Odorant lipid peroxidation

MahadikSP, MukherjeeS, Scheffer R, CorrentiEE, Mahadik JS. 1998. Elevated plasma lipid peroxides at the onset of nonaffective psychosis. Biol Psychiatry 43 674-679. Malaspina D, Coleman E, Goetz RR, Harkavy-Friedman J, Corcoran C, et al. 2002. Odor identification, eye tracking and deficit syndrome schizophrenia. Biol Psychiatry 51 809-815. 

Upon exposure to air, animal and vegetable fats and oils become rancid (i.e., develop color changes and a musty, rank taste and odor). Here, the hydrogen atoms of the —CH2—groups located between alternating double bonds (i.e., —CH=CH—CH2—CH=CH—) of a polyunsaturated phospholipid or fatty acid (LH) are very susceptible to abstraction by free radicals. This process can then lead to a general reaction known as autoxidation, which results in the formation of a lipid hydroperoxide (LOOH) and the generation of a new free radical hence, an autocatalytic reaction results (lipid peroxidation). 

Ishino, K., Wakita, C., Shibata, T., Toyokuni, S., Machida, S., Matsuda, S., Matsuda, T., and Uchida, K. Lipid peroxidation generates a body odor component trani-2-nonenal covalently bound to protein in vivo. J. Biol. Chem. 285 2010 15302-15313. 

Lipid peroxidation provides numerous volatile and nonvolatile compounds. Since some of the volatiles are exceptionally odorous compounds, lipid peroxidation is detected even in food with unsaturated acyl lipids present as minor constituents, or in food in which only a small portion of lipid was subjected to oxidation. 

Important aroma substances of raw and cooked mutton are listed in Table 12.25. A special feature is the two branched fatty acids, which are already present in the raw meat and produce the mutton odor. (E)-2-Nonenal and the other odor substances from lipid peroxidation are also present in not inconsiderable concentrations in the raw meat. Only HD3F is formed during cooking. 

The WOF appears in chicken much faster because its linoleic acid content is about 10 times higher than that in beef. Apart from the changes in concentration of the odorants listed in Table 12.27, the degradation of 2,4-decadienal, which is t) ical of an advanced lipid peroxidation... 

Trimethylamine also has a fishy odor. However, its odor threshold at the pH of fish meat is very much higher than that of the potent lipid peroxidation products, e. g., (Z)-l,5-octadien-3-one (cf. 3.7.2.1.8 and 11.2.4.4.4). Therefore, it plays a role as an off-flavor substance only on stronger bacterial infection of fish at temperatures >0 °C. 

Preparation and storage of products from both oilseeds is often inhibited by rancidity and bitter aroma defects caused mostly by volatile aroma active carbonyl compounds, e. g., (Z)-3-hexenal, (Z)-l,5-octadien-3-one and 3-methyl-2,4-nonan-dione. The rancidity-causing compounds are formed through peroxidation of linolenic acid, accelerated by the enzyme lipoxygenase and/or by hem(in) proteins (cf. 3.T.2.2). Furan fatty acids are the precursors in the case of the dione (cf. 14.3.2.2.5). Lipid peroxidation is also involved in the formation of another very potent odorant, 2-pentylpyridine, which produces grassy aroma defects in soybean products. Defatted soybean protein isolates contained 60-510 pg/kg of this compound, which with an odor threshold... 

U. C. Konopka, H. Guth, and W. Grosch, Potent odorants formed by lipid peroxidation as indicators for the warmed-over-flavor (WOF) of cooked meat, Z. Lebensm. Unters. Forsch. 201 339 (1995). 

Peroxide value. Peroxide value (PV) is the most common measurement of lipid oxidation. Hydroperoxides have no flavor or odor of their own, but they are unstable and break down rapidly to other products such as aldehydes that have a strong, disagreeable flavor and odor. Peroxide value measures the mUiequivalents of oxygen... 

Lipid oxidation during frozen storage of fat and medium-fat fish is an important quality problem, primarily due to effects on sensory properties such as rancid off-odor (appearing earlier than off-flavor), orange-brown discoloration, and texture changes. Changes in peroxide value (PV) and carbonyl compounds such as anisidine value (AsV), benzidine value, carbonyl value, and thiobarbituric acid (TEA) proceed... 

Sensory evaluation is a specialized discipline, using trained panels to measure and analyse the characteristics of food lipids evoked by the senses of taste, smell, sight and mouth feel. Sensory analyses are those most closely associated with the quality of food lipids, but their usefiilness is limited because they are costly and require a well-trained taste and odor panel and the proper facilities. However, sensory analyses provide sometimes ausefiil approach to identifying flavor or odor defects in the processing of food lipids that caimot be detected by other more objective chemical or instrumental analyses. For example, certain flavor defects characterized as grassy or fishy in linolenate-containing oils such as soybean and low-erucic rapeseed (canola) oils (Chapter 1) occur at such low levels of oxidation that they can only be detected by sensory analyses. The old term flavor reversion for soybean oil is based on the characteristic of this oil undergoing flavor deterioration at unusually low levels of oxidation that cannot be measured by peroxide value determination. Oils derived from fish... 

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