Ultraviolet-Visible Spectrophotometry in the Analysis of Lipid Oxidation

Pokorn_, Jan; Schmidt, S¢tefan; Parkanyiova, J.

doi:10.1201/9781439822395.ch3

Cited by 10 publications

(8 citation statements)

References 52 publications

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“…With increasing oxidation, the samples show a strong absorption below 300 nm overriding other absorption maxima, the onset of which increases to about 350 nm with increasing oxidation. These results largely coincide with literature results [35]. However, this method may warrant further investigation as procedure for determining the oxidation status of biodiesel since UV-VIS spectra are rapidly and easily acquired and instrumentation is moderate in price.…”

Section: Resultssupporting

confidence: 81%

Analysis of oxidized biodiesel by ¹ H‐NMR and effect of contact area with air

Knothe

2006

Eur. J. Lipid Sci. Technol.

104

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Biodiesel is continuously gaining attention and significance as an alternative diesel fuel. An important issue facing biodiesel is fuel stability upon exposure to air due to its content of unsaturated fatty acids. Numerous factors influence the oxidative stability of biodiesel, and several methods for its assessment have been developed. In the present work, a defined amount of biodiesel (methyl soyate) was heated in open beakers, with the only difference being the size of the beaker, i.e. the surface area of the biodiesel exposed to air. Biodiesel oxidized in this fashion was analyzed by 1 H-NMR, kinematic viscosity and acid value. Acid values and kinematic viscosity increased with time and surface area. A previously developed 1 H-NMR procedure was used to evaluate the unsaturation and "residual" fatty acid composition. The amounts of saturated fatty acids determined by this method increased, with monounsaturated and diunsaturated species increasing and then decreasing with time. After "flash" (3 h, 165 7C) oxidation, NMR shows the greatest effect on saturates and compounds with two double bonds, the former increasing and the latter decreasing. The double bond originally located at D15 in 18:3 is largely retained, showing that other double bond positions in 18:3 are initially affected by oxidation. The methyl ester signal decreases, coinciding with the increase in acid value. An increasingly strong absorption was observed in the UV-VIS spectra. Increasing surface area accelerated oxidation and affected fatty acid composition.

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Section: Resultssupporting

confidence: 81%

Analysis of oxidized biodiesel by ¹ H‐NMR and effect of contact area with air

Knothe

2006

Eur. J. Lipid Sci. Technol.

104

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“…The TBARS test involves the quantification of secondary oxidation products from the breakdown of hydroperoxides [21]. The assay is based on the reaction of 2-thiobarbituric acid (TBA) and malonaldehyde or malonaldehyde-type products which results in the formation of a colored compound that corresponds to a maximum absorbance at a wavelength of approximately 530 nm [10]. Figure 3 shows the changes in the TBARS of SSO as a function of time at the various storage temperatures.…”

Section: Thiobarbituric Acid Reactive Substances (Tbars)mentioning

confidence: 99%

“…The primary and secondary products of oxidation for instance are quantified by the PV and q-anisidine value (AnV) tests, respectively [2,8]. Some of the many techniques and instruments proposed to measure lipid stability and quality include traditional methods such as titration and iodometry, and instrumentation methods such as UV-Visible spectroscopy, liquid chromatography, Fourier transform infrared spectroscopy, and differential scanning calorimetry [3,10,11].…”

Section: Introductionmentioning

confidence: 99%

Effect of Temperature and Time on the Stability of Salmon Skin Oil During Storage

Aryee

Simpson

Phillip

et al. 2011

J Americ Oil Chem Soc

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The effect of 45 days of storage at 25, 4, -18 and -80°C on the quality indices; free fatty acid (FFA) content, peroxide value (PV), thiobarbituric acid reactive substances (TBARS), and changes in the fatty acid (FA) profile of crude oil recovered from salmon fish skins were evaluated at 5 day intervals using spectrophotometric and titrimetric methods. Higher temperatures and longer storage time resulted in higher quantities of oxidative products in the salmon skin oil (SSO). By day 45, SSO stored at 25 and 4°C had 8.50 and 8.29% FFA, 32.43 and 26.33 lg malondialdehyde (MDA) eq g -1 oil, and 88.19 and 64.53 mequiv peroxide kg -1 oil, respectively. No significant (p [ 0.05) changes in fatty acid profile were observed at all the storage temperature and time studied.

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“…The test is based on the reaction of oxidation products with TBA to give compounds that absorb light at 532-535 nm. The reaction is not specifi c and different oxidation compounds respond to the test and are referred to as TBA-reactive substances or TBARS (Pokorný et al, 2005). Originally, the coloured complex was characterised as being the result of the condensation of two TBA molecules with a molecule of malonaldehyde, an oxidation compound that in oils is only produced from polyunsaturated fatty acids with three or more double bonds (Pryor et al, 1976).…”

Section: Chemical Analysesmentioning

confidence: 99%

“…The test is particularly suitable for heated oils in which hydroperoxides have decomposed during heating. Thus, it can be used for the evaluation of deodorised oils and used frying oils (Pokorný et al, 2005). The AnV is often used in conjunction with the PV to obtain the so-called total oxidation value, or totox value, defi ne as 2PV + AnV.…”

Section: Chemical Analysesmentioning

confidence: 99%