Lipid Oxidation

Challenges in Food Systems

Amy S. Logan, Uwe Nienaber, Xiangqing (Shawn) Pan

• Publisher: Academic Press and AOCS Press
• Year: 2015
• ISBN:
  9780988856516
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

Lipid oxidation in food systems is one of the most important factors which affect food quality, nutrition, safety, color and consumers' acceptance. The control of lipid oxidation remains an ongoing challenge as most foods constitute very complex matrices. Lipids are mostly incorporated as emulsions, and chemical reactions occur at various interfaces throughout the food matrix. Recently, incorporation of healthy lipids into food systems to deliver the desired nutrients is becoming more popular in the food industry. Many food ingredients contain a vast array of components, many of them unknown or constituting diverse or undefined molecular structures making the need in the food industry to develop effective approaches to mitigate lipid oxidation in food systems. This book provides recent perspectives aimed at a better understanding of lipid oxidation mechanisms and strategies to improve the oxidative stability of food systems.

• Five chapters on naturally-derived antioxidants that focus on applications within food systems
• Contributors include an international group of leading researchers from academic, industrial, and governmental entities
• Discusses the oxidative stability of enzymatically produced oils and fats
• Provides overviews on the complexities of lipid oxidation mechanisms, and emulsion systems most suseptible to rapid lipid oxidation

CHAPTER 1

Challenges in Elucidating Lipid Oxidation Mechanisms

When, Where, and How Do Products Arise?

K.M. Schaich¹, ¹Dept. of Food Science, Rutgers University, 65 Dudley Rd., New Brunswick, NJ 08901-8520

Introduction

More than a century ago, researchers first noted that lipids oxidize by a free-radical mechanism, and more than 60 years ago, they identified the three stages (that is, initiation, propagation, and termination) of the chain reactions involved (Farmer et al., 1943; Boll and, 1945; Gunstone & Hilditch, 1945; Farmer, 1946; Holman & Elmer, 1947; Bolland, 1949). Several decades of intense research on both practical and theoretical aspects of lipid oxidation then developed current knowledge about lipid oxidation kinetics, processes, mechanisms, and products. This knowledge is used throughout the food industry to stabilize oils and foods, and it has also been applied to research on aging, cancer, and many other diseases. A number of excellent references have provided general overviews of lipid oxidation as well as detailed coverage of specific stages of the reactions (Swern, 1961; Frankel, 1962; Lea, 1962; Lundberg, 1962; Scott, 1965; Brodnitz, 1968; Frankel, 1980; Porter et al., 1981; Frankel, 1982, 1984; Porter et al., 1984; Porter & Wujek, 1984; Frankel, 1985; Porter, 1986; Chan, 1987; Porter & Wujek, 1987a; Porter, 1990; Frankel, 1991; Porter et al., 1995; Frankel, 2005; Schaich, 2005, 2006).

Despite this experience and research, preventing oxidation and maintaining the desired shelf life of foods formulated with high polyunsaturated fatty acids are still significant challenges. In fact, stability is often impossible to control or predict, even under established production protocols, oxidation kinetics are frequently inconsistent with expected reactions or product patterns, and preservation approaches based on the traditional free-radical chain reaction do not always work as expected. In addition, many routinely observed oxidation products cannot be explained by standard radical recombinations or alkoxyl radical scissions. The very fact that this book revisits the challenges of lipid oxidation demonstrates that we still have critical gaps in our understanding of lipid oxidation reactions and mechanisms.

The intent of this chapter, therefore, is not to rehash established material but rather to challenge anyone concerned with lipid oxidation—whether in fundamental chemical research, food quality deterioration, pathology or toxicology, cell signaling, or any other application—to think beyond hydrogen abstraction in established free-radical chain reactions and to consider other mechanisms that may alter the course, kinetics, and product distribution of lipid oxidation.

According to traditional explanations, hydrogen abstraction controls propagation, hydroperoxides are always the key intermediate, and products do not form until after hydroperoxides decompose. However, fundamental free radical chemistry shows that organic peroxyl radicals (ROO•) and alkoxyl radicals (RO•) also undergo independent rearrangement, addition, and scission or elimination reactions in competition with hydrogen abstractions in radical chain reactions. This means that end products other than hydroperoxides can accumulate in early stages of lipid oxidation, and secondary products can be generated without going through hydroperoxides. In lipid oxidation, these alternate reactions can have very important consequences for the course, kinetics, and analysis of lipid oxidation, as well as for the deterioration of food quality associated with lipid oxidation. Products of the various pathways—including alcohols, epoxides, dimers, ketones, and aldehydes—have different effects on the flavors and browning potential of food and, perhaps more importantly, different abilities to react with other molecules and broadcast oxidative damage. While all these product classes are well recognized in lipid oxidation, that they arise separately and from different mechanisms is not. Hence, multiple classes of oxidation products are seldom measured and important components of overall system oxidation (lipids plus other molecules) may be missed.

This chapter, thus, introduces the chemistry of alternate reactions to show that lipid oxidation is much more complex than the simplistic radical chain reactions normally presented, and to encourage m...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface
• Chapter 1: Challenges in Elucidating Lipid Oxidation Mechanisms: When, Where, and How Do Products Arise?
• Chapter 2: Challenges in Analyzing Lipid Oxidation: Are One Product and One Sample Concentration Enough?
• Chapter 3: Oxidation in Different Food Matrices: How Physical Structure Impacts Lipid Oxidation in Oil-in-Water Emulsions and Bulk Oils
• Chapter 4: Substrate and Droplet Size: Important Factors for Understanding Aqueous Lipid Oxidation
• Chapter 5: The Role of the Interfacial Layer and Emulsifying Proteins in the Oxidation in Oil-in-Water Emulsions
• Chapter 6: Oxidative Stability of Enzymatically Processed Oils and Fats
• Chapter 7: The Polar Paradox: How an Imperfect Conceptual Framework Accelerated Our Knowledge of Antioxidant Behavior
• Chapter 8: Role of Hydrophobicity on Antioxidant Activity in Lipid Dispersions: From the Polar Paradox to the Cut-Off Theory
• Chapter 9: Understanding Antioxidant and Prooxidant Mechanisms of Phenolics in Food Lipids
• Chapter 10: Antioxidant Evaluation and Antioxidant Activity Mechanisms
• Chapter 11: Strategies to Minimize Oxidative Deterioration in Aquatic Food Products: Application of Natural Antioxidants from Edible Mushrooms
• Chapter 12: The Natural Antioxidant Ergothioneine: Resources, Chemical Characterization, and Applications
• Chapter 13: Rosemary and Green Tea Extracts as Natural Antioxidants: Chemistry, Technology, and Applications
• Chapter 14: Using Natural Plant Extracts to Delay Lipid Oxidation in Foods
• Chapter 15: Strategies to Prevent Oxidative Deterioration in Oil-in-Water Emulsion Systems: Canola-Based Phenolic Applications
• Editors and Contributors
• Index