PCA was executed on both the MSC- and SNV-preprocessed FT-IR spectral data to extract relevant information. However, the data might be classified according to moisture content or particle size, rather than their chemical composition characteristics, because the IR data patterns are determined by not only absorption characteristics but also scattering characteristics. These spectral variations were removed by oven drying all of the samples and pretreating the spectra with MSC- and SNVpreprocessing methods. Neither the MSC- nor the SNVpreprocessed FT-IR data were able to quantify the level of adulteration by means of data clustering using PCA. The data were scattered over a vast range, and no distinct separations among the data groups were found from the PCA score plot (data not shown). PCA is a popular primary technique for data clustering. It is not, however, optimized for class separability. The loading plots of the first three PCs are depicted in Figure 6.