Nondestructive Analysis of Litchi Fruit Quality Using FT-NIR Spectroscopy

A non-destructive optical method based on near-infrared spectroscopy has been used for the evaluation of litchi fruit quality. Diffuse reflectance measurements (12500–3600 cm-1), physical, and biochemical measurements were performed individually on 100 litchi fruits of cv. Shahi cultivar harvested at different ripening stages. Relationships between spectral wavelengths and quality attributes were evaluated by application of chemometric techniques based on partial least squares (PLS) regression. The fruit set was divided into two groups: 60 fruits for calibration and 39 for validation. Good prediction performance was obtained for pH, soluble solids, and titratable acidity with correlation coefficients of 0.96, 0.91 and 0.94 respectively and root mean square errors of prediction of 0.009, 0.291ºBrix and 0.011% malic acid respectively. For the other quality traits such as vitamin C and color the prediction models were not satisfactorily accurate due to the high error of calibration and prediction.