Fat distribution analysis in salmon fillets using non-contact near infrared interactance imaging: a sampling and calibration strategy

An online NIR interactance imaging instrument was tested for fat distribution analysis in raw and salted salmon fillets. Approximately 3000 spectra were collected for each fillet when passing under the instrument on a conveyor bell (approximatety 1 s exposure). The instrument was calibrated using five cylindrical plugs (15mm diameter) from each fillet. The fat content was measured for each of these plugs using H-1-NMR spectrometry and the spectra from each plug region were averaged and used for calibration and validation. It was found that online NIR interactance imaging is well-suited for distributional fat analysis in raw and salted intact salmon fillets. The local sampling and calibration strategy using 15mm diameter plugs for reference analysis and spectral averaging was found to provide relevant information and robust models. The average prediction errors (root mean square error of cross-validation) for raw and salted fillets in combination were approximately 2% fat for local plug regions.