Food analysis quantitative data

H. Marse, C. Visscher, L. WiUemsens, and M. H. Boelens, Volatile Compounds in Food Qualitative and Quantitative Data, Vol. II, TNO-CIVO, Food Analysis Institute, A. J. Zeist, The Nethedands, 1989, pp. 661—679. 

Nijssen, L. M., Ed., Volatile Compounds in Food, Qualitative and Quantitative Data, 7th Edition, Division for Nutrition and Food Research TNO, Institute CIVO— Analysis TNO, Zeist, The Netherlands, 1996. 

Among the several pnrposes of food analysis, the two main objectives are to verify authenticity and quality of food. The latter may be applied both in the evaluation of nutritional value (in this case, quantitative data are mandatory) and peculiar characteristics (age, applied technology, origin, etc.). In any case, useful information can be obtained as thorough knowledge of food composition is available. 

Nijssen LM, Visscher CA, Maarse H, Willemsen LG (1996) Volatile Compounds in Food— Qualitative and Quantitative Data. TNO-CIVO Food Analysis Institute, Zeist... 

Maarse, H. and Visscher, C.A. 1989. Citrus fruits. Products 5. In Volatile Compounds in Food. Quantitative and Qualitative Data, TNO-CIVO, pp. 35-99. Food Analysis Institute, Ziest, The Netherlands. 

In food and flavor analyses, the accuracy of the quantitative data required from MS/MS may be limited by the variability of the sample itself. In analysis of a large number of samples, MS/MS provides a quick indication of the amounts of catpounds of interest. If variability falls outside of a preset tolerance, then only those sanples are flagged for more exhaustive workup and a more rigorous quantitative analysis. This ability to focus analytical resources on sanples of interest is a valuable property of the MS/MS experiment. 

H. Maarse and C. A. Visscher Volatile Compounds in Food - Qualitative and quantitative Data. Vol. I-III, 6th Edition TNO-CIVO Food Analysis Institute Zeist, 1989... 

This chapter will focus on the appHcation of FTIR spectroscopy in the quantitative analysis of foods. Following a brief discussion of the fundamental principles of IR spectroscopy, we wiU describe the instrumentation, data handling techniques, and quantitative analysis methods employed in FTIR spectroscopy. We will then consider the IR sampling techniques that are most useful in FTIR analysis of foods. Finally, a survey of FTIR applications to the quantitative analysis of food will be presented. Although important, the so-called hyphenated techniques, such as GC-FTIR, will not be covered in this chapter. Similarly, near-IR (NIR) spectroscopy, which has found extensive use in food analysis, is beyond the scope of this chapter. 

While as a technique, CE is stiU in a state of evolution, it is clear from this Hterature that it has a futirre in analysis of substances from complex matrices, such as food. Part of adaptation to CE is a learning experience. Since CE is an electrophoretic technique, while elution times may vary more than that of HPLC, mobihties should be a constant under defined conditions. Reporting the effective sample mobHity will give good reproducibihty in a well optimized system [67, 83, 84]. The situation of area reproducibility was addressed by those who reported quantitative data by the use of an internal standard, in many cases [70, 77, 82]. 

Maarse, H. Visscher, C.A., Eds. Volatile Compounds in F Qualitative and Quantitative Data. SixA edition. Volume I. TNO-CIVO Food Analysis Institute The Netherlands, 1989 p 387. 

In this chapter, the phenolic composition and content of regularly consumed fruits and vegetables are extensively discussed through the analysis of the current relevant literature, in order to provide a comprehensive summary of the current compositional and quantitative data on some flavonoid-rich foods. Furthermore, the formal relation of the in vitro antioxidant potential of these fruits and vegetables to the quality of the phenolic and, to a lesser extent, vitamin C content is emphasized. The potential for antioxidant activity of flavonoid-rich fruits and vegetables in vivo is also discussed. The data described here allow identification of the potentially most effective fruits and vegetables in terms of phenolic content and antioxidant activity. However, much research is still needed the elucidation of the metabolism and bioavailability of flavonoids in vivo, as well as of the amounts and the forms in which they are taken up into cells and tissues, is cmcial in order to establish the mechanisms and the forms in which dietary phenolics may act in vivo [58]. Finally, it... 

The voltanmietric electrochemical techniques discussed in this chapter are widely used in food sample analysis. While linear sweep and CV are preferred for exploring electron transfer reaction mechanisms, pulse techniques are used to achieve better detection and quantification limits of organic and inorganic species in food analysis. Together, these techniques can provide not only quantitative data but also important kinetic and thermodynamic information regarding the electron transfer processes of the complex food matrix. 

