ear-infrared (NIR) spectroscopy has been used for highly accurate measurement of the chemical composition of rice grain, including such constituents as moisture, protein, and amylose (Iwamoto et al., 1986;Natsuga et al., 1992;Villareal et al., 1994;Delwiche et al., 1995;Delwiche et al., 1996;Kawamura et al., 1997a;Sohn et al., 2004). However, to assess rice grain quality, in addition to chemical composition, various physicochemical properties of the rice must be analyzed. Several studies were previously carried out to estimate quality-related parameters such as fat acidity and the gelatinization characteristics of rice (Onda et al., 1994;Li and Shaw, 1997;Bao et al., 2001;Meadows and Barton, 2002). The physicochemical properties of rice are known to be correlated with its eating quality (Chikubu et al., 1985;Kawamura et al., 1997b;Windham et al., 1997;Barton et al., 2000;Mikami et al., 2000;Champagne et al., 2001;Meullenet et al., 2001).All common existing methods for measuring the physicochemical properties require some specific instruments and chemicals, and are labor-intensive or time-consuming. There is therefore intense interest in the rice breed improvement, culture, and production communities, as well as in the rice industry, for a quick and easy method to measure the physicochemical properties of rice. Although NIR spectros- The authors are Motoyasu Natsuga, ASABE Member Engineer, Associate Professor, Faculty of Agriculture, Yamagata University, Tsuruoka, Japan; and Shuso Kawamura, ASABE Member Engineer, Associate Professor, Agricultural Process Engineering Laboratory, Hokkaido University, Sapporo, Japan. Corresponding author: Motoyasu Natsuga, Faculty of Agriculture, Yamagata University, 1-23 Wakabamachi Tsuruoka, 997-8555 Japan; phone: +81-235-28-2906; e-mail: toko@tds1. tr.yamagata-u.ac.jp. copy is used for measuring rice constituent contents, a method for measuring the physicochemical properties using this technology has not yet been established.The objectives of this study were to: (1) develop VIS/NIR calibration models from brown rice and milled rice spectra to determine physicochemical properties of rice, and (2) validate the accuracy of the calibration models and determine whether VIS/NIR spectroscopy could replace various dedicated analytical methods.
MATERIALS AND METHODS
RICE SAMPLESFor this study, a total of 61 short-grain brown rice samples (at least 5 kg per sample) were collected from commercial varietal releases all over Japan. The samples consisted of 27 varieties of Japanese non-waxy rice. The brand names of the rice samples were