Deodorization sterols

Deodorization can be carried out ki batch, continuous, or semicontkiuous systems. Figure 4 shows a typical design for a semicontkiuous deodorizer. The heated ok is passed through a series of trays under vacuum. Steam is passed through the ok through a steam sparge ki the bottom of the tray. Volatiles are carried through the headspace and condensed. In addition to fatty acids and compounds responsible for odor, some tocopherols and sterols are also distilled kito the condensate. The amount of tocopherols distilled depends on deodorization temperature and vacuum. 

It is of interest that carotenoid pigments (xanthophylls), sterols (spinasterol and chondrillasterol) and a triterpene alcohol have been identified in cucurbit seed oil (31, 3 , 37L However, cucurbit oils such as that from Buffalo gourcT are amenable to refining, bleaching and deodorizing (38). 

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. 

Kamm el al. (2001) analysed intact steryl esters in the presence of silylated sterols by online transfer from HPLC to a 15 m low-polarity high temperature GC column. Steryl esters were quantified against a cholesteryl laurate internal standard and identified by offline thin layer chromatography-gas chromatography-mass spectrometry. When esters of sitosterol, stigmasterol and campesterol with the major cocoa butter acids were measured in cocoa butters from South America, Asia and Africa, no differences were apparent between cocoa butters of different geographical origin, or between deodorized and non-deodorized butters. 

Nagao, T., Kobayashi, T., Hirota, Y., Kitano, M., Kishimoto, N., Fujita, T., Watanabe, Y., and Shimada, Y. 2005. Improvement of a process for purification of tocopherols and sterols from soybean oil deodorizer distillate. J. Mol. Catal. B Enzym., 37, 56-62. 

Animal fats are subjected to deodorization when a very bland or essentially flavorless fat is desired, such as in margarines or cooking fats. The fats are heated at 200°C to 260°C in the absence of air (to prevent oxidation) and treated with dry steam under a vacuum of 5-10 milliatmospheres. Off-flavor compounds are volatile under these conditions and are captured and removed in the steam stream. In addition to flavor components, free fatty acids, which can also contribute undesirable flavors, and other minor constituents such as peroxides, sterols, sterol esters, toco-pherols, and other natural antioxidants are partially or completely removed from the fat by this treatment. 

Approximately 0.5% of crude coconut oil is not saponified by caustic treatment. The unsaponifiable matter consists mainly of tocopherols, sterols, squalene, color pigments, and carbohydrates. The odor and taste of coconut oil is largely due to 5- and y-lactones, which are present in trace quantities (24). Among the unsaponifi-ables, tocopherol contributes to the oxidative stability of crude coconut oil. A typical sample of crude coconut oil contained 55 ppm total tocopherols of which 40.7 ppm is cx-tocopherol (25). Most of the unsaponifiables are removed in the process of refining, bleaching, and deodorizing of crude coconut oil. 

Temperature—Increases in temperature combine with decreases in pressure to accelerate deodorization. However, an excessive increase in temperature promotes polymerization, tranr-isomer development, excessive removal of tocopherols and sterols, color reversion, and the formation of odoriferous low-boiling products. 

The deodorizer distillate, about 1% of deodorizer feed, contains tocopherols, tocotrienols, and sterols (Table 10). The tocols are shown in Table 11 and the sterols in Table 12. Its value is similar to other oil distillates. 

TABLE 12. Sterol Composition of Rice Oil Deodorizer Distillate (20). 

Refined oil usually retains little phospholipid, but damaged beans can have a significant content of phosphatidic acid, and the amount of iron in the oil is related to the amount of phosphorus (24). During deodorization, considerable amounts of sterol and tocopherol may be removed from the oil. The proportion removed depends on deodorization conditions, but a 30% to 40% decrease is not unusual (25). Much of the hydrocarbons and squalene are lost to the deodorizer distillate as well. Free fatty acids in fully refined oil are required to be <0.05% and unsaponifiable matter < 1.5% (26). 

