ISC programme aims to calibrate stevia purity testing methods

03-May-2011 - Last updated on 04-May-2011 at 12:33 GMT

The International Stevia Council has launched a new, independent proficiency testing programme (PTP) for stevia products, which is intended as a benchmark to ensure analytical methods used to determine composition and purity yield accurate results.

Stevia sweeteners have leapt to the forefront of food and beverage formulators’ toolkits in the last three years, since the first FDA GRAS (generally recognized as safe) notifications were received in the United States in late 2008, for extracts with a purity of rebaudioside-A exceeding 97 per cent.

The FAO/WHO JECFA committee has also established an acceptable purity level of 95 per cent of the nine named steviol glycosides on a dry basis, which has been used as the basis of the Australian and New Zealand approval.

In addition, approval in the European Union is expected this year; the European Food Safety Authority (EFSA) gave a positive safety opinion on stevia sweeteners based on the JECFA specifications a year ago.

However the ISC, the industry association for stevia sweetener processors, manufacturers and marketers formed last autumn, there are a wide variety of analytical methods and reference standards being used by industry to determine steviol glycoside content – and the quality of these is not consistent across the industry.

“This has resulted in inaccurate and inconsistent representation of product composition and purity levels,” it said. Establishing common ground for testing steviol glycoside purity has been one of the priorities of the organization, which includes large companies such as Cargill and Corn Products amongst its members.

The new PTP will initially be limited to stevia-based sweeteners that meet the JECFA specifications. It is billed as a “statistically-relevant, blind testing scheme managed in accordance with international quality standards”.

Companies and laboratories participating will send in samples of their stevia products for analysis alongside other anonymous samples, and their own testing results can then be compared with the results under the PTP.

Carl Horn, president of the ISC and managing director of Swedish stevia firm Granular told FoodNavigator.com that the intention is not the dictate which method should be used, but to calibrate methods that are in use and identify ways in which they can be refined so as to create a level playing field.

The ISC will also provide technical assistance to participants who are generating unsatisfactory or questionable results, or who are experiencing difficulties with methods or laboratory practices. This support will be provided by an independent technical advisor.

Asked whether he expects the PTP to show up major differences between the methods’ results, or just minor tweaks, Horn said there is “a handful at least of very good methods”, but it is a matter of managing those methods, and ensuring that the latest technical tools are used.

Open to all

The Council has selected LGC Standards Ltd as the vendor, but importantly it is not necessary for a lab wishing to use the scheme to be a member of the ISC – although they would need to enroll with it.

Horn pointed out that the programme is designed to provide inter-laboratory comparisons, so there is no need to invest in new equipment or methods.

“Participants are requested, however, to commit to a minimum full year of PT rounds (4 tests),” he said. “This is important to ensure the creation of trend analyses.

“We sincerely hope that not only corporations but also governmental agencies, private laboratories and universities will participate in the programme."

More information on the new PTP is available at www.internationalsteviacouncil.org/proficiency-testing