Flax oil

Cameron et al. (1989) reported that flax oil prevented tumor formation in mice whereas mice on the corn oil and safflower oil diets had the greatest number of tumors. A diet consisting of 10% flax oil was sufficient to reduce tumor growth and metastasis in mice compared with corn or fish oil diets (Fritsche and Johnston, 1990). Although flaxseed and flaxseed oil and lig-nans have been shown to be beneficial, additional studies are needed to identify the mechanisms by which flaxseed or its components function to reduce prostate cancer. 

Ingram AJ, Parbtani A, Clark WF, Spanner E, Huff MW, 180. Philbrick DJ, Holub BJ. Effects of flaxseed and flax oil diets in a rat-5/6 renal ablation model. Am. J. Kidney Dis. 1995 25 320-329. 

Roman Przybylski University of Manitoba, Winnipeg, Manitoba, Canada, Canola Oil, Flax Oil and High Linolenic Oils. 

Abbreviations HEAR—High erucic acid rapeseed LLCanola—Canola oil with low content of linolenic acid HOCanola—Canola oil with high content of oleic acid LLFlax—Flax oil with low content of linolenic acid P-8—Plastochromanol-8. 

Detailed fatty acid composition of canola, soybean, sunflower, corn (maize), and flax oils as well as some specialty canola oils and HEAR oil are given in Table 2. 

Flax, widely adapted to warm and cool climates, has been cultivated for centuries in various parts of the world for its stem fiber, linen cloth, and seed. Linseed is an alternative name used for flax. Crops grown for seed are termed linseed in India and in the United Kingdom and flaxseed in Canada and the United States, and flax oil or flax seed is used in many European countries. 

Canada is one of the major flaxseed producers and exporters, where a minimal amount of seeds is crushed to produce flax oil. Flax oil is mainly considered as a health food product but not a commodity oil. Figure 2 shows yearly production of flaxseeds in Canada for the past ten years. On average, Canada is producing above 800,000 MT (metric tons) of flaxseed per year (5). Part of this production is low linolenic acid varieties, which contribute from 10% to 15% to the total production. 

Unsaponifiable matter content, saponification value, and iodine value are characteristic for a high contribution of PUFA in the flax oil. The content of unsaponifiable matter in flax oil is similar to other vegetable oils. 

Main components of vegetable oils, including flax oil, are triglycerols and usually contribute more than 90% of all components (Table 1). Minor components in flax oils were found to be at the similar level as in canola and soybean oils (10). The presence of chlorophyll in flax oil usually indicates immaturity of flaxseed. 

Fatty acid composition of regular flax oil is different from other commercial oils because of the very high contribution of ALA, usually above 50% (Table 2). Because of the high content of this unique fatty acid, flaxseed and flax oil are often used as food supplements, where enrichment with omega-3 fatty acids is needed. This fatty acid is susceptible to oxidation it oxidizes 20 0 times faster than oleic acid and 2 times faster than linoleic acid (8). This property makes the oil a good material for paint and plastic production where fast oxidation is required. Flax oil contains low amounts of saturated fatty acids (SFA) compared with low linolenic flax oil (Linola), soybean, and sunflower oils however, it is higher than canola oil (Table 2). Canola oil contains the lowest amount of SFA among all commercial oils. 

Cool temperatures during the 10-25 days after flowering are the main cause for higher amounts of linolenic acid in flax oils (14). For the same reason, flaxseed grown in the Canadian prairies, northern latimde, produce oils with higher levels of polyunsaturated fatty acids and lower contributions of oleic acid and samrated fatty acids. This phenomenon was also observed for other oilseeds such as sunflower, canola, and soybean (7, 13, 14). Similarly, a wide variation in fatty acid composition in Australian flaxseed samples was observed 13-25% of 18 1 and 46-64% of 18 3 (6). 

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). 

