Rapid assessment of quality parameters for frozen cod using near infrared spectroscopy

Near infrared diffuse reflectance spectra were recorded from the skin of 11 5 thawed whole cod (Gadus morhua) of varying quality. In fish fillets from the same fish four frozen fish quality parameters (water holding capacity, concentration of total volatile nitrogen bases, dimethylamine, and formalde hyde) were determined. A principal component analysis showed that the four quality parameters were strongly correlated with each other. Partial least squares (PLS) regression models based on full spectra and on principal vari ables, respectively, were compared with respect to prediction ability towar ds the water holding capacity. PLS models based on only seven principal var iables of the 459 measured variables gave models with the same prediction a bilities as the full spectrum model. The high water content in fish is a ma jor limitation in the use of NIR analysis for the determination of chemical quality parameters in fish tissue. However, NIR-reflectance measurements p rovide an acceptable determination of the water holding capacity and so of other raw material properties.