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Amino acids against acrylamide – choice is critical for effects: Study

By Stephen Daniells , 25-Feb-2009

Using amino acids to compete with, and reduce, the sources of acrylamide should focus on the common additive cysteine, according to results from Belgium.

According to a study published in the journal Food Chemistry, L-cysteine may reduce the concentration of acrylamide by more than 99 per cent.

“Selectively increasing the free amino acid pool to compete with asparagine for available carbonyls and/or to enhance the elimination of acrylamide has already been proposed as a possible mitigation mechanism for acrylamide generation,” explained lead author Kristel de Vleeschouwer from the Leuven Food Science and Nutrition Research Centre (LFORCE) at the Catholic University of Leuven.

The study taps into the trend of reducing acrylamide in foods, as the industry aims to improve the public perception about food safety, which has suffered in recent years.

Acrylamide is a suspected carcinogen that is formed by a heat-induced reaction between sugar and an amino acid called asparagine. Known as the Maillard reaction, this process is responsible for the brown colour and tasty flavour of baked, fried and toasted foods.

The compound first hit the headlines in 2002, when scientists at the Swedish Food Administration first reported unexpectedly high levels of acrylamide, found to cause cancer in laboratory rats, in carbohydrate-rich foods.

Since the Swedish discovery a global effort has been underway to amass data about this chemical. More than 200 research projects have been initiated around the world and their findings co-ordinated by national governments, the EU and the United Nations.

New data

Using the model asparagine-glucose control system, de Vleeschouwer and her co-workers tested the effects of two amino acids, glutamine and cysteine, on acrylamide formation.

The researchers report that adding glutamine into the system produced the undesirable effect of slightly increasing the acrylamide yield.

On the other hand, cysteine had a “pronounced reducing effect (greater than 99 per cent) on the acrylamide yield”, they said.

This reduction was due to an additional acrylamide elimination reaction dependent on the cysteine concentration, said de Vleeschouwer.

However, “speculations have been made in literature concerning the exact mechanism(s) by which these amino acids affect acrylamide formation/elimination, but mechanistic studies are, however, lacking”, added the researchers.

Care needed

While the cysteine addition could reduce acrylamide levels in this model system, the authors urged caution with regarding to extrapolation of the results to finished foods, since “such treatment certainly also has an effect on the favourable qualities of colour, texture and flavour that are associated with heat-treated foods.

“Therefore, it would be advisable to first determine the mechanism by which different amino acids act on acrylamide formation and elimination reactions […]

“This will allow prediction of the impact of (pre)treatments with amino acids on the kinetic parameters of acrylamide formation and elimination on the one hand and of reactions responsible for colour and flavour on the other hand,” they concluded.

Enzymes leading anti-acrylamide approaches

The most attention for acrylamide reduction or removal has focussed on the potential of asparaginase enzymes to tackle the problem. The two main players in this area, DSM and Novozymes, both launched their solutions for use by the food industry in 2007, after having licensed the application rights from Frito Lay and Proctor and Gamble.

DSM's Preventase and Novozyme's Acrylaway are said to work in the same way: they convert asparagine into another amino acid called aspartic acid, thus preventing it from being converted into acrylamide. The effect is a reduction in acrylamide in the final product by as much as 90 per cent.

While Preventase is derived from Aspergillus niger, Acrylaway comes from a different strain, Aspergillus oryzae.

Source: Food Chemistry
Pages 535-546
“Role of precursors on the kinetics of acrylamide formation and elimination under low moisture conditions using a multiresponse approach – Part II: Competitive reactions”
Authors: K. De Vleeschouwer, I. Van der Plancken, A. Van Loey, M.E. Hendrickx