Application of the SAFES (systematic approach to food engineering systems) methodology to strawberry freezing process

Abstract

SAFES methodology has been applied in strawberry freezing process using data from references. Three cases of freezing have been studied. All of them start from the refrigerated temperature ( T c) and there is a first stage of cooling until the initial freezing temperature ( T m) is reached. However, the changes of components depend on the temperature reached and the rate of freezing. Case 1 studies the decrease of temperature from T m until the first layers of cells reach −18 °C, since this is the typical storage temperature in consumer’s freezer. In case 2, strawberries are frozen at the maximally cryoconcentrated temperature ( T m ′ ) of the matrix and then down to −100 °C. In case 3, a deep freezing process decreases the temperature of strawberries down to −196 °C. The last two cases are below the temperature of glass transition of strawberry (−51.3 °C) and therefore they have higher stability than in case 1. By means of this methodology it is possible to follow and predict the critical points (appearance or disappearance of components or phases) of the process to prevent quality loss. Components, phases and aggregation systems can also be analysed. Moreover, transport phenomena, chemical reaction and transition can actually be described. It has been demonstrated that SAFES methodology can describe the behaviour of strawberry freezing by using composition data, state diagrams and thermodynamic parameters. Nevertheless, to get better results more information about kinetic data related to freezing process would be required.