Compositional analysis, of foods

TABLE 11.1 Compositional Analysis of Foods and the Preferred Analytical Technique ... 

R. S. Kirk and R. Sawyer, Pearson s Composition and Analysis of Foods, Longmans Scientific and Technical Books, Essex, U.K., 1991, p. 537. Y. Pomeianz and C. E. Meloan, Food Analysis, Von Nostiand Reinhold, New York, 1987, p. 708. 

Near infrared spectroscopy (NIRS), a technique based on absorption and reflectance of monochromatographic radiation by samples over a wavelength range of 400-2500 run, has been successfully applied for food composition analysis, for food quality assessment, and in pharmaceutical production control. NIRS can be used to differentiate various samples via pattern recognitions. The technique is fast and nondestructive method that does not require sample preparation and is very simple to use compared too many other analytical methods such as HPLC. The drawback of NIRS, however, is that the instrument has to be calibrated using a set of samples typically 20-50 with known analyte concentrations obtained by suitable reference methods such as FIPLC in order to be used for quantitative analyses. Simultaneous quantification of the... 

HPLC analysis of food proteins and peptides can be performed for different purposes to characterize food, to detect frauds, to assess the severity of thermal treatments, etc. To detect and/or quantify protein and peptide components in foods, a number of different analytical techniques (chromatography, electrophoresis, mass spectrometry, immunology) have been used, either alone or in combination. The main advantages of HPLC analysis lie in its high resolution power and versatility. In a single chromatographic run, it is possible to obtain both the composition and the amount of the protein fraction and analysis can be automated. 

Kirk, R.S. and Sawyer, R. 1991. Person s Composition and Analysis of Foods, 9th ed. Logman Scientific Technical, Essex, England. 

Sample preparation is probably the most important step in any analytical procedure. Poor preparation of lipid samples will only yield inferior or questionable results. Some commonly performed sample-preparation procedures for gas-liquid chromatographic (GC) analysis of fatty acids in food samples are introduced in this unit. Since the introduction of gas chromatography in the 1950s, significant progress has been made in fatty acid analysis of lipids however, fatty acid methyl esters (FAMEs) are still the most commonly used fatty acid derivative for routine analysis of food fatty acid composition. 

The application of ion-pair HPLC in the analysis of food colors is summarized on Table 8. As indicated, TBA has been the most widely used ion pair. It can be observed that using gradient mobile phase elution, a larger number of synthetic dyes can be separated. However, the mobile phase programming should include a return to the initial condition as well as reequilibration of the column by maintaining the initial composition for a period of time. This procedure provides reproducible result (222). 

More than 20 years ago K.H. Norris first introduced near infrared spectroscopy as a powerful technology in the field of composition analysis of cereals [1]. However, classical spectroscopists did not want to recognize its potential. This tendency still persists but there is no doubt that NIR is now an established technique for characterization of food and provides a convenient analytical tool for quality and process control. 

Gramshaw, J.W., and Vandenburg, H.J., 1995. Compositional analysis of thermoset polyester and migration of ethylbenzene and styrene from thermosct polyester into pork during cooking. Food Add. and Contam. 12, 2, 223-234. 

Another application of ICP-MS in the area of food safety is the evaluation of food contact materials. Q [86] and TOF [87] mass spectrometers have been employed in the compositional analysis of paper and board material intended for food contact. Studies on the migration of metals from food contact plastics using food simulants and ICP-MS detection have also been reported. One of them showed how to analyze different simulants without the need of any time-consuming preparation, that is, aqueous acetic acid (3 percent w/v) directly, aqueous ethanol (15 percent v/v) after proper dilution, the olive oil simulant following emulsion preparation by means of tetralin and Triton X-100 [88]. 

Source Adapted from Hedrick, H.B. et al., Principles in Meat Science, Kendall-Hunt Publishing Co., Dubuque, 1994 Kirk, R.S. and Sawyer, R., Pearson s Composition and Analysis of Foods, Longman Science, London, 1991 Renner, E., Cheese Chemistry, Physics and Microbiology, Vol. 1, Fox, P.F., Ed., Chapman Hall, London, 1993, 557 Sikorski, Z.E., Seafood Raw Materials, WNT, Warsaw, 1992 Tamime, A.Y. and Robinson, R.K., Yoghurt Science and Technology, CRC Press, Boca Raton, FL, 1999. 

One of the first major texts on the composition of foods was that of Konig, Chemie der menschlichen Nahrungs- und Genussmittel, which first appeared in 1879 and was republished in several editions. Other early texts considering this topic were Blyth s Manual of Practical Chemistry—The Analysis of Foods and the Detection of Poisons (1879), later revised as Blyth and Blyth, Foods Their Composition and Analysis and that of Tibbles, Foods, Their Origin, Composition and Manufacture. ... 

The fats and oils obtained from various sources differ from one another in the proportion of the several esters present in each. This difference in composition results in a difference in physical properties, such as specific gravity, viscosity, index of refraction, and melting point. All the fats and vegetable oils are soluble in ether, however,—a fact made use of in the analysis of foods to separate fats from the other constituents of food-products. As the physical properties of a fat or an oil obtained from a definite source are more or less constant, the determination of these properties is of value in the analysis of such substances. The chemical analysis of fats and oils is based upon determinations of the proportion of unsaturated compounds present, of the relation between the acids of low and high molecular weight obtained on hydrolysis, and of the proportion of substances which do not undergo hydrolysis. This statement will be made clearer by a brief consideration of a few of the more important methods employed in the analysis of fats and oils. 

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