Significance of furosine as heat-induced marker in cookies Vural Go ¨ kmen a, * , Arda Serpen a ,O ¨ zge Çetinkaya Açar a , Francisco J. Morales b a Department of Food Engineering, Hacettepe University, Beytepe Campus, Ankara 06800, Turkey b Instituto del Frı ´o, Consejo Superior de Investigaciones Cientı ´ficas, Jose´ Antonio Novais 10, E-28040 Madrid, Spain article info Article history: Received 29 November 2007 Received in revised form 30 May 2008 Accepted 27 June 2008 Keywords: Furosine Maillard reaction Cookie Baking Recipe formulation abstract The effects of recipe formulation in terms of leavening agents (ammonium and sodium bicarbonates), sugars (sucrose and glucose), initial moisture content, and baking conditions (temperature and time) on furosine formation in cookies were studied. The cookies were baked at different temperatures for different times to monitor the progress of the early stage of the Maillard reaction. Change in furosine levels as an indicator of the Amadori products showed a typical kinetic behavior with a rapid increase to an apparent maximum followed by exponential decrease during baking. Initial water activity of cookie dough had no remarkable effect on the apparent maximum, but lowering the water activity decreased the time required to attain it. In addition, levels of furosine in the final product are highly correlated to the initial water content of dough at the same baking conditions. The levels of furosine attained were significantly lower in cookies composed of sucrose than in cookies composed of glucose. Early stage of the MR is rapidly overcome during baking as the Amadori product degraded in the advanced stage. Among the leavening agents, ammonium bicarbonate was the most effective for the progress of the Maillard reaction in cookies during baking. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Technological processes applied to food can give rise to modi- fications in their composition. One of the most important modifi- cations induced in food by heating is the Maillard reaction, which involves amino acids and reducing carbohydrates, and can also produce loss of nutritive value (Henle et al., 1991). The loss of available lysine is the most significant consequence of this reaction, and it is of the great importance in those foods where this amino acid is limiting, such as in cereals as well as other processed foods (Erbersdobler and Hupe, 1991). Recently, application of furosine as indicator of the nutritional quality of food has been reviewed (Erbersdobler and Somoza, 2007). Heat treatment is well-known to produce modifications of nutrients in foods. In particular, the development of the Maillard reaction is considered to be the most evident effect induced by heat treatment. Furosine (N-3-2-furoylmethyl-L-lysine or N-3-fructose- lysine) is an amino acid derivative formed during the acid hydrolysis of such Amadori products (N-substituted 1-amino-1- deoxy-2-ketose) as fructose-lysine, lactulose-lysine, and maltulose- lysine, which are generated in the early stages of the Maillard reaction during the heat processing of foods (Erbersdobler, 1995). For this reason, estimates of the extent of protein damage caused by heating in the first stages of that reaction are often based on determinations of the amount of furosine that forms during the acid hydrolysis of foods (Nursten, 1981). On the other hand, furo- sine is also applied for the evaluation of the extent of the early MR in vivo such as to predict retinopathy and nephropathy risk (Monnier et al., 2005). Furosine can also be considered as a marker of dietary intake of AGEs (Advanced Glycation End products), apart from carboxymethyllysine, which is involved with several compli- cations of degenerative diseases in vivo (i.e. diabetic nephropathy, uremia and cataract). Dietary AGEs were found to correlate with circulating AGE levels in several biological disorders (Uribarri et al., 2007). Furosine is recognized as a quality indicator in a number of dairy products, vegetable foods, such as soybeans, barley and malt (Molnar-Perl et al., 1986), potatoes, rice and carrots (Resmini and Pellegrino, 1991), infant cereals (Guerra-Herna ´ndez et al., 1999), eggs (Hidalgo et al., 2006), tomato products (Hidalgo et al., 1998; Sanz et al., 2000), honey (Sanz et al., 2003) and dehydrated fruits (Sanz et al., 2001). Cookies are cereal-based bakery products and particularly consumed by a wide variety of age groups. Leavening agents, which are a group of predominantly inorganic salts, are important ingredients of cookie recipes. When added to dough either singly or in combination, they react to produce gases, which form the nuclei for the textural development within a cookie during baking. Most * Corresponding author. Tel.: þ90 312 2977108; fax: þ90 312 2992123. E-mail address: vgokmen@hacettepe.edu.tr (V. Go ¨ kmen). Contents lists available at ScienceDirect Journal of Cereal Science journal homepage: www.elsevier.com/locate/jcs 0733-5210/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.jcs.2008.06.007 Journal of Cereal Science 48 (2008) 843–847