Is Nanotechnology Going to Change the Future of Food Technology?

Victor J. Morris Institute of Food Research Norwich, United Kingdom

Nanotechnology is seen by many as a growth area that will transform tomorrows' world. At the same time, advocates of the 'grey goo' hypothesis warn against the development and escape of self-replicating nanobots that could gobble up all the material on the planet, spelling doom for us all. Between these extremes what are the likely impacts on the food industry?

Most countries in the world see nanoscience and nanotechnology as important. In Japan expenditure was $400M in 2001 and is expected to be $960M in 2004. The USA's 21st Century Nanotechnology Research and Development Act, passed in 2003, has allocated approximately $3.7B from 2005-2008, compared to an expenditure of $750M in 2003. In Europe current funding for R&D in nanotechnology is around €1B, much of which is funded through national and regional programmes. In the United Kingdom the DTI initiative on Micro- and NanoTechnology Manufacturing offers £45M in support of commercial applications between 2003-2009.

Figure 1. Schematic diagram of an atomic force microscope. Like an old-fashioned gramophone a sharp probe attached to a flexible cantilever tracks the undulations of the sample surface. The resulting motion of the cantilever is monitored and used to generate a 3D image of the surface.

To consider the potential, and to address concerns, the UK government commissioned the Royal Society and the Royal Academy of Engineering to carry out an independent study into current and future developments in nanosciences and nanotechnology. Their report was published in July 2004¹. Although the report does not specifically address the impact on the food industry, it does discuss bionanotechnology, and potential developments in computing, materials and sensors. It also addresses concerns about the safety and systems by controlling the shape and size at the nanometre scale.

Some of the nanostructures in food are familiar compounds. Many food proteins are globular structures between 10s to 100s nm in size - true nanoparticles. The majority of polysaccharides and lipids are linear polymers less than one nm in thickness, and are examples of 1 dimensional nanostructures. When foams are prepared and stabilised and emulsions formed, 2 dimensional nanostructures are created, one molecule thick, at the air-water or oil-water interface. Setting a gel, or adding polymers to delay the sedimentation of dispersions or the creaming of emulsions, generally involves creating 3 dimensional nanostructures, by causing food biopolymers to assemble into fibrous networks. When starch is boiled to make custard, small 3 dimensional crystalline lamellae 10s nm in thickness are melted. The texture of the paste or gel formed on cooling depends on the re-crystallisation of starch polysaccharides, as does the long-term staling of bakery products.

Where there is a detailed understanding of the nanostructures present in food, rational approaches to the selection of new materials can be used, or quality through food processing can be enhanced. Protein crystallography provides atomic resolution information on protein structure. Site-directed mutagenesis allows the protein structure to be modified systematically, and structure-function relationships determined. Genetic engineering provides a route to the design of new structures and, if this is unacceptable to consumers, the scientific understanding allows targets to be defined for accelerated plant breeding or screening of natural varieties. Similarly knowledge of the crystal structures of fats allows the selection and tempering of particular crystal forms in order to optimise structure and texture. Where of nanoparticles and the possible needs for regulation or labelling. Hence it provides a starting point for considering developments in food technology.

WHAT IS NANOSCIENCE?

What exactly are nanoscience and nanotechnology? Nanoscience is defined as the study of phenomena and the manipulation of materials at the atomic, molecular and macromolecular scales, where properties differ significantly from those at a larger scale. The term 'nano' is derived from the Greek word for dwarf. To put things in perspective a nanometre (nm) is one-billionth of a metre, or approximately one hundred thousandth of the width of a human hair. Nanotechnology involves the design, production and application of structures, devices such detailed information is lacking then the selection and processing operations are still largely empirical.

Click to enlarge Figure 2. AFM images showing the displacement of a milk protein (green) surfactant increases the protein network is compressed and increases in height until it breaks. Images sizes are (a) 1.0 x 1.0 _m, (b) 1.6 x 1.6 _m, (c) 3.2 x 3.2 _m and (d) 10 x 10 _m. The cartoon illustrates the changes in the protein network.

IMPLICATION FOR THE FOOD INDUSTRY

One way the food industry can benefit from nanoscience is to use new physical tools developed to study nanostructures. Major microscopic methods developed to probe the nanoworld include the scanning tunnelling microscope invented in 1982, and its more versatile offspring, the atomic force microscope (AFM), reported in 1986. AFM has proved particularly useful for probing molecular structures in food². As a microscopic technique it allows heterogenous systems to be seen and this heterogeneity has proved to be important in understanding their behaviour. It has led to new molecular understanding of the behaviour of polysaccharide gelling and thickening agents, new molecular descriptions of the structure and functionality of starch, and a new mechanism of action for certain starch-degrading enzymes.

A good example of the power of nanoscience is how it has changed the understanding of the role of interfacial structures in controlling the stability of foams and emulsions.

When a foam or emulsion is created an air-water or oil-water interface is generated, and the molecules present at the interface determine its stability. A source of instability is the presence of both proteins and small molecules, like surfactants or lipids. Proteins or surfactants alone will stabilise interfaces, but by mechanisms that are mutually incompatible. When both are present they battle for control of the interface and the surfactants normally win. Although surfactants or lipids are more surface-active than proteins they actually find it difficult to displace the proteins.

