How does it work?
PEF application causes electroporation, or as we like to call it “eleaporation”, forming pores in cell membranes with low energy input and heat load. The mechanism of action is long known, but only in the last decade it has found broad use in vegetable processing industry. With 200 Elea PEF systems used in food industry Elea is the market leader in this field. This article will briefly look into history of PEF use, discuss process and product benefits for potato industry and into equipment design and give an outlook in upcoming application opportunities.
The early days
As far as we have found out fist reports on PEF use date back to the 1960s, researchers in Germany and the Ukraine have observed cell disruption and improvement of mass transport and separation processes after applying pulsed power. First industrial scale prototypes types have been erected in the 1980s for fish meal processing, but high power switching technology was not developed far enough. The technology took a step back into academia. In the 1990s universities including Ohio State University, Washington State University and Berlin University of Technology ran public funded projects on PEF use for microbial inactivation and plant cell disruption. Around 1997 first reports on PEF impact on potatoes, carrots or sugar beets have been published by Angersbach et al or Rastogi et al. Loss of turgor pressure and tissue softening have been observed making use of textural analysis.
First uses in potato processing
In 1998 technical scale systems have been developed for continuous testing in potato starch industry.First setups used gravity as a transport means, but very fast it has become obvious that forced product transport is required and water wheel and conveyor belt systems have been built. Making use of horizontal or vertical electrodes processing belts have shown high process performance, reliability as well as applicability in food industry. In 2006 an industrial scale system has been installed in French Fries processing. Since then, turn-key, industrial PEF systems have been developed at DIL, Germany.
PEF product benefits for French Fries
As the internal cell pressure (turgor) is lost, potatoes soften after a electroporation treatment. Similar than after preheating, the texture softening improves cutting and results in less feathering and breakage. In comparison to preheating, PEF use has a number of product and process benefits and energy and water consumption are reduced by up to 90 %. For PEF application an energy input of 0.3 to 1.5 kJ/kg of potato is applied, causing a temperature rise < 0.4°C. During the season process intensity is adapted during the season, being highest with fresh tubers from the field crop or harder varieties and going down towards the end of the season. Average product length is increased, and the starch loss into processing wtaer streams during cutting and blanching is reduced. That allows an up to 1.5 % yield improvement for a French fries processing line. Less tissue breakage also reduces oil uptake. Up to 10 % reduction are achieved. No holding time is required as the electric field effect is instant and volumetric, also, no start up or shut down time need. Today approx. 140 Elea PEF systems are in use in French Fries industry with processing capacities from 5 to 75 t/h. Recent projects are increasing treatment capacity up to 100 t/h on single lines or treatment of other raw material such as sweet potato or cassava.
Fry the perfect chip with PEF
Raw material quality and optimized processing are key drivers for high quality potato and vegetable chips. Slicing quality and consistency are key factors in that industry, as all subsequent processing steps and product quality depend on them. PEF reduces breakage and number of fines and broken particles during slicing of potatoes as well as other vegetables. A smother cut surface will reduce starch loss and the extent of free starch on product surface. This is beneficial for product yield and texture, as well as to reduce product stickiness and doubles. Keeping starch in the slices contributes to improved texture and crunch. With reduced starch loss and improved cutting up to 2 % yield increase can be achieved. Due to faster release of water frying temperature and / or time can be reduced. On continuous frying lines – dependent on line setup – up to 10 % frying time reduction is possible, which in combination with a reduced final frying temperature results in less heat load and increased product quality. For batch frying up to 15 % capacity increase can be achieved due to facilitated moisture removal. Most potato chips lines do not include a blanching step, but where applied PEF can help to revert undesired effects of blanching on product texture. Less slice surface damage will result in less oil uptake, approximately 10 % for typical product and frying conditions. For raw materials such as carrots, parsnip, sweet potato or cassava similar benefits are observed. PEF will improve product cutting and allow faster water removal and reduced oil uptake. Reducing frying time and temperature will allow lighter product color and more natural product appearance. At present approx. 40 Elea PEF systems are in use in snacks industry, ranging from 1 to 12 t/h treatment capacity for single lines or up to 28 t/h where multiple slicing and frying lines are combined. See a PEF user testimonial below.https://www.linkedin.com/embeds/publishingEmbed.html?articleId=9036411920855038759
