Vegetables lipid oxidation

They are widely distributed in vegetable lipids, and in the body fat of animals, though animals cannot synthesize them. They have vitamin E activity and can protect unsaturated lipids against oxidation. Four are found naturally ... 

The oxidation products of lipids include volatile aldehydes and acids. Therefore, lipids are one of the major sources of flavors in foods. For example, much of the desirable flavors of vegetables such as tomatoes, cucumbers, mushrooms, and peas (Ho and Chen, 1994) fresh fish (Hsieh and Kinsella, 1989), fish oil (Hu and Pan, 2000) and cooked shrimp (Kuo and Pan, 1991 Kuo et al., 1994), as well as many deep-fat fried foods such as French-fried potatoes (Salinas et al., 1994) and fried chicken (Shi and Ho, 1994), are contributed by lipid oxidation. LOX-catalyzed lipid oxidation produces secondary derivatives, e.g., tetradecatrienone, which is a key compound of shrimp (Kuo and Pan, 1991). The major difference between the flavors of chicken broth and beef broth is the abundance of 2,4-decadienal and y-dodeca-lactone in chicken broth (Shi and Ho, 1994). Both compounds are well-known lipid oxidation products. A total of 193 compounds has been reported in the flavor of chicken. Forty-one of them are lipid-derived aldehydes. 

Tressl, R. Bahri, D. Engel, K.-H. In "Lipid Oxidation in Fruits and Vegetables" Teranishi, R. Barrera-Benitez, H. Eds. ACS SYMPOSIUM SERIES No. 170, American Chemical Society Washington, D.C., 1980 pp. 213-232. 

Lipids in foods can be oxidized by both enzymatic and nonenzymatic mechanisms. One of the enzymes that is considered important in lipid oxidation is lipoxygenase, which has recognition for its off-flavor development in vegetables and... 

Oxidation effects Characterization of lipid oxidation by ID and 2D NMR Formation of cyclic fatty acids Analysis of non-volatile components produced upon heating of fatty acid esters Oxidative stability of sesame oil Effects of hydrogenation in vegetable oils 1999 (233, 235) 1997 (234) 1998 (236) 1997 (237) 1996 (238) 1998 (239, 240)... 

Figure 10 summarizes some results of the lipid-oxidation system in basldlomycetes, leaves, fruits, vegetables, and cereals. It can be seen that there is a development with evolution and differentiation. The enzyme system is highly substrate specific to a (Z,Z)-1,4-pentadiene system converting linoleic- and linolenic acids into carbonyls and oxoacids which may undergo further isomerization (E3) and/or reduction (E4). Some of the components formed are very potent aromatics, pheromones, and wound hormones. Basidio-mycetes and Fungi produce (-)-1-octen-3-ol as their sensorial principle. 9-Oxodecanoic acid is known as queen substance and is the sex pheromone of honey bees. 

Figure 10. Lipid-oxidation system in basidiomycetes, leaves, fruits, vegetables,...

Figure 3.10 Comparison of three gas chromatographic methods for volatile analyses of oxidized vegetable oil (peroxide value 9.5). Chromatographic conditions 30 m x 0.32 mm fused silica column coated with DB-5, 0°C (10 min), then 5°C min" to 250 C. Reproduced from Snyder, J. M., Frankel, E. N., Selke, E. et al.. Comparison of gas chromatographic methods for volatile lipid oxidation compounds in soybean oil. Journal of the American oil Chemists Society,...

The types of flavors imparted by lipid oxidation in foods are more difficult to assess because there is wide variation in the sensory impact of different volatile products, and in the vocabulary used by taste or odor panels to describe their effect on quality. The diversity of sensory vocabulary used by different investigators to describe the same flavor defect in an edible oil has led to controversy on the origin of different flavor defects in soybean and other vegetable and fish oils. 

Steenhorst-Slikkerveer, L., Louter, A., Janssen, H.-G. and Bauer-Plank, C. Analysis of nonvolatile lipid oxidation products in vegetable oils by normal-phase high-performance liquid chromatography with mass spectrometric detection. J. Am. Oil Chem. Soc. 77, 837-845 (2000). 

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