PEF processing is based on electroporation, a non-thermal effect forming pores in cell membranes. In potato processing the technique has turned into a standard process for texture management and cutting improvement. With more than 200 PEF systems installed in food industry Elea is the market leader. This expert view will discuss PEF and its benefits in potato processing and highlight recent equipment design upgrades.
The PEF effect
PEF has an instant effect on tubers and roots as well as fruits and vegetables. Opening nanometer sized pores causes release of intracellular liquid and tissue softening. Dependent on concentration gradient in- and outside of the cells the uptake or extraction of soluble substances are accelerated. Being a volumetric technique PEF works independent of tuber size. The process and extent of tissue softening are controlled by pulse parameter such as electric field strength and specific energy applied. In contrast to thermal processing there is no delay after startup or when changing process conditions.
Product benefits for French Fries
Like after preheating, PEF induced texture softening improves cutting and results in less feathering and breakage. But, in comparison to thermal treatment energy and water consumption are reduced by up to 90 %. Typical energy input for a PEF processing of potato tubers is 0.3 to 1.5 kJ/kg, corresponding to a temperature increase of 0.01 to 0.4°C. Process intensity is adapted during the season, being highest with fresh from the field crop or harder tuber varieties and lower at the end of the season. As a result, the average product length is increased, and the starch loss into cutting and blanching water streams is reduced. That causes an up to 1.5 % yield improvement for a French fries processing line.
Due to less tissue breakage the oil uptake during frying is reduced by approximately 10 %. As the electric field effect is instant and volumetric, there is no holding time requirement and no start up or shut down time need. Today approx. 150 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 non-potato raw material such as sweet potato, parsnip or cassava.
Fry the perfect chip
Potato and vegetable chips processing is dependent on high quality raw material and optimized processing. Slicing quality and consistency are key factors, as performance of subsequent processing steps and product quality depend on them. During slicing of potatoes and other vegetables PEF reduces tissue breakage and the number of fines and smaller particles. 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 during frying. 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 water release frying temperature and / or time can be reduced. On continuous frying lines – dependent on process 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, up to 15 % for typical product and frying conditions. With today´s frying oil costs, reducing oil uptake provides a major contribution toward fast return of investment. Less fines and particle carry-over into the fryer will also help to reduce oil degradation and increase frying oil lifetime. 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. 50 Elea PEF systems are in use in snacks industry, ranging from 1 to 12 t/h treatment capacity for single lines or up to 32 t/h where multiple slicing and frying lines are supplied from one PEF system.
Savings potential
PEF implementation delivers savings at various levels of the production chain. Replacing preheating and reducing blanching time, less starch release, increased yield and a reduced oil uptake will result in reduced energy, raw material and frying oil expenditure. On a standard sized French Fries line of 30 t/h final product output the water and energy savings can amount up to 20 million kWh of thermal energy and 60 million liters of processing water in comparison to preheating. Reduced starch losses will generate up to 500 t of extra yield per year, whilst oil uptake is reduced by up to 700 t per year. Other product quality benefits such as more consistent product quality or color improvement and the potential to use different raw materials or cuts provide further process and financial benefits.
In potato chips processing yield increase and reduced oil uptake contribute towards a fast payback. Dependent on raw material quality and product shape up to 1.5 % yield increase is achieved due to less starch losses. On a 1,300 kg/h final product line an annual extra yield of up to 47 t is observed. Less fines or doubles as well as reduced fryer heat load will reduce level of defects and increase product yield even further. Lowering the oil content from 33 to 28 % translates to up to 175 t less oil consumption per year. Again, product benefits such as better crunch or lighter color will provide extra benefits. Our PEF experts are available to discuss expected benefits and return of investment as well as for line optimization to make use of the full savings potential.
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 it may cause undesired solids and yield losses. For process monitoring and optimization Elea has developed two tools: PEF Control and Cut Control. 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.
Our largest processing system
All Elea systems are designed with a focus on ease of operation and reliability. This year we have launched the new B1000-850 system. We have distilled the know-how and experience of 10 years of industrial scale potato processing into the design, capable of processing up to 100 t/h. The design features the largest free cross section on the market for hassle free product transport and to achieve high product load ratio and maximum energy efficiency. Similar than for our B1-200 and B10-320 models all safety features are included into the vessel design, no extra safety fencing is required. The system can host different belt types and is suitable for sinking or floating products. Other new features include enhanced water management, easier cleaning and servicing and new pulsed power cabling for increased maximum length. For smaller treatment capacities the new B100-535 (up to 32 t/h) and new B10-535 (up to 20 t/h) are available with same design features. With same footprint and power level those new designs allow processing more for less.
What´s next and where to trial?
Our PEF experts work closely with clients to provide tailor made solutions to best suit individual requirements. Current development work focusses on process optimization and product development for new 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 in combination with thermal treatment can also be used to manage tissue texture by targeted pectin modification. That allows to reduce texture degradation during cooking or canning of potatoes and other vegetables. The Elea pilot hall in Quakenbrück, Germany is available to develop the best solution for your potato product. Making use of our network of regional agents and technology partners demo activities or on-site-trials in your area or your production can be arranged.
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