Deodorizer distillate is the material collected from the steam distillation of oils. It is a mixture of free fatty acids (especially during physical refining) tocopherols, phytosterols and their esters, hydrocarbons, and hpid oxidation products. The quality and composition of deodorizer distillate depends on the feedstock oil composition and processing conditions. Tocopherols and sterols are the most valuable components that can be recovered from the distillate, and they are used in the nutrition supplement and pharmaceutical industries (201). Typical soybean deodorizer distillate contains about 33% unsaponifiable matters, of which 11% is tocopherol and 18% sterol (202). 

The preparation of high-purity tocopherols and phytosterols involves steps such as molecular distillation, adduct formation, liquid-liquid extraction, supercritical fluid extraction, saponification, and chromatography (175). The extraction of tocopherols from soybean oil deodorizer distillate by urea inclusion and saponification of free fatty acids resulted in good recovery of tocopherols (208). To improve the separation of sterols and tocopherols, Shimada et al. (209) used a lipase to esterify sterols with free fatty acids. Then the steryl esters and tocopherols were separated better by molecular distillation. Chang et al. (210) used supercritical fluid CO2 extraction to recover tocopherols and sterols from soybean oil deodorizer distillate. A patent by Sumner et al. (211) advocated treatment of the distillate with methanol to converted free fatty acids and other fatty acid esters to methyl esters that can then be removed by a stripping operation. Then separation of sterols and tocopherols could be carried out by molecular distillation. 

Part of the unsaponifiable matter (such as tocopherols, sterols, and sterolesters) is distilled together with the free fatty acids during deodorization/deacidification, as... 

Crude citrus seed oils need to be refined before use as edible oils. Only triacylglycerols, diacylglycerols, and polar lipids remain after degumming, refining, bleaching, and deodorization. However, trace amounts of phosphatides (lecithin) and plant sterols may also remain in the oil (37). 

Phytosterols are industrially isolated from the distillates, resulting from the deodorization of vegetable oils (1, 34—36). Phytosterols are sometimes hydrogenated to produce phytostanols (37). As the solubility of sterols and stanols is very low (< 1% at 25°C), it limits their application in food products. Esterification of sterol and stanols is, therefore, performed to make them fat-soluble and easy to incorporate in food products (37, 38). Two margarines containing 8-9% sterols (Becel Proactiv of Unilever) or stanols (Benecol of Raisio), in the form of esters, are now available in the markets in Europe and the United States. 

Tocopherols and (phyto) Sterols from Deodorizer Distillate... 

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. 

The use and value of deodorizer distillate is dependent on its composition. Deodorizer distillate is a complex mixture of tocopherols, sterols, esters of sterols, mixed fatty glycerides, hydrocarbons, and other materials contained in a substantial amount of fatty acids (104). If the material is high in unsaponifiable components, the tocopherols can be used in the manufacture of natural source vitamin E and sterols for drug manufacmre. The quality of the distillate is dependent on the feedstock oil composition, processing equipment, and operating conditions. 

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. 

Although the process is commonly named deodorization, it is actually a combination of three different effects on the oil (1) stripping Stripping of volatile components (free fatty acids, odorous compounds, tocopherols, sterols, and contaminants such as pesticides and light polycyclic aromatic hydrocarbons, etc.), (2) actual deodorization Removal of different off-flavors, and (3) temperature effect Thermal destruction of pigments and unwanted side reactions such as cis-trans-iso-merization, polymerization, conjugation, and so on. 

Free sterols are slightly less volatile than tocopherols (Figure 2). Deodorization of soybean oil under varying process conditions (temperature 220-260°C, low pressure 1.5 mbar and 1.5% steam) resulted in a 10-35% reduction of the total sterol content (20). This sterol reduction is totally attributed to the free sterol fraction because esterified sterols are not volatile under the conditions prevailing inside the deodorizer. In case of steam refining, an increase of the steryl ester content can sometimes be observed, probably because of a heat-promoted esterification reaction between free sterols and fatty acids (20). This phenomenon will not take place during deodorization of chemically neutralized oil because the initial FFA concentration is much lower in that case. 

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