Writing in the Journal of the Science of Food and Agriculture, the scientists outline a new, commercially viable method of measuring the proanthocyanidin (PAC) content of cranberry products using an ‘improved’ version of the 4-dimethylaminocinnamaldehyde (DMAC) method.
In 2004 France became the first country to approve a health claim for the North American cranberry (Vaccinium macrocarpon) with at least 36mg of proanthocyanidins (PAC) to “help reduce the adhesion of certain E. coli bacteria to the urinary tract walls”, and subsequently fight urinary tract infections (UTIs).
Disagreement
There are several methods for measuring PACs that deliver vastly different results, however, and the major players in the cranberry industry are said to be unable to reach agreement.
PACs are also not exclusive to cranberries, but can be found in a range of foods, including green tea, grapes, apples, and chocolate. However, the main type of PACs in cranberry – called A-type PACs - are different from those in these other source – called B-type PACs. Only cranberry PACs may prevent bacterial adhesion.
Ronald Prior, PhD, from the US Department of Agriculture’s Agricultural Research Service (USDA-ARS) and lead author of the new study is hoping the industry will unite behind the new method.
“Universal adoption of this standard worldwide by the cranberry industry will allow producers to use one standard method to ensure accurate labelling of PAC levels in products, and aid consumers in selecting products with sufficient PAC levels to obtain bacterial anti-adhesion activity,” said Prior.
Method details
To evaluate the new method, Dr Prior and his co-workers obtained 11 samples of cranberry products, including five from American sources and six from Europe. The powdered samples were coded and sent off to five different analytical laboratories. Three labs were in the US, one was in France, and the other in China.
Using the BL-DMAC method, the researchers reported consistent results for PACs levels in the products.
“It is important to have an accurate, standard method for cranberry PAC quantification that can be performed quickly and inexpensively in any commercial lab,” said Prior. “In our study, we have shown that the BL-DMAC method is validated for this use. It utilizes a commercially available standard, which is vital to obtaining accurate results among different laboratories.”
Industry acceptance
The new method appears to stand an excellent chance of uniting the industry. Reacting to the study, Geoff Woolford, VP research and development for Ocean Spray Cranberries told NutraIngredients: “The multi-laboratory validation of DMAC assay is a great step towards providing a commercially available consistent method for quantification of PACs content for most cranberry samples.
“However, we should be cautious that cranberries do not get compared unfavourably with other PAC- containing foods. Samples with shorter, less complex PACS will result in higher values than cranberries due to the larger, complex mixtures and unique Type-A PACs found in cranberries,” he added. “It is important to understand how the choice of standards may enhance the accuracy of the method for samples with high or low molecular weight PACs.
“The development of this method provides a commercially available quantification method for a natural food product like the cranberry, and is a good tool for further advancement in cranberry flavonoid science,” added Woolford.
Dan Souza, director of sales and marketing for Decas Botanical Synergies told NutraIngredients that he was both “pleased and excited” by the development.
“The industry did their homework and assembled an A-list of cranberry experts from around the world to develop, validate and publish a method that works for the industry as a whole,” said Souza. “By all accounts the improved DMAC method is accurate, reliable, reproducible, cost-effective, less tedious/time consuming and the standard is commercially available.
“An industry standardized method will help ensure that formulators are developing products that offer an efficacious dose of cranberry. This is beneficial to the consumer who is typically purchasing cranberry products for their health benefits; such as support for UTI prevention and prostate health and want standardized efficacious products,” said Souza.
“I am hopeful that cranberry players worldwide will come together and embrace this method,” he added.
The initiative was also welcomed by Lallemand Health Ingredients. A spokesperson for the company said: “There has been much confusion over cranberry proanthocyanidin test methods on the European market. It is in the best interest of consumers that cranberry products contain an adequate dose of PACs to ensure the efficacy of the product.
“We therefore welcome the initiative from researchers and laboratories around the world to develop a method that can be used to compare the quantity of PACs in cranberry ingredients from different suppliers on an equal basis.”
Not everyone was supportive, however. David Tournay from France’s Tournay Biotechnologies, and president of Euracran, the European Association for the Valorization of Cranberry Extracts, told this website that when AFSSA granted the French health claim it did not validate the initial DMAC method and instead allowed the use of any published and validated method for assaying the PACs content of cranberry.
Of the methods available, said Tournay, Euracran judged the European Pharmacopoeia method as the best compromise.
Speaking as president of Euracran, Tournay said: “The fact that some want to improve the DMAC today - which can be understood as an acknowledgement of the shortcomings of the initial method - can be welcomed but could nonetheless be a problem because this method simply did not exist at the time of the publication of the health claim in France and cannot be used to support it now, and this is especially true as the other published and recognized methods for the determination of PACs existed prior to the French health claim.
“Now, concerning the results of this new BL DMAC, it seems that not all problems pertaining to previous DMAC assays have been fixed, and especially reproducibility (a strong feature of any validated analysis method) does not seem very much improved, with laboratories (some of the most reputed) finding huge differences between the same sample,” said Tournay.
“So it just seems to us that this new method - as it does not appear to be a major improvement and cannot supersede other validated methods – cannot represent a new standard and might just leave the cranberry industry more confused,” he added.
Source: Journal of the Science of Food and Agriculture
July 2010, Volume 90, Issue 9, Pages: 1473-1478, doi: 10.1002/jsfa.3966
“Multi-laboratory validation of a standard method for quantifying proanthocyanidins in cranberry powders”
Authors: R.L Prior, E. Fan, H. Ji, A. Howell, C. Nio, M.J. Payne, J. Reed