Lipids analytical methodology

The first two sections of this book provide the reader with a background on the thermal generation of aromas. Included in these sections are perspectives on the regulatory aspects and the analytical methodologies at the forefront of aroma research. Subsequent sections present original research on aromas derived from various food sources. In addition, we have included a section on mechanistic studies to provide insights into aroma formation through thermal decomposition of lipid, carbohydrate, and amino acid precursors. The final section is entirely... 

The development of objectionable flavor compounds by oxidation has significant detrimental effects on consumer acceptability of edible oils. In the last four decades, much progress has been made in the chemistry of volatile products of lipid oxidation, mainly as a result of advances in separation techniques and analytical methodology, particularly gas chromatography-mass spectrometry. 

How do chemical analyses of foods differ from analyses used in chemistry, biochemistry and biology The same methods and techniques are often used only the purpose of the analysis may differ. But foods are to be used by people. Therefore, methodology to determine safety (presence of dangerous microbes, pesticides, and toxicants), acceptability (flavor, odor, color, texture), and nutritional quality (essential vitamins, minerals, amino acids, and lipids) are essential analyses. Current Protocols in Food Analytical Chemistry is designed to meet all these requirements. 

Several new methodologies have been developed in recent years for the surface analysis of lipids. These methods allow direct detection of lipids from surfaces such as tissue sections and intact cells without prior extraction and thus enable the determination of spatial distribution of the lipids. There are three basic requirements for the surface analysis. The analytes of interest must be desorbed from the surface by the interaction of a sampling probe such as spray, laser, or plasma. The desorbed analytes must first be ionized and then... 

One limitation of LC-MS/MS methodology is that compounds in the sample extract, typically lipids, can affect the initial ionization of the analyte. This is referred to as matrix effects and can either enhance or suppress the electrospray ionization, leading to considerable inaccuracies in both qualitative and quantitative analyses [96, 97]. As such, the cleanup methodology employed, especially when working with biological samples, is of the utmost importance. In addition, the use of mass-labelled internal standards and matrix-matched standards, can minimize matrix effects [93, 94]. 

The importance of zinc to growth and development in all forms of life was first established through zinc deficiency studies of microorganisms followed by those in plants and animals see Nutritional Aspects of Metals Trace Elements) The involvement of zinc in a wide variety of metabolic processes including carbohydrate, lipid, protein, and nucleic acid synthesis and degradation paralleled the technical advances in analytical methods that could detect the presence of zinc in minute amounts coupled with advances in the methodology for protein isolation and purification. 

The determination of the sites of the C—C double bonds in unsaturated fatty acid derivatives and other lipids plays an outstanding role in the analytical application of mass spectrometry. Much work has been published on the localization of double bonds in monoolefins, and a number of extensive reviews has appeared on the topic . Two major methodologies have been employed. In the first one, unsaturated C—C bonds are converted to appropriate derivatives by synthesis in the liquid phase, which are then subjected to mass spectrometric analysis mostly by using standard El techniques. These methods will be mentioned only briefly in the next section, including some recent work which has not yet been mentioned in the reviews. The second methodology takes advantage of the bimolecular reactivity of neutral olefins with ionic reagents in the gas phase,... 

The nature of environmental samples often requires a clean-up step between sampling and the application of the analytical method. There are a variety of clean-up procedures available, most of which can be implemented in an automated fashion (see Chapters 3 and 4), in both segmented and unsegmented flow-methods, robotic methods and HPLC. Liquid-liquid and solid-liquid extraction [12-14], filtration [14,15], dialysis [12,15], evaporation [12,13], low-temperature precipitation of lipids and column-switching methods [16] are all cleanup methodologies of proven efficiency with environmental samples. 

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