Assessment of internal quality attributes of mandarin fruit. 1. NIR calibration model development

The utility of near infrared spectroscopy as a non-invasive technique for the assessment of internal eating quality parameters of mandarin fruit ( Citrus reticulata cv. Imperial) was assessed. The calibration procedure for the attributes of TSS ( total soluble solids) and DM ( dry matter) was optimised with respect to a reference sampling technique, scan averaging, spectral window, data pre-treatment ( in terms of derivative treatment and scatter correction routine) and regression procedure. The recommended procedure involved sampling of an equatorial position on the fruit with 1 scan per spectrum, and modified partial least squares model development on a 720 - 950-nm window, pre-treated as first derivative absorbance data ( gap size of 4 data points) with standard normal variance and detrend scatter correction. Calibration model performance for the attributes of TSS and DM content was encouraging ( typical R-c(2) of > 0.75 and 0.90, respectively; typical root mean squared standard error of calibration of < 0.4 and 0.6%, respectively), whereas that for juiciness and total acidity was unacceptable. The robustness of the TSS and DM calibrations across new populations of fruit is documented in a companion study.