A mini revolution

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A mini revolution
The introduction of nanotechnology is being heralded as the dawn of a new industrial age. John Dunn discovers exactly what it promises for food manufacturers

Plants, animals, and other forms of life in the food chain are all built by nature from atoms. So could human beings use nanotechnology to assemble food products using the same microscopic building blocks?

Instead of harvesting cattle and grain for protein and carbohydrates, suggests Marvin Rudolph, director of DuPont Food Industry Solutions in the US, why can't we build microscopic machines -- nano robots -- that can make steaks and flour from carbon, hydrogen, and oxygen atoms? While we're at it, why not insert other nanobots into our 'nano food' to circulate through the blood system, cleaning out fat deposits and killing harmful pathogens?

It would be easy to dismiss Rudolph's ideas as science fantasy if DuPont were the only company with a nanotechnology vision of food production. But it's not.

This is the area of science where physics, chemistry, biology, and electronics collide to enable scientists to control the microscopic structure and behaviour of materials. When these get down to the nano scale of a few tens of billionths of a metre in size, their behaviour lies between the quantum effects of atoms and molecules and conventional bulk properties. It is this no man's land that is exciting food companies.

Particles and material structures made and controlled on the nano scale exhibit special characteristics, offering food scientists the potential to develop tailor-made foods and fresher, tastier, healthier, safer products.

Dr Manuel Marquez-Sanchez, senior scientist at Kraft Foods dreams of creating products that incorporate nano-sensors to detect a consumer's food profile. He believes they could pick up personal likes and dislikes, allergies, and a person's nutritional deficiencies. Nanotechnology could then be used to release precisely controlled amounts of the appropriate molecules to tailor the smell, taste, and goodness of the product for the individual consumer.

Marquez-Sanchez is director of Kraft's NanoteK world-wide research consortium that is exploring nanotechnology for food production. It is already looking at 'smart' nano-filters that could allow only the beneficial molecules to reach the consumer, trapping the ones that could cause an allergic reaction, and investigating 'smart' packaging that could release a dose of calcium molecules, for instance, to people suffering from osteoporosis.

Nestlé, too, is looking at the possibility of using nanotechnology to customise and personalise food. In a paper to July's annual bash of the Institute of Food Technologists in Las Vegas, Nestlé said nanotechnology would create new food and packaging materials with self-assembly, self-healing, and self-maintaining properties. These would allow the precisely targeted delivery of nutritional and health benefits, it said.

But back in the real world, nanotechnology is already being put to work for more immediate needs. Professor Andrew Mills of the pure and applied chemistry department at Strathclyde University is developing oxygen indicators for food packaging that use an ink consisting of light-absorbing nano-particles of titanium dioxide. Shine ultraviolet (UV) light on the ink and it becomes oxygen sensitive, changing colour as it picks up oxygen molecules.

"You have this harmless ink that you print on to a label, and then just before it leaves the factory, you activate the label with UV so that it becomes oxygen sensitive," explains Mills. "The food now has a label monitoring its travels. So if the package is damaged and air gets in, the label changes colour to tell you. We're talking to ink manufacturers and printers about incorporating the ink into food packaging."

Nano-sized titanium dioxide particles are semiconductors that absorb UV energy to create electron-hole pairs that migrate to the particle's surface and do chemistry, says Mills. He envisages the end of sell-by dates as smart inks based on this technology record what's happening to food. By combining time-temperature inks with others that can detect bacteria growth you could build safety alerts into products, says Mills. Imagine a barcode printed with smart inks. "If a package is damaged, then one of the bars would disappear. So, when the pack was scanned at the check-out, the till would flash up and say: 'Actually, we will not sell this product to you because it is dodgy'."

Titanium dioxide has been used for years as a pigment in paints and inks, in sun block, and for whitening foodstuffs. But its nanoscale photo-active properties only hit the headlines when Pilkington launched the world's first self-cleaning glass three years ago. Its Activ glass uses a coating of UV absorbing titanium dioxide nano-particles to break down the organic matter or 'glue' that holds dirt and muck particles on windows so that rain can wash them away.

Now Dr David Sheel, former project leader on the Activ project, has set up CVD Technologies in Salford to help companies develop light activated self-cleaning surfaces, particularly in the food industry. Lab tests show that the same chemistry that breaks down the 'glue' holding dirt to glass can also destroy bacteria, says Sheel.

The trick now is to transfer the process from the lab to the workplace but, at the moment, these titanium dioxide coatings are not sufficiently active in ordinary daylight or under factory lighting. Once these problems are overcome, Sheel says anti-bacterial surface coatings could slow bacterial growth between clean downs.

By using nanotechnology to modify the surface of filter membranes, scientists can create microscopic pores or holes that precisely match the shape of a chosen molecule. These nano-filters can then be specifically tailored to remove selected molecules, bacteria, or even viruses.

Dr Meirion Jones at the University of Wales in Swansea, is working on nano-filters for extracting food colouring and flavouring.

"Beetroot is a well-known food colouring material but beetroot also has a flavour. It's not very nice, a bit earthy. However, using nano-filter technology we have been able to filter out just the colour, leaving it tasteless."

In other experiments, Jones has used nano-filtration to turn red wine into white and he has been able to extract the colours from red cabbage and onions to produce natural pH indicator dyes -- an alternative, maybe, to chemicals such as phenolphthalein, which has come under fire as a possible carcinogen.

Because nano-filtration and nano-concentration of colours and flavours is a gentle process that doesn't involve a phase change or a lot of heating or chemical extraction, it produces fresher flavours. It's cheaper too because it uses less energy.

Milk whey is currently concentrated using nano-filtration, says Jones. "It gets rid of a lot of the water before you spray dry, cutting the cost of spray drying dramatically." And he suggests that the dairy industry will use nano-filtration to remove lactose from cows' milk in order to replace it with another sugar for lactose intolerant consumers.

As an alternative to nano-filters and 'smart' inks, Dr Subryal Reddy in the school of biomedical and molecular sciences at Surrey University, is working on polymer membranes that incorporate surfactant or possibly liquid crystal molecules at selected sites on their surface. His idea is to produce membranes with selective diffusion, what he calls "nano-recognition"

"They will be able to let in or screen out small molecules that you might be interested in detecting, such as molecules indicating food freshness or food spoilage. And they could then change their own physical properties to act as sensors or indicators."

For each binding event or repulsion event between the food molecule and the surfactant or liquid crystal, the membrane could change colour or its mechanical properties, says Reddy. It could become a self-contained sensor without the need to attach an electronic circuit, he suggests.

"The idea is to use these materials in the form of a strip or patch as part of the food packaging in contact with the food," says Reddy. For example, by putting the right functional molecule into the membrane, it could detect the aldehydes given off when fatty foods go rancid.

Nanotechnology may not be new -- chemists have been juggling with atoms for years -- it's just that quantum physics has enabled chemists to become designers of molecules as well as jugglers. And in order to help the UK's molecular jugglers and designers compete in the international nano circus, the government is investing £90m in a new Micro and Nanotechnology Network -- MNT -- in Liverpool to help industry harness the opportunities offered by nanotechnology. It already has 150 UK organisations signed up and is looking for more.

This month, the network is launching Forum, a web-based information and communication tool for the nanotechnology community. Later this year, Professor Hugh Clare, director of MNT , will be inviting the food industry to join the Forum.

"It's a way of swapping information and asking questions about nanotechnology," says Clare. "It will enable companies, SMEs particularly, to find out what is going on in nanotechnology in the UK." FM

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