Rapeseed detection

Despite the difficulties in extracting and identifying colorless catabolic products that are extremely labile and detectable only in trace amounts, several of the mysteries of chlorophyll catabolism have been revealed and about 14 non-fluorescent chlorophyll catabolytes (NCCs) from higher plants, mainly in senescent leaves, have been detected and analyzed structurally. Among them, NCCs from rapeseed (Bms-sica napus) from Liquidambar styraciflua, from Cercidiphyllum japonicum, five NCCs from degreened leaves of spinach Spinacia oleracea) and, more recently, two NCCs from tobacco Nicotiana rusticd) and five NCCs from Arabidopsis thaliana have been identified. 

Some phenolic acids such as ellagic acid can be used as floral markers of heather honey (Cherchi et al., 1994 Ferreres et al., 1996a,b), and the hydroxyciimamates (caffeic, p-coumaric, and ferulic acids) as floral markers of chestnut honey (Cherchi et al., 1994). Pinocembrin, pinobanksin, and chrysin are the characteristic flavonoids of propolis, and these flavo-noid compounds have been found in most European honey samples (Tomas-Barberan et al., 2001). However, for lavender and acacia honeys, no specific phenolic compoimds could be used as suitable floral markers (Tomas-Barberan et al., 2001). Other potential phytochemical markers like abscisic acid may become floral markers in heather honey (Cherchi et al., 1994). Abscisic acid was also detected in rapeseed, lime, and acacia honey samples (Tomas-Barberan et al., 2001). Snow and Manley-Harris (2004) studied antimicrobial activity of phenolics. 

It is impossible to reveal the botanical species from which the seed oil used in the examined lamps was actually produced, e.g. to say whether the oil came from radish as reported by Pliny or from another Brassicaceae plant such as rapeseed. However, the detection of the characteristic markers in lamps from Antinoe, one of the main urban centres of Roman Egypt, represents a chemical confirmation of the widespread use of cmciferous oil at that time, and is consistent with ancient documents [61,62]. This identification is... 

Viinanen and Hopia (145) described an evaporative light-scattering detector (ELSD) that can be used to detect autoxidation products of TAG standards [trilinolenin (TLn), trilinolein (TL), and triolein (TO)] and of a natural mixture of rapeseed oil (RSO) TAGs. The samples were oxidized at 40°C in the dark in open 10-ml test tubes. Sample aliquots of 500 mg were taken for... 

Monsalve, R.I., Gonzalez de la Pena, M.A., Lopez-Otin, C. et al. 1997. Detection, isolation and complete amino acid sequence of an aeroallergenic protein from rapeseed flour. Clin Exp Allergy 27 833-841. 

The above shows that rapeseed oil can easily be detected, or eliminated, as a contaminant by sterol analysis. It is also, at least in Europe, the oil most likely to be used to dilute another oil. Although low levels (as a percentage of the total sterols) have been reported in some other oils (Desbordes etal., 1993), the presence of brassicasterol in an oil is good evidence of contamination in any oil from a non-Brassica species. It is likely that the traces reported as present in some other oils arise from contamination of the sample with rapeseed oil, or from some other Brassica species, or from traces of some similarly behaving non-sterol not fully separated from the sterol fraction during the work-up of the sample (Desbordes et al., 1983). 

Sterol analysis can be useful other than for detecting rapeseed oil. Accepted ranges for many oils and all major oils, given as a percentage of the total sterols, are available (Codex Alimentarius, 1997 FOSFA, 1994 AOCS, 1997). In all... 

Non-refined oils are easier to detect and authenticate than organic oils, though the absence of a small percentage of some refined oil in the product would be difficult to prove. Where unrefined palm oil was adulterated with rapeseed has already been described above. Where an oil is authentic as to its source, but possibly at least partially refined, in order to check its authenticity, it would then be necessary to build up a database of the expected ranges of values for refined and non-refined oils. Chemical and physical techniques that should be checked are ... 

Although many vegetable oils are quite similar in sterol composition, there are some important differences. Detection of brassicasterol can be used to detect adulteration of many oils by rapeseed oil as this sterol is only present in most oils in small amounts but rapeseed oil contains up to 780 mg/kg brassicasterol (see Table 6.1). The detection of adulteration of vegetable oils with animal fats can be achieved by analysis of the cholesterol content, since this sterol is either absent or present at very low concentrations in vegetable oils. 

Most oils contain low levels of saturated and unsaturated hydrocarbons. In olive oil, the unsaturated hydrocarbon squalene can constitute up to 40% of the unsaponifiable fraction (Boskou, 1996). Other hydrocarbons commonly present in olive oil are straight chain alkanes and alkenes with 13 to 35 carbon atoms, along with very low amounts of branched chain hydrocarbons. Variations are found between different olive varieties but the main hydrocarbons are those with 23, 25, 27 and 29 carbon atoms (Guinda et al., 1996). Olive oil can clearly be differentiated from other vegetable oils on the basis of hydrocarbon components, and levels of 2.6% crude rapeseed oil or crude sunflower oil can be detected by hydrocarbon analysis (Webster et al., 1999). Terpenes have been identified in the volatile fraction of crude sunflower oil (Bocci and Frega, 1996). 

It is known that the rapeseed oil had been adulterated with aniline, and that the aniline reacted with fatty acids present in the oil to form anilides. These were detected in the oil collected from victims. A good correlation between the amount of a particular anilide and the occurrence of the syndrome was found, which suggests a relationship between consumption of contaminated oil and the syndrome. However, there were individuals who had apparently consumed the contaminated oil but had not shown symptoms, and vice versa. 

