Carrier optimisation in a pilot-scale high pressure sterilisation plant – An iterative CFD approach employing an integrated temperature distributor (ITD)

High pressure thermal (HPT) processing is a candidate for commercial scale food sterilisation. During HPT processing, heat is generated volumetrically within the vessel as a result of rapid pressurisation, typically to pressures of 600 MPa or more. As for traditional retort processes, the temperature profile in the vessel should ideally be uniform at all stages of the process in order to minimise the occurrence of under- and over-processing of individual food containers. Insulating polymeric carriers are employed in (pilot-scale) HPT processing with the aim of maximising heat retention and improving temperature uniformity. However, polymeric carriers can occupy a large portion of the vessel volume, thus compromising load capacity. Load capacity issues are a limiting concern for scale-up of HPT processing to commercial scale. As tool for optimising polymeric carrier design, we have developed an iterative software routine that progressively alters the carrier wall thickness in a previously developed computational fluid dynamics (CFD) model, and coupled this with an integrated temperature distributor (ITD) routine, which allows us to describe, in a single parameter, overall process performance in terms of heat retention and uniformity. The use of the combined carrier wall thickness/ITD routines was demonstrated for optimising the design of a polymeric carrier in a 35 L pilot-scale high pressure sterilisation plant, the ITD concept to have applications in HPT processing beyond carrier design, including as a parameter to describe process safety.

[1]  P. Juliano,et al.  C. botulinum inactivation kinetics implemented in a computational model of a high‐pressure sterilization process , 2009, Biotechnology progress.

[2]  V. M. Balasubramaniam,et al.  Determining Thermal Effects in High-Pressure Processing , 2002 .

[3]  B. Launder,et al.  The numerical computation of turbulent flows , 1990 .

[4]  M. Bull,et al.  Synergistic Inactivation of Spores of Proteolytic Clostridium botulinum Strains by High Pressure and Heat Is Strain and Product Dependent , 2008, Applied and Environmental Microbiology.

[5]  K. Knoerzer,et al.  Adiabatic compression heating coefficients for high-pressure processing of water, propylene-glycol and mixtures - A combined experimental and numerical approach , 2010 .

[6]  H. Ramaswamy,et al.  Inactivation Kinetics of Geobacillus stearothermophilus Spores in Water Using High-pressure Processing at Elevated Temperatures , 2006 .

[7]  P. Fryer,et al.  7 – Modelling particular thermal technologies , 2001 .

[8]  C. O. Ball.  Short-Time Pasteurization of Milk , 1943 .

[9]  Laura Otero,et al.  A model to design high-pressure processes towards an uniform temperature distribution , 2007 .

[10]  R. W. Berg,et al.  Advantages of high pressure sterilisation on quality of food products , 2004 .

[11]  Experimental and numerical analysis of the thermofluiddynamics in a high-pressure autoclave , 2004 .

[12]  Antonio Delgado,et al.  Convective and diffusive transport effects in a high pressure induced inactivation process of packed food , 2003 .

[13]  V.M. Balasubramaniam,et al.  Combined pressure-thermal inactivation kinetics of Bacillus amyloliquefaciens spores in egg patty mince. , 2006, Journal of food protection.

[14]  D. Knorr,et al.  Kinetic studies on high-pressure inactivation of Bacillus stearothermophilus spores suspended in food matrices , 2001 .

[15]  A. Delgado,et al.  The influence of transport phenomena during high-pressure processing of packed food on the uniformity of enzyme inactivation. , 2003, Biotechnology and bioengineering.

[16]  D. Sun.  Modeling Thermal Processing Using Computational Fluid Dynamics (CFD) , 2012 .

[17]  Antonio Delgado,et al.  Numerical simulation of thermal and fluiddynamical transport effects on a high pressure induced inactivation , 2005, Simul. Model. Pract. Theory.

[18]  Volker Heinz,et al.  High-Pressure-Mediated Survival of Clostridium botulinum and Bacillus amyloliquefaciens Endospores at High Temperature , 2006, Applied and Environmental Microbiology.

[19]  Siegfried Denys,et al.  Modeling Conductive Heat Transfer and Process Uniformity during Batch High‐Pressure Processing of Foods , 2000, Biotechnology progress.

[20]  Laura Otero,et al.  Modelling heat transfer in high pressure food processing: a review , 2003 .

[21]  P. Juliano,et al.  A computational model for temperature and sterility distributions in a pilot‐scale high‐pressure high‐temperature process , 2007 .

[22]  Numerical simulation of thermodynamic and fluid-dynamic processes during the high-pressure treatment of fluid food systems , 2002 .

[23]  R. Vogel,et al.  Comparison of pressure and heat resistance of Clostridium botulinum and other endospores in mashed carrots. , 2004, Journal of food protection.

[24]  Wojciech Kowalczyk,et al.  Modelling and numerical simulation of convection driven high pressure induced phase changes , 2004 .

[25]  P. Richardson,et al.  Thermal Technologies in Food Processing , 2001 .

[26]  Behaviour of bacterial endospores and toxins as safety determinants in low acid pressurized food , 2005 .

[27]  M. Farid,et al.  Numerical simulation of solid–liquid food mixture in a high pressure processing unit using computational fluid dynamics , 2007 .