Food preservation by pulsed electric fields: Evaluation of critical processing parameters and process optimization

Today's consumers are more interested than ever in foods that are safe, convenient, good-tasting, nutritious, and able to fit into their active and busy lifestyles. This has spurred a search for new processing alternatives. Pulsed electric field (PEF) technology has been proven to inactivate pathogenic and spoilage microorganisms as well as enzymes with minimal losses of food quality, potentially making it the answer to current consumer demands. However, before the industrialization of PEF is launched, there are some problems that need to be overcome. This dissertation is organized into seven self-contained chapters dealing with some of these problems. Chapter One covers the underpinnings and downsides of PEF in the areas of engineering principles, inactivation potential, and regulations. The next chapter reviews the preservation of fruit and vegetable juices, including the inactivation of predominant flora and enzymes, product shelf life, and energy required to pasteurize these products. The third chapter evaluates the inactivation of different strains of Pseudomonas fluorescens suspended in liquid whole egg (LWE) by a hurdle approach to PEF involving antimicrobials, in comparison to high hydrostatic pressure (HHP), another nonthermal technology. Using mathematical simulations, Chapter Four explores the dielectric breakdown phenomena due to the presence of air bubbles trapped in foods during PEF processing. Paschen's Curve is proposed to obtain a first estimate of the pressurization required to prevent arcing during processing. The following two chapters elaborate on the development and implementation of a metrology system to automate the accurate evaluation of critical electrical PEF processing parameters. These include the proper location of high voltage sensors in the PEF system, the implementation of differential voltage measurement of the transients received by the PEF chamber, and maximization of the signal-to-noise ratio. Using the metrology system developed and implemented in Chapters Five and Six, the seventh chapter evaluates the effect of different processing conditions and the energy required to extend the refrigerated shelf life of LWE.