Acrylamide formation is prevented by divalent cations during the Maillard reaction

https://doi.org/10.1016/j.foodchem.2006.08.011Get rights and content

Abstract

The effects of mono- and divalent cations on the formation of acrylamide were studied in a fructose-asparagine model system at 150 and 180 °C. At amounts equivalent to those of asparagine and fructose, added divalent cations, such as Ca2+, were found to prevent acrylamide formation completely, whereas monovalent cations, such as Na+, almost halved the acrylamide formed in the model system. It was confirmed by mass spectrometric analyses of pyrolyzates that the formation of the Schiff base of asparagines, which is the key intermediate leading to acrylamide, was prevented by the cations. Meanwhile, the reaction proceeded to form brown coloured products. Dipping potatoes into calcium chloride solution inhibited the formation of acrylamide by up to 95% during frying. The sensory quality of fried potato strips, in terms of golden yellow colour and crispy texture, was not adversely affected by this treatment.

Introduction

Detection of high concentrations of acrylamide in common heated foodstuffs in April 2002 (Swedish NFA, 2002) caused considerable public concern, since acrylamide was found to be carcinogenic in rodents (Johnson et al., 1986) and is classified as a probable human carcinogen (IARC, 1993). These findings caused the European Community (EC, 2002), and the WHO (FAO/WHO, 2002) to initiate projects for the minimization of acrylamide content in commercial as well as in homemade foods.

A number of theoretical mechanisms have been proposed for the formation of acrylamide in heated food. Most probably, acrylamide in food results largely from the Maillard reaction between asparagine and a reactive carbonyl, proceeding through intermediates that include a Schiff’s base (Mottram et al., 2002, Stadler et al., 2002, Zyzak et al., 2003). Several factors, such as the initial concentration of reactants and their ratio, temperature and time of processing, pH and water activity, have been shown to influence the formation levels of acrylamide in heat-processed foods (Friedman, 2003). The influence of temperature on the formation of acrylamide has been repeatedly demonstrated (Becalski et al., 2003, Biedermann and Grob, 2003, Rydberg et al., 2003, Stadler et al., 2002, Tareke et al., 2002).

Recent studies have indicated that polyvalent cations reduce acrylamide formation in thermally processed snack foods and bakery products (Elder et al., 2005, Lindsay and Jang, 2005). In this study, model Maillard and real food systems were employed to investigate the potential formation and degradation of acrylamide during heating in the presence of mono- and divalent cations.

Section snippets

Chemicals and consumables

Acrylamide (99+%) and 13C3-labelled acrylamide (99% isotopic purity) were obtained from Sigma (Diesenhofen, Germany) and Cambridge Isotope Laboratories (Andover, MA, USA), respectively. Fructose and asparagine were obtained from Sigma. Acetic acid, formic acid, sodium chloride, potassium chloride, calcium chloride and magnesium chloride were all reagent grade and obtained from Merck (Darmstadt, Germany). The analytical column Zorbax SB-Aq (250 × 4.6 mm, 5 μm) was supplied by Agilent Technologies

The effects of cations on acrylamide formation in asparagine–fructose reaction system

It has been shown that Maillard-driven generation of flavour and colour in heated foods can be linked to the formation of acrylamide. Free asparagine in combination with reducing sugars generates significant amounts of acrylamide when pyrolysed at temperatures greater than 120 °C (Mottram et al., 2002, Stadler et al., 2002).

We heated equimolar amounts of asparagine and fructose at 150 and 180 °C in sealed glass tubes. The formation of acrylamide followed typical kinetic patterns (Fig. 1). The

Acknowledgements

We thank Turkish Academy of Sciences (GEBIP Study Grant) and Scientific and Technical Research Council of Turkey (Project TOVAG COST 927-2) for financial support, Agilent Technologies for supplying some consumables, Ankara Test and Analysis Laboratory for LC-MS analyses.

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