So, what’s PEF?
The ‘Pulsed Electric Field’ (PEF) technology is a mild food processing technology, suitable for preserving liquid and semi-liquid food products. This processing method uses short electric pulses to achieve microbial inactivation in food products while preserving the fresh characteristics. These short electric pulses introduce a potential difference between the inside and outside of the membrane of microorganisms, which results in permeation of the cell membranes. Because of this, microorganisms can be inactivated by this method.
PEF can be applied at relatively low temperatures for pasteurization of food products with minimal effects on the fresh characteristics like colour, taste, and nutrients. The process itself has only limited effect on the inactivation of enzymes. Chilled storage is therefore necessary to maintain the quality during shelf life.
Which are the barriers for a wider implementation of PEF?
Continuous discussions with the first users of this technology as well as with enterprises that are in general open to innovation have revealed that the lack of process guidelines with respect to complying with the relevant food legislation is one, if not the most dominant, factor hindering a broader application of PEF.
In general, processors require a HACCP concept that identifies critical control points, process conditions and monitoring tools. As PEF is a technology with multiple process and operation parameters (electric field strength, pulse waveform, energy input, and temperature), there is no general dose concept available so far to describe and monitor the treatment intensity and its distribution. Present users of the technology have identified their own, application specific concepts for process monitoring, which requires a high level of technical and scientific background as well as case by case discussions with food authorities. The development of a standardized, on-line process monitoring concept based on the specific energy delivered and the determination of treatment intensity distribution is crucial.
PEF treatment intensity can be characterized based on 1) initial temperature, 2) energy delivery electrical field strength and 3) temperature after treatment. Commonly the liquid flow is heated before the treatment, to increase the efficiency. After the treatment, the flow is cooled to stop quality decreasing processes, such as enzyme reactions.
The main step in the PEF process is the application of pulses of an electrical field of a part of a liquid stream. The frequency, shape and amplitude of the pulses result in the intensity of the treatment. Together with the shape of the treatment chamber the efficiency is determined.
Depending on the configuration of the treatment chamber and the product viscosity, a three-dimensional spatial treatment intensity matrix can be compiled. Whereas the overall energy delivery can typically be detected by pulse monitoring, its spatial distribution can only be indirectly measured by temperature increase. Due to the presence of high electric field strength, conventional thermocouples can only be used far away from the application area. In contrast to that, the use of fibre optic sensors will allow temperature detection in the treatment zone. Selection of suitable positions for temperature measurements, implementation of sensors and online data analysis are core elements for the application of a standardized HACCP concept.
Despite the fact that suitable fibre optic sensors are available, their use for the development of a standardized HACCP concept needs to be demonstrated. The robustness of the process monitoring concept e.g. in cases of deviation of inlet temperature or product flow will have to be challenged and validated.
You can see how PEF works in this video from ELEA (one of the partners from the i3-food Consortium):
The innovation potential in the field of PEF is a wider implementation of this technology for the preservation of pumpable food products. Traditional thermal pasteurization destroys health promoting ingredients such as vitamins and leads to loss in fresh flavour.
The application of PEF allows the preservation of heat sensitive products such as juices or smoothies, for which fresh taste is the main quality parameter, without or with only minor detrimental effects on the quality. The continuous operation and simple equipment design with different capacity options allows an easy implementation into existing production lines. The online evaluation of the
intensity of important process parameters (e.g. specific energy and temperature) is crucial for guaranteeing the production of safe products with high quality.
Process benefits are independent of product categories and could also be transferred onto other industries such as biotechnology and pharmaceutical industry where a reduced thermal intensity during pasteurization (media for fermentation, vaccines etc.) would be beneficial as well.