Fat, fatty acids and fat soluble nutrients in fillet of farmed and wild Atlantic salmon (Salmo salar L.)

Abstract

One of the main reasons for the advise to consume more seafood is to obtain adequate dietary levels of long chain polyunsaturated fatty acids, eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). The recommended dietary intake of these fatty acids is between 0.2-0.5g/day, or consumption of at least two servings of fish, preferably fatty fish per week. The aquaculture industry today provides almost half of all fish and fish products consumed around the world. Traditionally, fish meal and fish oil have been the main ingredients in formulated feed used in intensive farming of marine and diadromous fish. Due to the rapid growth in aquaculture production, the demands for fish meal and fish oil has exceeded the supply, leading the industry to find other sources of protein and oils to satisfy the nutritional quality of the fish. It is now common to substitute some of the marine ingredients with vegetable meal and oil. Atlantic salmon (Salmo salar L.) is the major species in the diadromous group with Norway as the leading producer. In 2010, about one million tons were produced in Norway, accounting for approximately 68% of the world’s total production of farmed Atlantic salmon. The overall aim of this thesis was to evaluate human nutritional value of farmed Atlantic salmon produced in Norway with regard to the composition and content of fatty acids, astaxanthin and vitamin D3, and to compare with wild Atlantic salmon. The results showed that farmed Atlantic salmon had total lipid content of 11.4% which is twice the amount in wild Atlantic salmon. Furthermore, the content of EPA and DHA was 0.42g and 0.61g/100g fillet, respectively in farmed Atlantic salmon. In wild Atlantic salmon the total content of EPA and DHA were 0.19g and 0.36g/100 g fillet. The n-6/n-3 ratio was 0.37 and 0.07 in farmed and wild Atlantic salmon, respectively. The content of astaxanthin in farmed and wild Atlantic salmon was similar. Farmed Atlantic salmon had an average astaxanthin content of 5.2mg/g sample, while wild had an average content of 4.8mg/g sample. In determining the vitamin D3 content the results were very ambiguous, leading us to dismiss all data. However, the high fat content makes the farmed salmon an excellent source of these health promoting fatty acids. Dependent on the suggested daily requirement of EPA and DHA, 20-50g of farmed Atlantic fillet is sufficient to satisfy the daily needs. In addition the ratio between n-6 and n-3 is very low and well below the value often recommended by nutritional experts.