Sunflower tocopherol

Beddows CG, Jagait C and Kelly MJ. 2000. Preservation of alpha-tocopherol in sunflower oil by herbs and spices. Int J Food Sci Nutr 51(5) 327—339. 

The saponifiable portion of the fatty oil accounts for about 90% of the total fixed oil and is characterized by a very high content of octadecenoic acids. Petroselinic and oleic acid occur at similar levels and jointly comprise 74-85%, linoleic 7-16% and palmitic 4-8%, of the constituent fatty acids. During prolonged storage of the spice, the free fatty acid content gradually increases and this is a good indicator of the age of the material. The contents of fatty acids, sterols and total tocopherols in a deodorized oil derived from coriander seeds (yield up to 28%) are compared with those in sunflower oil and tests on the biological effects of coriander oil are reported by Mironova et al. (1991). Of the fatty acids present, total C18 1 acids (petroselinic acid + oleinic acids) constituted 80—82% and petroselinic acid alone 50—60%, and the food value was lower than that of sunflower oif. Kim et al. (1996) found the production of petroselinic acid from cell suspension cultures of C. Sativum. 

Refined rice bran oil is an excellent salad oil and frying oil with high oxidative stability resulting from its high level of tocopherols and from the presence of the oryzanols (ferulic acid esters of sterols and triterpene alcohols). The oxidative stability of this oil is exploited in Good Fry Oil. This is a frying oil based on oleic-rich sunflower oil to which is added up to 6% of rice bran and/or sesame oil to confer high oxidative stability. Rice bran oil also finds several nonfood uses (45). 

The dominance of tocopherols, namely, alpha-, beta-, gamma-, and delta- and the corresponding tocotrienols, depends on the type of oil under investigation. Thus, tocotrienols occur primarily in palm and rice bran oils. Meanwhile, tocopherols are more widely present in different oils. However, their proportions in different oils is dependent on the source material. As an example, sunflower oil contains mainly alpha-tocopherol and very small amounts of other tocopherols, whereas soybean oil contains mainly gamma-tocopherol with decreasing amounts of delta-, alpha-, and beta-tocopherols as determined by high-performance liquid chromatography. 

Minor constituents tocopherols and phytosterols. Vegetable oUs are the primary source of tocopherols in the average diet. Canola oil is a relatively rich source of tocopherols (refer to Table 6) it is similar in total tocopherol content to com oil, cottonseed oU, safflower oil, and sunflower oil (60-70 mg/100 g). Only soybean... 

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). 

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. 

Sunflower oil—like most vegetable oils—is composed mainly of triacylglycerols (98-99%), and a small fraction of phospholipids, tocopherols, sterols, and waxes (all of the latter are commonly referred to as the unsaponifiable fraction ). 

Tocopherols Tocopherols are heterocyclic compounds with a phenolic group and a substituted side chain of branched hydrocarbon. Their high solubility in oil is caused by a long alkyl side chain. The Codex Alimentarius (Codex-Stan 210-1999) indicates levels of tocopherols and tocotrienols in crude regular sunflower oil (mg/kg), compiled in Table 5. 

TABLE 5. Levels of Tocopherols and Tocotrienols In Crude Regular Sunflower OII (ppm), According to the Codex-Stan 210-1999. 

Figure 7. Maximum values of major tocopherols (ppm) of crude sunflower, peanut, soybean, corn, and cottonseed oils, according to the Codex Alimentarius (Codex-Stan 210-1999).

Other Components of the Unsaponifiable Matter The unsaponifiable matter in a cmde regular sunflower oil is usually in the range of 0.5-1.5% (9, 17), or lower than 15 g/kg according to the Codex-Stan 210-1999. In addition to sterols (around 2.4. 6 g/kg) and tocopherols and tocotrienols (0.4-1.5 g/kg), there are minor components of sunflower oil. Aliphatic compounds and terpenoids occur naturally in oils. Of the terpenoid family, squalene is the most widely occurring compound. The occurrence of squalene in regular sunflower oil is fairly low 0.008-0.019% (5) or 15-20 mg/100 g (9). The aliphatic alcohol content is 100-mg/lOO-g oil (9). 

Sunflower oil processing byproducts depend on the kind of refining, whether chemical or physical. The so-called deodistillate of chemical refining of sunflower oil can be used as feedstock for obtaining tocopherols and sterols. The tocopherol composition of sunflower oil (over 90% alpha-tocopherol and only a low proportion of the beta and gamma isomers) makes deodistillates of great value for industrial Vitamin E production. Increased importance has been placed on vegetal sterols because they were found to reduce the risk of cardiovascular disease. As a result, the demand for tocopherols and sterols was increased as food additives. 

Deodistillate originated in physical refining, diluted in free fatty acids, is not an attractive feedstock for Vitamin E and sterol producers. Deodistillate originated in chemical refining of sunflower oil may contain 5-7% of total tocopherols, compared with only 1-2% for deodistillate of physical refining (68). 

Deodorization There are no major differences between deodorization procedures for sunflower oil and other vegetable oils. The loss of tocopherols in the oil is worth noting for sunflower oil, though. The average tocopherol content of sunflower oil is medium (440-1520 ppm, according to Codex-Stan 210-1999), nearly all of which is alpha-tocopherol (403-935 ppm). Table 18 shows the reduction in the tocopherol content upon deodorization of sunflower oil (69). Tocopherols may be recovered from the distillate of deodorization. 

TABLE 18. Total Tocopherol Content (ppm) of Sunflower Oil In Different Refining Stages [Based on (69)]. 

A low percentage of tocopherols is lost during operations of oil neutralization, bleaching, and deodorization of sunflower oil. The tocopherols lost during deodor-ization may be recovered together other volatile compounds, from the deodorizer distillate. The distillate obtained from sunflower oil is also a good source of phytosterols. Figure 40 shows typical tocopherol levels in deodorizer distillate obtained from crude oils [based on Walsh et al. (148)]. 

The distillate obtained from sunflower oil may be sold to pharmaceutical companies for tocopherol and sterol isolation. Tocopherols may be used as natural antioxidants or may be converted to vitamin E by methylating the heterocyclic ring. The interest in phytosterols is caused by the high potential of some of them to inhibit intestinal cholesterol absorption. 

The unsaponifiable matter of soy, corn, canola/rapeseed, sunflower, cottonseed, peanut, and palm ranges from 10-30%, and it is composed of 40% phytosterols and 15% tocopherols (199-202). The temperature, duration, quantity of skimming vapor, and the extent of vacuum used for deodorization are the parameters that greatly influence the quality and quantity of DOD. The low content of tocopherols and sterols in the DOD often requires a concentration step however, if the starting material is soybean, this is not an issue because of the high concentration of these compounds. 

Alfa-tocopherol is a good antioxidant against photooxidation (38). Table 2 shows that corn and cottonseed oils are rich in gamma-tocopherol, while sunflower oil contains very little gamma-tocopherol. This may explain why cottonseed oil and com oil have superior frying stability than the sunflower oil even without hydrogenation. 

Tocopherol (ppm) Cottonseed Corn Soybean Palm Sunflower... 

Comparisons of the tocopherol and sterol contents from various oils indicate that some oils have appreciably higher contents of specific tocopherols and sterols (94). For example, sunflower is high in a-tocopherol, whereas soybean is higher in y-tocopherol. As deodorization strips tocopherols and sterols from the oil, different feedstock oils yield different concentrations and types of tocopherols. 

Consequently, oils rich in a-tocopherol (sunflower seed, cottonseed oil) in particular have a high Vitamin E content. 

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