Rye’s reputation as a cereal particularly at risk of acrylamide formation could be unfounded, according to a new study published in the Journal of Agricultural and Food Chemistry.
Acrylamide forms naturally during the cooking of starchy foods at high temperatures by a process called the Maillard reaction, in which sugar reacts with an amino acid called asparagine to give baked and fried foods their brown color and tasty flavor.
But the alarm was raised in 2002 when Swedish scientists found unexpectedly high levels of acrylamide in carbohydrate-rich foods and published evidence linking it to cancer in lab rats. Since then, research has poured into the area and industry has rallied to find ways to slash the chemical from foods.
Rye crispbreads in particular were identified in an earlier study as a major source of dietary acrylamide, and the British and Hungarian researchers note that crispbread manufacturers responded rapidly by changing baking processes. However, manufacturers are under pressure to reduce levels further, and this latest study focused on the possibility for reducing acrylamide precursors in rye grain at an agricultural level.
However, in the course of their work, the researchers recognized that free asparagine levels are significantly higher in the whole grain, due to its concentration in the bran – as is the case for wheat flour – but rye-based products are far more likely to employ the whole grain.
“It is rye’s use almost exclusively in wholegrain products that are baked to give a relatively dark color and crisp texture rather than its intrinsic properties that gives rise to high acrylamide levels,” they wrote.
Therefore, they concluded that the cereal’s reputation as a grain associated with high acrylamide risk may not be warranted. In fact, they found that less acrylamide was formed per unit of asparagine in rye than in wheat flour.
“Rye crispbreads are generally made from the whole grain and, although this means that acrylamide levels are probably higher than they would be if the bran fraction were removed, it should be noted that there are well-established health benefits associated with eating wholegrain rye products.”
Nevertheless, by examining the free amino acid and sugar concentrations in the grain of a range of rye varieties grown in different locations, the researchers sought to determine how acrylamide could be reduced while retaining the cereal’s healthy properties.
They found that it could be possible to screen existing rye varieties and breed new ones for low free asparagine levels, so the potential for acrylamide formation is reduced before rye flour reaches the manufacturer.
Daily dietary intake of acrylamide varies from three to six micrograms per kilogram of bodyweight for adults, and is higher for children and teenagers, they wrote, with intake contributed by cereal products making up 33 percent of the total in the United States.
Source: Journal of Agricultural and Food Chemistry
Published online ahead of print
“Free Amino Acids and Sugars in Rye Grain: Implications for Acrylamide Formation”
Authors: Tanya Y. Curtis, Stephen J. Powers, Dimitrios Balagiannis, J. Stephen Elmore, Donald S. Mottram, Martin A. J. Parry, Mariann Rakszegi, Zoltan Bedo, Peter R. Shewry, and Nigel G. Halford.