Near infrared spectroscopic evaluation of fruit maturity and quality of export Thai mango (Mangifera indica L. var. Namdokmai)

Mango fruit var. Namdokmai were harvested from tagged trees at 91-119 days from full bloom at weekly intervals. Selected fruit were subjected to near infrared spectroscopy (NIRS) in reflectance mode at short wavelength of 700-1100 nm at 2 nm increments and calibrated to give predicted brix value (NIRS value). Fruit weight, firmness and dry matter content (DMC) were measured. At the ripe stage, peel and pulp color, total soluble solids (TSS), titratable acidity (TA), TSS:TA ratio and sensory taste were determined. To assess the predictability of maturity and quality parameters, linear regression models were developed. NIRS value increased with increasing fruit maturity, showed high coefficient of determination (R² = 0.88), and was positively correlated with DMC (R² = 0.96) and negatively correlated with fruit firmness (R² = 0.99). NIRS values also predicted TSS of ripe fruit with 99% accuracy. Other quality parameters had lower predictability values of 70-84%, except for fruit weight and L* values of the peel and pulp, which had no or weak correlation with NIRS values. Based on the results, optimum harvest maturity was reached at 105-112 days from full bloom (DAFB). The present harvest maturity recommendation (91-105 DAFB) needs to be revised to reduce heterogeneity in fruit maturity and quality from the same harvest and increase quality outturn. The results further provide strong basis of the utility of NIRS facility in continuous fruit packing line as a component of the quality assurance system.