Candidate
Ahmed Gad
Title
A Study of Electrode Material Performance During Food Processing by Pulsed Electric Fields
Supervisor
Sheshakamal Jayaram
Abstract
The use of pulsed electric fields (PEFs) provides an alternative way to preserve liquid food products (for example: milk, juices, and beer) instead of the conventional thermal pasteurization. Upon the application of the high-field pulses, electric charge accumulates across the membrane of any microbial cell present in the processing zone between the two electrodes. Within a few hundred nanoseconds, this charge accumulation results in an irreversible membrane breakdown which causes the cell to lose its viability. By this means, an extended shelf life could be achieved. The advantages of using the PEF processing over the conventional thermal pasteurization include more retention of the original nutritional value and fresh taste, less usage in the processing energy, and lower contamination in the processing equipment.
Physical and electrical contact between the liquid food product and the metallic electrodes during the PEF processing is unavoidable and causes some metallic ions to be released from the electrodes into the processed food. This undesirable phenomenon of releasing metallic ions from the electrodes can affect food safety and taste, degrade food compounds/color, and shorten the electrode lifetime. As a result, it represents one of the challenges against the commercialization of such non-thermal preservation technique.
In this study, a better understating of the aforementioned phenomenon is presented by means of a thorough investigation of the operating factors that may eliminate, or at least reduce, the rate at which the metallic ions are being released. This rate is analytically measured in terms of the concentration increase of the metallic ions in the PEF-processed products. To reflect on the quality of PEF-processed products, trained and untrained sensory panels are held over a shelf-life of twelve weeks.