Refining and deodorization

Trans fatty acids in refined and deodorized oils... 

A typical chemical composition of crude, refined, and deodorized canola oils is presented in Table 12. The deodorized oil data represents the oil quality used as a food ingredient. 

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). 

The salad oil may contain properly refined and deodorized cottonseed, corn, peanut, soybean, sesame, sunflower, or safflower vegetable oils or a mixture of these oils. Olive oil shall not be used. Edible vegetable oils not specified may also be used provided they are in accordance with good commercial practice. Specifications per announcement PV-50-1 dated June 17, 1976, issued by Agricultural Stabilization and Conservation Service, US. Department of Agriculture, Shawnee Mission, Kansas. 

Sunflower oil extracted from different types of hybrid may have different compositions. It is expected that the degree of unsaturation will influence the oxidative stability of sunflower oil markedly. AOM time measurements were used to determine the influence of oleic/linoleic ratio on the oxidative stability of sunflower oil (36). Oil samples extracted (refined and deodorized) from three progenies of cultivar Per-venets were analyzed, as well as other oil samples from different regions of the United States. The oleic acid content thus ranged from 18% to 89%, and the linoleic acid content decreased from 69% to 1 % the saturated fatty acid content was nearly constant. AOM values increased from 11 hours for the oil containing the least amount of oleic acid to 100 hours for that with the oleic acid highest content. These results show the importance of monounsaturated fatty acid content on the oxidative stabihty of sunflower oil. 

Producing bland fluid lecithins is possible by redispersing the de-oiled lecithin in clean oils that have been properly refined and deodorized. Lecithin flavors are not typically a problem in food applications because lecithins are used in most foods at low levels. Laboratory tests have shown that in finished food formulations, lecithins can either accentuate or reduce the flavor intensity of salt, acids, and some spices. However, lecithin flavors can penetrate bland dairy-based systems. Studies have shown that 0.25% de-oiled lecithin could be detected in cottage cheese (31). 

Proper refining and deodorization removes peroxides which are the source of trace free radicals. Oil should be processed, transported, and stored under a nitrogen atmosphere. Metal ions in the oil can be inactivated by chelation with citric acid. Finally, the exposure of oil to light should be minimal. With these precautions oxidative stability can be increased several-fold. 

There remain some exciting challenges in the oil-refining industry for the future. The introduction of new technologies (e.g., use of enzymes, ultrafiltration, etc.) may require the development of specific refining and deodorization methods. 

Unrefined canola oil is said to contain low levels of sulfur-containing fatty acids, resulting in the presence of sulfur in the oil in the stable form of triglycerides. These triglycerides resist refining procedures. See Table II for the sulfur content of crude, refined, and deodorized canola oils. ... 

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... 

Canola oil contains mostly a- and y-tocopherol, with the amount of the latter twofold higher. The content of tocopherols in refined, bleached and deodorized (RBD) oils is reduced by processing, mainly by extraction, refining and deodor-ization. The lowest content of tocopherols was found in cold pressed canola oil. However, when the temperature of pressing was increased, the amount of... 

Examples of typical margarine blends are given by Andersen and Williams (1965) and Van Stuyvenberg (1969). For an optimal taste stability of the finished product, the raw materials should be refined and deodorized properly (see Section 5.4). 

Table 10.11 Chemical analyses of free fatty acids (FFA), iodine values (TV), peroxide values (PV) and anisidine values (AV) of menhaden oils from successive refining and deodorization steps (adapted from Lin et al., 1990)...

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