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Reducing waste and enhancing quality: help is coming

20 February 2017

Dr Craig Leadley, of the food manufacturing technologies department at Campden BRI reviews a range of emerging preservation technologies, outlining the key principles and commercial status of each. 

The global food supply chain faces significant challenges in the years ahead and shelf life extension, as a means of preventing food waste, will become ever more important.  Consumers increasingly demand additive free products that are as close to freshly prepared as possible.  In this context, emerging preservation technologies have a key role to play – extending shelf-life, reducing waste and improving product quality.  

High pressure processing (HPP)
HPP is, essentially, a non-thermal process in which packaged products are subjected to very high pressure (applied via water) to pasteurise the product.  Pressures applied are typically up to 600 MPa with hold times of typically no more than 5 minutes. Twenty years ago there were only a handful of commercial products available and the consensus was that HPP was not commercially viable.  However, today it is a vibrant multi-million pound industry with over 300 commercial systems in operation globally.  A significant factor in the success of HPP has been the widespread availability of contract packing facilities as this has given ready access to large scale equipment without companies having to make a significant capital investment. 

Pulsed electric field processing (PEF)
PEF is a continuous non-thermal processing technique used for both pasteurisation and extraction/mass transfer enhancement applications. Pulses of high voltages (typically 20-80 kV/cm for antimicrobial purposes) are applied for short time periods (<1s) to fluid foods passing between two electrodes. The field is cycled about 1,000 times per second and the fluid is exposed to multiple pulses, often by passing it through several chambers. After the treatment the food needs to be aseptically or clean filled, packaged and stored, typically under refrigerated conditions.  Pumpable, homogeneous products are best suited to PEF. The treatment is usually limited to products with no air bubbles, low electrical conductivity (i.e. low salt content) and particles smaller than the gap in the treatment region in the chamber (a few millimetres). As of 2015, there were approximately 50 commercial PEF installations globally, most for extraction applications, with around five commercial installations for pasteurisation. 

Cold plasma
Cold plasma is otherwise referred to as the fourth state of matter. When enough energy is applied to a gas, a plasma discharge can be achieved. Hot plasmas may exist where heat is applied to a gas. If the energy applied is electrical, cold plasma can be achieved.  Relatively speaking, the technology is in its infancy but it shows considerable potential as a non-thermal preservation technology to extend product shelf-life and reduce waste without impacting on product quality.  Cold plasma is a surface decontamination technique that is not likely to achieve pasteurisation but which could impact on microbial counts or growth to extend product shelf-life and reduce waste. The technology could offer significant benefits for short shelf-life products because even small reductions in microbial counts could increase shelf-life.  Industrial research is ongoing at Campden BRI and by other applied research groups, so it seems likely that commercial applications are not too far away.  

Ultraviolet light
Ultraviolet light applications exist for both dry surface decontamination (of produce for example) and continuous flow decontamination ( of UV transmissible fluids, for example). UV treatment involves the use of lamps emitting in the UV-C (germicidal) wavelength. This is a wavelength of 200 to 280nm. A wavelength of 254nm is usually used as this is the optimal wavelength for microbial inactivation.  While far from ‘new’, UV treatment is somewhat under-utilised and could yield significant benefits for shelf-life extension if it were more widely applied. Effective UV treatment relies on ‘line-of-sight’ – if any part of the product is in shadow and not directly exposed to the UV then inactivation will not occur.  This challenge can be addressed by correct light and reflector design and placement as well as by introducing mechanisms to re-orientate the product. A number of commercial suppliers sell UV technologies so it is now very much an ‘off-the-shelf’ technology. While supplying a UV lamp is relatively trivial, understanding lamp positioning, dosimetry and optimisation is not, so choose carefully. 

Ohmic heating
Ohmic heating is a process in which, typically, an alternating electrical current is passed through the food product. The electrical resistance of the food rapidly causes it to heat up. The product is finally cooled using conventional procedures. Ohmic heating is a continuous process and can be used on pumpable foods, including fluids containing large particles. It was first commercialised in the early part of the 20th century, but was unsuccessful due to materials science issues. Viable processes were developed in the 1980s, but the full potential of the technology was not realised commercially at that time.  

Ohmic heating can improve the sensory quality of food products due to the very rapid heating, which cannot be achieved by conventional heating. Most pumpable foodstuffs, with water contents in excess of 30% (w/v), conduct sufficiently for Ohmic heating to be usefully applied. Insulators cannot be heated directly by the process. These include fats, oils, alcohols, sugar syrups and non-metallic solids (bone, cellulose), and crystalline structures including ice.  

Ohmic heating is used commercially to for liquid egg treatment, for the pasteurisation and sterilisation of fruit and vegetable products and bread-crumb production.  It is estimated that over 30 ohmic installations are in commercial use globally. 

A wide range of emerging food preservation technologies is now available. These can be categorised broadly as having non-thermal or thermal mechanisms for inactivation of microorganisms. In either case, the key driver for using these technologies is to extend shelf-life and reduce waste whilst also significantly improving product quality. This article really only scratches the surface of what is available and developments continue at a pace. There have been a number of interesting rapid heating technologies developed based around microwave and radio-frequency heating. Similarly, new modes of application for the technologies outlined above are constantly in development.

The question of capital investment is inevitably raised when new preservation technologies are discussed and it is true that many of these technologies can be expensive.  Work is starting at Campden BRI exploring energy use for a range of these technologies. We hope that by demonstrating the total cost of ownership, investment in emerging preservation technologies will be a more attractive proposition.  Truly disruptive preservation technologies are, almost by definition, likely to be higher risk.  The question is which companies are willing to take the risk and reap the potentially, substantial rewards?

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