Authentication studies

Exa.mina.tlon, The technical examination of stone objects begins with the use of the low power stereomicroscope. This study yields information regarding toolmarks and, hence, cutting techniques, wear patterns, and wear of toolmark edges. Such information is clearly significant in authenticity studies, but also provides an insight into the skill and the tools of the carver. 

In practice, there are no great differences among the methods for extracting factors. Thus, PCA could be suggested in authentication studies because it is simply a mathematical transformation of the raw data. Figure 7.2 illustrates the case of monovarietal virgin olive oils characterized by volatile compounds described in the cluster paragraph. 

Assumptions need to be checked concerning these regression procedures prior to their implementation. For example, it is assumed that the residuals are distributed normally. However, it is always a good idea, before drawing any final conclusions, to review the distributions of the major variables of interest, in order to inspect the distribution of the residual values (distances of the samples from the estimated model). Furthermore, residuals are also useful for detecting outliers (abnormal data) that is of special interest in authenticity studies. 

Considerations When Designing a Food Authenticity Study 117... 

CONSIDERATIONS WHEN DESIGNING A FOOD AUTHENTICITY STUDY... 

In the following sections, an overview of some of the techniques commonly used in food authentication studies is given, along with an explanation as to why a particular technique (or combination of techniques) might be chosen. 

However, it is not just the presence or absence of an element that is useful (as most elements will be present at some concentration), but it is the relative variation in the trace element profile that is the parameter that provides the major discriminatory power. McHard et al. [16] were possibly some of the first researchers to apply a normalization procedure to multielement data in order to maximize the differences between two sets of samples. Their approach, which is now accepted as being a standard tool for use in chemometric investigations, was to identify an element whose concentration was constant, irrespective of the geographical origin of the samples, and then to normalize all other elemental data against it. In McHard s study on fruit juice, they used Zn. The authors of this chapter used Ca in an egg authenticity study, where eggshells were used as the sample matrix (unpublished data) and Mg was used in a study of Welsh onions [14]. 

Kelly and coworkers concluded that a combination of only seven (of the 50) elements measured, and the isotopic ratios of C and O, gave 100 percent discrimination between rice samples from any of the three continental land masses, and that measurement of just B and Mg was sufficient to allow a reasonable indication to be gained as to whether the rice had originated in the United States. This statement underlines the comment made in an earlier section of the chapter, regarding the importance of establishing the question-to-be-asked, or the answer-that-is-required, when designing an authenticity study. 

Finally, it should be noted that there are several other techniques that can provide data and are of great use when performing food authenticity studies, such as liquid... 

One of the main purposes of archaeological chemistry is to deduce history from the analysis and investigation of artifacts. Other major areas of importance include authenticity studies, identification of sources, deduction of production techniques, and dating. 

X-ray fluorescence analysis had been used for composition studies of various materials. Probably among the most important applications are research on metals and on inorganic pigments. Analyses similar to the ones I quoted are very helpful in authenticity studies and can aid the cosmetic industry, metallurgy, and so on. The demands archaeological chemistry made (nondestructiveness, small sample size, quick analysis, sensitivity) has helped significantly to develop x-ray fluorescence instrumentation. 

Crews, H.M. (1998) Trace element analysis for food authenticity studies. In Ashurst P.R. Dennis M.J. (Eds.) Analytical methods of food authentication. International Thomson Publ., pp 270-291. 

E. Richling, M. Appel, E. Heckel, K. Kahle, M. Kraus, C. Preston, W. Hummer, P. Schreier (2006, in press) Flavor authenticity studies isotope ratio mass spectrometry - perspectives and limits. ACS Symposia Ser. 

K. Hor, C. Ruff, B. Weckerle, T. Konig, P. Schreier (2001a) Flavor authenticity studies by H/ H ratio determination using on-line gas chromatography pyrolysis isotope ratio mass spectrometry. 1. Agric. Food Chem. 4 , 21-25... 

Radiocarbon dating was used in the authentication study of the Shroud of Turin. It is an essentially nondestructive technique and is valuable in estimating the age of historical artifacts. 

The origin and nature of the food material is of public concern for health and cultural reasons. Various DNA-based molecular techniques have been studied so far to accomplish the difficult task of determining the nature of foods. As a biological macromolecule, DNA offers more possibilities when compared to proteins in terms of testing advantages. First, DNA is more heat stable than many proteins therefore, it can endure many heat transfer-based operations. Second, DNA contains more data than proteins for many authentication studies. Additionally, DNA is found in many foods and can be analyzed through several weU-developed methods [49]. 

H/ H)i values of honey aguardentes point out that the honeys were probably made from C3 plants nectars, because they are similar to those of C3 plants and to those found in honey authenticity studies . ... 

POMODORO DIPACHINO AN AUTHENTICATION STUDY USING H-NMR AND CHEMOMETRICS - PROTECTING ITS P.G.I. EUROPEAN CERTIFICATION... 

Other application areas of non-destmctive /uXRF are in forensic science (spectral fingerprint), microelectronics (uniformity of deposited films - thickness and composition), and in art and archaeology (especially using handheld equipment). Historic iron gall inks used in handwritten manuscripts by Bach, Mozart and Goethe were characterised by /U.XRF [759]. The technique has developed into a significant analytical tool for authentication studies of artefacts. 

Trace levels of inorganic chemical species, e.g. lead, arsenic, cadmium, are aiso monitored in food stuffs, often using ICP-MS. The advantage of MS over AAS is that severai eiements may be measured simultaneously and the concentrations of individual isotopes may be measured, facilitating metabolism/ nutrient studies with stable isotope materials. Precise determination of isotope ratios (e.g. C, N and O) by IRMS is also important in agricultural and food authenticity studies. Accelerator mass spectrometry is used in tracer studies, for the determination of extremely low levels of carbon-14 (and other) isotopes. 

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