Determination of sweetness for fresh-cut mango processing using near infrared spectroscopy (NIR)

The aim of this study was to determine the potential of near infrared (NIR) spectroscopy for predicting total soluble solids (TSS) as related to sweetness of fresh-cut mango for processing. Mango cv. Golden Nam Dokmai was selected. The matured fruits were treated prior to NIR measurement. Forty matured fruits were ripened for nine days at ambient temperature. Ten fruits were taken for the experiment on days 5, 7, 8 and 9 after ripening. NIR spectra of each fruit were scanned for both sides from 700-1100 nm using a portable NIR. After measuring the NIR spectrum, total soluble solids (TSS), titratable acidity (TA), and firmness of the same region where spectrum was measured were determined using conventional destructive methods. Subsequently, sugar-acid ratio (TSS/TA) was calculated. The NIR spectra (original and mathematically pretreated), the physical and chemical data were subjected to multivariate calibration techniques using Partial Least Squares (PLS). The best correlation was observed for TSS with R=0.9, SEC=0.6 and SEP=0.8 when Savitzky-Golay smoothing (Left and Right averaging: 14, polynomial order: 2) was applied to the spectra. Therefore, NIR has high potential for raw material inspection in terms of sweetness for production of fresh-cut mango.