Simple changes in farming methods could reduce levels of acrylamide in wheat-based foods

Simple changes in farming methods could help reduce levels of acrylamide, the suspected carcinogen and possible neurotoxin, in wheat-based foods, according to UK researchers. 

Acrylamide was first discovered in foods in 2002 and since then research teams around the world have been looking at ways to reduce concentrations of the compound in foods. Strategies so far have included lowering pH and reducing cooking times and temperatures.

The latest work, a collaboration between Rothamsted Research and the University of Reading, stemmed from a Rothamsted discovery by Nigel Halford and colleagues that growing wheat in sulfate-depleted soil changes its amino acid composition.

The Reading group, led by Donald Mottram, discovered that the flour from wheat grown in sulfate-depleted soil had far higher concentrations of the amino acid asparagine, the main acrylamide precursor. ’We were expecting maybe double the amount of asparagine, but the 30-fold increase we found was much bigger than we’d ever expected,’ said Mottram.

Heating the flours from the sulfate-deprived wheat generated between 2600 and 5200 micrograms/kg acrylamide, compared with 600-900 micrograms/kg for wheat grown with normal levels of sulfate fertilisation.

According to the Home Grown Cereals Authority, 23 per cent of all land cereal growth in the UK is deficient in sulfate. Sulfur deficiency in cereals has also been reported in many countries including northern and western Europe, Australia, and New Zealand. ’The implications of the data could be widespread,’ said Mottram.

’The irony is that this problem has got worse since we cleaned up the air. When we were burning lots of coal and a lot of sulfur was going into the air we had acid rain but that provided sulfate,’ he said.

Acrylamide expert Richard Stadler, quality manager at Nestl?, Switzerland, described the work as ’very important,’ adding that it will help fill the gap in acrylamide knowledge. ’We still need to understand the scope for improvement in agronomy to reduce asparagine levels,’ he said. This will include looking at fertilisation regimes and choice of crop variety.

Apart from possible health implications, the increased asparagine concentration could have an impact on flavour. Acrylamide is primarily produced by the Maillard reaction, when asparagine reacts with sugars. This reaction is vital for generating the flavours that make baked, roasted and fried foods so tasty. ’We have been looking at aroma volatiles [in the wheat samples] and we certainly do get significant differences,’ said Mottram. The team has yet to discover whether these differences will be detected in the taste of wheat-based foods, but Mottram thinks that it is likely. ’If the amino acid composition changes, then the flavour precursors will also change and so you could get perceived flavour changes.’