Chemically specific lipid requirements

Should the need arise in the future for emulsions containing any specific lipids it is likely that this requirement can be met. It is to be noted that the main ingredients of fat emulsions which have been teste in humans are not chemically pure, as for example when egg lecithin and soybean oil are used. Again in the future, it may become desirable to use pure or even synthetically produced lipids however, at present costs alone forestall their use. 

Although analytical procedures based on GC/MS analysis usually involve a relatively long analysis time, requiring a wet chemical pretreatment of the samples, they are unsurpassed in their capacity to unravel the molecular composition of the lipids used in works of art and in archaeological findings at a molecular level. In addition to obtaining a qualitative molecular profile, GC permits quantitative or semi-quantitative measurements on specific molecules. 

Some basic food analytical methods such as determination of °brix, pH, titratable acidity, total proteins and total lipids are basic to food analysis and grounded in procedures which have had wide-spread acceptance for a long time. Others such as analysis of cell-wall polysaccharides, analysis of aroma volatiles, and compressive measurement of solids and semi-solids, require use of advanced chemical and physical methods and sophisticated instrumentation. In organizing the Handbook of Food Analytical Chemistry we chose to categorize on a disciplinary rather than a commodity basis. Included are chapters on water, proteins, enzymes, lipids, carbohydrates, colors, flavors texture/ rheology and bioactive food components. We have made an effort to select methods that are applicable to all commodities. However, it is impossible to address the unique and special criteria required for analysis of all commodities and all processed forms. There are several professional and trade organizations which focus on their specific commodities, e.g., cereals, wines, lipids, fisheries, and meats. Their methods manuals and professional journals should be consulted, particularly for specialized, commodity-specific analyses. 

The brief discussion above shows the difficulty of a straightforward paleoenvironmental assessment based on OSC. Their occurrence seems not to be related to any special type of environment on the contrary, they are widespread. However, several of the encountered compounds cannot be related chemotaxonomically to specific biological contributions yet, because information on the lipid composition of appropriate organisms is still scant. Nevertheless, it is clear that much information is contained in the extractable OSC, information which is not evident when only the aliphatic hydrocarbon fraction is investigated. Furthermore, high-molecular-weight sulfur species not directly amenable to GC-MS analysis is another source of information, but chemical treatment (desulfurization) is required for its disclosure. 

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