Development of a Common Calibration Model for Determining the Brix Value of Intact Apple, Pear and Persimmon Fruits by near Infrared Spectroscopy

Calibrations developed using near infrared (NIR) spectroscopy to determine the quality of fruits or vegetables are usually applicable to a single species. The ability to determine the quality of several species using a common calibration would have advantages in some situations. A method to develop a common NIR calibration model that could be applied to many fruit species was examined. NIR spectra of apples, pears and persimmons were measured in the short-wavelength region using an interactance method. Partial least-squares (PLS) regressions based on second-derivative spectra were performed for Brix-value determination using calibration samples comprising each fruit species independently and the three species combined. Each single species calibration model predicted the Brix value in validation samples of the same species with a low standard error of performance ( SEP) (0.34–0.40°Brix (°Bx) and with low bias (0.01–0.08 °Bx) but with much higher SEP and bias errors when used to predict the Brix value in other species. The common calibration model developed from the combined sample set predicted Brix values in the apples, pears and persimmons with an SEP = 0.43 °Bx and a bias of −0.03 °Bx.