Equipment design and line integration
Continuous systems are used for industrial scale potato processing. They consist of a pulse modulator for energy supply and a treatment area. System power and mechanical design are dependent on processing capacity needs. Electric field strength (~1 kV/cm) and specific energy input (0.3 to 1.5 kJ/kg) are key process and design parameters. The maximum cross section is defined by the field strength required. Specific energy input and throughput determine the average power rating. To allow smooth product transport the treatment chamber cross section should be wide and free of obstacles, it´s dimensions determine the system peak power rating. Current pulse generators are either based on pulse transformer or Marx generator design. Pulse transformer-based systems allow smaller footprint, but peak currents are limited to 1 or 2 kA. Due to their higher peak currents of up to 10 kA Marx generators allow wider treatment channels and are preferred for higher throughput systems. For solid products such as roots or tubers belt systems have shown best performance and reliability with constant treatment intensity over varying throughput or product size. Water is used for energy transfer, to control treatment efficacy and reduce water requirements process water quality is continuously monitored and managed. Dependent on treatment capacity and generator power ratings both horizontal and vertical electrode configurations can be used. Whilst PEF works peel on or off, most systems are installed after peeling, where subsequent hydrojet cutting or slicing benefits from improved consistency and longer knife durability. For larger scale installations pulsed generator and treatment unit are separated to ensure small footprint withing the actual processing line. To suit the demand in snack sector, Elea has designed a dedicated, compact all in one unit with treatment capacity of up to 9 t/h. This allows easy implementation into existing production lines.
Process control and optimization
With increasing PEF energy input pore size increases and besides water also sugar or starch are released. The more the better is not the right approach here, as that may cause undesired solids and yield losses. For process monitoring and optimization Elea has developed two tools, PEF Control and Cut Control. Following a concept suggested by Angersbach et al, PEF Control is based on impedance measurement to detect the number of open cells in a tissue and to predict mass transport improvement e.g. in extraction, infusion or drying processes. Cut Control measures compressing and cutting force for tubers and hence allows selection of suitable processing parameters dependent on raw material variety, season and desired cut. Together with our clients as well as line integrators we have run in person or remote supported installation and line optimization projects. Making use of our own video support app the process is handled from first trials in pilot scale through proof of principle testing at place to system installation, startup and commissioning. Remote diagnosis and support are available for customer service as well as product development. When integrating a PEF system into turnkey projects or for retrofit, our team of experts is available to maximize overall line performance by optimization of process equipment and settings on all stages of the production line.
Sustainability implications
With an energy requirement of approx. 1 kWh per ton of product, PEF is the most efficient cell disruption technique. PEF water usage ranges from 30 to 50 l per ton of product, dependent on infeed water and product conductivity. To minimize water use soil or free starch should be removed prior to entering the treatment bath, after treatment the process water can be reused in other process stages. A number of PEF users have run and published sustainability analyses after PEF implementation. For a typical 26t/h line water savings in a range of 24.000 m3 and energy savings of 10 million kWh per year have been reported. Those savings in combination with a yield increase of approx. 950 t and an oil uptake reduced by 368 t per year help to save money, resources, and the environment.
What´s next and where to trial?
We work closely with clients to provide tailor made solutions to best suit their individual requirements. Current work focuses on process optimization and new product development for new product shapes or using so far underused crops. PEF enhanced infusion and uptake of color, flavor or active ingredients allows to impact on product taste and appearance. PEF can not only be used for tissue softening, but with thermal treatment can be used to preserve tissue texture by targeted pectin modification. That allows to reduce texture degradation during cooking or canning of potatoes and other vegetables. And finally, combinations of PEF and vacuum frying or microwave vacuum drying allow to create novel, tasty and crunchy product textures. With PEF Pilot we have developed the most versatile R&D system available on the market.
Reach out to us at www.elea-technology.com to develop the best solution for your potato product.
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