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An improved method for the determination of pectin degree of esterification (DE) by diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) was developed. Pectin samples with a range of DE as determined by gas chromatography were used for developing a calibration curve by DRIFTS. A linear relationship between the DE of pectin standards and FTIR peak ratio for ester carboxyl peak area to total carboxyl peak area was found (R(2) = 0.97). Pectin DE of various samples was calculated from the linear fit equation developed by DRIFTS. Accuracy of the DRIFTS method was determined by comparing the DE values of four commercial pectins obtained by DRIFTS methods to the values obtained by the gas chromatography method. Greater precision was obtained for the FTIR measurement of test pectin samples when the ester peak ratio was used relative to the ester peak area.

The volatile components of commercially milled head and broken rice samples and the effect of water washing on volatile components were investigated over 30 d of storage at 37°C and 70% relative humidity. Pentanal, pentanol, hexanal, pentylfuran, octanal, and nonanal were the major volatile components identified by gas chromatography-mass spectrometry (GC-MS) analysis in both head and broken rice samples. The concentration of volatile components was greater in broken rice than in head rice and increased significantly during the storage period for both rice types. Water washing was found to be effective in reducing the volatile components for both head and broken rice.

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