Sterols or phytosterols are present in flax oils at a level lower than those in many vegetable oils, 2.3 mg/g in flaxseed oil versus 4.1 to 6.9 mg/g in other oils (Table 2). The composition of sterols was similar to other oils, where p-sitosterol was the main component followed by campesterol and A -avenasterol. Brassicasterol was found in trace amounts in flax oil. This phytosterol is characteristic to plants from the Brassica family and often is used as a marker for oil adulteration (Table 2). 

As expected from fatty acid composition, the main triacylglycerols contain linolenic acid in their molecules and 84% of all triacylglycerols have this acid in their structure (Table 3). Among them, 21% of total acylglycerols contained three ALA in molecule, second by contribution were acylglycerols with two ALA, and linoleic acid had the second-most abundant fatty acid present in the flax oil (17). 

The presence of plant lignans in flax oil makes it nutritionally more valuable than any other oil. When high levels of ALA and hnoleic acid are considered in the whole equation, flaxseed oil serves as the best oil in terms of its nutritional and health value. 

The fatty acid composition of the new crop has been modified, and the level of linolenic acid has been reduced from over 50% to 2% (6). This greatly improves oxidative stability of the oil, which by fatty acid composition is very close to sunflower and soybean oils (Table 2). Linola has been found to be more resistant to oxidation than regular flax oil, and its stability is comparable with soybean, canola, and sunflower oils (Przybylski, unpublished data). 

Figure 5. Processing of flaxseed to produce cold-pressed flax oil.

Oil from expeUer is filtered, packaged under nitrogen or other neutral gas into bottles protecting from light exposure, and ready for distribution. Flax oil is very susceptible to oxidative deterioration, and treatment to eliminate oxygen needs to be applied. On the North American continent, flax oil is considered as a health food oil. 

The seed of perilla contains 31-51% of oil, which is similar in composition to flaxseed oil, with a higher contribution of PUFA of over 70% (Table 4). The oil is highly unsaturated, with an iodine value of 192-208-g iodine /100-g oil (Table 4). Perilla oil contains over 60% linolenic acid with equal amounts of both linoleic and oleic acids (Table 4). Specific gravity of this oil is higher than flax oil because of a higher contribution of PUFA. Other physical parameters of this oil reflect the composition of its fatty acids. 

The amount of tocopherols in perilla oil is higher compared with flax oil, and a similar contribution of gamma-tocopherol, above 90%, was observed (Table 4). Shin and Kim (49) analyzed perilla oil for lipid composition and established that it contained more than 90% triacylglycerols, 4% glycolipids, and 2% of each phospholipids and sterol esters. 

Composition and content of tocopherols in camelina oil was similar to perilla oil, where more than 80% of all tocopherols were gamma isomer (Table 4). Alpha and delta tocopherols were detected as minor antioxidants (77). The total content of tocopherols was comparable with perilla oil, and higher than that in flax oil (Tables 4 and 2). The total content of tocopherols in camelina oil is higher than canola, flax, soybean, and sunflower. 

Cold-pressed camelina oil had an attractive yellow color, a mustard-like taste, and a characteristic pleasant odor. This type of flavor is acceptable in India and other Asian countries, but in Europe and North America, it is difficult to find acceptability among consumers, mainly because of a different expectation from vegetable oils. However, commercial camelina oil needs to be refined and deodorized to produce an odorless and colorless product as expected by consumers (76). Crude camelina oil, refined following typical steps as described for flax oil (Figure 6), afforded a product similar to typical commercial oils (76). 

Chia oil is high in polyunsaturated fatty acids, particularly a-linolenic acid the content of this fatty acid is higher than flax oil (Table 4). Linoleic acid is the second-most abundant acid in chia with a contribution of 17-26%, which gives PUFA content of 83%, the highest amount among edible oils. Additionally, chia oil has the lowest content of saturated fatty acids (Tables 2 and 4). 

Plastochromanol-8 is a derivative of y-tocotrienol which has a longer side chain. This compound was detected in canola and flax oils and its antioxidative activity was established to be similar to a-tocopherol (Zambiazi 1997). 

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