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Spectroscopic Evaluation of the Surface Quality of Apple

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  036013,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.15045) @2003
Authors:   Els A. Veraverbeke, Jeroen Lammertyn, Bart M. Nicolaï, Joseph Irudayaraj
Keywords:   apples, wax, quality, NIR spectroscopy, FTIR spectroscopy

Different spectroscopic techniques based on infrared and Raman, were used to evaluate the natural wax and related surface quality of apple fruit. Transmission near-infrared (NIR) spectroscopy was applied to solutions of single wax components and extracted apple wax. Fourier transform infrared (FTIR) spectroscopy was used for transmission measurements of wax films on NaCl crystals, diffuse reflectance spectroscopy (DRIFTS) was used to analyze wax powders and FTRaman was explored to examine intact wax layers on whole fruit. The natural wax layer of apple fruit from a maximum of three different cultivars (Jonagold, Jonagored, and Elshof) from three picking dates (early, commercial, and late), 3 CA storage durations (0, 4, and 8 months), and 3 shelf life periods (0, 1, and 2 weeks) within each storage duration were examined. Canonical discriminant analysis was carried out on the first derivative NIR and FTIR spectra to describe the information contained in the spectra. Discrimination between cultivars and between storage duration based on surface characteristics was achieved with reasonable accuracy from both the techniques. Information contained in the spectra of apples from different picking dates and shelf life periods was not significant. Differences between cultivars and storage periods in this analysis mostly related to differences in the number of aliphatic chains (e.g. alkanes and esters) and the presence of alpha farnesene. Raman and DRIFT methods did not provide satisfactory results.

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