Discrimination between Glutinous and Non-Glutinous Rice by Vibrational Spectroscopy. I: Comparison of FT-NIR DRIFT,PAS and Raman Spectroscopy

Rice is a major cereal crop in Japan and in Asia. Its taste is determined by such factors as protein and water content as well as stickiness. It has been well established that protein and water content can be estimated by near infrared spectroscopic measurements. However, the measurement of amylose content, which is closely related to rice stickiness, at present, must be carried out by wet chemical methods. Vibrational spectroscopic techniques are possible alternative approaches for the determination of amylose content in rice and, in this paper, we report on the initial steps for the development of methodology for this purpose, namely on the comparison of FT-NIR DRIFT (Diffuse Reflectance Infrared Fourier Transform Spectroscopy), PAS (Photo-Acoustic spectroscopy) and FT-Raman spectroscopy for the discrimination of glutinous and non-glutinous rice. Perkin-Elmer System 2000 FTIR (equipped with DRIFT and PAS accessories) and System 2000 NIR FT-Raman spectrometers were used to collect spectra from ground samples of seven glutinous and 12 non-glutinous rice. When SIMCA (Soft Independent Modelling of Class Analogy) was used to classify raw spectral data, the best discrimination was achieved with the FT-Raman results followed by those from the PAS measurements. FT-Raman spectra of some samples of non-glutinous rice showed strong fluorescence effects. When these samples were excluded from analysis, modelling and classification improved.