Hexane formation

Jo and others (2006) applied this assay to determine the antioxidant properties of methanolic extracts from Japanese apricot in chicken breast meat. Likewise, Pearson and others (1998) assessed two types of Japanese green tea from Japan and two of their active compounds, catechin and epicatechin, for their relative abilities to inhibit the oxidation of LDL. Also, Pearson and others (1999) assessed the ability of compounds in apple juices and extracts from fresh apple to protect LDL. Heinonen and others (1998b) observed that berry phenolics inhibited hexanal formation in oxidized human LDL. 

Cyclohexane dehydrogenates rather rapidly to benzene. Its rearrangement has not been reported over pure metals until now. Cg Ring opening is negligible over platinum and palladium 48, 5i) slight hexane formation was reported over carbon supported rhodium, iridium, and, especially, osmium and ruthenium (702), as well as over nickel on alumina (99). 

The phenolic antioxidant activity in the corn oil emulsions of 17 selected Spanish wines and two Californian wines was examined for their preventive capability for lipid oxidation as dietary antioxidants. The inhibition of hydroperoxide formation [measured as percent of control for 10 iM gallic acid equivalents (GAE)] was increased from 8.4 to 40.2% in the presence of the red wines, from 20.9 to 45.8% with the rose wines, and from 6.5 to 47.0% with the white wines. The inhibition of hydroperoxide formation at 20 xM GAE was increased from 11.9 to 34.1% in the presence of red wines, from 0.1 to 34.5% with the rose wines, and from 3.3 to 37.2% with the white wines. The inhibition of the hexanal formation at 10 (jlM GAE was increased from 23.6 to 64.4% in the presence of red wines, from 42.7 to 68.5% with the rose wines, and from 28.4 to 68.8% with the white wines. Moreover, the inhibition of the hexanal formation at 20 xM GAE was increased from 33.0 to 46.3% in the presence of red wines, from 11.3 to 66.5% with the rose wines, and from - 16.7 to + 21.0% with the white wines. The antioxidant effect declined apparently with increasing concentration. The antioxidant activity might be ascribed to the five main groups of phenolics identified in the wines benzoic acids, anthocyanins, flavan-3-ols, flavonols, and hexanal [38]. 

Dimethvihexane Formation. Dimethyl hexane formation Is believed to result largely from reactions of butene-l. This includes (I) codimerization of butene-l and isobutene, (2) dimerization of butene-l, and (3) dimerization of isobutene, and (4) isomerization of dimethylhexyl carbonlum Ions each of these reactions is followed by abstraction of a hydride ion from isobutane. Reactions follow ... 

The results obtained with the MCP hydrogenolysis indicate that HTR causes two different effects on the catalytic behavior of the Pt/SiO model catalysts (i) a fast change of the selectivity to less n-hexane formation followed by (ii) a slow decrease of activity. 

Additional detail about the photodissociation of CO from 13 has come from time-resolved Raman spectroscopy.It was shown that the loss of CO occurs within the duration of a nanosecond laser pulse into the LF band and leads to a transient species that decays on a microsecond time scale to regenerate 13 in solvents such as CH2CI2, benzene or /i-hexane formation and decay of this transient species are the only observable processes while in acetonitrile there is also rapid formation of 34. The suggested sequence of reactions is shown in Scheme 2. 

By analogy to the cleavage reaction of bicyclo[2.2.0]hexane, formation of a boat-like biradical followed by rapid conformational interconversion with a chairlike biradical and then cleavage can provide both CODs. The heat of formation of S and A were reported to be 56 and 53 kcal/mol, respectively/ and if the biradicals are comparable in energy to the transition state producing them, they are roughly 12 kcal/mol less stable, enthalpically, than the bisally lie biradicals which figure so prominently in the other thermal interconversions. Considerations of entropy would make them at least another 5 kcal/mol less stable. 

Casein has been found to be an excellent candidate to produce oil-in-water emulsions that have both high physical and oxidative stability. The differences in the physical properties and oxidative stability of com oil-in-water emulsions stabilized by casein, WPI, or SPI at pH 3.0, have been investigated. Emulsions have been prepared with 5 per cent com oil and 0.2-1.5 per cent protein. Physically stable, monomodal emulsions have been prepared with 1.5 per cent casein, 1.0 or 1.5 per cent SPI, and 2=0.5 per cent WPI. The oxidation stability of the different protein-stabilized emulsions was in the order of casein > WPI > SPI, as determined by monitoring both lipid hydroperoxide and headspace hexanal formation. The degree of positive charge on the protein-stabilized emulsion droplets was not the only factor involved in the inhibition of lipid oxidation, because the charge of the emulsion droplets... 

Table 9.1. Effect of concentration of a- and 7-tocopherols on inhibition (in percentage) of hydroperoxide and hexanal formation in bulk com oil and oil-in-water emulsions oxidized at 60°C...

Figure 9.8. Effect of different concentrations of a-tocopherol on the inhibition of hexanal formation at different stages of oxidation of bulk com oil. From Frankel et al (1994).

Figure 9.7, 3-5 days). At later stages of oxidation (6-7 days), a-tocopherol inhibited hydroperoxide formation at all concentrations tested. After 7 days, a-tocopherol showed its highest inhibition of hydroperoxide formation at 100 ppm. In mixtures, whether tocopherols acted as antioxidants or prooxidants seemed to depend on the relative concentration of a-tocopherol. In contrast to hydroperoxide formation, a-tocopherol inhibited hexanal formation at all levels tested (Figure 9.8). Inhibition of hexanal formation increased with... 

Table 9.10. Percent inhibition of hydroperoxides and hexanal formation by a-tocopherol and Trolox in bulk corn oil and com oil-in-water emulsion at 60°C ...

The antioxidant activities of rosemary extracts, carnosol and camosic acid were also significantly influenced by the oil substrates and the type of system tested, bulk oils versus oil-in-water emulsions, the methods used to measure oxidation and the concentration of test compounds. The rosemary extracts, carnosol and camosic acid effectively inhibited hydroperoxide formation in com oil, soybean oil, peanut oil and fish oil, when tested in bulk (Table 9.12). The rosemary extract and pure constituents were more active antioxidants in bulk corn, peanut and fish oils than in bulk soybean oil. This difference may be attributed to the relatively higher concentrations of tocopherols in soybean oil that are known to have a negative effect on the antioxidant activity of rosemary constituents. Test compounds also inhibited hexanal formation in bulk vegetable oils, and propanal and pentenal formation in bulk fish oils. In marked contrast, these test compounds were either inactive or promoted oxidation in the corresponding vegetable oil-in-water emulsions. In fish oil emulsions, however, the rosemary compounds inhibited conjugated diene and pentenal formation, but not propanal. 

Table 11.11. Effect of lactoferrin on the inhibition of hydroperoxide and hexanal formation in two infant milk formulas supplemented with different concentrations of iron ...

Figure 4. Hexanal formation of the soybean LOX null mutant backcross lines (see Fig. 1). The results shown represent means of at least four replications. Three sets of experiments were performed 1. Finely ground powder from lyophilized seeds (0.5 g) was added to 20 ml water in a sealed reaction system and the volatiles produced during 60 min trapped and analyzed as described (Andersen et al, 1986). 2. As in 1. but 50 mg sodium linoleate v/as dissolved in the water prior to addition of seed powder and the reaction was only carried out for 20 min. 3. As in 2. but 0.1 M sodium phosphate, pH 6.8 was used instead of water. 

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