
The susceptibility of lipids to oxidation is a major cause of quality deterioration in food emulsions. The reaction mechanism and factors that influence oxidation are appreciably different for emulsified lipids than for bulk lipids. This article reviews the current understanding of the lipid oxidation mechanism in oil-in-water emulsions. It also discusses the major factors that influence the rate of lipid oxidation in emulsions, such as antioxidants, chelating agents, ingredient purity, ingredient partitioning, interfacial characteristics, droplet characteristics, and ingredient interactions. This knowledge is then used to define effective strategies for controlling lipid oxidation in food emulsions.

Lipid Oxidation in Oil-in-Water Emulsions: Impact of Molecular Environment on Chemical Reactions in Heterogeneous Food Systems

Integrated approach to deep fat frying: engineering, nutrition, health and consumer aspects

Lipid oxidation is a major cause of quality deterioration in food emulsions. The design of foods with improved quality depends on a better understanding of the physicochemical mechanisms of lipid oxidation in these systems. The oxidation of emulsified lipids differs from that of bulk lipids, because of the presence of the droplet membrane, the interactions between the ingredients, and the partitioning of ingredients between the oil, aqueous and interfacial regions.

Lipid oxidation in food emulsions

Publisher Summary This chapter presents the ubiquitous nature and pervasiveness of lipid oxidation ex vivo in foods and in vivo , and demonstrates that oxidation generally has deleterious results in both systems. This dramatizes the need for more effective strategies for controlling lipid oxidation, both in food materials and in tissues in vivo . The chapter discusses the existing practices using antioxidants, chelators, enzyme inactivation, and anoxic and low-temperature storage conditions. The oxidative degradation of the unsaturated fatty acid components of food lipids may be beneficial in some foods in generating low levels of desirable flavorful carbonyl compounds. However, in general, oxidation causes deleterious changes in flavor, taste, color, texture, and possibly safety of foods. The polyunsaturated fatty acids (PUFA)—particularly the trienoic, pentaenoic, and hexaenoic PUFA commonly found in oilseeds and seafoods—render these foods, which are particularly sensitive to oxidative changes which limit their self-life.

Oxidation of polyunsaturated fatty acids: mechanisms, products, and inhibition with emphasis on fish.

Degradation during application of ultrasound in food processing: A review

Oxidation was measured by oxygen consump-tion in a Warburg apparatus, modified to main-tain constant partial oxygen pressure by auto-matic electrolytic generation of oxygen with automatic recording of the oxygen consumed.

Fat oxidation at low oxygen pressure. i. kinetic studies on the rate of fat oxidation in emulsions

Earlier reported kinetic studies on the dependence of lipid oxidation on oxygen pressure in emulsions were continued by studying this relationship in the presence of antioxidants. The substances tested represented two types of antioxidants, phenolic inhibitors (α-tocopherol, BHA, PG) and amino acid-retarders (glycine, alanine, histidine, tryptophane). The inhibiting effect of the first mentioned group, i.e., the formation of an induction period was, in general, not dependent on oxygen pressure, while the retardation caused by amino acids was stronger at low oxygen pressure than in air. The effect of lowering oxygen pressure was practically the same, when phenolic inhibitors were added as without such addition. It was, however, enhanced by the addition of amino acid-retarders. When representatives of these two types of antioxidants were added in combination, their synergistic effect was considerably enhanced at low oxygen pressure.

Fat oxidation at lwo oxygen pressure: II. Kinetic studies on linoleic acid oxidation in emulsions in the presence of antioxidants

Earlier studies on lipid oxidation at low oxygen pressure were continued to cover the effect of low oxygen pressure in the presence of added metal salts. Addition of Cu2+ and Fe3+ salts was shown to exert a catalytic effect, which, on increasing metal concentration, may reach a maximum and then decrease. This so called conversion is favored at low oxygen pressure (e.g., corresponding to 1% O2 at atmospheric pressure). Under certain conditions it may result in an antioxidative effect. The phenomenon is more pronounced at pH 5 than at pH 7, and it is dependent on the anions present and the ratio between the concentration of the catalyst and that of the substrate. A tentative explanation of these effects of Cu2+ and Fe3+ salts at low oxygen pressure, which are not given by Fe2+ and Co2+ salts, is offered.

Per-Olof Fredriksson

Papers

Fat oxidation at low oxygen pressure. i. kinetic studies on the rate of fat oxidation in emulsions

Fat oxidation at lwo oxygen pressure: II. Kinetic studies on linoleic acid oxidation in emulsions in the presence of antioxidants

Fat oxidation at low oxygen pressure: III. Kinetic studies on linoleic acid oxidation in emulsions in the presence of added metal salts