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This study was conducted to investigate the possibility of nondestructive evaluation of water soluble pectin (WSP) and methoxyl content in ´Fuji´ apple fruit. Samples were scanned over the range 1100∼2500 ㎚ using near∼infrared (NIR) reflectance spectroscopy (InfraAlyzer 500C). The relevant reference laboratory data were correlated with the spectra using the software SESAME. WSP was extracted from the alcohol insoluble solid (AIS) residues of fresh and stored apple fruits, and methoxyl content was measured by colorimetric method, titration, and gas chromatography, respectively. NIR spectra of AIS showed to be significant difference over the range 2000∼2400 ㎚ compared to apple fruit. The result of multiple linear regression analysis between physical firmness and NIR spectra of AIS showed good linearity and acceptable error. The standard error of prediction (SEP) was 0.088 ㎏ in the range of 0.89∼1.84 ㎏. The data indicated that fruit firmness was correlated to AIS. In contrast, low accuracy was obtained for the estimation of WSP content in apple fruit compared with that measured by the reference method. The ability of NIR to predict methoxyl content in AIS was found to be better than in apple fruit. Three wavelengths, 2248, 2264 and 2396 ㎚, seemed to be suitable for NIR analysis, SEP was 0.33% in the range of 4.01∼6.53%. In NIR spectra of both pectin powders and hydrated pectin solutions, it was observed that the absorption of sample in around 2250 ㎚ increased in proportion to methoxyl content. This result indicated that around 2250 ㎚ was characteristic bands of methoxyl group.
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