According to the USDA Agricultural Research Service, harsh preparation of food samples can affect the quality of the bioactives present, so that the results of the testing are inaccurate and inconsistent. Lead scientist Devand Luthria presented the ARS' steps at a meeting of the American Chemical Society in Chicago yesterday. FoodNavigator.com has not been privy to full details of the steps, but they are said govern validation sampling and preservation methods, as well as recommend the use of modern extraction techniques such as pressurized liquid and ultrasonic radiation. "These steps support optimal extraction of bioactive phytochemicals from different plant sources," said the ARS. "Describing such methods is an important step towards consistency in reporting." They will be particularly important for private and public research laboratories measuring compounds that provide health benefits beyond basic nutrition. The knock-on effect is that that accurate analysis of plant compounds present in foods can help identify associations between consumption and benefits, informing dietary advice and formulation of healthy food products. The ARS concedes that variations reported bioactive chemicals will continue to exist as a result of differences between factors like cultivars, environmental conditions, post-harvest conditions, and maturity at time of harvest. But reducing uncertainty introduced by sample preparation and analytical methods could go some way towards improving overall accuracy. The issue of testing methods affecting results raised its head in the furore surrounding the presence of benzene in soft drinks last year. The National Institutes of Health funded the development of a new analysis method, following evidence that existing protocol actually raises the levels of benzene in the samples. Chemical reactions are accelerated by heat, liquid and pressure, and the previous test protocol involves heating the sample to 80 to 90 degrees Celsius for 30 to 60 minutes in a sealed container. However it seems that the requirement for a new testing method for benzene was not global. A spokesperson for the UK's Food Standards Agency said: "The method we use would minimize any formation of benzene in the analytical phase."