Electron Spin Resonance in Food Science

Electron Spin Resonance in Food Science covers, in detail, the ESR identification of the irradiation history of food products and beverages to investigate changes that occur during storage, with an aim of improving hygienic quality and extending shelf-life with minimal tempering in nutritional profile.

The book also includes ESR studies on the interaction of food items and packaging materials, along with a section on new approaches in ESR identification of irradiated foods that is followed by a chapter on international legislation relevant to irradiated food.

A section on ESR applications in characterizing ROS/antioxidants in food items and lipid oxidation, including spin labeling, spin trapping and imaging applications is also covered, as are ESR applications in nutrition and pharmaceutics.

• Serves as a complete reference on the application of ESR spectroscopy in food science research
• Focuses on applications and data interpretation, avoiding extensive use of mathematics so that it fulfils the need of young scientists from different disciplines
• Includes informative pages from leading manufacturers, highlighting the features of recent ESR spectrometers used in food science research
• Includes information on different, active, worldwide groups in ESR characterization of food items and beverages

• Language: English
• Publisher: Academic Press
• Release date: Dec 23, 2016
• ISBN: 9780128133644

Book preview

States

Preface

Ashutosh Kumar Shukla, Allahabad, India

This book intends to describe the applications of electron spin resonance (ESR) spectroscopy in the area of Food Science. Electron paramagnetic resonance (EPR) and ESR: both names are equally valid for the technique. A relatively new term, electron magnetic resonance (EMR), is also gaining popularity. Authors have freely adopted the title and style of their chapters in this book. These expert authors are from different disciplines, and accordingly interdisciplinary character has come up in a natural way. The emphasis is on the application side, and mathematical details have been kept to a minimum.

This book contains eight chapters. Constantin Daniel Negut and Mihalis Cutrubinis have described standard ESR methods for detection of irradiated food in Chapter 1, Electron Spin Resonance Standard Methods for Detection of Irradiated Food. In Chapter 2, Electron Paramagnetic Resonance Investigation of the Free Radicals in Irradiated Foods, Octavian G. Duliu and Vasile Bercu have described quantitative ESR analysis of the time and temperature dependence of free radicals in irradiated foods. In Chapter 3, Electron Spin Resonance Techniques in the Quality Determination of Irradiated Foods, Kaushala Prasad Mishra has discussed quality issues related with food irradiation, and emphasized the role of ESR in quality determination. Chapter 4, Electron Spin Resonance Detection of Irradiated Food Materials is an attempt by Grzegorz Piotr Guzik and myself to introduce the actual subject matter of this book, with some examples from a wide range of food materials. Kashif Akram, Umar Farooq, and Afshan Shafi have especially covered ESR identification of irradiated fruits and vegetables in Chapter 5, Electron Spin Resonance Spectroscopy for the Identification of Irradiated Fruits and Vegetables. Alex I. Smirnov has described ESR applications to beverages in Chapter 6, Electron Paramagnetic Resonance Spectroscopy to Study Liquid Food and Beverages. Siavash Iravani has reviewed the ESR of irradiated drugs and excipients for drug control and safety in Chapter 7, Electron Spin Resonance of Irradiated Drugs and Excipients for Drug Control and Safety. In Chapter 8, Free Radicals in Nonirradiated and Irradiated Foods Investigated by Electron Spin Resonance and 9 GHz Electron Spin Resonance Imaging, Kouichi Nakagawa has covered ESR imaging as it is applied to the investigation of food items. I learnt many things from these chapters, and hope that readers will also enjoy reading it in a fruitful way.

I sincerely thank to Nina Bandeira, Food Science Acquisitions Editor, Elsevier, for giving me an opportunity to present this book to readers. I wish to thank Mariana Kühl Leme, Editorial Project Manager, Elsevier, for providing all the support during the development of this project. I thank the authors for taking time out of their busy academic schedules to contribute to this book. It is their cooperation which led me to develop this project. My special thanks to anonymous reviewers for their contributions to improve the quality.

I am grateful to Prof. Ram Kripal, Head, Department of Physics, University of Allahabad, who introduced me to ESR spectroscopy. My sincere thanks to Prof. Raja Ram Yadav, Department of Physics, University of Allahabad, Dr. M. Massey, Principal, Ewing Christian College, Allahabad, and my colleagues for their constant encouraging remarks and suggestions during the development of this book project.

It is difficult to express my gratitude in words to my parents who have blessed me to complete this task. My brother Dr. Arun K. Shukla, Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur has always been there to help me. My special thanks are also due to my wife Dr. Neelam Shukla, my daughter Nidhi, and son Animesh for their patience during this work.

December 2016

Chapter 1

ESR Standard Methods for Detection of Irradiated Food

C.D. Negut and M. Cutrubinis,    Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH), Măgurele, Romania

Abstract

This chapter presents electron spin resonance (ESR) spectroscopy as a detection method for irradiated food. In the first part the criteria to be fulfilled by a reliable detection method are summarized. ESR spectroscopy, which satisfies most of the detection criteria, can be used for a wide variety of irradiated foodstuffs and it is standardized for food containing bone, cellulose, and crystalline sugar. Typical spectra for these categories of foodstuffs are presented and discussed. The absence of specific-to-irradiation free radicals in the irradiated food or their poor stability can be a serious limitation for the detection of irradiation by ESR spectroscopy. In the last two decades, different improvements in the technique were proposed in order to overcome this problem. The most promising of them are discussed.

