Fatty acid in canola oil

Flavor deterioration has been attributed mainly to secondary oxidation products of linolenic acid, which normally makes up 9-15% of the fatty acids in canola oil. Storage tests of canola oil showed sensory changes after 2—4 days at 60-65°C in comparison to 16 weeks at room temperature. Canola oil seems to be more stable to storage in light than cottonseed oil and soybean oils, but is less stable than sunflower oil. In addition, the effects of various factors on sediment formation in canola oil have been repotted. ... 

As mentioned earlier, both MCTs and LCTs are used in tube feeding products. Corn, soy, and safflower oils have been the mainstay sources of fat in these products, providing mainly co-6 polyunsaturated fatty acids (PUFAs). On the other hand, some newer EN products contain higher quantities of co-3 PUFAs from sources such as fish oil [i.e., docosahexenoic acid (DHA) and eicosapentenoic acid or (EPA)]. Still other formulas contain higher quantities of monounsaturated fatty acids from canola oil and high-oleic safflower or sunflower oils. The essential fatty acid (EFA) content (mainly linoleic acid) of EN... 

The saponification value is defined as the weight of potassium hydroxide, in milligrams, needed to saponify 1 g of fat. This parameter is inversely proportional to the molecular weight of the fat. In other words, the higher the molecular weight, the lower the saponification value. Replacement of long-chain fatty acids such as erucic acid in canola oil by octadecenoic fatty acids increased the saponification numbers from 168-181 to 188-192 because of the reduction in molecular weight (Table 13). 

The fatty acid distribution in esterified sterols differs from that of canola oil the sterol esters contain higher levels of palmitic and stearic acids. In canola oil, sitosterol and campesterol are equally distributed in the esterified and free sterol fractions. Twice the amount of brassicasterol was found in free sterols than in esterified sterols. The total amount of sterols in rapeseed and canola oils ranges from 0.7 to 1.0%. 

The US imports large amounts of canola oil from Canada in addition to some domestic production. Currently, about 90% of the canola oil is consumed in liquid form as salad oil and in salad dressings. This is a direct result of the emphasis on consuming oils which are low in saturated fatty acids and canola oil is lowest in saturated fat among vegetable oils. Canola oil is also being used in blended salad oils to achieve certain fatty acid profiles, as mentioned earlier. The relatively high use of canola oil in the US is remarkable, since none was used before 1983. 

Unsaturated fats, found in plants, are better choices for a healthful diet. These fats, usually soft or liquid at room temperature, vary from mono-unsaturated (the major fatty acid in olive oil) to polyunsaturated fatty acids (found in cottonseed, soybean, corn, and canola oils). Hydrogenation, a process that changes fatty acids from liquid to solid, creates trans fats. Trans fats raise blood cholesterol levels and may contribute to heart disease. 

Oleic acid was increased to 48% of total milk fatty acids by feeding oleamide as a rumen-protected source of oleic acid (Jenkins, 1998). The response was nearly linear up to 5% of supplement in the diet dry matter. Proportions of all de uovo-synthesized milk fatty acids, except butyric, were reduced (Jenkins, 1999). LaCount et al. (1994) abomasally infused fatty acids from canola or high oleic acid sunflower oil into lactating cows. The transfer of oleic acid to milk fat was linear (slope = 0.541 0 350 g infused/ day) the proportion of oleic acid in milk fat increased and proportions of all de novo-synthesized fatty acids, except C4 and C6 decreased. The proportion of Ci8 o also was unchanged. Linoleic acid from canola also was transferred linearly (slope = 0.527 0-90 g infused/day). These transfers from the intestine are nearly identical to that reported by Banks et al. (1976). Hagemeister et al. (1991) reported 42 to 57% transfer of abomasally-infused linolenic acid to milk fat. 

Seedfats are characterized by low contents of saturated fatty acids. They contain palmitic, oleic, linoleic, and linolenic acids. Sometimes unusual fatty acids may be present, such as erucic acid in rapeseed oil. Recent developments in plant breeding have made it possible to change the fatty acid composition of seed oils dramatically. Rapeseed oil in which the erucic acid has been replaced by oleic acid is known as canola oil. Low linolenic acid soybean oil can be obtained, as... 

