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Abstract
In 2010 the European Commission placed a limit on the amount of free formaldehyde in carrageenan and processed Eucheuma seaweed (PES) of 5 mg kg−1. Formaldehyde is not used in carrageenan and PES processing and accordingly one would not expect free formaldehyde to be present in carrageenan and PES. However, surprisingly high levels up to 10 mg kg−1 have been found using the generally accepted AOAC and Hach tests. These findings are, per proposed reaction pathways, likely due to the formation of formaldehyde when sulphated galactose, the backbone of carrageenan, is hydrolysed with the strong acid used in these conventional tests. In order to minimise the risk of false-positives, which may lead to regulatory non-compliance, a new high-performance liquid chromatography (HPLC) method has been developed. Initially, carrageenan or PES is extracted with 2-propanol and subsequently reacted with 2,4-dinitrophenylhydrazine (DNPH) to form the chromophore formaldehyde-DNPH, which is finally quantified by reversed-phase HPLC with ultraviolet light detection at 355 nm. This method has been found to have a limit of detection of 0.05 mg kg−1 and a limit of quantification of 0.2 mg kg−1. Recoveries from samples spiked with known quantities of formaldehyde were 95–107%. Using this more specific technique, 20 samples of carrageenan and PES were tested for formaldehyde. Only one sample had a detectable content of formaldehyde (0.40 mg kg−1), thus demonstrating that the formaldehyde content of commercial carrageenan and PES products are well below the European Commission maximum limit of 5 mg kg−1.
Graphical Abstract
Acknowledgements
The authors acknowledge Marinalg International for its support for the method development. In addition the authors would like to acknowledge Katja Søholm Hildebrandt and Ramzi Georgis Shlimon for the experimental work performed to achieve the results published in this article. Bettina Høj Hornshøj and Markus Klinger are DuPont employees. Sara Kobbelgaard was a DuPont employee when the method development work was carried out, but is now an employee at Teknologisk Institut. Markus Klinger is a member of the technical working group in Marinalg International. William Blakemore is owner and principal of Celtic Colloids Inc., a consulting company providing advice on hydrocolloids technology, including leadership on analytical methods development to private companies. For this method development work, William Blakemore was contracted by FMC Corporation (FMC) under a cost-reimbursable contract; and is a member of the technical working group in Marinalg International. Henrik Stapelfeldt is a CP Kelco employee and member of the technical working group in Marinalg International. Harris Bixler is the retired CEO of Ingredients Solutions Inc. (ISI) and formerly President of Marinalg International, a sponsor of this work. The research work detailed in this publication was carried out for Marinalg International. Marinalg International is a global organisation supporting the interests of seaweed farmers, consumers and the hydrocolloids industry. Its primary communication efforts include the delivery of sound science and technical expertise related to the safety and efficacy in the production and use of hydrocolloids from seaweed farms to family tables. It represents the regulatory interests of the seaweed-processing industry before various international bodies such as Codex Alimentarius, and national regulatory authorities including the European Food Safety Authority (EFSA), the US Food and Drug Administration (USFDA) and the US Department of Agriculture (USDA). CP Kelco, DuPont, FMC and ISI are manufacturers of carrageenan and processed Eucheuma seaweed (PES) products, and members of Marinalg International. The method development and validation reported in this paper is the professional work product of the authors. CP Kelco, DuPont, FMC and ISI were given the opportunity to review this paper and to offer comments on the content. Those comments did not alter the professional opinions of the authors. The authors have not appeared in any legal proceedings related to the findings reported in this paper. The conclusions drawn are not necessarily those of CP Kelco, DuPont, FMC or ISI.