Formation of advanced glycation endproducts in ground beef under pasteurisation conditions Xiaohua Sun a , Juming Tang b , Jing Wang a , Barbara A. Rasco c,⇑ , Keqiang Lai a , Yiqun Huang a,c,⇑ a College of Food Science and Technology, Shanghai Ocean University, No. 999 Hucheng Huan Road, LinGang New City, Shanghai 201306, China b Department of Biological System Engineering, Washington State University, Pullman, WA 99164-6120, USA c School of Food Science, Washington State University, Pullman, WA 99164-6376, USA article info Article history: Received 13 May 2014 Received in revised form 9 September 2014 Accepted 11 September 2014 Available online 28 September 2014 Keywords: Beef Carboxymethyllysine Carboxyethyllysine Advanced glycation endproducts Thermal process Kinetics abstract Advanced glycation endproducts (AGEs) in food products may pose health risks, and thermal processing of foods accelerates the formation of AGEs. The effects of heat treatments (65–100 °C, 0–60 min) on the formation of AGEs including N e -carboxymethyllysine (CML) and N e -carboxyethyllysine (CEL) in ground beef were investigated. The levels of CML and CEL in ground beef steadily increased with heating time and heating temperature. A strong linear relationship (r 2 = 0.920) between the amounts of CML (2.76–19.96 mg/kg) and CEL (2.32–11.89 mg/kg) in raw and thermally treated beef was found. The formations of both CML and CEL in ground beef during heat treatments basically fitted zero-order reactions (CML: r 2 = 0.851–0.995, rate constant = 0.031–0.224 mg kg 1 min 1 ; CEL: r 2 = 0.907–0.971, rate constant = 0.044–0.118 mg kg 1 min 1 ) with an activation energy of 61.01 kJ/mol for CML and 29.21 kJ/ mol for CEL. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction The Maillard reaction involves a series of complicated reactions starting from the reaction between the carbonyl group of reducing sugars and amino group of amino acids or free amino groups of proteins to form a Schiff base, then undergoing Amadori rearrange- ment. From the Amadori products, various reactive intermediate products are produced following different pathways before more stable products are formed, such as aroma and browning com- pounds, and advanced glycation endproducts (AGEs). AGEs were initially believed to be formed at later or advanced stages of the Maillard reaction as a result of the attachment of saccharides (most often monosaccharides) or their derivatives to a protein or its derivatives, from which the term ‘‘advanced glycation endprod- ucts’’ came (Rabbani & Thornalley, 2012). Recent studies indicate that AGEs in foods can be formed in the early stages of the Maillard reaction through potent glycating agents such as a-dicarbonyl compounds formed directly from degradation of glucose or Schiff base, or from lipid oxidation (Fu et al., 1996; Poulsen et al., 2013; Rabbani & Thornalley, 2012). AGEs can be formed in vivo and in foods during thermal processing and storage. In the human body, AGEs may promote aging and oxidative stress and increase risks for various diseases such as diabetes, obesity, and cardiovascular diseases, though the risk effects of dietary AGEs on human health are still controversial (Ames, 2007; Nguyen, 2006; Poulsen et al., 2013; Uribarri et al., 2010). Assessments of various foods such as infant formulas (Birlouez- Aragon et al., 2004), milk and beverages (Ahmed et al., 2005), almonds (Zhang, Huang, Xiao, & Mitchell, 2011), sauces and sauce treated meat and fish (Chao, Hsu, & Yin, 2009), as well as several hundred commonly consumed foods (Goldberg et al., 2004; Hull, Woodside, Ames, & Cuskelly, 2012; Uribarri et al., 2010) indicate that heat treatments significantly affect the levels of AGEs in foods; and high protein/high fat foods (such as meat, pork, chicken) have higher levels of AGEs compared to low fat or carbohydrate-rich foods (such as fruits, vegetables, grains, legumes, and nonfat milk). Although the effects of heating on the levels of AGEs in foods have been acknowledged (Chao et al., 2009; Wellner, Huettl, & Henle, 2011; Zhang et al., 2011), very few studies have been published on how thermal processes (such as heating temperature and heat- ing time) affect the amounts of AGEs in foods. What is more, among these limited number of reported studies on AGEs, simple model systems (such as monosaccharide-lysine mixtures) instead of real food systems were often used (Fu, Li, & Li, 2012; Morales & Van Boeckel, 1996). Since foods in general contain numerous components that may participate in or interfere with the formation http://dx.doi.org/10.1016/j.foodchem.2014.09.129 0308-8146/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors. Tel.: +1 (509)335 1858; fax: +1 (509)335 4815 (B.A. Rasco). Tel.: +86 (21)6190 0370; fax: +86 (21)6190 03659 (Y. Huang). E-mail addresses: rasco@wsu.edu (B.A. Rasco), yiqunh@hotmail.com (Y. Huang). Food Chemistry 172 (2015) 802–807 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem