Sterol degradation products

The precision of the Padley and Timms (1980) and Young s (1984) procedures has been improved by the incorporation of data derived from sterol degradation product analysis which helps to identify the type of fat present and therefore narrows the range along the C54-C50 band in which the fat falls (Macarthur el al., 2000). These improvements to the method have been proposed for adoption into the Codex standard (Codex Alimentarius Commission, 2001). 

Crews, C., Calvet-Sarret, R. and Brereton, P. (1997) The analysis of sterol degradation products to detect vegetable fats in chocolate. J. Am. Oil Chem. Soc., 74(10), 1273—1280. 

In some cases where extreme refining conditions have been used, complete removal of the sterols, both free and esterified, may occur (Grob et al., 1994). By removing the sterols from an oil in this way, it is possible to prepare an adulterant that is undetectable by sterol analysis. As with adulteration of virgin olive oil with refined olive oil, this type of adulteration may be detected by analysis of sterol degradation products. 

Naturally occurring fats contain small amounts of soluble minor consituents pigments (carotenoids, chlorophyll, etc.), sterols (phytosterols in plant fats, cholesterol in animal fats), vitamin A (from carotenes), vitamin D (calciferol), waxes (esters of long-chain alcohols and fatty acids), ethers, and degradation products of fatty acids, proteins, and carbohydrates. Most of these minor compounds are removed in processing, and some are valuable by-products. 

Grob, K., Artho, A. and Mariani, C. (1992) Determination of raffination of edible oils and fats by olefinic degradation products of sterols and squalenes, using coupled LC-GC. Fat Sci. Technol., 94, 394-400. 

Valuable minor components Fat degradation products Contaminants Tocopherols, sterols, squalene, oryzanol Trans-fatty acids, polymeric and oxidized triacylglycerols, cyclic fatty acids Pesticides, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, dioxins, furans ... 

Triacylglycerols (acyl easters of glycerols) constimte nearly 99% of cmde vegetable oils. The remaining components include phospholipids, FFAs, pigments, sterols, carbohydrates, proteins, and their degradation products (2). 

Because of die difficulties in creating optimal inhibitoiy concentrations, do you think that incubation of a culture of sterol degrading oiganisms in the presence of cholesterol and inhibitor will lead to the production of a single steroidal product ... 

The quaHty, ie, level of impurities, of the fats and oils used in the manufacture of soap is important in the production of commercial products. Fats and oils are isolated from various animal and vegetable sources and contain different intrinsic impurities. These impurities may include hydrolysis products of the triglyceride, eg, fatty acid and mono/diglycerides proteinaceous materials and particulate dirt, eg, bone meal and various vitamins, pigments, phosphatides, and sterols, ie, cholesterol and tocopherol as weU as less descript odor and color bodies. These impurities affect the physical properties such as odor and color of the fats and oils and can cause additional degradation of the fats and oils upon storage. For commercial soaps, it is desirable to keep these impurities at the absolute minimum for both storage stabiHty and finished product quaHty considerations. 

Sterols are seldom detected in archaeological residues due to their low concentration and the tendency to undergo chemical degradation. In any case, the presence of sterols or of their oxidation products in a sample can help distinguish between animal and plant lipid materials cholesterol is the most abundant animal sterol, while campesterol and sitosterol are the two major plant ones. 

Prokaryotes do not synthesize sterols. Instead they create hopanotds, which have four six-membered carbon rings and one five-membered ring (Figure 22.8f). They provide rigidity to cell membranes and are very stable. Because of their widespread use by microbes and their resistance to degradation, they are well preserved in sediments and petroleum deposits, making them the most abundant natural products on Earth. 

The example of a total extract composition of a tropical soil from the Amazon, Brazil, shows mycose as the major compound, numerous other monosaccharides, lipid components such as fatty acids and fatty alcohols, and natural product biomarkers (Fig. 9a). The mycose and elevated levels of the other saccharides reflect the efficient fungal/microbial degradation of plant detritus in the tropics. This can be compared to the saccharides in the soil from an almond orchard in California, where glucose and mycose are the main sugars with lipids, sterols and triterpenoids (Fig. 9b, ). 

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