Enhancing near infrared spectroscopy models to identify omega-3 fish oils used in the nutraceutical industry by means of calibration range extension

Abstract

The high demand for omega-3 fish oil nutraceuticals (dietary supplements) is due to the numerous health benefits contributed by the polyunsaturated fatty acids. The nutraceutical industry is required to follow good manufacturing practice standards in order to ensure label claims and prevent adulteration. It is vital that the quality control procedures will be able to detect adulterated products. It is thus necessary to ensure that the analytical techniques are adequate by using validated methods. The qualification or identification of natural fish oils is a difficult task due to overlapping concentration ranges of polyunsaturated fatty acids and other similar properties. Gas chromatography is the prescribed technique in the nutraceutical industry for analysis of omega-3 fatty acids, but it is time-consuming and costly. Near infrared spectroscopy is a rapid and cost-effective technique which can replace the prescribed method if it is proven to be equivalent, through validation, to the criteria as prescribed by the pharmacopoeias and other industry guidelines. In this study, near infrared spectroscopy in combination with chemometrics was considered as an alternative method to gas chromatography to identify various commercial fish oils and to quantify the polyunsaturated fatty acids. Identification methods were developed for nine commercial omega-3 fish oils by using spectral libraries. Quantitative near infrared methods were developed for arachidonic acid, docosahexaenoic acid and eicosapentaenoic acid in fish oils expressed as mg.g⁻¹ as well as % area using partial least squares regression and independent validation by superimposing datasets with mutual properties. Based on the statistics in terms of standard error of calibration, R², standard error of prediction and r of the polyunsaturated fatty acid models, the near infrared method was equivalent to the prescribed gas chromatography methods, and precision results obtained were also within the prescribed criteria. Near infrared spectroscopy and chemometrics can be used for conclusive identification and quantification of omega-3 fish oils, thereby minimizing the risk of adulteration. The method also complied with the prescribed pharmaceutical method validation criteria, and therefore was proven as an alternative method to gas chromatography for the nutraceutical industry.