Fast-fase NMR-spektroskopi og MRI-studier av fettsyreprofiler direkte på fiskekjøtt. En sammenligning av oppdrettslaks og villaks

Abstract

The purpose of this project has been to determine the fat content, fat distribution and fatty acid composition in wild and farmed salmon using solid-state Nuclear Magnetic Resonance (NMR) spectroscopy and Magnetic Resonance Imaging (MRI). Rapid growth in the aquaculture industry over the past decades has, due to lack of enough marine resources, resulted in limited access to marine ingredients in the salmon feed. This has led to an increased use of alternative vegetable ingredients causing important long-chain marine ω-3-fatty acids like EPA and DHA to be replaced by shorter acyl chain fatty acids from vegetable oils like ALA. The composition of fatty acids in the salmon diet has shown to be reflected in the fatty acid composition of the filet, as well as affecting the fat profile in other parts of the fish. There is a lot of ongoing research on the use of alternative ingredients in the feed. For this purpose, effective and accurate analytical tools for control of salmon filet quality are required. The development of the feed composition causes a continuous change in quality and fatty acid composition in farmed salmon. Therefore, fast and direct techniques for analyzing salmon is of national and international interest. To quantify the fatty acids in salmon, it is important to have a precise analytical and quantitative method. In this project, solid-state 13^C NMR is used to verify a method that has recently been prepared to quantify the fatty acid composition in salmon. Further, solid-state 31^P NMR, both static and magic angle spinning, is used to investigate the phosphorous compounds in phospholipids in the salmon meat. MRI is used to investigate the fat distribution in the fillet and heart. Results showed that farmed salmon had a total fat content of 10%, twice the amount as in the wild salmon. Furthermore, the content of EPA and DHA is found to be 9.0% and 14.5% in the wild salmon, compared to 3.3% and 4.7% in farmed salmon, respectively. In addition, the farmed salmon contained 9,1% ALA. The phosphorus spectra showed differences in the phosphorous profiles of the salmons. The results from MRI showed differences in fat content and fat distribution in the fillets. In addition, MRI of the hearts of the salmons showed that the farmed salmon stored fat around the heart. The conclusion of this research is that there are significant differences in fat content, fat distribution and fat composition in farmed and wild salmon, and that solid-state NMR spectroscopy and MRI are reliable alternatives to current established methods