This review shows how the basic kinetics of lipid oxidation can be simplified for application to the study of food deterioration. The physical and chemical factors that control oxidation are examined and analyzed in terms of food structure and composition. Studies of oxidation of several food items are examined in light of these kinetics and mechanisms.

Kinetics of lipid oxidation in foods

Oxidative processes in meat and meat products: Quality implications

Lipids become rancid as a result of oxidation, and this oxidative rancidity is a major cause of food deterioration. The acceptability of a food product depends on the extent to which this deterioration has occurred. Thus some criterion for assessing the extent of oxidation is required. This paper reviews the experimental techniques for the measurement of lipid oxidation. The spectrum of tests ranges from simple organoleptic evaluations to chemical and physical methods. There is no ideal chemical method which correlates well with changes in organoleptic properties of oxidized lipids throughout the entire course of autoxidation. The methods discussed each give information about particular stages of the autoxidative process, and some are more applicable to certain lipid systems than others. The method of choice depends on a number of factors including the nature and history of the oxidized sample, the type of information required, the time available, and the test conditions. Clearly, there is a need for a more thorough assessment of the available methods so that unreliable, cumbersome methods may be discarded and modifications made to the remaining methods to maximize the information obtained. The ultimate criterion for the suitability of any test is its agreement with sensory perception of rancid flavors and odors.

Measurement of lipid oxidation: A review

Volatile lipid oxidation products.

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.

The steam volatile monocarbonyl compounds in mildly autoxidized esters of oleic, linoleic, linolenic acids, and animal and vegetable fats were quantitatively estimated. The major aldehydes in oleate and linoleate were those that might be expected from the scission of reported monomeric hydroperoxide isomers. The predominance of hept-2,4-dienal and propanal in linolenate suggested that the major monomeric hydroperoxides were 12-and 16-hydroperoxy conjugated dienoic isomers. The number of minor aldehydes increased with degree of unsaturation of the fatty acid. The amounts of monocarbonyl compounds in the fats examined generally agreed with their average fatty acid composition. Appreciable amounts of heptanal in lamb and beef fat and heptanal and decanal in butterfat, under the conditions of oxidation, could not have come from the three unsaturated acids. Heating at 165°C. in all samples increased the proportions of the most unsaturated major aldehydes.

Carbonyls in oxidizing fat. V. The composition of neutral volatile monocarbonyl compounds from autoxidized oleate, linoleate, linolenate esters, and fats

SUMMARY

-Oxidation of freezer-stored, sodium chloridecured pork was characterized by a rapid rate and moderately high monocarbonyl/peroxide ratios. Increase in the concentration of NaCl accelerated autoxidation, but did not affect hydroperoxide decomposition to monocarbonyl compounds. High proportions of lean increased autoxidation and the monocarbonyl-peroxide ratios. Sodium nitrite (0.03%) catalyzed autoxidation by reaction with the meat pigment in an apparently independent effect to that exerted by NaCl. Composition of the free monocarbonyl compounds indicated linoleate specificity in peroxide decomposition, although hematin catalysis is nonspecific in its attack on unsaturated fatty acids. Possible direct effects of NaCl did not appear to involve a reactive chloride ion.

Carbonyls in Oxidizing Fat. 11. The Effect of the Pro‐oxidant Activity of Sodium Chloride on Pork Tissue

Evidence suggested that the low proportions of C10 alk-2,4-dienal found in mildly autoxidized linoleate or lard was basically due to a selective scission mechanism of the 13 and 9 conjugated linoleate hydroperoxide isomers. Spontaneous scission tended to be at the carbon linkage between a double bond and the hydroperoxide group. Thus the 13 hydroperoxide isomer produced the typically predominant amounts of hexanal. The 9 hydroperoxide isomer formed little C10 dienal and scission between the 9 and 10 carbons possibly led to some C9 alk-2-enal. Earlier studies of free aldehyde formation by autoxidized oleate, linoleate, linolenate and arachidonate support such a scission mechanism. Autoxidized linoleate was decomposed by dilute acid to C6 alkanal, some C9 enal and no dienal. Under different stress, such as heat, alkaline conditions and Cu++, large proportions of C10 dienals were formed. This appeared due to a shift in the point of scission to the saturated side of the hydroperoxide group.

A. M. Gaddis

Papers

Carbonyls in oxidizing fat. V. The composition of neutral volatile monocarbonyl compounds from autoxidized oleate, linoleate, linolenate esters, and fats

Carbonyls in Oxidizing Fat. 11. The Effect of the Pro‐oxidant Activity of Sodium Chloride on Pork Tissue

Precursors of alk-2,4-dienals in autoxidized lard

CARBONYLS IN OXIDIZING FAT. I. SEPARATION OF STEAM VOLATILE MONOCARBONYLS INTO CLASSESa

CARBONYLS IN OXIDIZING FAT III. THE DISTRIBUTION OF’VOLATILE and NON‐VOLATILE CARBONYLSa