Application of chemometrics to low-field H-1 NMR relaxation data of intactfish flesh

The possibilities for application of low-field H-1 nuclear magnetic resonan ce (NMR) as a rapid method for simultaneous assessment of basic quality par ameters in fish were explored. In a first experiment, 200 salmon (Salmo sal ar) samples mapping the variation over an entire fish were measured by NMR and subsequently analysed for oil or water content by standard chemical met hods. In a second experiment, 58 differently thawed cod (Gadus morhua) samp les were measured by NMR and subsequently analysed for water-holding capaci ty. Correlations between chemical data and NMR data were evaluated using pa rtial least squares (PLS) regression on complete relaxation curves and comp ared with conventional regression models on exponential fitting parameters. Predictions on an independent test set were superior for the PLS regressio n 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 capacit y 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, wit h an R-2 of 0.9 over the range 30-90%, as determined by a centrifuge test. (C) 1999 Society of Chemical Industry.