title: Formation kinetics of hydroxymethylfurfural, lactulose and furosine in milk heated under isothermal and non-isothermal conditions.
abstract: A detailed kinetic study of hydroxymethylfurfural, lactulose and furosine formation was performed upon heating milk at temperatures between 90 degrees C and 140 degrees C. In case of prolonged heating, formation kinetics could be described by a fractional conversion model. Considering only the first phase of the model, kinetics could be simplified to a pseudo-zero order model. A first assessment of kinetic parameters was made by isothermal experiments. Data were analysed using both a 2-step linear and a 1-step non-linear regression method. Only for furosine, did the global 1-step regression approach seem to give better results than the individual 2-step regression approach. Next, the estimated parameters k(ref) and Ea were re-evaluated under non-isothermal conditions by subjecting milk to a time variable temperature profile. Given the complexity of Maillard reaction, it seemed better to estimate kinetic parameters under non-isothermal conditions when using a simplified model. Formation of hydroxymethylfurfural, lactulose and furosine was characterized by an Ea value of 90.2 kJ/mol (k(110 degrees C) = 1.2 micromol/l, min), 99.1 kJ/mol (k(110 degrees C) = 51.5 mg/l, min) and 88.7 kJ/mol (k(110 degrees C) = 16.3 mg/100 g protein, min) respectively. Additionally, 90% joint confidence regions were constructed in order to obtain an accurate representation of the statistical confidence associated with the simultaneously estimated parameters.
authors.affiliation: Department of Food and Microbial Technology, Faculty of Agricultural and Applied Biological Sciences, Katholieke Universiteit Leuven, Heverlee, Belgium.
authors.forename: W L
authors.initials: WL
authors.lastname: Claeys
authors.forename: L R
authors.initials: LR
authors.lastname: Ludikhuyze
authors.forename: M E
authors.initials: ME
authors.lastname: Hendrickx
mesh_terms: D000818:Animals; D002417:Cattle; D005662:Furaldehyde / Q000031:analogs & derivatives* / Q000138:chemical synthesis*; D005765:Gastrointestinal Agents / Q000737:chemistry; D006358:Hot Temperature; D007700:Kinetics; D007792:Lactulose / Q000138:chemical synthesis*; D008239:Lysine / Q000031:analogs & derivatives* / Q000138:chemical synthesis*; D008892:Milk / Q000737:chemistry*; D008956:Models, Chemical; D012044:Regression Analysis; D013816:Thermodynamics
chemical_list: D005765:Gastrointestinal Agents; C018948:furosine; D007792:Lactulose; C008046:5-hydroxymethylfurfural; D005662:Furaldehyde; D008239:Lysine