Giving fish oil the laser treatment

Scientists at Plant & Food Research and the University of Otago have laid the foundation for a new quality control method for testing omega-3 and other health-enhancing polyunsaturated fatty acids (PUFA) in soft gel capsules, such as those used in fish oil supplements.

The researchers explored Raman spectroscopy as a means for establishing the concentration of PUFA in capsules, testing the consistency of this concentration across individual capsules, and distinguishing oil that may have become oxidised beyond acceptable limits.

Raman spectroscopy involves directing a laser at the target material, in this case the capsule and oil, and measuring the small fraction of light that is scattered. The scattered light provides a fingerprint of the chemical composition of the oil as well as other useful information

The researchers used eleven brands of PUFA oil capsules commonly available on New Zealand shelves, which included five fish oil and six omega-3 concentrate brands.

“Our analysis of Raman spectral variance allowed us to generate models for a range of saturated, monounsaturated and polyunsaturated fatty acids,” says Plant & Food Research Marine Products Scientist Dr Daniel Killeen.

“Although the sample size was relatively small, the preliminary results strongly suggest that the method is a useful tool for rapid quality control of soft gel capsules without compromising the structure of the capsule itself.

“Interestingly, in performing our research, we found the concentration of omega-3 oils across all eleven commercially available samples to be in-line with their label claims, which should give consumers reassurance regarding the quality of the oil in the capsules.”

The study also revealed that Raman spectroscopy could be used to distinguish capsules where the oil may have become oxidised to an unacceptable level.

“Polyunsaturated oils are vulnerable to oxidation, especially at higher temperatures and when exposed to UV radiation. Some studies have associated oxidised fish oil with negative health outcomes,” says Dr Killeen.

The researchers filled empty capsules with oil that had been deliberately oxidised and compared the results with the unoxidised oil in the purchased capsules.

“We found Raman spectroscopy to have high sensitivity for distinguishing fresh oils from those that had been oxidised. This positions the method as a faster, more direct and more sensitive way to identify oxidation in fish oils than other approaches,” says Dr Killeen.

“The deficiency of polyunsaturated fatty acids, such as omega-3 in the Western diet has created a high global demand for dietary supplements, such as fish oil. This makes rapid and effective quality control methods highly desirable to give consumers assurance and help producers in markets with strict regulations.”

The research has been published in the Journal of Agricultural and Food Chemistry.