Nanotechnologies in the Food Arena: New Opportunities, New Questions, New Concerns

QASIM CHAUDHRY, RICHARD WATKINS AND LAURENCE CASTLE

The Food and Environment Research Agency, Sand Hutton, York YO41 1LZ, UK

1.1 Background

It has been suggested for sometime that materials and substances may be manipulated at the very small size scale through atom-by-atom assembly. The advent of nanotechnology in recent years has provided a systematic way for the study and 'fine-tuning' of material properties in the nanometer size range. Nanotechnology is a broad term used to represent an assemblage of processes, materials and applications that span physical, chemical, biological and electronic science and engineering fields. The common theme amongst them is that they all involve manipulation of materials at a size range in the nanometer scale. One nanometer (nm) is one-billionth of a meter. A nanomaterial has been defined as a 'material having one or more external dimensions in the nanoscale or which is nanostructured', where the nanoscale size range is approximately 1–100 nm (Figure 1.1). Materials with all three external dimensions in the nanoscale are classed as nanoparticles. Nanomaterials also exist in other forms, such as nanorods or nanotubes with two dimensions in the nanoscale, or nanolayers, coatings or sheets with just one dimension in the nanoscale.

Of particular interest to most nanotechnology applications are engineered nanoparticles (ENPs) that are manufactured specifically to achieve a certain material property or composition. Although ENPs are produced in free particulate forms, they tend to stick together to form larger agglomerates due to enormous surface free energies. In final applications, ENPs may be in fixed, bound or embedded forms in different matrices, such as food packaging plastics. Other applications, such as certain cosmetics, personal care products and functional foods may contain free ENPs. The chemical nature of substances used to manufacture ENPs can be inorganic (e.g. metals and metal oxides) or organic (e.g. food additives and cosmetics ingredients). Some nanomaterials are also obtainable from natural sources, most notably montmorillonite (also known as bentonite) that are nanoclays commonly obtained from volcanic ash/ rocks. To help visualise nanomaterials in context, organic life is carbon based, and the C–C bond length is about 0.15nm. So placed in a food context, most ENPs are bigger than molecules such as lipids, are a similar size to many proteins, but are smaller than the intact cells in plant- and animal-based foods (Figure 1.2).

The fundamental driver at the heart of most nanotechnology applications is the promise for improved or new functionalities of materials, and a possible reduction in the use of (chemical) substances. On an equivalent weight basis, ENPs have much larger surface to mass ratios (also known as the aspect ratio) due to their very small sizes compared to the conventional bulk forms. Thus, a relatively small amount of an ENP may provide a level of functionality that would otherwise require a much greater amount of the conventional material. The notion 'a little goes a long way' is probably the single most powerful reasoning behind many of the nanotechnology applications in different sectors. The very small size of ENPs can also offer other benefits. For example, nano-sizing of water-insoluble substances can enable their uniform dispersion in aqueous formulations. This makes it possible to reduce the use of solvents in certain applications such as cosmetics, paints and coatings, and allows the dispersion of food additives such as water-insoluble colours, flavours and preservatives in low-fat systems. Nano-sized nutrients and supplements have also been claimed to have a greater uptake, absorption and bioavailability in the body compared to bulk equivalents. This aspect alone has attracted a lot of commercial interest in the use of nano-sized ingredients, supplements and nutraceuticals in (health)food applications.

The current applications of nanotechnology span a wide range of sectors, predominantly cosmetics and personal-care, health-care, paints and coatings and electronics. As in these sectors, nanotechnology is also promising to revolutionise the food industry – from food production, processing, packaging, transportation and storage to the development of new food tastes and textures and innovative food packaging applications. Nanotechnology has also emerged as one of the major converging technologies, offering the potential for further new developments through integration with other sciences and technological disciplines. Already there are examples where integration of nanotechnology with biotechnology and information technology is enabling the development of miniaturised devices, such as nanobiosensors. The use of the latter to detect pathogens and contaminants during food processing, transportation and storage is expected to enhance safety and security of food products. In view of the new technological developments, it is not surprising that the food industry is amongst the main sectors eagerly seeking ways to realise the potential benefits offered by nanotechnology.

This book is aimed at providing an impartial view of the potential prospects, benefits and risks that nanotechnology can bring to the food sector and its customers, and it also aims to discuss some of the main questions and concerns that the new technological developments have started to raise. In turn, this first chapter sets the scene for the subsequent chapters on individual application areas that are written by acknowledged experts in their respective fields.

1.2 Evolution of New Technologies in the Food Sector

The main driver that has shaped our present-day food industry is the basic human need for a sustained supply of safe,...