Pulsed electric field (PEF) technology applied to food processing was firstly used in the late
1960s. The currently available systems use either conventional Blumlein generators or
generators similar to those found in radar power sources to produce the required high voltage
pulses. The liquid to be processed is passed through a number of treatment chambers or cells
which each contain a pair of electrodes in contact with the liquid. An electric field is thereby
applied to the liquid, leading to the technology being termed invasive and it can be used only
with liquid food.
A novel and non-invasive PEF technology for use in the food processing industry is
introduced and investigated in this thesis. The technology represents a novel way of
performing PEF treatment. A proof of concept arrangement uses two ceramic cylinders
mounted inside the non-invasive PEF cell with a gap of 3 mm between them. A displacement
current of the order of mA passes through the non-invasive PEF cell during treatment, as
compared with the kA of current usually produced during an invasive treatment. The low
current is not only economic in electric energy but also maintains a low food temperature,
which implicitly maintains food flavour.
In the thesis the electro-optic Kerr effect technique is used to perform accurately the PEF
measurement and convincingly prove that strong electric fields are present. Two Kerr water
cells were designed and used to determine the Kerr constant for water, since the data
presented in the literature is unreliable. The first Kerr water cell uses a pair of Bruce profile
stainless steel electrodes and the second a pair of parallel plate stainless steel electrodes. An
electro-static solver (Maxwell software) was used to determine the electric field distribution
and to calculate the electric field integral to accurately determine the Kerr constant for water.
Water samples containing the E-coli bacteria were prepared and filled in the non-invasive
PEF cell by the Flavometrix Company. Eight PEF experiments were successfully performed
during this research programme and the results show unequivocally that the novel noninvasive
technique is effective in significantly reducing the initial concentration of E-coli
bacteria. This opens the door for the future design of an industrial prototype
Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.