Nanoscience in the form of AFM explains how this happens. It shows that the proteins form networks and thus, to displace the proteins, the surfactants have to break the network. They do this by finding weaknesses in the network where proteins are only weakly attached. These proteins can be removed, allowing the surfactant to gain a foothold at the interface. More surfactant pours into these breeches, expanding the area they occupy and compressing the protein network until it eventually breaks, and proteins can be displaced.

As all proteins used to stabilise foams and emulsions form networks this newly identified displacement mechanism is generic. Strategies for improving the stability of the protein networks can thus be suggested and these can be applied widely in the baking, brewing and dairy industries. Components can be added that bind or mop up small molecules such as lipids, or the cross-linking of the protein network can be enhanced, making it harder to break. In the future more complex multilayer structures can be designed using nanofabrication. Adding an extra layer can be used to consolidate the weaknesses in the protein network and to stabilise it against surfactant or lipid attack. By carefully choosing the molecular components the properties of the interfacial layers can be designed. Coalescence of droplets can be enhanced or inhibited, or the porosity of the interface regulated to optimise encapsulation and release. Similar approaches can be used to design new surface coatings or barriers. Nanoscience provides understanding that allows conventional technologies to be used rationally to improve food structure.

Nanotechnology is generally regarded as new approaches to manipulation of materials and structures. This new type of material science will impact on the food industry. The electronics industry already uses nanotechnology and there are likely to be continued advances in the miniaturisation of computer chips and enhanced data storage. In the long-term, the advent of quantum computing and cryptography would offer new applications, currently difficult, or impossible using conventional computing. Apart from IT applications advances in computing will allow the improved analysis of large sets of data, in areas such as genomics and proteomics, which will undoubtedly lead to improvements in food safety and authentication.

Improved nanofabrication is likely to lead to new higher density and more efficient and reproducible arrays, and the development of more comprehensive and sophisticated sensors. The idea of assembling interfacial structures, coatings or barriers layer by layer has already been discussed. Molecular fabrication will lead to new materials and new surface structures. The question here is whether the food industry will sit back and hope that they will be able to exploit developments in material science, or whether they will grasp current funding opportunities to work with nanotechnologists to design the types of structures they need. It might be possible to design surfaces that repel bacteria and inhibit biofilm formation, or create novel layered structures that can be peeled to remove contamination. Will it be possible to develop new and improved packaging materials, and can they be used to monitor and record the quality of the material during storage?

The applications described above involve the production of large-scale assemblies by molecular fabrication. They would not introduce nanoparticles, as such, into food. Should nanoparticles be added to food? One area where there might be a future drive to the use of nanoparticles lies in the blurring of the distinction between functional foods and pharmaceuticals. Nanoparticles may seem attractive as delivery vehicles. Small particles can go where other particles cannot reach and surfaces could be designed to target release of drugs or nutrients. The health implications of the use of nanoparticles is thoroughly discussed in the Royal Society and Royal Academy of Engineering report¹, and they also address the implications for future research in this area, the assessment of risk, and the potential needs for approval and labelling. The general public has already begun to voice concerns about possible long-term side effects associated with the use of nanoparticles. Future proponents of such approaches will need to weigh potential benefits against the need to ensure the safety of such products and, more importantly, the possibility of convincing consumers that such an approach is needed.

CONCLUSION

At present there are clear opportunities for nanoscience and nanotechnology in food technology. Some applications can be anticipated and can result in targeted advances in technology. However, new scientific advances usually lead to new technological innovations that might not have been predicted at the outset. At present the food industry is at a crossroads. It can pass by and hope to exploit developments in nanotechnology as they emerge serendipitously or otherwise in the future, or it can embrace these new skills and set targets to drive scientific advances in pursuit of specific goals.

REFERENCES

1. Nanoscience and nanotechnologies: opportunities and uncertainties. RS policy document 19/04, July 2004. ISBN 0 85403 604 0: http://www.nanotec.org.uk/finalReport.htm
2. Scanning Probe Microscopy: http://www.ifr.bbsrc.ac.uk/spm/

FURTHER READING

Probing molecular interactions in foods, VJ Morris. Trends in Food Science & Technology, 15, 291-297 (2004).

Atomic Force Microscopy of Pea Starch: Origins of Image Contrast. Ridout MJ, Parker ML, Hedley CL, Bogracheva TY, Morris VJ. Biomacromolecules 5, 1519-1527 (2004)

Using Atomic Force Microscopy to Probe Food Biopolymer Functionality. Morris VJ, Kirby AR, Gunning AP. Scanning 21, 287-292 (1999).

The orogenic displacement of protein from the air/water interface by competitive adsorption. Mackie AR, Gunning AP, Wilde PJ, Morris VJ. J. Colloid & Interface Sci. 210, 157-166 (1999).

BIOGRAPHY

Dr Victor J Morris has worked at the Institute of Food Research, Norwich, UK [www.ifr.bbsrc.ac.uk] since 1979. He is a physical scientist working in food research, and is a Fellow of the Royal Society of Chemistry, the Institute of Physics and of the Institute of Food Science & Technology. His research interests lie in understanding the molecular origins of the functional properties of foods, in order to allow rational choice and manipulation of raw materials, and improved food quality. During the last 15 years he has pioneered the use of probe microscopes to study molecular structure in foods [www.ifr.bbsrc.ac.uk/spm] and this research has been rewarded by recognition from ISI as a 'highly cited researcher' in Agricultural Sciences [www.isihighlycited.com]. In addition to his own research interests he manages a major research programme on 'Complex Foods' at the Institute.