3D numerical simulation of asparagus sterilization in a still can using computational fluid dynamics

The heating and cooling cycles during thermal processing of asparaguses in a still can using Computational Fluid Dynamics (CFD) is the subject of this paper. The CFD code “Fluent®” was used to predict the temperature distribution and the velocity profile in the can. Experiments were run using a metal can containing 1 and 8 asparaguses filled with 4% NaCl brine and immersed in boiling water. Results obtained by CFD for temperature profiles were in good agreement with experimentally determined values. After validation of the model, further simulations were carried out for cans containing 0, 1, 8 and 19 asparaguses and for glass jars containing 19 asparaguses. It was shown that the brine flow depends on the number and spacing of the asparaguses in the can. By increasing the number of asparaguses in the can, the brine velocity increased being higher at the beginning of the heating and cooling phases. The slowest heating zone and the slowest cooling zone are located at a height of about 13.5% of the can height from the bottom and about 13.5% of the can height from the top, respectively, and they are not affected by the number of asparaguses. The final temperature during the heating phase was slightly affected by the number of asparaguses, while the heating rate was affected by the type of the container. Brine velocity did not affect the temperature inside the asparaguses indicating that the main resistance to heat transfer lies inside the asparaguses. The results clearly show that heating of the asparaguses is not uniform but the top of the asparaguses receives higher heat treatment than the bottom since the top of the can is heated faster and is cooled at a slower rate. These results could contribute to the optimization of thermal processing of asparaguses in order to minimize quality losses, such as texture, flavor and nutritional value, while keeping the product safe.