Canola minor components

The stability of canola oil is limited mostly by the presence of linolenic acid, chlorophyll, and its decomposition products and other minor components with high chemical reactivity, such as trace amounts of fatty acids with more than three double bonds. These highly unsaturated fatty acids can possibly be formed during refining and bleaching (52). The presence of 7% to 11% of linolenic acid in the acylglyce-rols of canola oil places it in a similar category with soybean oil with respect to flavor and oxidative stability. The deterioration of flavor as the result of auto -and photo-oxidation of unsaturated fatty acids in oils and fats is referred to as oxidative rancidity. 

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. 

Table 3.95 Typical values for minor components in Canola oil (Mag, 1983 Teasdale, 1975 Pritchard, 1983)...

Subsequent work by Zambiazi and Przybylski (1998) also showed that fatty acid composition could only explain half of the oxidative stability of vegetable oils including canola oil. The other half was attributed to the amount and composition of endogenous minor components which can shorten or extend the shelf-life of an oil. Such endogenous components were later discussed by Przybylski and Eskin (2006) and included tocopherols, mono- and diacylglycerols, free fatty acids, phospholipids, chlorophylls and derivatives, carotenoids, phytosterols, phenolic compounds and trace metals. In addition, the position that the fatty acid occupies in the triacylglyc-erol can also affect stability. For example, the location of linolenic and linoleic acids on the sn-2 position has been reported to cause faster oxidation and lower stability compared to the same fatty adds on ml- and sn-3 positions. In contrast oleic acid at the sn-2 position proved stabler compared to its location on sn-1 and sn-3 positions (Neffetal., 1994,1997). 

Minor components of canola oil include tocopherols (700-1200 ppm of mainly a and Y tocopherols) and chlorophylls (5-35 ppm). The a-tocopherol (vitamin E) content of canola oil is 2.44 mg/tablespoon (USDA, 2010). This is higher than most vegetable oils except snnflower and safflower oils (USDA, 2010). The y-tocopherol content is not readily reported, but in canola oil is typically abont 1.5 times that of the a-tocopherol content (Przybylski, 2010). The RDA for Vitamin E for adults is 15 mg/day. Most of the trace elements found in the canola plant such as phosphorus, iron, calcinm, snlphnr, zinc and lead are removed or minimzed during processing (Przybylski, 2010). 

Some of the minor components that remain in the refined oil may act as antioxidants within the body and thus may be beneficial for chronic disease prevention, inclnding metabolic syndrome, however, there are no data as to the levels of these componnds present in canola oil and their effects on health. For example, Siger et al. (2008) have documented a relatively high amount of phenolic componnds (256.6 + 0.73 pg/lOO g) and antioxidant activities in cold-pressed canola oil... 

Minor acids present in oils often differ from the major components by the location of the double bond. Generally these acids are present in canola oil in the 0.01-0.1% range, except for 16 ln-7 which is around 0.3%. Most of these minor fatty acids are from the n-1 series, rather than the more common n-9 isomers (Ackman 1990). A similar series of minor fatty acids was found in B. rapa variety Candle (Sebedio and Ackman 1981). Conjugated 18 2 fatty acids have also been found in canola oils. Some of these acids are artefacts of refining and deodorization, although some were also observed as natural components in... 

---