Many biological structures and systems have nanoscale features which affect their properties and behaviour. As our understanding of synthetic nanotechnology increases, we are beginning to see more and more clearly how these relationships between size, shape, and functionality work in biological systems.
As we understand more and more about biological processes, it seems likely that some of the first applications of this knowledge will be to food processing. In developed countries, the vast majority of the food consumed undergoes some sort of processing which changes its biological properties and nutritional values. There is a constant R&D effort to improve these processes, and using our knowledge of nanotechnology to inform this development is becoming more and more common.
Nanotechnology has the potential to affect the food production industry at almost every stage, through agriculture, storage and transport, manufacturing, packaging, and disposal. This article will focus on one particular aspect of these applications – using nanotechnology to add additional value or functionality to food products.
This is an area which is particularly controversial, as it involves human ingestion of significant quantities of nanomaterials. The benefits must therefore be shown to greatly outweigh any risks, and a deep understanding of the products’ effects on the body must be demonstrated.
Nanoemulsions and Nanocapsules
Many functional ingredients in food, such as vitamins, antimicrobial agents, flavourings, etc., can benefit from being encapsulated in a delivery system, rather than being used in a free form in the food. A good delivery system can ensure that biologically active ingredients like vitamins or antioxidants can reach the site in the body where they can be most effective without degrading. It can also help to release the ingredient at a controlled rate, to keep the concentration in the body at the optimum level.
Various nanoencapsulation systems have been proposed which could provide many of these features. They generally revolve around micelles and emulsions – droplets which form when oily material is dispersed into water. These are of interest because they form spontaneously under certain conditions, and could easily contain oil-soluble functional ingredients within an aqueous environment.
The problem with most emulsions is that they are dependent on conditions – just as they spontaneously form under certain conditions, they can also spontaneously disassociate if the temperature or concentration changes too much – not very useful for a system which may need to remain stable through various areas of the human digestive tract. Stabilization of some materials also requires addition of significant amounts of surfactant, or emulsifier, which has to be food-grade, and may adversely affect the taste or texture of the food.
Figure 1. Nanoemulsions can be used as delivery systems for active ingredients in food products. Using multiple layers of encapsulation with a range of materials could keep the nanocapsules stable, and control the release of the ingredient within the body.
The most promising solutions are more complex systems, which are assembled in several steps, composed of several layers of biocompatible surfactants and polymers (proteins, carbohydrates, etc.). The manufacturing techniques needed to produce multilayer emulsions like this would be a simple progression from the methods currently used to make emulsions in food processing, so integration of this technology would be relatively easy.
These systems can retain their payload through a variety of environments, and be tailored to release the active ingredient at the right point, triggered by specific environmental parameters like pH or temperature.
|Figure 2. The taste, texture and shelf-life of fresh fruit such as strawberries could be improved with a multifunctional edible nanolaminate.|
Nanolaminates: Edible Coatings
Manipulation of materials at the nanoscale can allow food scientists to create edible laminate films. These are constructed from several nanolayers of various materials, added one at a time by taking advantage of the electrostatic attractions between one layer and the next.
This layer-by-layer approach allows very detailed control over the properties of the nanolaminate, which is the main benefit over the conventional edible coatings, such as waxes and gums, often used as barrier layers to prolong shelf life.
Materials which could be used as functional components of a nanolaminate food coating include lipids or clays, as moisture barriers, biopolymers like carbohydrates, as an oxygen and carbon dioxide barrier, or nanoparticulates and emulsified nanodroplets, which could contain active ingredients to improve taste, texture or appearance.
The recent resurgence in using electrospinning to produce nanofibres with a wide distribution of sizes and properties for bulk applications has led to discussion of using these nanofibres in food technology.
The electrospun fibres used in other applications are usually composed of synthetic materials, which may be useful in food packaging. However, recent work has moved towards applying the technology to biopolymers, primarily for medical applications. Electrospun biopolymers could be used in food products as a texture modifier or filler. It is even conceivable that completely synthetic food could be constructed from a mesh of electrospun protein and carbohydrate fibres, embedded with nanoencapsulated flavourings and vitamins, and coated with a nanolaminate to enhance colour and texture, and preserve the product.
|Food giant Tate & Lyle has taken advantage of a partnership with a nanotech spin-out from the University of Nottingham to produce one of the first food products using micro- or nano-technologies in the UK. Soda-Lo® uses nanostructured salt crystals to deliver salty taste at a lower concentration, without the issues of agglomeration usually encountered with very fine salt powders.|
Whilst nanotechnology-enhanced packaging for food products is beginning to emerge on the market, commercial applications of nanotechnology in food have been slow to develop, compared to the rate of research in the last few years. This is largely due to consumer reluctance to accept nano-enhanced food, and an unclear legislative position.
Consumers in the Far East seem much more accepting of nanotechnology as a positive move for the food industry than those in the US, and certainly more than in Europe. In the UK in particular, manufacturers, consumers and legislators alike seem hesitant about adopting the new technologies, primarily due to concerns over long term health and environmental effects.
Key figures in the industry are pushing for more development, however. Nanotechnology could increase the shelf-life of food, and enhance the effectiveness of flavour-enhancing and colour-enhancing additives, allowing the overall quantity of additives to be reduced. It could also make processed food healthier, by delivering fats, sugar and salt in nanoformulations which deliver taste at lower concentrations, and by delivering vitamins and other nutrients using nano-carrier systems.
Despite these benefits, it seems unlikely that the food industry in Europe will begin to take full advantage of food nanotechnology for quite some years.
- “Functional Materials in Food Nanotechnology” – Weiss et al, J. Food Sci. 2006. DOI: 10.1111/j.1750-3841.2006.00195.x
- “Nanotechnology for Food Applications: Current Status and Consumer Safety Concerns” – Dr. Quasim Chaudry, DEFRA.
- “Nanotechnology in Food” – ETH Zurich