Title
Modelling supercooling in frozen strawberries: Experimental analysis, cellular automation and inverse problem methodology
Date Issued
01 May 2007
Access level
metadata only access
Resource Type
journal article
Author(s)
Technical University of Lisbon
Abstract
The quality of frozen strawberries (Fragaria ananassa) is influenced by the supercooling capacity during freezing. This present research aims at (i) evaluating the supercooling capacity of strawberries as function of the operational variables: initial temperature, air temperature, air velocity and strawberry maximum diameter; (ii) use the data records to develop a cellular automata model of supercooling inside a finite element space domain; and (iii) use the inverse problem methodology to validate the developed model and estimate the strawberry thermal capacity and thermal conductivity, of both pulp and vascular tissues during phase transition. Experimental data emphasises that the nucleation temperature is dependent on the thermocouple position. Higher supercooling capacities are obtained at the surface and middle positions than at the centre. Nucleation at the surface shows to be dependent upon the initial temperature, where maximum supercooling capacities are obtained with temperatures near +2.9 °C. Furthermore, a pattern of increasing nucleation temperatures towards the centre was detected during principal components analysis. This observation is used to derive thermodynamic restriction rules to nucleation inside the cellular automata model. Thermal capacity and conductivity were successfully obtained by the inverse problem methodology. The optimised model proved to be statistically similar to the experimental freezing curve (p < 0.001); although minimal systematic errors were still found. Supercooling and nucleation was modelled in macroscopic terms and considered inherently stochastic. Cellular automation proved to be a powerful tool to reproduce and explain the temperature patterns across the strawberry's physical domain during the freezing of strawberries inside an air blast freezer. © 2006 Elsevier Ltd. All rights reserved.
Start page
126
End page
141
Volume
80
Issue
1
Language
English
OCDE Knowledge area
Biología celular, Microbiología Ingeniería química
Scopus EID
2-s2.0-33750954212
Source
Journal of Food Engineering
ISSN of the container
02608774
Sponsor(s)
The authors R.C. Martins and V.V. Lopes gratefully acknowledge their Pos-Doctoral grant (SFRH/BPD/9486/2002 and SFRH/BPD/20735/2004, respectively) to the Fundação para a Ciência e Tecnologia (FCT).
Sources of information: Directorio de Producción Científica Scopus