Citric acid, glycine addition could cut acrylamide, keep flavour

By Stephen Daniells

- Last updated on GMT

Related tags: Citric acid, French fries, Acrylamide

Addition of citric acid and glycine could reduce the formation of
acrylamide, but not affect flavour, suggests a model study from the
UK.

"It is clear that acrylamide formation and flavour generation are intricately linked through the Maillard reaction and that attempts to mitigate acrylamide formation would have a significant impact on flavour,"​ explained the researchers.

"However, differences in the effect on flavour between [citric acid and glycine] can be exploited to minimise the overall impact on sensory quality."

Acrylamide is a carcinogen that is created when starchy foods are baked, roasted, fried or toasted. It 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.

The new study, published on-line in the Journal of Agricultural and Food Chemistry​ (doi: 10.1021/jf060328x), reports that formation of this carcinogen can be limited by adding glycine and citric acid to potato cakes before cooking.

The Maillard reaction, initiated above 154 C, occurs when sugar molecules (carbohydrates) are heated with amino acids (proteins). Hundreds of different flavour compounds are formed during the reaction, which can then go on to form other flavours.

However, it has also been reported that acrylamide is formed during the Maillard reaction, with asparagines - the major amino acid in potatoes - being the main precursor.

This leaves the conundrum of how to suppress the formation of acrylamide without detrimentally affecting flavour formation.

The researchers, led by Professor Don Mottram from the School of Food Biosciences at the University of Reading, prepared potato cakes using drum-dried potato flakes provided by McCain Foods.

Four sets of cakes were prepared: normal; with glycine; with citric acid; with citric acid plus glycine. The cakes were baked at 180 C for 10 to 60 minutes.

Two classes of flavour compounds were analysed - the Strecker aldehydes and the alkylpyrazines, and acrylamide formation was followed using GC-MS.

After cooking, it was found that citric acid alone limited the generation of volatile flavour compounds, in particular the alkylpyrazines.

Glycine, on the other hand, promoted the formation of certain alkylpyrazines, but did suppress the formation of certain Strecker aldehydes.

When the additives were present together, the researchers observed that for a combination of 0.39 per cent (w/w) of citric acid and 0.39 per cent (w/w) glycine, the overall acrylamide formation was reduced by approximately 40 per cent, while the effects on the volatile flavour compounds was small, compared to the normal potato cake (no additives).

"Overall, the effect of glycine addition appeared to dominate over that of citric acid for the volatiles studied, particularly for those alkylpyrazines whose yields were greatly enhanced by glycine addition,"​ wrote lead author Mei Yin Low.

And lower concentrations of each additive would reduce the effect on the flavour profile, say the researchers, but would still significantly affect the production of acrylamide by the Maillard reaction, suggesting similar strategies could be employed by food formulators to maintain flavour profiles but reduce the production of this carcinogen.

"It was proposed that the opposing effects of these treatments on total volatile yield may be used to best advantage by employing a combination treatment at lower concentrations, especially as both treatments were found to have an additive effect in reducing acrylamide.

"This would minimised the impact on flavour but still achieve the desired reduction in acrylamide levels,"​ concluded the researchers.

The results of this study are of particular interest following a global risk analysis last year that reported that french fries and potato crisps have the highest levels of acrylamide.

Related topics: R&D, Proteins, Flavors and colors

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