Keywords

Bone; cellulose; crystalline sugar; detection method; free radical; irradiated food

Contents

1.1 Introduction 1

1.2 Standardized ESR Detection Methods 2

1.2.1 Basic Instrumentation 2

1.2.2 Food Containing Bone 3

1.2.3 Food Containing Cellulose 5

1.2.4 Food Containing Crystalline Sugar 6

1.3 Improvements to ESR Detection Methods 10

1.3.1 Thermal Annealing 10

1.3.2 Saturation Behavior 11

1.3.3 Spin Probe 12

1.3.4 Alcoholic Extraction 12

References 13

1.1 Introduction

Although the biocide effect of ionizing radiation has been known since the late 19th century, the first food irradiation facility was commissioned only in 1959. In 1980, the Joint FAO/IAEA/WHO Expert Committee on the wholesomeness of irradiated food concluded that irradiation of food up to an average dose of 10 kGy presents no toxicological hazard and introduces no special nutritional or microbiological problems [1]. Nowadays, irradiation is a regulated technology for preventing losses or for microbial decontamination of food. In 2011, the International Organization for Standardization (ISO) issued a standard for treatment of food by ionizing radiation [2]. According to the Irradiated Food Authorization Database [3], irradiation of food has been approved in more than 50 countries. Regulations regarding categories of food approved for irradiation and maximum permitted doses vary widely from country to country. In many countries of the European Union, only dry vegetables and spices can be treated by ionizing radiation at a maximum dose of 10 kGy, while in Brazil any category of food can be irradiated at any dose.

Regulations across the world require accurate labeling in order to inform the consumers whether foodstuffs or ingredients within them have been irradiated. Thus, methods were developed for the detection of irradiated food which can be used in two ways: to see if irradiated foodstuffs are correctly labeled, or if foodstuffs labeled as irradiated are really irradiated. Most of the research on the detection of irradiated food was done between 1985 and 1995, resulting in the adoption of 10 standards by the European Committee for Standardization (CEN). The standards are complementary techniques, allowing the detection of irradiation treatment for a wide variety of foods. Among these, three are based on ESR spectroscopy.

Electron spin resonance (ESR) detects free radicals induced by ionizing radiation and trapped in the dry parts of irradiated food. Their stability is related to the moisture content and the crystallinity of the solid region of food. In principle, ESR signals (as well as any other parameters used in the detection of irradiated food) induced by ionizing radiation should be absent in nonirradiated food and specific to irradiation, meaning that it cannot be induced by any other food processing methods. It should appear at the usual doses applied to the specific food under test, and should be stable at least over the storage life of the irradiated food [4]. Ideally, the signal intensity monotonously increases with the dose, making an estimation of the applied dose possible. This is the case of very stable free radicals such as carbonate radicals in the hydroxyapatite crystal of bone. According to the practical criterion that a detection method should apply to a wide range of food types, there are standardized ESR-based detection methods for food containing bone [5], cellulose [6], and crystalline sugar [7].

1.2 Standardized ESR Detection Methods

1.2.1 Basic Instrumentation

Food irradiation control by ESR is usually performed in X-band (about 9.1–9.7 GHz) by continuous wave (CW) mode. The main task is to find radiation-induced signals with characteristic shapes and g factors. The value of the g factor is obtained from the values of the resonant magnetic field and microwave frequency. The microwave frequency can be measured with high precision by a frequency counter. The magnetic field is usually determined by means of a Hall sensor. A higher accuracy can be achieved by using a nuclear magnetic resonance (NMR) gaussmeter. Another way to determine the g factor is to use a reference material with a well-known g value. The reference is measured together with the sample such that their spectra are obtained for the same frequency and magnetic field [8]. The unknown g factor is derived from the resonant magnetic field and the g factor of reference. Ideally, the g factor of the reference differs from that of the sample enough that their spectra will not overlap. A powder of Mn²+ ions in CaO is a very convenient reference material. Its ESR spectrum consists of a hyperfine sextet with a g factor of 2.0010. The lines are spaced by 8−9 mT, thus both the third (g about 1.9810) and the fourth lines (g about 2.0330) can be used as a reference. In general, ESR signals found in irradiated food are large. In the case of sugars, the spectrum width can reach 10 mT, thus in acquiring the spectrum a sweep of 20 mT around the central field (342 mT for 9.5 GHz) is recommended.

One of the advantages of the ESR method is the simplicity of sample preparation. Usually, a scalpel is enough to obtain dry parts of the food by removing soft tissues which can affect the signal. When seeds from fresh fruit are being analyzed, additional common instruments and materials are needed to separate the seeds from the pulp, such as an electric blender and purified water to dilute the pulp and filter paper to absorb residual water from the seeds. The high moisture content of samples can cause difficulties in tuning the spectrometer resonator. In such cases it is recommended to dry the samples using a freeze dryer or a laboratory vacuum oven at a temperature up to 40°C. Excessive heating may drastically reduce the radiation-induced signal and, at the same time, induce free radicals that are not specific to