Instrumentation of a semi-industrial oven to monitor non-enzymatic browning kinetics during baking
Résumé
A semi-industrial convective oven was designed and characterized in this study to monitor the kinetics of thermal reactions like Maillard and caramelization reactions occurring during baking. The thermal environment was characterized by measuring the heat fluxes received by the surface of the cakes under different temperature (140, 170 and 200°C) and ventilation (min, max) conditions. Excellent reproducibility of the convective heat transfer coefficient was obtained from one baking operation to another and the heat fluxes were shown to be uniform on the whole baking floor. Temperature and air humidity sensors were used to observe heat and mass transfers during baking. Besides, the oven was equipped with two original sampling devices enabling to acquire synchronous kinetic data on reaction products in the food matrix as well as in the vapors emitted by the product during baking and this, without disturbing the thermal environment. The production of 5-hydroxymethylfurfural (HMF), which was used as an indicator of the development of nonenzymatic browning, was thus monitored synchronously in the sponge cake and vapors. A good reproducibility of the reaction development was obtained with maximum 8.7 % variations of HMF concentration at all sampling times of independent baking operations. Furthermore, the volatilization of Maillard products in the oven chamber was proved to be proportional to the load of sponge cake being baked, showing the relevance of observing thermal reactions in the baking vapors. This oven should be of precious help for further kinetic modeling of complex thermal reactions occurring in solid food matrix baked under real process conditions.
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