title: Modelling the interactions between free phenols, L-ascorbic acid, apple polyphenoloxidase and oxygen during a thermal treatment.
abstract: The kinetics of degradation of chlorogenic acid (CG), (-) epicatechin (EPI), L-ascorbic acid (AA) and polyphenoloxidase (PPO) activity from Marie-Ménard apple in pH 3.8 solutions at 20 and 50°C were investigated to provide information on the impact of the presence of CG, EPI and/or AA on PPO thermostability. The effect of the heat treatment on their degradation by enzymatic and/or nonenzymatic ways was also studied. Stoechiokinetic reactions on the basis of experimental data and literature and determination of the kinetic constants (k) at 20 and 50°C were elaborated before modelling the interaction among reactants, by fitting the reaction curves to predictive model. Apple PPO was thermolabile, denaturing after 10min at 70°C. Losses of PPO activity were favoured by the presence of EPI in model solutions, compared with CG, due to the formation of o-quinones of EPI (QEPI) lowering PPO stability. Temperature quickened both enzymatic phenol oxidations before PPO deteriorated and the whole set of the chemical reactions, including the production of secondary oxidation products and CG or EPI regeneration. Results also confirmed that AA in excess induced a fast regeneration of CG and EPI from the corresponding o-quinones formed enzymatically via redox chemical reactions.
authors: Conservatoire National des Arts et Métiers, Chaire des Industries Agro-Alimentaires, UMR 1145 Ingénierie Procédés Aliments, 75141 Paris Cedex 03, France. jeanpierreaka@yahoo.fr
authors: Jean-Pierre
authors: JP
authors: Aka
authors: Francis
authors: F
authors: Courtois
authors: Loïc
authors: L
authors: Louarme
authors: Jacques
authors: J
authors: Nicolas
authors: Catherine
authors: C
authors: Billaud
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry*; D004156:Catechol Oxidase / Q000737:chemistry*; D005511:Food Handling; D006358:Hot Temperature; D007700:Kinetics; D027845:Malus / Q000737:chemistry / Q000201:enzymology*; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*
chemical_list: D010636:Phenols; D010940:Plant Proteins; D004156:Catechol Oxidase; D001205:Ascorbic Acid; D010100:Oxygen