Improving Raman spectroscopic differentiation of the geographical origin of rice by simultaneous illumination over a wide sample area

This research substantially improved the differentiation of rice of two geographical origins utilizing a wide area illumination (WAI) scheme capable of collecting Raman spectra of a large sample area (28.3 mm 2 ) synchronously without sample rotation. For the purposes of comparison, we also employed a conventional scheme in which the laser illuminated only small areas. Principal component analysis (PCA) was used to differentiate the two geographical origins using the Raman spectra collected through both the conventional and the WAI schemes. The WAI scheme exhibited improved differentiation, primarily due to the fact that the WAI scheme could efficiently produce Raman spectra with a more reliable sample representation, as well as better reproducibility. The spectral feature obtained using the conventional scheme appeared to be more variable; however, this variation resulted more from unsuccessful sample representation than from an actual change in the sample composition. We conclude that the WAI scheme has a good potential for the analysis of diverse agricultural samples that consist of solid granules.