It is of course of interest to determine which of the methods of quantitation provides the most accurate and precise quantitative data. It is equally important to consider the constant trade-off for precision and sensitivity. At very low concentrations, precision often becomes limited by extraneous factors, such as wall effects. In such cases, high-precision measurements are becoming virtually unobtainable. In analogy to the Quantitative Ingredient Declarations (QUID) in food analysis, which require statements as to the uncertainty of the measurement and the variability of the results (sampling ), also for industrial polymer analysis intra- and interlaboratory variation and the meaning of average analytical results needs to be established. It is the responsibility of the analyst to adequately describe the instrumentation and performance to duplicate the repeatability and accuracy of the developed method. 

However, most of the time, due to the complexity of the food samples and the need to minimize the sample treatment, that is, the chemical separation of the interferences from the compounds of interest, more powerful instrumental measurements, such as 2D spectroscopies, for example EEM fluorescence spectra, or hyphenated separation techniques, for example gas chromatogra-phy/MS (GC/MS), HPLC/DAD or HPLC/MS, are used. As mentioned in previous sections, obtaining a data table per sample is a much more natural scenario for the application of MCR techniques. In these instances, the typical strategy is to perform the simultaneous analysis of data tables related to standards of known concentration together with tables from unknown samples, in which the concentration(s) of the analyte(s) are determined. Either using multiset analysis or multiway analysis, these determinations benefit from the so-called second-order advantage, which means that analytes can be determined in the presence of interferences, even if those are absent from the calibration samples [48]. The reason why this second-order advantage exists is that MCR techniques describe the information of the compounds in separate concentration profiles and spectra, that is, they make a mathematicar separation of the information related to aU compounds in the analysed sample, analytes and interferences. Afterwards, only the information of the profiles related to the analytes is used for quantitation purposes. 

Work starts with the analysis of the aroma composition and is completed when the aroma of the food can be simulated in an appropriate matrix on the basis of the quantitative data obtained. The last step is essential and validates the analytical results (78). Recently published data on stewed beef (79) and coffee brew (80) impressively demonstrate the potential of this approach. However, a crucial... 

Because of peak overlappings in the first- and second-derivative spectra, conventional spectrophotometry cannot be applied satisfactorily for quantitative analysis, and the interpretation cannot be resolved by the zero-crossing technique. A chemometric approach improves precision and predictability, e.g., by the application of classical least sqnares (CLS), principal component regression (PCR), partial least squares (PLS), and iterative target transformation factor analysis (ITTFA), appropriate interpretations were found from the direct and first- and second-derivative absorption spectra. When five colorant combinations of sixteen mixtures of colorants from commercial food products were evaluated, the results were compared by the application of different chemometric approaches. The ITTFA analysis offered better precision than CLS, PCR, and PLS, and calibrations based on first-derivative data provided some advantages for all four methods. ... 

As in the case in the analysis of food samples, the introduction of relatively inexpensive MS detectors for GC has had a substantial impact on the determination of methylxanthines by GC. For example, in 1990, Benchekroun published a paper in which a GC-MS method for the quantitation of tri-, di-, and monmethylxanthines and uric acid from hepatocyte incubation media was described.55 The method described allows for the measurement of the concentration of 14 methylxanthines and methyluric acid metabolites of methylxanthines. In other studies, GC-MS has also been used. Two examples from the recent literature are studies by Simek and Lartigue-Mattei, respectively.58 57 In the first case, GC-MS using an ion trap detector was used to provide confirmatory data to support a microbore HPLC technique. TMS derivatives of the compounds of interest were formed and separated on a 25 m DB-% column directly coupled to the ion trap detector. In the second example, allopurinol, oxypurinol, hypoxanthine, and xanthine were assayed simultaneously using GC-MS. 

High-performance liquid chromatography (HPLC) is one of the premier analytical techniques widely used in analytical laboratories. Numerous analytical HPLC analyses have been developed for pharmaceutical, chemical, food, cosmetic, and environmental applications. The popularity of HPLC analysis can be attributed to its powerful combination of separation and quantitation capabilities. HPLC instrumentation has reached a state of maturity. The majority of vendors can provide very sophisticated and highly automated systems to meet users needs. To provide a high level of assurance that the data generated from the HPLC analysis are reliable, the performance of the HPLC system should be monitored at regular intervals. In this chapter some of the key performance attributes for a typical HPLC system (consisting of a quaternary pump, an autoinjector, a UV-Vis detector, and a temperature-controlled column compartment) are discussed [1-8]. 

To perform quantitative analyses of food using NIR, it is necessary to initially establish a calibration equation which relates spectral data to objective chemical data. Multiple linear regression (MLR) analysis is typically used to make a calibration equation using a calibration sample set analyzed accurately by a conventional chemical method. The general calibration equation can be written as ... 

---