Conjugated dienes value , secondary

Conjugated dienes value (CDV), secondary oxidation products, 663, 671-2 Coordination compounds O NMR spectroscopy, 185 silyl peroxides, 808-10 Coordination ionospray mass spectrometry,... 

Secondary oxidation products oxidation indices, 656, 665-72 acid value, 672 anisidine value, 656, 666 carbonyl compounds, 656, 669-71 conjugated dienes value, 671-2 thiobarbituric acid reactive substances, 656, 666-9... 

Shelf Storage Test The test material is stored under similar conditions as in retail and is evaluated for the effectiveness of antioxidants in prolonging the premium quality of the product. Periodic evaluation of the hpid oxidation products (primary or secondary) by chemical tests (e.g., peroxide value, conjugated diene value, 2-thiobarbituric acid reactive substances, hexanal content) or sensory evaluation will be used to find out the onset of oxidation. The main drawback of this kind of evaluation is the time taken therefore, rapid evaluation or accelerated methods are often preferred (19, 51). 

From the UV spectrum it became apparent that a conjugated hetero-annular diene comparable with that of buxamine-E and buxaminol-E (cf. Vol. IX, p. 405) is involved. The IR spectra showed the amide bands and the PMR spectra revealed the presence of three tertiary and one secondary C-methyl, one dimethylamino group, one primary alcohol, a proton adjacent to the secondary alcohol, and one amidic and two methylene protons. Moreover, 226 displayed signals of two methyls of the isobutyramide side chain whereas 227 showed benzamide substitution. The measured values are in accordance with the mass-spectrometric fragmentation pattern. 

Conjugated dienoic fatty acids have a 234 nm chromophore (e = 24,-000), and their formation can be followed continuously in optically clear mixtures or discontinuously by solvent extraction (Surrey, 1964). The method is specific and is particularly suitable for purified enzymes at high pH where fatty acids form soap solutions. In crude extracts, the method has limited value because of interfering absorptions and, more importantly, secondary reactions of the unstable hydroperoxide produets (see later) resulting in chromophore destruction (Berkeley and Galliard, 1976). It should be noted that even some purified LOX preparations contain lipoperoxidase activity (Grosch et al., 1972). Thus the diene absorption method should be used with caution and, preferably, checked for stoichiometry. 

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