Study backs CO2 extraction technique for higher quality fish oils

20 Oct 2011

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The use of supercritical carbon dioxide for the extraction of omega-3 oils could boost quality by removing heavy metal contaminants and reducing oxidation during processing, according to a team of Spanish researchers.

The study, published in the Journal of Food Engineering, reports on the potential of supercritical fluid extraction as an extraction method rather than current techniques, claiming that it may be useful for reducing oxidation.

The Spanish researchers noted that the technique could also help to remove free fatty acids and improve fish oil quality, as an alternative to physical and chemical refining procedures.

“Comparison of the oils obtained by supercritical fluid extraction over freeze-dried fish by-products and by other methods carried out in the laboratory (cold extraction, wet reduction and enzymatic extraction), shows that supercritical fluid extraction may be a useful method to prevent lipid oxidation, especially in fish oils rich in omega-3 such as salmon oil, and, to reduce significantly the amount of certain pollutants such as some arsenic species,” said the authors, led by Dr Sagrario Beltrán, from the University of Burgos, Spain.

The research team noted that the extraction process used to obtain omega-3 rich oils has been also shown to be important to obtain the best oil quality regarding lipid oxidation, pollutants content and sensory properties.

“In addition, the extraction method may not only affect the oil extraction yield and quality, but also the quality of the fish protein or fish meal obtained, which has also a great interest as add value ingredient,” they noted.

Beltrán and his colleagues added that extraction with supercritical carbon dioxide (CO2) has been proposed as a good method for obtaining fish oil with a high amount of omega-3 fatty acids, “since it involves the use of a nonoxidant atmosphere and mild temperatures, which prevent the oxidation of the polyunsaturated fatty acids.”

Study details

Beltrán and his team compared supercritical fluid extraction (SFE) to conventional fish oil extraction processes such as cold extraction (CE), wet reduction (WR) and enzymatic extraction (EE), using four different fish byproducts supplied by Pescanova (a Spanish fish company located in Pontevedra, Spain).

Fish by-products were characterized by determining their water, protein and fat content, and the amount of trace metals present. Extracted fish oil was then characterised and profiled to assess its chemical and sensory properties.

The researchers reported that SFE with carbon dioxide under moderate conditions of 25 MPa and 313 K “may be useful for reducing fish oil oxidation.” They also noted that in the case of hake off-cuts and jumbo squid livers, the only successful method for obtaining oil was SFE, as the other methods did not provide enough oil for the oil characterisation and quality comparison to be made.

Beltrán and his colleagues added that SFE “is an advantageous process for obtaining oil from freeze dried, low fat, fish by-products and can prevent lipid oxidation and reduce extraction of certain pollutants.” However, the team noted that the success of a SFE method is highly dependent on the quality and freshness of the raw material and, in some cases, coupling a subsequently deodorization step would be required.

Source: Journal of Food Engineering