Fig. 1.13. Separation of a product of partial transesterificaiion of rapeseed oil with methanol using combined RPC and NARPC gradient elution. Column Separon SGX Cm, 7 pm, 150 x 3 mm i.d. Ternary gradient from 30% A + 70% B to 100% B in lO min and to 50% B -t- 507r C in 20 min. followed by isocratic elution with the final mobile phase composition for 5 min, at I ml/min. Injection volume 10 pi. UV detection at 205 nm. Notation of sample compounds Ln. L, O and G are used for linolenic acid, linoleic acid, oleic acid, gadoleic acid, respectively, and for their acid parts in mono-, di- aixl tri-acylglycerols and methyl esters Me means methyl in methyl esters.

Canola Oil Canola oil is obtained from low erucic acid, low glucosinolate rapeseed. The unique polyunsaturated fatty acid and low saturated composition of canola oil differentiates it from other oils. It has a higher oleic acid (18 1) content (55%) and lower linoleic acid (18 2) content (26%) than most other vegetable oils, but it contains 8-12% of linolenic acid (18 3) (58). Canola oil is most widely used in Canada and is considered a nutritionally balanced oil because of its favorable ratio of near 2 1 for linoleic to linolenic acid content. Unlike most other edible oils, the major breakdown products of canola oil are the cis, trans- and tram, trans-2,4-heptadienals with an odor character generally described as oily, fatty, and putty. Stored canola oil shows a sharp increase in the content of its degradation products, which are well above their odor detection thresholds. The aroma is dominated by cis, tram-, tram, frani-2,4-heptadienals, hexanal, nonanal, and the cis, trans- and... 

The analysis of sterols and sterol esters has been proposed as one way to identify oils in blends (311, 312). Johansson and Croon (313) discussed the use of 4-des-methyl-, 4-monomethyl-, and 4,4-dimethylsterols in characterizing different vegetable oils, and the results are summarized in Table (8). The levels of total sterols and sterol classes as well as the relative distribution of the individual sterol members vary between oils. The presence of steradienes can also be used as a marker for the presence of refined oils (314, 315). High oleic acid oils can easily be used to adulterate olive oil. The presence of rapeseed oil in other oils can be detected by the analysis of brassicasterol and its dehydration product, campestatriene. The presence... 

For ecological and political reasons, so-called biodiesel, most often in the form of RME (rapeseed oil methyl ester), has received much attention, especially in Europe. Biodiesel can be used as a replacement for conventional diesel fuel, however, in certain cases it can be beneficial to adapt the engine control if biodiesel is used [5], Thus there is interest in a sensor detecting the presence of biodiesel and, for a mixture with conventional diesel, the mixing ratio in the fuel tank. 

The composition of major sterols in common vegetable oils is presented in Table 4.8. Brassicasterol is a major sterol in rapeseed and canola oils and as it is unique to brassica oils it is often used to detect adulteration of other oils with rapeseed/canola oils (Strocchi 1987 Ackman 1990). Sterols are affected by processing and about 40% of these components can be removed from the oil during deodorization. Refining also causes changes in the chemical structure of sterols (Kochar 1983 Marchio el al. 1987). 

ELISA Systems Mustard Seed Protein Residue kit was released in June 2007. A polyclonal rabbit antiserum was raised and used to develop a quantitative sandwich ELISA that has been demonstrated to detect mustard seed protein from aU three species of mustard plants S. alba, B. nigra, and B. juncea [5]. The detection limit of the kit has been shown to be less than 0.5 ppm (mg/kg) of soluble mustard protein, which corresponds to mustard seed concentrations below 3.4ppm S. alba, below 4.9 ppm B. nigra, and below 5.5 ppm B. juncea. An example of a calibration curve is presented in Figure 23.1. Cross-reactivity studies were conducted on full-strength extracts from 50 plants and other common foods, and cross-reactivity was observed only with rapeseed (Canola), Brassica napus. This cross-reactivity was approximately 50%, but purified canola oil did not cross react. 

In May 2008, Malmheden-Yman et al. reported the development of a competitive ELISA to analyze food products for the presence of S. alba and B. juncea [8]. This qualitative assay has a detection limit below 1 ppm (1 mg/kg) mustard seed, and crossreactivity has been observed only with extract from rapeseed B. napus). 

The determination of mustard oil in other edible oils is based on the detection and estimation of allyl-isothiocyanate, a volatile constituent present in mustard oil but not in other edible oils. The Association of Official Analytical Chemists (AOAC) method consists of distilling the sample, and precipitating the allylisothiocyanate as a black precipitate and dark color with silver nitrate. The intensity of the dark color and the amount of black precipitate formed are directly related to the amount of mustard oil present.The detection sensitivity is about 0.05% of mustard oil in other edible oils. Erucic acid is characteristic of mustard and rape, and hence the estimation of erucic acid number by selective oxidation to dihydroxybehenic acid with KMn04 can be used as an index of the purity of rapeseed and mustard oils. ... 

Selenium is allied with sulfur chemically, and is regarded as an essential micronutrient (Beare-Rogers et a ., 1974 Levander, 1975). The levels of selenium in crude rapeseed oils (Elson, 1980) are given in Table XX. There is no evidence that the Se level varies between HEAR and LEAR oils, and the levels approach or fall below the limits of detectability on refining. There is certainly no public health concern. 

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