Determination of the total lipid and the long chain omega-3 polyunsaturated fatty acids, EPA and DHA, in deep-sea fish and shark species from the North-East Atlantic

Kuzey-Doğu Atlantik derin deniz balık ve köpekbalığı türlerinde total lipid, uzun zincirli çoklu doymamış omega-3 yağ asitleri, EPA ve DHA’nın belirlenmesi

Özet

Tüketilmeyen 22 derin deniz balığı türünde yağ ve uzun zincirli çokdoymamış omega-3 yağ asitleri (uzun zincirli ω-3 PUFA) analiz edilmiştir. Total lipid içeriği hızlı ekstraksiyon tekniği ile belirlendimiş. Bu teknik anhydrous sodyum sülfat kullanarak balıktaki nemi immobilize etme ve dokulardan yağın heptan kullanılarak 80-85°C$Box$de çıkarılması prensibine dayanmaktadır. Heptan ekstraktı, NaCl camları arasında sıvı bir hücre içinde IR spektrofotometrede analiz edilmiştir. Ekstraktın lipid içeriği IR spektrofotometrik ester bandında 1700 ve 18000 cm-1 aralığında belirlenmiştir. Heptan evapore edildikten sonra, kalıntı gravimetrik olarak belirlenirken, IR ve gravimetrik ölçümler (yeterli ham yağ örneği miktar olduğunda) genel olarak benzer bulunmuştur. 18 balıkta lipid içeriği

Abstract

The lipid and long chain omega-3 polyunsaturated fatty acid (LC ω-3 PUFA) contents of spot samples of 22 under-utilised species of deep-sea fish were determined. The total lipid content was determined by a rapid extraction technique which used anhydrous sodium sulphate and ethanol to immobilise the moisture in the fish tissue followed by extraction of lipid with hep-tane at 80-85°C. The heptane extract was analysed in a liquid cell between NaCl windows on an infra-red (IR) spectrophotometer. Lipid content of the extract was calculated from the area of the IR spectrophotometric ester stretching band between 1700 and 1800cm-1. After evapora-tion of the heptane, the residue was determined gravimetically. The IR and gravimetric (where sufficient crude lipid quantities were present) results were generally in good agreement. Eigh-teen fish had lipid contents < 1.1g/100g, ranging from 0.18 (birdbeak dogfish, Deania calceus) to 1.1g/100g (forkbeard, Phycis blennoides), while four had lipid contents ranging from 4.25 (Baird’s smoothead, Alepocephalus bairdii) to 16.2g/100g (snake mackerel, Nessiarchus nas-sutus). However, both snake mackerel and orange roughy (Hoplostethus atlanticus) produced IR spectra consistent with the literature findings that they contain high levels of undigestible wax esters. The ω-3 PUFA, eicosapentaenoic acid (C20:5ω-3, EPA) and docosahexaenoic acid (C22:6ω-3, DHA) were determined using capillary gas chromatography. As a source of dietary ω-3 PUFA, the low-fat fish were generally poor suppliers with amounts ranging from 0.04g/100g (birdbeak dogfish) to 0.29g/100g (greater argentine, Argentina silus) but several species were not substantially inferior to cod (Gadus morhua). The two high lipid species containing large amounts of wax esters, although having appreciable levels of ω-3 PUFA would not be desirable from a dietary point of view. In most of the fish DHA was present at 3 to 6 times the level of EPA.