The stigma of the emcic acid (C22 ln - 9) in rapeseed oil has lingered despite firm evidence that this fatty acid was more of a threat to rats than to humans. It is sufficient to say that the discovery of chain shortening of emcic acid to oleic acid by peroxisomes was one of the most fundamental breakthroughs in understanding fatty acid metabolism in the last few decades. Once in the oleic acid form, the emcic acid residue is as readily catabolized by mitochondria, as are palmitic and other fatty acids (4). The reduction of emcic acid in rapeseed oil resulted in a marked increase in octadecanoic acids, and their contribution in canola oil is around 95% of all fatty acids present (Table 2). 

In the sediment from industrial winterization, additional minor fatty acids and alcohols with 26 to 32 carbon atoms in the chain have been found in waxes and triacylglycerols (15). Most of these compounds are extracted from the seed coat and can initiate sediment formation in canola oil (16). 

Triacylglycerols are the most abundant lipid class found in canola oil. The combination of fatty acids on the glycerol moiety represent the most complex mixture with n possible molecular species, where n is the number of fatty acids present in the oil. 

Sterols are present in canola oil in two forms in equal amounts, free sterols and esterified sterols (19, 37). The fatty acid composition of the esterified sterol fraction in canola oil is shown in Table 7. 

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. 

The current interest in dietary fat, however, stems primarily from its implication in the origin of several chronic diseases. Interest has centered on both the amount and type of dietary fat in the development of cardiovascular disease, cancer, hypertension, and obesity. As a result, dietary recommendations in many countries call for a reduction in total fat intake, to 30% of energy, and in saturated fat intake, to less than 10% of energy. In addition, some nutrition recommendations specify recommended levels of n-6 and n-3 fatty acids in the diets. Hence, the source of fat in the diet has assumed considerable importance over the past few years. Interest in the nutritional properties of canola oil developed because of its fatty acid composition (Table 2). Canola oil is characterized by a low level of saturated fatty acids, a relatively high level of monounsaturated fatty acids, and an appreciable amount of the n-3 fatty acid ot-linolenic acid (18 3 n-3). 

Saturated fatty acids. The adverse effect of saturated fat on blood cholesterol level and its implication in cardiovascular disease has stimulated concern over the level of saturated fatty acids in the diet. Canola oil contains a very low level (<7%) of saturated fatty acids about half the level present in corn oil, olive oil, or soybean oil and about one-quarter the level present in cottonseed oil. Furthermore, canola oil contains only 4% of the saturated fatty acids (viz., lauric, myristic, and palmitic) that have been found to increase blood cholesterol level. Hence, canola oil fits well with the recommendation to reduce the amount of saturated fat in the diet. 

Appreciable research on the effect of canola oil on plasma cholesterol and lipoproteins has been reported. The primary impetus for this research was the finding that dietary monounsaturated fatty acids were as effective as polyunsaturated fatty acids in lowering plasma total and LDL cholesterol (100, 109). These findings also provided a possible explanation for the observation that canola oil was as effective as soybean oil in lowering plasma cholesterol in normolipidemic men (110). Prevailing theory had held that saturated fatty acids raised plasma cholesterol, polyunsaturated fatty acids lowered plasma cholesterol, and monounsaturated fatty acids were neutral, they neither raised nor lowered plasma cholesterol (111, 112). 

Canola oil is characterized by a low level of saturated fatty acids (less than 4% palmitic acid) and relatively high levels of oleic acid (60%) and a-linolenic acid (10%). It is second only to olive oil, among the common fats and oils, in oleic acid level and, except for soybean oil, the only common dietary fat that contains a significant amount of a-linolenic acid. Furthermore, there is a favorable balance in the levels of linolenic and linoleic acids (viz., 18 3/18 2 ratio of 1 2) in canola oil. Canola oil has been found equally as effective as soybean oil, safflower oil, and sunflower oil in reducing plasma total and LDL cholesterol levels in normolipi-demic subjects. It also was effective in reducing plasma total and LDL cholesterol levels in hyperlipidemic subjects when it replaced saturated fat in their diets. Canola oil diets also have been shown to affect the fatty acid composition of blood... 

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