Edible oils, determination

The composition of an oil and the progress of its hydrogenation is expressed in terms of its iodine value (IV). Edible oils are mixtures of unsaturated compounds with molecular weights in the vicinity of 300. The IV is a measure of this unsaturation. It is found by a standardized procedure. A solution of ICl in a mixture of acetic acid and carbon tetrachloride is mixed in with the oil and allowed to reac t to completion, usually for less than I h. Halogen addition takes place at the double bond, after which the amount of unreacted iodine is determined by analysis. The reaction is... 

Thin Laver Chromatography. - The technique has been applied to the determination of tricresyl phosphate in edible oils,265 and insecticides in tobacco leaves.264... 

Allen LB, Siitonen PH, Thompson HC Jr. 1998. Determination of copper, lead, and nickel in edible oils by plasma and furnace atomic spectroscopies. Journal of the American Oil Chemists Society 75(4) 477-481. 

The original applications of NIR were in the food and agricultural industries where the routine determination of the moisture content of foodstuffs, the protein content of grain and the fat content of edible oils and meats at the 1% level and above are typical examples. The range of industries now using the technique is much wider and includes pharmaceutical, polymer, adhesives and textile companies. The first in particular are employing NIR spectrometry for the quality control of raw materials and intermediates and to check on actives and excipients in formulated products. Figure 9.26(b) demonstrates that even subtle differences between the NIR spectra of enantiomers can be detected. 

Watts JO, Holswade W. 1967. Gas chromatographic determination of residual hydrocarbon solvents in solvent-extracted edible oils. J AOAC 50(3) 718-726. 

Food Additives and Contaminants 20, No.5, May 2003, p.438-44 DETERMINATION OF POLYDIMETHYLSILOXANES BY PROTON-NMR IN WINE AND EDIBLE OILS Mojsiewicz-Pienkowska K Jamrogiewicz Z Lukasiak J Gdansk,Medical University... 

Automatic Pipettes (Transfer Pipettes) Automatic pipettes are always preferred to ordinary transfer pipettes because of their ability to handle corrosive and toxic liquids in routine analytical laboratories, e.g., determination of Iodine Value in edible oils by iodine-monochloride (IC1) solution. 

Allan Walsh, in 1955, was the pioneer for the introduction of atomic absorption spectroscopy (AAS), which eventually proved to be one of the best-known-instrumental-techniques in the analytical armamentarium, that has since been exploited both intensively and extensively in carrying out the quantitative determination of trace metals in liquids of completely diversified nature, for instance blood serum-for Ca2+, Mg2+, Na+ and K+ edible oils-Ni2+ beer samples-Cu+ gasoline (petrol)-Pb2+ urine-Se4+ tap-water-Mg2+ Ca2+ lubricating oil-Vanadium (V). 

The variety of applications emphasizes the versatility of naphtha. For example, naphtha is used in paint, printing ink, and polish manufacturing and in the rubber and adhesive industries, as well as in the preparation of edible oils, perfumes, glues, and fats. Further uses are found in the dry-cleaning, leather, and fur industries and in the pesticide field. The characteristics that determine the suitability of naphtha for a particular use are volatility, solvent properties (dissolving power), purity, and odor (generally the lack thereof). 

Untreated silica column can be advantageously used for HPLC preseparation of PAHs from triglycerides. The capacity of a silica column to retain fat (for columns of the same particle size) depends on the column size, the mobile phase composition, as well as the type and by-products (free acids and polymerized material) of the fat injected [706,713]. Off-line HPLC-HPLC, employing silica column (250 X 4.6 mm i.d., 5 pm of particle size) for sample preparation before RP-HPLC and spec-trofluorometric detection, was successfully applied for PAH determination in edible oils [659,691] and fish [714]. After PAH elution, the silica column needs to be backflushed with dichloromethane to remove the fat. The entire sample preparation step can be automated by using a backflush valve and a programmable switching valve box [691]. 

A correlation may be established between the concentration of oxidized lipids and the TEARS value, expressed as MDA equivalents, in uM units. Correction is due in some cases for the interference by dyes or other factors. For example, the presence of anthocyanins in red cabbage leaves or turbiditjf causes overestimation of lipid hydroperoxides in plant tissue by the TEARS method. TEARS was used to assert the level of endogenous peroxides in hypo- and hyperthyroidism, both conditions being characterized by low lipid and lipoprotein plasma levels and enhanced oxidative metabolism . In a procedure for determination of TEARS in edible oils, the sample is placed in a centrifuge at 12000 g before measuring at 532 nm (e = 1.56 x 10 M cm ) . A usual procedure for determination of TEARS in certain complex matrices involves steam distillation of the aldehydes responsible for the value, instead of extraction. In nitrite-cured meats, excess nitrite may cause nitrosation of MDA, thus interfering with distillation. To avoid this interference sulfanilamide is added, which is converted to a diazonium salt and... 

