Application of chemometrics to low-field1H NMR relaxation data of intact fish flesh

Abstract

The possibilities for application of low-field 1H nuclear magnetic resonance (NMR) as a rapid method for simultaneous assessment of basic quality parameters in fish were explored. In a first experiment, 200 salmon (Salmo salar) samples mapping the variation over an entire fish were measured by NMR and subsequently analysed for oil or water content by standard chemical methods. In a second experiment, 58 differently thawed cod (Gadus morhua) samples were measured by NMR and subsequently analysed for water-holding capacity. Correlations between chemical data and NMR data were evaluated using partial least squares (PLS) regression on complete relaxation curves and compared with conventional regression models on exponential fitting parameters. Predictions on an independent test set were superior for the PLS regression models, with optimal prediction errors of 12 g kg−1, 6 g kg−1 and 3.9% for oil and water content in fresh salmon flesh and water-holding capacity in thawed cod flesh respectively. Thus rapid, non-invasive low-field NMR can be used to simultaneously determine both oil and water content of fish flesh. Furthermore, it can predict water-holding capacity of cod flesh, with an R2 of 0.9 over the range 30–90%, as determined by a centrifuge test. © 1999 Society of Chemical Industry