A rapid test for measuring erucic acid levels in rapeseed can give false positive results, according to research.
Levels of erucic acid have been creeping up over the past few years, leading to price penalties and outright rejections of rapeseed loads.
The problem is set to get worse with the European Commission looking to reduce the legal limit for erucic acid in food products from the current 5% down to 2%.
As part of investigations into the problem, Niab Tag compared a relatively rapid method of detecting erucic acid with the traditional method.
Near infrared spectrophotometer scanning (NIRS) techniques are rapid because they can be used at the intake on whole rapeseed.
In contrast, the traditional method is much more laborious, involving the extraction of the oil and then using gas chromatography techniques in a laboratory.
Over the full erucic acid range (0-40%) detected in the study, NIRS gave an erucic acid test accuracy very close to that of gas chromatography analysis.
However, NIRS accuracy was found to be significantly reduced at the critical 0-5% ranges, with “considerable inaccuracy” at the 0-2% range.
This is especially important if the legal limit is reduced to 2%.
Dhan Bhandari, who manages grain quality research at AHDB, said it shows that NIRS can give false results.
“It can show that loads have exceeded threshold values, when gas chromatography tests show that this is not the case.”
He added that while NIRS is getting better all the time, especially at lower levels, it lacks the accuracy of traditional methods.
The latest developments have been published in a new AHDB report and further information on the research project can be found on a dedicated webpage.