasma - Presents novel information and updated results in microbial, spore, and enzyme inactivation in different food products - Explores the use of cold plasma in disinfection of food products, including packaged food and food packaging materials and discuss how some food components are modified - Includes the description of some of the current equipment devices and the requirements to design specific food processing systems - Investigates specific uses of cold plasma in some applications such as space food - Details current regulatory status of cold plasma for food applications

Part I

Fundamentals of cold plasma technology

Chapter 1

Engineering principles of cold plasma

Patrick Pedrow^a; Zi Hua^b; Shuzheng Xie^a; Mei-Jun Zhu^{b a} School of Electrical Engineering and Computer Science, Washington State University, Pullman, WA, United States
^b School of Food Science, Washington State University, Pullman, WA, United States

Abstract

This chapter presents key engineering concepts, including overviews of the plasma state, Maxwell's equations for electromagnetic fields, kinetic theory of plasma, and discharge phenomena. Six common cold plasma reactor types are explained: dielectric barrier, jet, corona, capacitively coupled, inductively coupled, and microwave; the first three predominantly use atmospheric pressure and the last three predominantly use low pressure. Engineering principles and reactor functionalities are then described. Some specific examples of cold plasma processing are presented.

Keywords

Plasma discharge; Electron avalanche; Streamer; Dielectric barrier discharge; Cold plasma; Reactive oxygen species; Reactive nitrogen species; Microorganisms

Contents

• 1 Introduction
• 2 Cold plasma fundamentals
  • 2.1 Plasma state
  • 2.2 Maxwell's equations
  • 2.3 Kinetic theory of plasma
  • 2.4 Plasma discharge phenomena
• 3 Cold plasma reactor types
  • 3.1 Atmospheric pressure cold plasma reactors
  • 3.2 Low-pressure cold plasma reactors
  • 3.3 Features and phenomena found in various cold plasma reactor types
• 4 Conclusion
• References
• Further reading

1 Introduction

In recent years, cold plasma has gained increasing attention for its potential use in food preservation. Cold plasma as an emergent technology can be an effective approach for inactivating pathogenic and spoilage microorganisms without significantly impacting food quality. The antimicrobial efficacy of cold plasma processing can be enhanced when combined with a sanitizer or essential oil. Cold plasma processing of food is a complex topic and substantial additional multidisciplinary research is still required.

There are a broad array of cold plasma reactors, each of which is capable of generating ionized chemical species mixed randomly with free electrons and activated neutral chemical radicals, all coexisting in the plasma phase. As charged chemical species disappear via recombination and via transport, the plasma phase reverts to the gas phase. Electron avalanches and streamers result in ionization of neutral species. When molecules are present there are many collisions that result in bond scissions, generating chemically active neutral species. In many cold plasma systems, these activated neutral chemical species are transported to and are incident upon the processed food. Depending upon the precursor gas admixture, cold plasma reactors generate a wide variety of reactive chemical species. For example, cold plasma generated in admixtures containing dry air will produce reactive oxygen and nitrogen species (RONS) that have been shown effective at reducing microbial contamination not only on food but also in wounds and water suspensions.

There are many ways to initiate the plasma state; however, not all methods result in cold plasma. Cold plasma is required to prevent thermal damage in food. Generation of plasma via addition of thermal energy results in plasma that is in thermodynamic equilibrium with neutrals, positive ions, negative ions, and free electrons all having the same temperature and usually that temperature is too high for food processing. Sustaining the plasma state via E-field-accelerated free electrons results in systems where massive chemical species (those not free electrons) retain low temperature (near room temperature for many cold plasma reactors) while the E-field accelerates free electrons to velocities high enough for impact ionization of target chemical species. Just as important is the fact that many electron-to-neutral collisions with molecules involve enough kinetic energy for bond scission (but no ionization) and concomitant generation of activated neutral chemical radicals. Substantial technical details are required for food processing engineers to fully analyze cold plasma reactors and some of these technical specifications are the subject of this chapter.

While ultraviolet light and high velocity electron beams can both be lethal to microorganisms, this chapter focuses less on those mechanisms of microbial inactivation that are discussed in other chapters but emphasizes instead the use of cold plasma reactors for production of reactive chemical species used for food preservation. Electromagnetic field theory and kinetic theory of plasma are essential disciplines for understanding engineering principles involved in cold plasma processing of food. It is important to know the salient reactive chemical radicals to be generated by the cold plasma reactor but also to know details regarding transport of and fate of these radicals as they are used to process food. The goal is to maximize the radical's lethality for microorganisms while maintaining overall food quality and keeping the processed food safe for human consumption.

2 Cold plasma fundamentals...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Contributors
• Preface
• Introduction
• Part I: Fundamentals of cold plasma technology
• Part II: Food preservation by cold plasma
• Part III: Equipment
• Part IV: Special applications of cold plasma and regulatory status
• Index