Vegetable oils measurements

In the characterization of alkyd resin formulations the palmitic acid to stearic acid (P/S) ratio, often used to identify the type of oil in a binder, cannot be applied as many different oils other than the traditional ones are commonly employed in industrial formulations. Moreover, they are often in mixtures, with the additional complication that fatty acids are also sometime added to the vegetable oils, thus making it impossible to rely on measured P/S values. In any case it is important to always derivatize the samples if Py-GC/MS is used and an alkyd is suspected. Phthalic anhydride will be detected also in an underivatized alkyd pyrogram however, isophthalic acid will not, leading to confusion and the possibility of uncorrected identification [92]. 

Previously (Cataldo and Braun, 2007), it has been noted the interesting correlation between C60 fullerene solubility and the unsaturation level of the fatty acids present in the vegetable oils and measured by the iodine number , an analytical test, which determines the number of double bonds present in the oil by the addition of iodine (Martinenghi, 1963). This correlation is confirmed for C also with the new measurements and is extendable also to C, . The correla-tion is shown in Fig. 13.1 and suggests that the solubility S expressed in milligrams per litre (mg/1) is linked to the iodine number of the oil (NI) according to the following equations ... 

Some methods measure more compounds than other methods because they employ more rigorous extraction techniques or more efficient solvents for the extraction procedure(s). Other methods are subject to interferences from naturally occurring materials such as animal and vegetable oils, peat moss, or humic material, which may result in artificially high reported concentrations of the total petroleum hydrocarbons. Some methods use cleanup steps to minimize the effect of nonpetroleum hydrocarbons, with variable success. Ultimately, many of the methods are limited by the extraction efficiency and the detection limits of the instrumentation used for measurement. 

RP-HPLC with nonaqueous solvents and UVD at 246 nm was developed for the determination of low level POVs of vegetable oils. These measurements are specific for conjugated diene peroxides derived from vegetable oils with relatively high linoleic acid content. These measurements may be supplemented by nonspecific UVD at 210 nm and ELSD for detection of all eluted species. The elution sequence of the triglycerides in a nonaqueous RP-HPLC is linearly dependent on the partition number of each species, Vp, which is defined as = Nq — 2Ni, where Nq is the carbon number and is the double bond number. In the case of hydroperoxides = Nq — 2Nd — Vhpo, where Vhpo is the number of hydroperoxyl groups in the molecule (usually 1 for incipient POV). For... 

Dupuy and coworkers have reported a direct gas chromatographic procedure for the examination of volatiles in vegetable oils (11). peanuts and peanut butters (12, 13), and rice and com products (14). When the procedure was appTTed to the analysis of flavor-scored samples, the instrumental data correlated well with sensory data (15, 16, 17), showing that food flavor can be measured by instrvmental means. Our present report provides additional evidence that the direct gas chromatographic method, when coupled with mass spectrometry for the identification of the compounds, can supply valid information about the flavor quality of certain food products. Such information can then be used to understand the mechanisms that affect flavor quality. Experimental Procedures... 

Colloid stability enters our daily life in many different ways. A visit to the kitchen provides numerous examples of food colloids with microstructure and stability that are, in no small measure, an important aspect of their appeal to the palate For example, mayonnaise —a mixture of vegetable oil, egg yolk, and vinegar or lemon juice —is an emulsion of oil in water and is stable because the lecithin molecules in the egg yolk provide the needed stability. Milk is another example. We have seen others in the vignettes in Chapters 1 and 4. 

Iodine Value (or Number)—the percentage of iodine that will be absorbed by a clieimcally unsalurated substance, such as vegetable oil, in a given time under specified conditions. The iodine value is a measure of degree of unsaturation. Two methods are described in the Food Chemicals Codex the Hanus method and the Wijs method. 

This unit describes the attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopic method (AOCS, 1999a AOAC International, 2000), a novel method for measuring the total amount of fat with isolated trans double bonds. It is applicable to natural fats (ruminant fats) and processed fats and oils (partially hydrogenated fats and oils or refined vegetable oils) consisting of long-chain fatty acid methyl esters or triacylglycerols with trans levels >5%, as percent of total fat (AOAC International, 2000). 

The presence of vegetable oils of high linoleic acid content in olive oil can be detected by measuring its authenticity factor (Au) as follows ... 

Early testing of vegetable oils and biodiesel focused on engine power, reliability, and durability emissions were rarely measured. Those proposing to use biodiesel in blends with diesel fuel have performed some emissions tests, and from these tests some generalizations about the emissions characteristics of biodiesel can be made [1.31]. 

This is a performance-based method that avoids the use of chlorofluorocarbon solvent. The method is applicable to aqueous matrices, using -hexane as the extraction solvent and gravimetry as the determinative technique. Because hexane is a hydrocarbon solvent, and if this solvent is employed for extraction, the method performance cannot be evaluated by IR measurement. The substances that may be determined by this method are relatively nonvolatile hydrocarbons, vegetable oils, greases, waxes, animal fats, and related materials. The method permits the use of other extraction solvents also, provided that the QC criteria are met. 

In the present experiment, we measure the amount of the active ingredient, acetylsalicylic acid (see also Experiment 35), in common aspirin pills. Companies use different fillers and in different amounts, but the active ingredient, acetylsalicylic acid, must be the same in every aspirin tablet. We separate the acetylsalicylic acid from the filler based on their different solubilities. Acetylsalicylic acid is very soluble in ethanol, while neither starch, nor other polysaccharides, or even mono- and disaccharides used as a fillers, are soluble in ethanol. Some companies may use inorganic salts as fillers but these too are not soluble in ethanol. On the other hand, some specially formulated aspirin tablets may contain small amounts of ethanol-soluble substances such as stearic acid or vegetable oil. Thus the ethanol extracts of aspirin tablets may contain small amounts of substances other than acetylsalicylic acid. 

Measure 23 mL of a vegetable oil into a 250-mL Erlenmeyer flask. Add 20 mL of ethyl alcohol (to act as a solvent) and 20 mL of 25% sodium hydroxide solution (25% NaOH). While stirring the mixture constantly with a glass rod, the flask with its contents is heated gently in a boiling water bath. A 600-mL beaker containing about 200 mL of tap water and a few boiling chips can serve as a water bath (Fig. 39.1). 

The measurements were executed with the material system 30 % vegetable oil/ water under the addition of a fast absorbing emulsifying agent (Laurylethylenoxid... 

Breas, O., Guillou, C., Reniero, F., Sada, E. and Angerosa, F. (1998) 17 O Measurement by continuous flow pyrolysis/isotope ratio mass spectrometry of vegetable oils. Rapid Commun. Mass Spectrom., 12, 188-192. 

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