Instantaneous quantitative and qualitative assessment of pear quality using near infrared spectroscopy

A comparative study was made of the performance of different spectrophotometers as part of a research into the potential of NIR reflectance spectroscopy as a non-destructive method for predicting soluble solid content, firmness and postharvest shelf-storage time in intact pears. Three commercially available spectrophotometers were used: a scanning monochromator (SM) of 400–2500 nm, a combination of diode array and scanning monochromator (DASM) of 350–2500 nm and a diode array (DA) of 900–1700 nm. A total of 332 pears (Pyrus communis L.) cv. ‘Blanquilla’ and ‘Conference’ were used to develop calibration models in different spectral regions, using various spectral signal pretreatments. Models to predict soluble solid content yielded coefficients of determination (r2) ranging from 0.39 to 0.76, and a standard error of cross-validation (SECV) of between 0.59 and 1.49 °Brix, depending on the instrument used. Models for predicting firmness yielded r2 values of between 0.45 and 0.79 and SECVs ranging from 5.33 to 7.36 N. Subsequently, the ability of these instruments to classify fruit as a function of postharvest shelf-storage time (0, 6 and 8 days) was tested using partial least squares discriminant analysis (PLS-DA), which yielded percentages of correctly classified samples (ratio of correctly classified samples to total samples) ranging from 81.1 to 94.4%, depending on the instrument used. The results obtained highlight the potential of these NIR instruments for assessing internal quality indices and predicting postharvest storage duration in pears, particularly when the instruments SM and DASM were used.