Flaxseed tocopherol

Tocopherols consist of a, (3, y, and 8 isomers and are effective antioxidants. Oomah et al. (1997a) observed that y-tocopherol (9.04 mg/100 g seed) was the predominant isomer of Canadian flaxseed cultivars. Total tocopherol ( r = 0.42) and y-tocopherol (r = 0.41) values were correlated with seed oil content. Kamm et al. (2001) reported the distribution of tocopherols and tocotrienols in high and low linolenic flaxseed. Results were similar to the findings of Oomah et al. (1997a) in which y-tocopherol content was greater (430-575 mg/kg oil) in high ALA flaxseeds, whereas low linolenic flaxseed exhibited lower (170 mg/kg oil) values. Bozan and Temelli (2002) compared tocopherol levels in oil extracted by supercritical C02 fluid and soxhlet (Table XI). Soxhlet-extracted oil had greater tocopherol levels (76.4 mg/100 g oil). These authors speculated that the temperature-pressure combination may have influenced the tocopherol extraction by supercritical C02 fluid. 

In order to improve oxidative stability, supercritical C02 fluid extraction could be used for flaxseed oil extraction (Bozan and Temelli, 2002). This method demonstrated higher ALA content compared to soxhlet extraction. In contrast, tocopherol content was lower (Table XI). Temperature and pressure profiles did not alter the fatty add profile and exhibited similar results at 50 and 70°C and pressures of 35 and 55Mpa. Stability of oil was not reported, and since limited knowledge is available further research is required with regards to shelf life and comparisons to cold-pressing operation. 

Oomah, B.D., Kenaschuk, E.O., and Mazza, G. 1997a. Tocopherols in flaxseed. J. Agric. Food Chem. 45, 2076-2080. 

Flaxseed oils contain much lower amounts of tocopherols, half of the amount present in sunflower and canola oils and one-third of that present in soybean oil (Table 2). A lower content of these antioxidants makes these oils even more susceptible to oxidation. Gamma-tocopherol was found as the main tocopherol in flax oils, with a contribution of about 80% to the total amount. This makes flax oil comparable with soybean oil. Among unique antioxidants detected in flax oils was plasto-chromanol-8. This compound is a derivative of gamma tocotrienol with twice as long unsaturated side chain. Plastochromanol-8 was found to be a more efficient antioxidant than any tocopherols isomer (15). A low content of tocopherols in flaxseed did not make them more susceptible to oxidation experiments showed that milled flaxseed could be stored for 28 months at ambient temperatures without measurable changes in oxidation products. This can be attributed to the presence of antioxidants other than tocopherols in the seeds (16). 

The fate of endogenous antioxidants in vegetable oils, especially tocopherols, due to microwave heating has also been studied. In com and soybean oils, 90% of the original tocopherol level was retained after 8-10 min of microwave heating, however, in olive, palm and flaxseed oils the content of tocopherols was decreased substantially. When soybean oil was heated for 12 min, 40% of the total tocopherols was lost, but microwave treatment for 6 min retained 90% of their original amounts (Yoshida et al, 1990 1995). 

There are conflicting reports as to whether fishy off-flavors, from fish oils and flaxseed, in eggs can be eliminated by incorporating tocopherols into the feed (Sim, 1998 Surai and Sparks, 2001), although off-flavors are apparently absent if the level of fish oil (preferably stabilized) in the diet is 1.5% or less, and for flaxseed 5% or less (Surai and Sparks, 2001). Off-flavors have been reported to be absent if the feed contains micro-algae (Haumann, 1998). The cooking characteristics of co3 eggs are reported to be normal (Surai and Sparks, 2001). 

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