The correlation between the TEARS assay and MDA dnring oxidation of edible oils may be complicated by the presence of tocopherols (e.g. Vitamin E, 21) . An evaluation was carried of MDA, determined by an independent method , and TEARS as indices for direct oxygen uptake of edible oils and unsatnrated fatty acids. The linear increase of MDA and TEARS with oxygen consumption of soybean oil, in a closed vessel at 170 °C, stops when the latter value reaches 500 p.molL, when both MDA and TEARS start to decrease on further O2 consumption. The same process carried out at 40 °C, using 2,2 -azobis(2,4-dimethylvaleronitrile) (171) as initiator, shows linearity up to 1500 p,molL O2 consumption . A similar behavior is observed for nnsatnrated fatty acids snch as oleic, linoleic and linolenic acids . On the other hand, depletion of Vitamin E (a-tocopherol, 21) and its analogs y- and 5-tocopherol (172, 173) present in the oil show a linear dependence on O2 consumption of the oil, np to 1800 p,molL . This points to the consumption of these antioxidants, and especially 21, as a good index for the O2 uptake in oils at high temperature. The determination of the tocopherols is carried ont by HPLC-FLD (Xex = 295 nm, Ah = 325 nm) . ... 

An evaporative light scattering detector was coupled with a UV spectrophotometer, and was applied to HPLC for the quantitative determination of cholesterol oxides in edible oils and fats. 

Toivo, J., Piironen, V., Kalo, P., and Varo, P. 1998. Gas chromatographic determination of major sterols in edible oils and fats using solid-phase extraction in sample preparation. Chroma-tographia 48 745-750. 

A capillary gas chromatographic method is described for determination of major phytosterols and cholesterol in edible oils and fats. To extract the unsaponifiable matter and for sample cleanup, solid-phase extraction with C18 absorbent was used. 

Oishi et al. (1992) compared the results from classical iodometric PV determinations of edible oils and fats to those using a coulometric detector. Results from each technique expressed as meq active oxygen/kg sample, were consistent with one another. Typical results were sesame oil (4.1), corn oil (8.7), cottonseed oil (14.5), rapeseed oil (33.2), peanut oil (30.5), olive oil (17.0), palm oil (8.9), beef tallow (2.5), and lard (35.0). 

Table D2.1.2 PVs of Edible Oils and Fats Determined by the AOAC and Modified FOX Methods"...

Various protocols and modifications have been reported in the literature on how to perform the TBA test. In foodstuffs, malonalde-hyde can be bound to various constituents of the food (e.g., proteins), and therefore it must somehow be released prior to determination. It is difficult to determine the optimal conditions for release of malonaldehyde as they differ from one material to another and require different conditions for hydrolysis. Heat and/or strong acid are thought to be essential for the liberation of malonaldehyde from precursors or bound forms, for condensation with TBA, and for maximal color development. For edible oil samples or lipid extracts, the test is simplified in that samples are directly dissolved in butanol and then an aliquot is reacted with TBA. Alternatively, a food sample can be heated with TBA solution and the red pigment that is formed can be extracted from the reaction mixture with butanol or a butanol/pyridine solution (Turner etal., 1954 Sinnhuberand Yu, 1958 Placer et al., 1966 Uchiyama and Mihara, 1978 Ohk-awa et al., 1979 Pokorny and Dieffenbacher, 1989). 

Muakazato, M Kanmuri, T Ariga, K Fujinuma, Y Naoi. Systematic detection and determination of antioxidants in edible oil. Shokuhin Eiseigaku Zasshi 22 239-245, 1981. 

AW Archer. The determination of phenolic antioxidants in edible oils and fats by high-performance liquid chromatography. Anal Chim Acta 128 235-237, 1981. 

Ethanol and aqueous ethanol mixtures play important roles as food simulants for the determination of migration of substances from packaging into foods. Depending on the polarity of the plastic one can use pure ethanol (for nonpolar plastics) or aqueous ethanol mixtures up to 50/50 % (for polar plastics) as alternative simulants to edible oils (see Chapters 9,10 and 11). The estimation of partition coefficients in poly-mer/simulant systems is consequently of practical importance. It is possible to do this for polyolefins in contact with alcohol and aqueous alcohol mixtures with the help of an equation analogous to Eq. (4-100) (Piringer, 1993) ... 

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