Calibration transfer of intact olive NIR spectra between a pre-dispersive instrument and a portable spectrometer

•Intact olive calibrations were transferred from off-line to on-line near infrared spectroscopy instruments.•Calibration transfer was demonstrated with SBC, PDS and TOP strategies.•The TOP strategy was successful for transferring fat, moisture content, and free acidity calibrations.•Ten standardization samples were sufficient to perform a suitable data transfer.

The recent development of new portable devices enables the establishment of NIRS technology at industrial setting (on-line). However, the numerous existing NIRS databases based on a particular parameter, have been constructed with laboratory instruments (off-line), which have required a considerably effort in terms of time, labor and costs. For this reason, the transfer of calibrations between devices of different characteristics is a clearly crucial step. In this study, three different standardization algorithms: Slope/Bias Correction (SBC), Piecewise Direct Standardization (PDS) and Transfer by Orthogonal Projection (TOP) were tested and evaluated for transferring olives quality databases between an off-line NIRS monochromator (FOSS NIRSystem 6500) and a portable NIRS diode-array spectrometer (CORONA 45 visNIR). The results obtained showed that the use of TOP yielded the best Standard Error of Prediction (SEP) values for the fat content (1.97%) and free acidity (2.52%) parameters, while PDS for moisture content (2.24%). These results suggest that good calibration models for quality evaluation in intact olives can be obtained, based on spectral databases transferred between diverses NIRS spectrometers.