Nanotechnology: Shaping the oils industry atom by atom?

By Fiona Case
Posted 2/24/06 2:24 PM

The U.S. National Nanotechnology Coordination Office (www.nano.gov) defines nanotechnology as “the understanding and control of matter at dimensions of roughly 1 to 100 nanometers, where unique phenomena enable novel applications.” Eric Drexler introduced the term in 1986 in his book, Engines of Creation. Since then, things “nano” have captured the public imagination— from the visions of self-replicating nanobots taking over the world in Michael Crichton’s book Prey, to promises of injectable nano-robots that could locate and correct diseases at a molecular level.

New methods of characterization such as scanning probe microscopy, and new developments in theory and modeling opened a window onto the nanoscale world. Scientists were fascinated by what they found. However, nanotechnology might have remained an intellectual curiosity if there had not been a pressing commercial need for smaller length scale devices in the electronics industry.

The desire for smaller and faster computer chips provided the initial impetus and investment; the energy, drug delivery, and materials industries are now actively involved. The U.S. National Science Foundation predicts that within 15 years technology identified as “nanotech” will have had a trillion-dollar impact on a wide range of industries.

A computer simulation of the formation of nanoscale structure using self assembly: An equimolar mixture of cationic surfactants (pink heads green tails) and anionic surfactants (white heads, green tails) are predicted to self assemble to form a small hollow vesicle. The eight snapshots are taken from a simulation of 30 microseconds. In the last snapshot the water is also displayed. The simulation was carried out by Fiona Case using dissipative particle dynamics software developed by Culgi BV, Leiden, Netherlands.

Uses in the oils industry

The early days of nanotechnology were hard, literally. Most of the talk was about hard nanostructures—nano-patterned silicon, quantum dots, nanoparticles, and carbon nanotubes. It is perhaps not obvious that these materials would have an impact on the edible oils industry, but there are already a few examples in this, and in the related foods industry.

The OilFresh catalyst system for deep fat frying is based on nanoparticle technology. “Nanoceramic catalytic pellets are fused together to create a huge surface area on the catalyst surface,” explains Sonny Oh, cofounder of the OilFresh company, Sunnyvale, California, USA. This structure is critical to the action of the system, which, he claims, significantly extends the fry life of oils by reducing oxidative degradation.

The OilFresh device is already in use in a number of individual restaurants. Oh believes that the technology could help large fast-food chains such as KFC, McDonald’s, and Burger King maintain cost-neutrality if they decide to transition to more expensive oils in response to consumer concerns about trans fatty acids.

Another example is the inclusion of nanoparticles in packaging materials. Microscale TiO2 particles are brilliant white pigments because they scatter all wavelengths of light. Nano-scale TiO2 particles no longer scatter visible light (they are transparent), but they still block ultraviolet (UV) light. Clear plastic food wraps incorporating TiO2 nanoparticles provide excellent UV protection. Other inorganic nanoparticles (for example, derived from clays) can provide a transparent oxygen barrier in food packaging materials preventing the oxidation of fats and oils.

A 1998 patent granted to Mars, Incorporated, McLean, Virginia, USA, claims that coatings of edible inorganic particles on candy will prevent it from getting sticky, that nanoparticle coatings on cookies will increase their shelf life, and that they may reduce the need for antioxidants and preservatives. According to the inventors, the coatings should be thin to respect texture and “mouthfeel” considerations: the ideal coating would be somewhere between 0.1nm and 500nm thick.

Soft Nanotechnology

Initially, people working on nanotechnology did indeed think of creating structures “atom by atom.” When, in 1989, Donald M. Eigler and Erhard K. Schweizer, physicists working at IBM (headquartered at Armonk, New York, USA) were able to move atoms of xenon across a nickel crystal surface to spell out their company’s name the image quickly became iconic. But this was never going to be a practical approach for mass production.

In recent years interest has shifted to nanostructured materials that self-assemble (so called “bottom up” approaches). Amphiphilic molecules that include segments with different properties can be induced to self-assemble, forming nano-scale structure. The obvious examples are surfactants, block copolymers and proteins. These self-assembled nanostructures are soft and can almost as easily be disassembled, however approaches such as crosslinking surfactants or block copolymers, inducing crystallization, or using the soft structures as templates for mineralization, or as resists for photolithography, can lead to the formation of more durable nanostructured materials.

When IBM started to reach the limits of patterning using bottom-down approaches such as lithography, they turned to block copolymer templating—for example to generate arrays of floating gates in the latest generation of flash memory chips.

In some applications the tendency for selfassembled materials to disassemble or change their nanoscale structure when, for example, the temperature of the material is changed, can be an advantage. The polymers in the material shown of the cover of this month’s inform stack up to form a twisted nanostructure. The pitch of the twist (the distance over which the ordered stack of molecules makes a complete turn) is on the same order as the wavelength of visible light – so the material is colored. When the temperature increases the pitch changes, creating a color change. These cholesteric polymer films can used as temperature indicators on food packaging.

