Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Orange juice is submitted to thermal treatment to increase its shelf life, which may result in loss of ascorbic acid. This paper uses mathematical models and simulations to reproduce the experimental data of ascorbic acid thermal degradation kinetics. Two different models were considered, and all kinetic parameters were identified using linear regression on the logarithmic curves of experimental data. A quick analytical method based on ultra high-performance liquid chromatography with tandem mass spectrometry was developed to quantify ascorbic acid degradation during the process at three different operating temperatures, allowing the determination of Arrhenius' equations. Ascorbic acid losses were simulated in a tubular industrial pasteurization system by developing an appropriate mathematical modeling, and the residence time presents a higher influence on the process than temperature. In addition, some thermodynamic parameters were evaluated, confirming that the process is not spontaneous but irreversible. PRACTICAL APPLICATIONS The mathematical modeling developed in this research can be used to estimate the ascorbic acid losses during industrial pasteurization processes. The case study of this paper concerns on tubular systems. However, the kinetic parameter estimation and the degradation rate obtained can be used in any industrial situation by an appropriate modeling adaptation, e.g., considering the common plate systems.396683691FAPESP [2013/21306-0]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)