The influence of geometrical and operational factors on supercooling capacity in strawberries : a simulation study

Abstract

Supercooling is still today one of the most challenging physical phenomena to be modelled in food bioprocess engineering. In this study, we evaluate the capacity of a finite-element-cellular automata (FEM-CA) approach to model the propagation of nucleation inside supercooled strawberries with five different morphologies (higher and lower volumes of vascular tissue, pulp, and central air void) frozen inside an air blast freezer under different operational conditions: initial temperature (0 to +20 °C), air temperature (−45 to −20 °C), and velocity (1 to 10 m s − 1). Results show that nucleation is highly affected by the initial temperature and heat transfer rate during phase change. The stochastic nature of nucleation only allowed us to consider it a random variable inside the model temperature restriction interval, it not yet being possible to know what triggers nucleation. However, this study allowed us to conclude that: (1) the structure of liquid water in the supercooled region plays a very significant role during the supercooling effect, (2) nucleation temperatures increase in the supercooled region due to the release of latent heat, and (3) strawberry morphology and operational variables have a profound effect on the supercooling capacity. In our opinion, supercooling is still an open subject, and only a deeper understanding of the structuring of water and dynamics of nucleation at the molecular level may lead to significant advances in the quality of frozen foods and cryopreservation.