The idea that self-assembly of molecules and crystallization can create nanometer to micron sized structures in soft materials is hardly new to researchers who study oils and fats. Many of the new characterization techniques that spurred the nanotechnology revolution have also been used to elucidate the nanoscale structure of these materials. AOCS member Paul Smith and Annika Dahlman from the YKI Institute for Surface Chemistry, Stockholm, Sweden, have used atomic force microscopy to measure the formation and development of nanoscale structures on the surface of chocolate pralines. Oleksandr Mykhaylyk and Ian Hamley from the University of Leeds, UK, have used small angle X-ray scattering to clarify the γ and β structures of triacylglycerols and the driving forces for their polymorphic transformations. Peter Schurtenberger from the University of Fribourg in Switzerland has been working with researchers from Nestlé to develop new light scattering methods to characterize oil droplets in milk and yoghurt.

“Food science in general has always dealt with the nanoscale,” says AOCS member Alejandro G. Marangoni, Canada Research Chair in Food and Soft Materials Science and professor of Food Science at the University of Guelph. “The question one has to ask oneself,” he suggests, “is ‘are you deliberately manipulating the structure of your material at the nanoscale?’ If the answer is yes, then you’re doing nanotechnology.”

Marangoni has been working with AOCS members Stefan Idziak (University of Waterloo, Ontario) and Gianfranco Mazzanti (University of Dalhousie, Newfoundland) to develop a method for “nanotemplating” fats. “We can orient fat structure crystallographically by using high shear mixing,” he explains. “The nanotemplating process increases the mechanical strength of the fat, which is advantageous when strong, thin fat laminates are needed in food applications.”

The deliberate creation of specific nanostructure in foods has been claimed as a method for enhancing microbial stability. In their 2002 patent on “Use of mesomorphic phases in food products” inventors from the Van den Bergh Foods Co. division of Unilever (UK) claim that by using edible surfactants (such as monoglycerides, diglycerides, fatty acid esters or phospholipids) they can create lamella structures. The water (up to 95% of the material) is denied to the microorganisms by being entrapped in layers approximately 100nm wide. This far below the size of the microorganisms– they cannot access the water and so their growth is limited. Understanding and control of nanoscale structure in foods is also critical for physical stability (to prevent phase separation, sedimentation or creaming).

A dramatic example of the benefits of reducing particle size is provided by nanodroplets of hydrophobic materials (such as oil-soluable vitamins) in water-based systems like soda or sports-drinks. If the droplet size is brought down into the sub-micron range these normally incompatible substances can easily be mixed even with cold water, and their bioavailability in the human body increases. BASF produces “nano-scale” particles containing carotenoids (antioxidants that can be converted to vitamin Ain the body) which it sells to major food & beverage companies for use in lemonades, fruit juices and margarine. The Nutralease Company, founded by AOCS member Nisim Garti from the Hebrew University in Israel, is using novel emulsification methods to create what they describe as “nano-sized liquid vehicles and technology for solubilization of nutraceuticals in foods.” Their success stories include the creation (with Shemen Industries Ltd. Haifa, Israel) of Canola Active: Canola oil fortified with free phytosterols, which is claimed to reduce human cholesterol levels. Another example is the application of nanostructuring materials developed by Danisco (Brabrand, Denmark) to stabilize emulsions of liquid oils. Their edible surfactant emulsifiers allow formulation of trans-fat free liquid oils (such a soybean oil) for baked goods. Emulsification prevents the oil from migrating to the food surface. It also reduces the interaction of oils with the proteins in applications like cake mixes. This is important since liquid oil can denature proteins, preventing them from carrying out the task of stabilizing air bubbles in the mixture.

In a recent Nature Materials review Peter Schurtenberger and authors from Nestlé discuss the prospects for creating stimuli responsive functional foods capable of changing their properties or releasing active components based on pH or temperature changes. This would require understanding and control of food structure over a wide range of length scales.

It seems unlikely that the edible oils industry will instigate major nanotechnology research initiatives. However, the materials we work with do contain nanoscale structures. New techniques and methods developed by the growing nanotechnology industry will continue be adopted, and it is likely that new nanotechnology based devices will impact the industry.

Fiona Case is a freelance writer based in Burlington, Vermont, USA. She is also an AOCS member and one of the organizers for the NSTI Nanotech conferences, which feature new developments in soft nanotechnology. Contact her by e-mail: fiona@casescientific.com

Further reading on nanotechnology:

• “Nanotechnology, Science, Innovation and Opportunity”, edited by Lynn E. Foster, Prentice Hall, 2006.
• “Understanding Foods as Soft Materials” a review article by Raffaele Mezzenga, Peter Schurtenberger, Adam Burbidge, and Martin Michel, Nature Materials (4): 729–740, 2005.
• “The use of atomic force microscopy to measure the formation and development of chocolate bloom in pralines” Smith P. R., Dahlman A. JAOCS 82: 165–168, 2005.
• “The packing of Triacylglycerols from SAXS measurements: Application to the structure of 1,3-distearoyl-2-oleoyl-sn-glycerol crystal phases”, Mykhaylyk O. O., Hamley I. W., Journ. Phys. Chem. B 108: 8069–8083, 2004.
• ETC Group Report “Down on the Farm: The Impact of Nano-Scale Technologies on Food and Agriculture” available online at netlink: www.etcgroup.org.

Story location: http://www.aocs.org/...

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