Serving Up Alternative Sterilisation

The potential market for sterilisation globally is vast; in the US alone, the food safety testing sector is currently worth around $3.5bn according to an updated report by BCC Research, and tipped to increase at a compound annual growth rate of 6.6% over to $4.7bn by 2015.

Worldwide, the picture is broadly similar – and with an innovative range of alternate technologies poised on the brink of greater acceptance and wider uptake, some believe that we are about to see the beginning of a revolution in food preservation and processing.

Microwave technology

The view that the sterilisation market is poised for massive growth is advocated by Professor Juming Tang, leader of the collaborative team of US military and food industry scientists at Washington State University. They are behind a revolutionary microwave sterilisation technique recently approved by the FDA regulators. “It’s a milestone that could pave the way for commercialisation,” he says of the innovative system – the first of its kind to be approved for pre-packaged, low-acid foods – which not only significantly extends shelf life, but also preserves its nutrient value, taste and texture.

The underlying principle is a simple one: packaged food is immersed in pressurised hot water and heated by microwave energy at 915MHz – a more deeply penetrating frequency than the 2450MHz produced by conventional domestic microwaves. Within eight minutes, any pathogens or other microorganisms will have been destroyed, and the food product that emerges is said to be superior in quality to ready-to-eat meals processed conventionally.

There is nothing new about microwave energy as Evan Turek, senior research fellow at Kraft Foods – one of the major food companies participating in the work – makes clear. “Since the introduction of industrial microwave ovens in the late 1940s, the food industry has been interested in exploiting the rapid heating capability of microwaves to improve the quality of canned food. The technical issue has always been ensuring uniform and reproducible heat treatment.”

By developing a new chemical marker to identify cold-spots, the team has demonstrated to the FDA’s satisfaction that this problem has been successfully overcome.

Tang believes that a commercial version of the approach – which won one of the Institute of Food Technologists’ 2010 awards for achievement – could be market-ready in under two years.

Cream and the e-beam

One alternative sterilisation technology that is already making a commercial impression is the low power electron beam used by UK-based Farmright Group.

Using e-beam technology developed by Advanced Electron Beams (AEB), they treat the packaging of Dairystix’s individual tear-and-pour portions of milk and creamer prior to filling, achieving a shelf-life of 180 days and significantly reduced costs.

In addition, the need for chemicals, steam and wash water is removed from the sterilisation process, bringing a little extra shine to the company’s green credentials – and a welcome marketing point too.

While around 150 of AEB’s proprietary systems are now in use around the world, mostly in similar food applications, the technology in general has undoubtedly created a bit of a stir, speculation that e-beams are the future of chemical-free aseptic packaging is probably a little premature, at least for now.

The development of the latest generation of compact, cost effective, low voltage emitters has opened up the possibility of a host of new applications, but the unavoidable corollary of low-powered systems is limited penetration. While this is clearly no problem for the surface treatment of films, at present extending e-beam sterilisation to preformed HDPE or PET containers represents a more difficult proposition.

Nevertheless, with the aseptic sector seen by many as a major growth area for the mid- to long-term, it is a challenge that all sides of the industry are evidently keen to address.

In 2009, for instance, Shibuya Kogyo brought an innovative bottle sterilisation system onto the Japanese market and AEB is currently working on their own, while the Commonwealth Scientific and Industrial Research Organisation has joined up with the Fraunhofer Institute and Evonta-Service to help make the technology mainstream in Australia.

Even though this march towards commercialisation has really only just begun – and there is still more innovation to come – the approach now seems comfortably destined for wider uptake across the industry in the coming years.

Photocatalysis and UV

As consultant microbiologist Clare Miles explains, microwaves and e-beams are not the only alternative methods attracting current interest. “Bacteria in general, and pathogens in particular, they’re the big players in this game, which means that any technology that deals with them effectively is going to have potential commercial uses. Take some of the things going on with photocatalysts and nano-coatings at the moment, for example.”

She cites the work of food scientists at the University of Athens, where researchers have recently made an important breakthrough with an approach based on nano-structured titanium dioxide (TiO₂) photocatalytic films and ultraviolet-A (UVA) light.

In laboratory tests, glass surfaces coated with the photocatalyst and then deliberately contaminated with biofilm-forming Listeria monocytogenes, were found to be rapidly disinfected when exposed to UVA at a wavelength of between 315nm and 400nm.

Although the exact mechanism is currently unknown, it is believed that the highly active free hydroxyl radicals are generated when TiO₂ particles become photoexcited to play a major role in the effect.

While further work will, of course, be necessary before this kind of technology enters an actual processing plant, its demonstrable efficacy against a pathogen known to thrive under the conditions of food production facilities could herald a step-change in surface sterilisation.

Ultimately, as Dr Miles points out, it all comes down to regulatory approval and industry acceptance.

Sterilisation techniques based on gas plasma atmospheres, she says, are probably a good five years away from the market, and other technologies will wait even longer.

It is a point also echoed by Professor Tang. “Our team patented system designs in October 2006 after more than 10 years of research. We spent another three years, developing a semi-continuous system, collecting engineering data and microbiologically validating the process before receiving FDA acceptance.”

It may take time, but the prevailing trends of sustainability, food safety and changing consumer tastes, which are shaping the future of food processing, will almost certainly make the wider deployment of the current crop of alternatives inevitable, and the innovation of others too.