Applications to Food Analysis

Miller, Chromatography, Concepts Contrasts, John Wiley Sons, USA, 1988. 

Christian and J. E. O Reilly, Instrumental Analysis, Allyn Bacon, USA, 1986. 

Pavia et al.. Introduction to Organic Laboratory Techniques, 2nd edition, Saunders College Publishing, USA, 1982. 

Abbott and Andrews, An Introduction to Chromatography, Houghton Mifflin Company, Boston, 1965. 

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Table 13.2 summarises the different approaches used to construct enzyme electrochemical biosensors for application to food analysis based on the different types of enzymes available. Generally, the main problems of many of the proposed amperometric devices have been poor selectivity due to high potential values required to monitor the enzyme reaction, and poor sensitivity. Typical interferences in food samples are reducing compounds, such as ascorbic acid, uric acid, bilirubin and acetaminophen. Electrocatalysts, redox mediators or a second enzyme coupled reaction have been used to overcome these problems (see Table 13.2), in order to achieve the required specifications in terms of selectivity and sensitivity. 

HIGH-RESOLUTION CONTINUUM SOURCE AAS AND ITS APPLICATION TO FOOD ANALYSIS... 

Changes in the focus of SFE can be easily followed through its reported applications. Thus, in 1993 [3], environmental applications prevailed (45.9% versus 21.9% devoted to foods and 11.6% to industrial analyses). By 1996, however, SFE applications to food analysis had risen to 38%, environmental uses fallen to 41% and industrial analyses levelled off at 11% [48]. More recently [17], the extraction of food components (particularly fat) has become one of the major applications of SFE, so much so that the current boom in SF extractor sales has been ascribed to it. The book by Luque de Castro et al. [3] contains comprehensive tables of SFE applications in various fields. Also, one review of SFE in food analysis [148] includes four tables with applications involving the extraction of fat from various types of sample (viz. meat and animal products, fish, cereal, seed and animal feed, plants and vegetables). On a more specific level, Eller and King reviewed determinations of the fat content in foods [149]. Finally, the Analytical Chemistry issues devoted to reviewing techniques provide periodic updates on SFE and SFC [150]. 

S. Rezzi, C. GuiUou, F. Reniero, V.M. Holland, S. Ghelli (2004) Natural abundance H-NMR spectroscopy. Application to food analysis. In P.A. de Groot (ed.), Handbook of Stable Isotope Analytical Techniques, Vol. I, Elsevier B.V, Amsterdam, pp. 103-121... 

Treatment of ICPAES from different perspectives and to varying degrees of comprehensiveness appears in a number of chapters in volumes not solely dedicated to ICP-AES, but treating spectrometry and analysis in general. An early excellent chapter on ICP-AES is by Tschopel (1979) on plasma excitation in spectrochemical analysis, in Wilson and Wilson s Comprehensive Analytical Chemistry. A very brief historical introduction to ICP-AES, basic principles and considerations of absorption and emission lines, and applications to food analysis is in a book on modern food analysis (Ihnat (1984), and Van Loon (1985), in his practical analyst-oriented book on selected methods of trace analysis biological and environmental samples includes a chapter (pp. 19-52) on techniques and instrumentation including ICPAES. Moore (1989) (Introduction to Inductively Coupled Plasma Atomic Emission Spectrometry) provides... 

Tsuji, A Maeda, M. Recent advances in iiiununoassay and its application to food analysis. Shokuhin Eiseigaku Zasshi, 30 199-208. 1989. Japanese. 

A. Berna, Metal oxide sensors for electronic noses and their application to food analysis. Sensors 10, 3882-3910 (2010). doi 10.3390/sl00403882... 

Immunological methods in food analysis offer the intrinsic advantage of very high sensitivity and specificity, and of ease of automation. However, interferences from the complex food matrices and the requirement for sample preparation steps contribute to make their application to food analysis less straightforward than in other analytical fields. 

Schmid, E. R., Grundman, H. and Fogy, I. (1981) Determination of isotope ratios and their application to food analysis. Ernahrung, 10, 459. 

As it can be seen, the number of publications is enormous. The aim of this chapter, rather than attempting a systematic review of the field, is to show in a didactic manner the possibilities of electrochemical immunosensing for food analysis. There are some parts that could be found in other chapters of this book, such as, for example, the use of miniaturized electrodes, nanomaterials, or electrochemical techniques. However, a focus on the knowledge required for understanding their application to food analysis is always made, leaving a deeper treatment for those chapters. On the other hand, the reader can find many important references to the field in recent reviews, from the most general to the particular ones. Thus, recent trends in antibody-based sensors [2] (immunosensors) or smart electrochemical biosensors (from advanced materials to ultrasensitive devices)... 

