Seed oil triacylglycerols

Jaarsma, J. and de Bruin, B. (1990) Fatty add composition at position sn-2 of seed oil triacylglycerols in high and low emdc add varieties of Brassica napus L. at different stages of seed development, in Plant Lipid Biochemistry, Structure and Utilization, eds. P.J. Quinn and J.L. Harwood, Portland, London, pp. 33-35. 

Figure 29 shows the separation of triacylglycerols from sunflower seed oil. In the analysis of linoleic acid-rich seed oils, well-shaped peaks are obtained, and excellent resolution of all the main fractions is achieved, with species containing linoleic acid being predominant. 

Fig. 29 Separation of triacylglycerols from sunflower seed oil by HPLC with a silver ion column and mass detection. For conditions see text. S = saturated fatty acid M = monounsaturated fatty acid D = di-unsaturated fatty acid.

Fig. 30 Silver ion high-performance liquid chromatography (Ag-HPLC-FID) with flame ionization detector (FID) analysis of the triacylglycerols of chromatographed Crepis alpina seed oil. Ag-HPLC-FID conditions 0.5-mg sample 5-micron Chromspher Lipids column (Chrompack International, Middelburg, The Netherlands) (4.6 X 250 mm) mobile phase 0.5% acetonitrile in hexane (v/v) flow rate 1.0 ml/min FID. Chromatogram peak triacylglycerol fatty acid abbreviations S, saturated (palmitic and stearic) O, oleic L, linoleic and Cr, crepenynoic fatty acids.

Figure 25.1. Proposed biosynthetic pathway of castor oil. Heavy arrows show the key enzyme steps driving ricinoleate into acylglycerols. Two arrows with solid bars show a complete block. Two dashed arrows show the phospholipase C hydrolysis which can be targeted to block the incorporation of non-hydroxyl fatty acids into triacylglycerols to increase presumably the content of ricinoleate in transgenic seed oils.

Safflower seed oil is a minor oil obtained from the seed of Carthamus tinctorius, grown particularly in India as a source of a valuable red-yellow or orange dye. Annual production of seed varies between 600,000 and 800,000. Normally it is a linoleic-rich oil ( 75% linoleic acid) with LLL (47%), LLO (19%), and LLS (18%) as the major triacylglycerols. An oleic-rich variety ( 74% oleic acid) has been developed and designated saffola (52). 

Sunflower seed oil is obtained from Helianthus annus grown mainly in the USSR, Argentina, Western and Eastern Europe, China, and the United States. The oil normally contains 60-75% of linoleic acid, >90% of oleic and linoleic acids combined, and virtually no linolenic acid. Its major triacylglycerols are typically LLL (14%), LLO (39%), LLS (14%), LOO (19%), LOS (11%), and other (3%). 

Sal fat (Shorea robusta). This tree, which grows in Northern India, is felled for timber. Its seed oil is rich in stearic acid, and it can be used as a cocoa butter equivalent (CBE). The major acids are palmitic (2-8%), stearic (35 8%), oleic (35 2%), linoleic (2-3%), and arachidic acid (6-11%). Its major triacylglycerols are of the SUS type required of a cocoa butter equivalent. Sal olein is an excellent emolhent, and sal stearin, with POP 1%, POSt 13%, and StOSt 60%, is a superior cocoa butter equivalent (122-124). It is one of the six permitted fats (palm oil, iUipe butter, kokum butter, sal fat, shea butter, and mango kernel fat), which, in some countries at least, can partially replace cocoa butter in chocolate (86). 

The fatty acid composition of soybean oil changes considerably with maturity and with seed oil deposition (15, 35, 43, 44). In typical soybean triacylglycerols, the palmitate and linolenate tend to decrease with maturity, whereas hnoleate increases. Oleate tends to increase to a maximum and then dechne slightly. Soybeans selected for atypical fatty acid compositions show quite different patterns of change with maturity from typical soybeans. 

Analyzed by thin layer chromatography, cmde citrus seed oils are reported to have eight classes of chemical constituents triacylglycerols, free fatty acids, diacyl-glycerols, monoacylglycerols, sterols, phospholipids, alcohols, and hydrocarbons... 

Table 6). Triacylglycerols are the major oil class in all citrus seed oils, followed by free fatty acids and then diacylglycerols. The presence of partial acylglycerols and free fatty acids is due to partial enzymatic hydrolysis of reserve triacylglycerols during seed storage (9). 

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). 

Linoleic (>30%), oleic (>18%), and Unolenic (2-12%) acids are the most predominant unsaturated fatty acids present (9). Lemon, lime, and citron oils contain the highest amount of linolenic acid. In addition, very small amounts of myr-istoleic acid (C14 l) in polar lipids fraction, myristoleic (C14 l) and palmitoleic (C16 l) acids in diacylglycerols fraction, and myristoleic (C14 l) and eicosaenoic (C20 l) acids in triacylglycerols fraction of citms seed oil were also identified (39). 

There is considerable interest in the chemical composition and properties of citrus oils and essences as well as the role they play in food and nonfood industries. Citrus peel oils and essences possess a pleasant aroma, with oxygenated compounds being the major constituents that account for their characteristic odor. Terpenes, the most abundant components in cold-pressed citms peel oil, are removed in concentrated oil production, usually by use of adsorbant and supercritical carbon dioxide, to increase the concentration of oxygenated compounds and to enhance the qualification of the oil. Meanwhile, citms seed oils are composed largely of triacylglycerols and are rich in oleic and linoleic acids. 

Jahaniaval, F., Kakuda, Y., and Marcone, M. (2000). Fatty add and triacylglycerol compositions of seed oils of five amaranthus accessions and their comparison to other oils. ]. Am. Oil Chem. Soc. 77(8), 847-852. 

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