Spectrum Descriptive Analysis

F ure 1.1 Analysis of the spectrum of methodological options for sensory descriptive analysis. 

The development of rapid sensory profiling methods may have potential consequences on sensory activities themselves, since it broadens the spectrum of available methods and opens way for measurements that were previously not possible. Besides offering new opportunities in the use of sensory data in R D and research projects, this development may also have an organizational impact on sensory services and their relationships with stakeholders. As a result of this evolution, the practice of sensory descriptive analysis certainly becomes richer but also more complex and challenging. 

There are six or seven other descriptive analysis methods described in the sensory literature. The methods include Flavor Profile (CairuCTOSS and Sjdstrom, 1950) or its current version. Spectrum Analysis (Meilgaard et al., 2006), Texture Profile (Brandt et al., 1963), Free Choice Profiling (Williams and Arnold, 1985), and its successor Hash Descriptive Analysis (Dairou and Sieffermann, 2002). There are other methods described in the literature, but all appear to be based on methods previously described. 

Conventional descriptive analysis, such as Quantitative Descriptive Analysis (QDA) or Spectrum, has been successfully implemented and used for years in many food companies as a standard measurement tool to assist product development. When we decided to implement sensory analysis methods in our company in 2001, we soon realized that we faced several constraints that made the implementation of such methodologies rather difficult in our situation. 

One possibility for this was demonstrated in Chapter 3. If impact theory is still valid in a moderately dense fluid where non-model stochastic perturbation theory has been already found applicable, then evidently the continuation of the theory to liquid densities is justified. This simplest opportunity of unified description of nitrogen isotropic Q-branch from rarefied gas to liquid is validated due to the small enough frequency scale of rotation-vibration interaction. The frequency scales corresponding to IR and anisotropic Raman spectra are much larger. So the common applicability region for perturbation and impact theories hardly exists. The analysis of numerous experimental data proves that in simple (non-associated) systems there are three different scenarios of linear rotator spectral transformation. The IR spectrum in rarefied gas is a P-R doublet with either resolved or unresolved rotational structure. In the process of condensation the following may happen. 

To reduce intensity effects, the data were normalized by reducing the area under each spectrum to a value of 1 [42]. Principal component analysis (PCA) was applied to the normalized data. This method is well suited to optimize the description of the fluorescence data sets by extracting the most useful data and rejecting the redundant ones [43]. From a data set, PCA assesses principal components and their corresponding spectral pattern. The principal components are used to draw maps that describe the physical and chemical variations observed between the samples. Software for PCA has been written by D. Bertrand (INRA Nantes) and is described elsewhere [44]. 

The quantitation of products that form in low yields requires special care with HPLC analyses. In cases where the product yield is <1%, it is generally not feasible to obtain sufficient material for a detailed physical characterization of the product. Therefore, the product identification is restricted to a comparison of the UV-vis spectrum and HPLC retention time with those for an authentic standard. However, if a minor reaction product forms with a UV spectrum and HPLC chromatographic properties similar to those for the putative substitution or elimination reaction, this may lead to errors in structural assignments. Our practice is to treat rate constant ratios determined from very low product yields as limits, until additional evidence can be obtained that our experimental value for this ratio provides a chemically reasonable description of the partitioning of the carbocation intermediate. For example, verification of the structure of an alkene that is proposed to form in low yields by deprotonation of the carbocation by solvent can be obtained from a detailed analysis of the increase in the yield of this product due to general base catalysis of carbocation deprotonation.14,16... 

William Frederick Meggers. Physicist at the U. S. Bureau of Standards since 1914. Chief of die spectroscopy section. Author of many papers on optics, astrophysics, photography, measurement of wave-length standards, and description and analysis of spectra. The instrument in the foreground is a concave grating spectrograph, used for photographing the emission spectrum of rhenium (41). 

Chapter 3 presents methods of describing targets for vulnerability analysis and again covers a wide spectrum of military targets. A number of computer programs for target description are discussed... 

A complete description of the translational motion-internal motion coupling and its effects is, in principle, contained in eqs. (11-29), (11-30), and (11-31). Unfortunately, even for the simplified form of hypothetical molecular spectrum studied by Rice, McLaughlin, and Jortner, it has not yet been possible to perform the indicated quadratures. Even without actual calculation, our previous analysis of the theory of radiationless processes suffices to define the following general properties of the photo-dissociative act ... 

If there is no interaction between similar reactants (traps) B, they are distributed according to the Poisson relation, Ab (r, t) = 1. Besides, since the reaction kinetics is linear in donor concentrations, the only quantity of interest is the survival probability of a single particle A migrating through traps B and therefore the correlation function XA(r,t) does not affect the kinetics under study. Hence the description of the fluctuation spectrum of a system through the joint densities A (r, ), which was so important for understanding the A4-B — 0 reaction kinetics, appears now to be incomplete. The fluctuation effects we are interested in are weaker here, thus affecting the critical exponent but not the exponential kinetics itself. It will be shown below that adequate treatment of these weak fluctuation effects requires a careful analysis of many-particle correlations. 

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