Mushrooms lipid oxidation

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. 

Ketones Aliphatic ketones formed by autoxidation of lipids also contribute to the flavor of oils and food products. For example, Guth and Grosch (13) identified l-octen-3-one as one of the odor-active compounds in reverted soybean oil. This compound was described as metallic and mushroom-like. The reaction pathway for the formation of l-octen-3-one from the linoleate-10-hydroperoxide via the p-scission route is illustrated in Figure 2. 10-Hydroperoxide of linoleate is not the usual hydroperoxide formed by autoxidation of linoleate however, it is one of the major hydroperoxides formed by the photosensitized oxidation (singlet oxygen reaction) of linoleate (14). 

Furan fatty acids (3-32) are present in plants, fishes, amphibians, reptiles and mammals, including man. In some fish, F-acids can typically represent 1-6% of the fatty acids in the liver lipids. In some freshwater fish, however, furan fatty acids may represent up to 25% of the total fatty acids. They also occur in butter, meat, vegetable oils, shrimps and mushrooms in small amounts. For example, virgin oHve oils contain non-olefinic 10,13-epoxy-ll,12-dimethyloctadeca-10,12-dienoic acid co = 8, n = 4, R=CH3) and 12,15-epoxy-13,14-dimethyleicosa-12,14-dienoic acid ( = 10, n = 4, R = CHj) and two olefinic derivatives 12,15-epoxy-13,14-dimethyleicosa-12,14,16-eicosatrienoic acid (ct)= 10, n = 2, R=CH3) and 12,15-epoxy-13,14-dimethyleicosa-10,12,14-eicosatrienoic acid a> = 8, = 4, R = CHj). Furan fatty acids also arise as products of Hpid oxidation. Autoxidation or photoxidation of fiiran fatty acids yields a,p-unsaturated y-lactones known as bovoHdes (see Figure 8.54). 

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