Non‐newtonian Canned Liquid Food, Unsteady Fluid Mechanics and Heat Transfer Prediction for Pasteurization and Sterilization

Abstract

Unsteady fluid mechanics and natural convective heat transfer during pasteurization and sterilization for aqueous (CMC solution) and fatty (soybean oil) liquid foods were numerically predicted by means of noncommercial computational program developed in this work. This software is based on the finite volume method and the food simulants are assumed to be non‐Newtonian fluids with a temperature‐dependent power‐law viscosity model. Different cylindrical container materials were analyzed (LDPE, PA, PP, galvanized steel), with h/d equal to 0.53, 1.56 and 3.12. Results obtained show that the time required for sterilization is strongly dependent on the liquid food rheological behavior. A recirculating flow pattern was found inside the cylindrical container for the aqueous food stimulant. The Tshz variation with the dimensionless time was faster heating when the h/d decreases. The fastest heating pasteurization and sterilization processes were obtained for CMC solutions inside cylindrical packages with a pseudoplastic behavior. PRACTICAL APPLICATIONS There is a vast body of literature about transport phenomena of thermal treatment of packaged food. However, this literature is restricted when the analyzed foods show a non‐Newtonian behavior. The methodology described in this paper aims to contribute to the understanding of pasteurization and sterilization of packaged non‐Newtonian liquid foods through the implementation of a fast and accurate tool for the optimization of the operational parameters in these treatments, as well as in the design of packaging materials. Commercially available computational fluid dynamics is a powerful tool for the analysis of transient heat transfer packages that allow it to simulate almost any geometry or even import it as Computer Aided Design (CFX, FLUENT and others). Also, rheological properties can be introduced by applying user‐defined functions. The noncommercial computational program developed in this work allows modifying operation, rheological and design parameters without restrictions. The versatility of these tools can complement experimental studies decreasing the time required to the design of the package and its associated costs. On the other hand, an accurate prediction of the unsteady fluid mechanics and natural convective heat transfer during thermal treatments allows estimating the adequate conditions to preserve the quality of packaged foods, along with reduction in energy consumption, resulting in low contamination.

Effect of two viscosity models on lethality estimation in sterilization of liquid canned foods

“…(a) First sophistication level and (b) second sophistication level. , in comparison with reported results of similar problems (Abdul-Ghani andFarid, 2006;Boz and Erdogdu, 2013;Boz et al, 2014;Moraga et al, 2011).…”

“…Natural convection reduces sterilization times of liquid canned viscous foods, therefore, the apparent viscosity of the food is a key variable in the convection rate (Augusto and Cristianini, 2010;Erdogdu and Tutar, 2012). The food fluids usually exhibit a non-Newtonian behavior (Moraga et al, 2011), modelled via Power Law, Bingham, Casson, Herschel-Bulkley, etc. This circumstance implies the development of suitable governing equations, starting from microscopic momentum balance for incompressible fluids (Bird et al, 2002), substituting the tensorial version of the rheological model of interest in stress tensor term r Á ð…”

Computational Simulation and Developments Applied to Food Thermal Processing

“…Taking into account all these considerations, the use of this computational software is highly recommended to simulate the liquid food sterilization process using low CPU time for calculations. Moraga et al [96] studied a thin cylindrical can containing a non-Newtonian liquid food: CMC suspended in water (0.85% w/w) as aqueous food simulator (Fig. 9).…”

“…Examples of food freezing, drying, and sterilization processes have been described by using different numerical methods, with and [96] without the direct use of convective coefficients as an external boundary condition input for the mathematical model. A new procedure defined as conjugated model, without the use of convective coefficients in the mathematical model that includes the external environment surrounding the food, has been reviewed through different investigations which were analyzed and discussed.…”

Computational Fluid Dynamics (CFD) Modelling and Application for Sterilization of Foods: A Review

“…As the temperature of the product becomes uniform, buoyancy forces then decrease, which results in the cessation of recirculation and a reduction in velocity [6]. To investigate the flow pattern and the position of the SHZ during sterilization, CFD has been widely used in canned liquid foods, such as beer, carboxyl-methyl cellulose (CMC), cherry juice, corn starch, soup, soybean oil, and milk [8,11,13,20,[65][66][67][68][69]. The CFD models for canned liquid foods were To investigate the flow pattern and the position of the SHZ during sterilization, CFD has been widely used in canned liquid foods, such as beer, carboxyl-methyl cellulose (CMC), cherry juice, corn starch, soup, soybean oil, and milk [8,11,13,20,[65][66][67][68][69].…”