Received for review August 10, 2006. Revised manuscript received September 17, 2006. Accepted September 18, 2006. The study was financially supported by the Biotechnology and Biological Sciences Research Council in conjunction with the Food Standards Agency (grants BB/C508634/1 and BB/C508669/1).

Abstract:

When wheat was grown under conditions of severe sulfate depletion, dramatic increases in the concentration of free asparagine were found in the grain of up to 30 times as compared to samples receiving the normal levels of sulfate fertilizer. The effect was observed both in plants grown in pots, where the levels of nutrients were carefully controlled, and in plants grown in field trials on soil with poor levels of natural nutrients where sulfate fertilizer was applied at levels from 0 to 40 kg sulfur/Ha. Many of the other free amino acids were present at higher levels in the sulfate-deprived wheat, but the levels of free glutamine showed increases similar to those observed for asparagine. In baked cereal products, asparagine is the precursor of the suspect carcinogen acrylamide, and when flours from the sulfate-deprived wheat were heated at 160 C for 20 min, levels of acrylamide between 2600 and 5200 g/kg were found as compared to 600-900 g/kg in wheat grown with normal levels of sulfate fertilization.

Keywords: Acrylamide; wheat; asparagine; agronomy; sulfate fertilizer

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