Siwalak Pathaveerat

Application of Near Infrared Spectroscopy for Indirect Evaluation of “Monthong” Durian Maturity

Durian contains thick rind which restricts light penetration into the pulp region. Indirect prediction of pulp dry matter as a reference of maturity was investigated using spectral information from the rind and stem. Partial least squares regression was performed to model variation in the pulp dry matter using the rind and stem absorbance. The rind model showed better performance in predicting the dry matter content than the stem model. However, the accuracy was relatively poor (correlation coefficient of prediction, rp = 0.76 and root mean square error of prediction, RMSEP = 1.82%) compared with that of the reference pulp model (rp = 0.83 and RMSEP = 1.61%). The rind model was superior to the stem model in the classification of durian samples into immature, early-mature, and mature classes based on the number of days after anthesis and the dry matter content. Effective wavelengths were chosen from the regression coefficients of the corresponding models and used to create a simplified classification model. A combination of both rind and stem spectral data at selected wavelengths provided the highest accuracy of classification (94.4%).