Rapeseed sensitizer

Reported activation energy values for the thermal i-rra i-isomerization of linoleic and linolenic acid are rather low (178 kJ/mole vs. 144—148 kJ/mole, respectively) (8). This is an indication that TFAs are relatively easily formed at elevated deodorization temperature. Different studies show that the relative isomerization rate can be expressed as follows Cig 3 (100) Cig 2 (10) Cig i (1) (11-13). Consequently, oils with a high linolenic acid content, such as soybean and rapeseed oils, are most sensitive to di-fra i-isomerization during deodorization. 

Peroxide value (P V) is the most commonly used measurement of lipid oxidation. The standard iodometric method requires a relatively large sample (5 g) when the lipid is only slightly oxidized. The ferric thiocyanate method, based on the oxidation of ferrous to ferric ion, involves colorimetric measurement of ferric thiocyanate. This method is more sensitive than the iodometric method and requires a relatively small sample (0.1 g). The PV is a useful measure for samples with low levels of oxidation and when the hydroperoxides are not decomposed. During prolonged oxidation, a maximum PV is reached and the value then begins to decrease due to peroxide degradation. This maximum value occurs early for soybean and rapeseed oil, due to the more rapid decomposition of the hydroperoxides of the polyunsaturated fatty acids. 

For example, many thousands of papers were pubhshed between 1970 and 1990 addressing the antinutritional and toxic effects of rapeseed meals on farm livestock and poultry. The vast majority of these were focused on the effects of glucosinolates and their breakdown products. In retrospect one can see the eat divergence between chemical and biological investigations. The former, centered on development of analytical approaches, became focused on increasingly rapid, sensitive, and specific methods, in almost total isolation from the biological studies. 

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. ... 

It becomes more apparent that the rat is uniquely sensitive when it is compared with other species in which the incidence and severity of the heart lesions is much lower and certainly not related to the consumption of LEAR oils. The studies in primates are particularly interesting since they indicate that feeding of low erucic acid rapeseed or soybean oil did not cause heart lesions (Kramer et ai, 1978a, 1978b). 

The rat is much more sensitive to myocardial lipidosis than most other species and rapidly accumulates triglycerides and erucic acid in the myocardium when fed mustard oil or high erucic acid rapeseed oil. 

Corresponding curves (Woodbury et al., 1995) relating to the adulteration of maize oil with rapeseed oil are shown in Fig. 8.8. Thus, when small amounts of rapeseed oil are added to maize oil, the influence on the isotope ratio of the palmitic acid in the blend is initially quite small [Fig. 8.8(a)] as rapeseed oil contains less palmitic acid than does maize oil. The opposite is true with oleic acid [Fig. 8.8(b)] since rapeseed oil has more oleic acid than does maize oil. Linoleic acid has a similar mixing curve [Fig. 8.8(c)] to that of palmitic acid. The use of oleic acid to detect adulteration of maize oil with rapeseed oil is thus the most sensitive, as this is the steepest of the curves in the region of interest (Woodbury et al., 1995). Other cases of adulteration may merit consideration of different mixing curves to get maximum sensitivity, depending on the fatty acid compositions of the components. 

Most other test animals, including ducklings, guinea-pigs, pigs, hamsters and mice, have been reported to be affected similarly, but rats seemed particularly sensitive. The feeding of rapeseed oil caused... 

Enzyme studies on the enzyme over-expressed in E. coli revealed that the rapeseed enzyme is quite unstable at temperatures above 30 °C, although it is not as rapidly heat inactivated as the enzyme encoded by the temperature sensitive E. coli strain with the envM2,92 (Is) allele (not shown, [1]). These data revealed that the growth defect at 42°C is most likely... 

This correlation was investigated ftirther by examining the ultrastructure and oil-body composition of seed and fruit tissues from olive and avocado. Olive seeds are desiccation tolerant and contain large numbers of oil bodies of similar diameter (Ipm) to those found in rapeseed. In contrast, the mesocarp tissues of olive and avocado fruits are desiccation sensitive and contain very large oil bodies of >20fim. It was found that olive seeds contained the expected amounts of oil-body proteins that exhibited all the characteristics of oleosins, whereas oil bodies from the mesocarp of olive and avocado fruits contained no detectable proteins [3]. Therefore, oil-body proteins were only present in tissues which naturally underwent desiccation rather than being associated with all tissues that contain oil bodies. 

---