A computational fluid dynamics study on the effect of sterilization temperatures on bacteria deactivation and vitamin destruction

The optimization of thermal processes such as sterilization relies on the a ccuracy of relevant kinetic data for bacterial inactivation and quality evo lution. It is also dependent on the geometry and heating mechanism involved in the process. In these processes or systems, profiles of temperature dis tribution, bacteria concentration and concentrations of vitamins C (ascorbi c acid), B-1 (thiamin) and BZ (riboflavin) in a can filled with cherry juic e during thermal sterilization have been obtained through numerical simulat ions. Different heating medium temperatures of 121, 130 and 140 degreesC we re tested. In order to generate these profiles, the continuity, momentum an d energy equations are solved numerically, together with those of bacteria and vitamins concentrations, using the computational fluid dynamics code PH OENICS, combined with reaction kinetics models. Natural convection that occ urs during thermal sterilization of viscous liquid (concentrated cherry jui ce, 74 degrees Brix) in a cylindrical can heated from all sides has been st udied in this work. The simulations show clearly the dependences of the con centration of live bacteria and different vitamins on both the temperature distribution and the flow pattern as sterilization proceeds. The results al so show that the best sterilization temperature may not always be 121 degre esC, depending on the quality requirements imposed on individual food mater ial of concern.