Chemists dispute technique for assessing acrylamides.

Fierce infighting among analytical chemists over the techniques used to measure concentrations of acrylamide, a possible carcinogen found in 'browned' foods such as crisps and chips, is revealed this month in correspondence to their professional journal ne arly two years after the controversy first emerged.

The researchers are understandably edgy. Without a reliable method of measuring acrylamide, they note, policy makers and organisations such as the UK Food Standards Agency and the US Food and Drug Administration find it difficult to make recommendations on acrylamide-related issues.

In April 2002, Swedish researchers from Stockholm University provoked global concern over the safety of everyday foods after they found that frying, baking or toasting carbohydrate-rich foods can cause acrylamide to form. Later that year, research teams from Sweden and the UK went some way to demystifying the chemical's presence. They discovered that acrylamide probably forms when asparagine, an amino acid, is heated, or 'browned', in the presence of sugar, a process known as the Maillard reaction (see Chem. Br ., November 2002, p 15).

But criticism of the way that the Anglo-Swedish team extracted the acrylamide, which involved homogenising, centrifuging and filtering food samples, surfaced last April at Arealia, a Swedish food company. JÖrgen Pedersen and Jim Olsson, researchers at the company, chose instead to boil food samples in methanol for several days, in a process known as the Sohxlet extraction technique, and then used gas chromatography-mass spectrometry to measure concentrations of acrylamide ( Analyst , 2003, 128 , 332).

The results were alarming. Pedersen and Olsson extracted more than seven times as much acrylamide from crisps (14500 μg kg ^-1) as conventional techniques had done (2000 μg kg ^-1). Widespread concern was again provoked and, this month, The Analyst is publishing a series of polemical papers from researchers in Switzerland, Germany, Japan and the US.

Criticism of the Sohxlet extraction technique comes from a joint team of researchers at the Official Food Control Authorit y in Zurich and at Wiertz-Eggert-JÖrissen, a German food company based in Hamburg. They claim that the technique itself generates acrylamide. The high concentration of acrylamide is an 'artefact of the extraction procedure', they note, adding that there is 'no good reason to question the [extraction] methods used so far'.

Researchers at Nissin Food in Tokyo also complain that the Sohxlet technique gives false results. Researchers at General Mills, a food company in Minnesota, agree with them: 'While striving to produce optimum results through method improvement is always a goal of analytical chemists, Sohxlet extraction into methanol is not a viable alternative.'

Pederson and Olsson, who are continuing their investigations, accept that the Sohxlet techniqu e generates acrylamide, but only in small amouts, they say. 'This new formation does not conclusively explain the difference compared to the other methods used', they note.

The debate has generated huge interest among readers of The Analyst , according to Sarah Day, the journal's editor. 'The original paper by Rosén and Hellenas (July 2002 issue) and the follow up from Olsson and Peterson (April 2003 issue) have been requested from our website many times since publication,' she notes. 'I'm hoping that the extended debate in the form of the comments and reply will be as popular.' Emma Davies

Such debates are not that common. 'This is only the second "comment(s) and reply" that we have published in The Analyst since I have been Editor [1999],' says Day. 'What was unique about this one was that all three comments arrived within several weeks of each other, so it was clear that the Pedersen and Olsson article.had touched a nerve in the food industry.'

Emma Davies