Study of colour and acrylamide formation in coffee, wheat flour and potato chips during heating Vural Go ¨ kmen a, * , Hamide Z. S ß enyuva b a Food Engineering Department, Hacettepe University, 06532 Beytepe, Ankara, Turkey b Ankara Test and Analysis Laboratory, Scientific and Technical Research Council of Turkey, Ankara 06330, Turkey Received 7 March 2005; received in revised form 8 June 2005; accepted 8 June 2005 Abstract The effects of heating on colour generation measured as CIE colour space parameters of L* a* b* and acrylamide formation were studied in various food matrices including green coffee, wheat flour and potato chips at different temperatures. Changes in both the acrylamide concentration and the redness parameter a* during heating at relatively higher temperatures followed a typical kinetic pattern in which an initial increase to an apparent maximum followed by a subsequent decrease was observed. The similarities between the changes in acrylamide and redness parameter a* during heating revealed that colour may be a reliable indicator of acrylamide levels in thermally processed foods. The overall results suggest that both acrylamide and redness parameter a* form as intermediate products during Maillard reaction. Since an apparent decrease was observed in its level during prolonged heating at certain temperatures, prediction of acrylamide level in foods during processing should be based on realistic reaction mechanism, instead of simple linear regression model. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Acrylamide; Colour; Heating; Green coffee; Wheat flour; Potato chips 1. Introduction Acrylamide formation was found to occur during the browning process by Maillard reaction of reducing sugars with asparagine at temperatures above 120 °C(Friedman, 2003; Mottram, Wedzicha, & Dodson, 2002; Stadler et al., 2002; Yaylayan, Wnorowski, & Locas, 2003). Coloured products are also formed in foods during heating as a result of Maillard reaction (Ma ´rquez & An ˇo ´n, 1986; Pedrechi, Moyano, Kaack, & Granby, 2005; S ß enyuva & Go ¨kmen, 2005). In the Maillard reaction, melanoidins are known as the main end product of the reaction. These brown polymers have significant effect on the quality of food, since colour is an important food attribute and a key factor in consumer acceptance. The mechanism of the formation of brown colour is not fully understood and the structure of melanoidins is largely unknown (Martins & van Boekel, 2003). Since colour can easily be measured, it may be used as an indicator of other Maillard reaction products like acrylamide. Colour of foods has been measured usually in units L* a* b* which is an international standard for colour measurements, adopted by the Commission Internationale dÕEclairage (CIE) in 1976. L* is the lumi- nance or lightness component, which ranges from 0 to 100 (black to white), and parameters a* (from green to red) and b* (from blue to yellow) are the two chromatic components, which range from 60 to 60 (Papadakis, Abdul-Malek, Kamdem, & Yam, 2000). This paper presents the changes in colour and acryl- amide levels with time in green coffee, wheat flour and potato chips during heating at different temperatures. The relation between the kinetic patterns of CIE colour 0308-8146/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2005.06.054 * Corresponding author. Fax: +90 312 2992 123. E-mail address: vgokmen@hacettepe.edu.tr (V. Go ¨ kmen). www.elsevier.com/locate/foodchem Food Chemistry 99 (2006) 238–243 Food Chemistry