Impact of PEF treatment inhomogeneity such as electric field distribution, flow characteristics and temperature effects on the inactivation of E. coli and milk alkaline phosphatase

Aplicación industrial de los pulsos eléctricos de alto voltaje para la pasteurización de alimentos: revisión de su viabilidad técnica y comercial

“…Esto ha de ser tenido en cuenta al definir las condiciones de procesado, ya que hay que garantizar que todo el alimento recibe el tratamiento mı´nimo adecuado (Meneses et al, 2011). Atendiendo a ello, en la u´ltima de´cada se ha generalizado el uso de me´todos nume´ricos de simulacio´n para mejorar el disen˜o de este tipo de ca´maras, tendiendo en cuenta tanto la distribucio´n del campo ele´ctrico y la temperatura como las caracterı´sticas del flujo de producto (Buckow, Schroeder, Berres, Baumann, & Knoerzer, 2010;Fiala, Wouters, van den Bosch, & Creyghton, 2001;Gerlach et al, 2008;Jaeger, Meneses, & Knorr, 2009;Lindgren, Aronsson, Galt, & Ohlsson, 2002).…”

Moderate and high intensity pulsed electric fields : Effect on microbial inactivation, shelf life and quality of fruit juices

“…Increase in gap/diameter ratio increases homogeneity (Van den Bosch, 2007) and rounded edges on insulator geometry improve electric field strength distribution Schroeder, Buckow & Knoerzer, 2009). Numerical simulations showed that increase of the flow velocity increases turbulence and provides a better mixing of the fluid, avoiding high (peak) temperatures generated in the zone near the insulator wall, leading to a more homogeneous temperature distribution in the treatment chamber (Jaeger, Meneses & Knorr, 2009;. To conclude, flow conditions are mostly laminar at laboratory and pilot scale equipment, while they are mostly turbulent at industrial scale equipment.…”

“…The velocity profile in the treatment chamber (laminar, transitional or turbulent) determines the residence time distribution in the treatment chamber. Longer treatment times will occur near the wall of the treatment chamber due to lower flow velocity, and shorter treatment times occur in the centre of the treatment chamber where a higher flow velocity exists (Jaeger, Meneses & Knorr, 2009), resulting in a larger homogeneity for turbulent flow than for laminar flow conditions. During the PEF treatment the liquid food is heated as a result of the dissipation of electrical energy and, as a consequence, temperature dependent food properties such as electrical conductivity, density, viscosity and thermal conductivity are modified (Fiala et al, 2001).…”

“…Changes in electrical conductivity may influence the electric field distribution and changes in viscosity, density and thermal conductivity may affect product flow. Measurements in the small treatment chamber volume are not possible without interference of the measuring device with the product flow and electric field (Jaeger, Meneses & Knorr, 2009), and it is therefore a difficult task to achieve experimental information (Saldaña et al 2010a). For experimental performance of PEF treatments, the determination of the average outlet temperature is still the most suitable method for an in-line process characterization due to the lack of alternative measuring possibilities (Jaeger, Meneses & Knorr, 2009).…”

“…Measurements in the small treatment chamber volume are not possible without interference of the measuring device with the product flow and electric field (Jaeger, Meneses & Knorr, 2009), and it is therefore a difficult task to achieve experimental information (Saldaña et al 2010a). For experimental performance of PEF treatments, the determination of the average outlet temperature is still the most suitable method for an in-line process characterization due to the lack of alternative measuring possibilities (Jaeger, Meneses & Knorr, 2009). However, numerical simulations of the fluid dynamics coupled with the distribution of electric field strength and temperature inside the treatment chamber can provide detailed knowledge on the spatial and temporal distribution of both parameters for various PEF treatment conditions.…”