The method involves an enzyme digestion, extraction with ethanol:dichloromethane and determination by reversed phase HPLC with a visible light absorbance detector.
In an international collaborative study conducted at 11 laboratories, the results of which will be published in the Sept-Oct issue of the Journal of AOAC International, the method was found to be a valid way of measuring both trans- and total beta carotene in a wide range of vitamin types, including vitamin tablets, softgels and capsules.
However its performance on a beadletted raw material was deemed "unsatisfactory" as there was a greater variation between the results from the 11 laboratories than is acceptable for an analytical study.
Ed Waysek of Caravan Products, chairman of the ERP for beta carotene, told NutraIngredients-USA.com: "This may have been because of inhomogeneity of the beadlets, or a too-small sample size."
He said that another study is already underway to examine the problem, and develop techniques for handling dietary supplements containing such beadlets.
Carotenoids are particularly sensitive to light and oxygen, so they are not sold as pure crystals but as a suspension in oil, or in dry form, sometimes beadletted. This both protects them and gives formulators greater flexibility when using them.
Although the precise means by which beadletted beta carotene will be validated is dependent on the results of the additional study, Waysek said that he expects it will be an adapted version of the main beta carotene method. The difference is likely to be in the first step - the sampling and dispersal of beadlets prior to extraction, the sample size, or the enzyme used to break apart the beadlet matrix.
He added that, until the development of this new method, devised by J Schierle, J Klipfel and B Pietsch at DSM, it was very difficult to separate beta carotene from the other carotenoids with which it generally occurs, such as lutein, zeaxanthin and astaxanthin.
Beta carotene is just one of the 20 ingredients for which the AOAC's Dietary Supplements Task Force program is developing standards under a five-year contract with the National Institutes of Health, Office of Dietary Supplements, and the FDA's Center for Food Safety and Applied Nutrition.
Since the contract began in September 2001, methods have been drawn up and validated for ephedra, beta-carotene and glucosamine, and standardized tests for ginkgo, saw palmetto, omega-3 and 6 fatty acids, chondroitin and SAMe are among those nearing completion.