Solid-phase sorbents are also used in a technique known as matrix solid-phase dispersion (MSPD). MSPD is a patented process first reported in 1989 for conducting the simultaneous disruption and extraction of solid and semi-solid samples. The technique is rapid and requires low volumes (ca. 10 mL) of solvents. One problem that has hindered further progress in pesticide residues analysis is the high ratio of sorbent to sample, typically 0.5-2 g of sorbent per 0.5 g of sample. This limits the sample size and creates problems with representative sub-sampling. It permits complete fractionation of the sample matrix components and also the ability to elute selectively a single compound or class of compounds from the same sample. Excellent reviews of the practical and theoretical aspects of MSPD " and applications in food analysis were presented by Barker.Torres et reported the use of MSPD for the... 

Capillary electrophoresis (CE) is a modem analytical technique that allows the rapid and efficient separation of sample components based on differences in their electrophoretic mobilities as they migrate or move through narrow bore capillary tubes (Frazier et al., 2000a). While widely accepted in the pharmaceutical industry, the uptake of CE by food analysts has been slow due to the lack of literature dedicated to its application in food analysis and the absence of well-validated analytical procedures applicable to a broad range of food products. 

So far, LSE is the most popular for extracting contaminants in food. However, over the last years LPME in its different application modes (single drop microextraction, dispersive liquid-liquid microextraction and hollow fiber-LPME) has been increasingly applied to food analysis because of its simplicity, effectiveness, rapidity, and low consumption of organic solvents. Different applications have been recently reviewed by Asensio-Ramos et al. [112]... 

Nowadays, a large number of applications are available therefore, in this chapter, a selection of more important and interesting ones will be presented. Particular attention will be paid to the official, reference or rontine methods, as well as to selected experimental approaches. The number of applications in food analysis is increasing at a rapid pace and it seems rather difficult to be exhaustive in this held. 

A number of criteria could be apphed to organize this chapter, depending on the point of view by which foods are considered. In this chapter, application of HPLC to food analysis will be described considering homogeneous classes of food components lipids, carbohydrates and related substances, proteins, peptides, amino acids, biogenic amines, phenolics, vitamins, and some selected contaminants. 

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. 

Detection of amino acids is typically by UV absorption after postcolumn reaction with nin-hydrin. Precolumn derivatization with ninhydrin is not possible, because the amino acids do not actually form an adduct with the ninhydrin. Rather, the reaction of all primary amino acids results in the formation of a chromophoric compound named Ruhemann s purple. This chro-mophore has an absorption maximum at 570 nm. The secondary amino acid, proline, is not able to react in the same fashion and results in an intermediate reaction product with an absorption maximum at 440 nm. See Fig. 5. Detection limits afforded by postcolumn reaction with ninhydrin are typically in the range of over 100 picomoles injected. Lower detection limits can be realized with postcolumn reaction with fluorescamine (115) or o-phthalaldehyde (OPA) (116). Detection limits down to 5 picomoles are possible. However, the detection limits afforded by ninhydrin are sufficient for the overwhelming majority of applications in food analysis. 

B Stancher, F Zonta. High performance liquid chromatographic determination of carotene and vitamin A and its geometric isomers in foods. Applications to cheese analysis. J Chromat 238.217-225, 1982. 

RA Williams, R Macrae, MJ Shepherd. Non-aqueous size-exclusion chromatography coupled online to reversed phase high performance liquid chromatography. Interface development and applications to the analysis of low-molecular weight contaminants andadditives in foods. J Chromatogr 477 315-325, 1989. 

JF Lawrence, C Van Buuren, UATh Brinkman, RW Frei. Use of ethylation for the gas and liquid chromatographic determination of linuron, diuron and metoxuron and two of its degradation products application to soil analysis. J Agric Food Chem 28 630-632, 1980. 

Several new methods and instruments based on infrared spectroscopy are being developed for food applications. Advances in spectroscopic instruments and data analysis have enabled the rapid and nondestructive analysis of cheese parameters in just a few seconds (e.g., Nicolet Antaris FT-NIR by Thermo Electron Corp.). Another recent development is the miniaturization of FTIR instrumentation, which would enable onsite analysis, while the cheese is being produced. The TruDefender FT handheld FTIR by Ahura Scientific, Inc. (Fig. 5.7) is a portable handheld spectrometer that could be applied to food analysis. With numerous developments in FTIR spectroscopy and several potential food analysis applications still unexplored, there is great research potential in this technique that could benefit the industry and research institutions. 

Watanabe, E., K. Baba, H. Eun, et al. 2006. Evaluation of performance of a commercial monoclonal antibody-based fenitrothion immunoassay and application to residual analysis in fruit samples. J. Food Prot. 69 191-198. 

Abad, A. and A. Montoya. 1997. Development of an enzyme-linked immunosorbent assay to carbaryl. 2. Assay optimization and application to the analysis of water samples. J. Agric. Food Chem. 45 1495-1501. 

It is worth stressing that everything that has ever been published on the application of AAS to food analysis can be done at least as well with HR-CS AAS. Since the same flames and burners, and the same type of electrothermal atomizers, are used in both systems, and only the spectrometer part from the radiation source to the detector has been re-designed, it is much more appropriate to talk about the improvements brought about by this change, and about the simplifications and the additional features that have become available this way. 

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