Nanotechnology in the food industry

Applications of nanotechnology in the food industry mean different things to different people and this influences the perception of benefits and risks of nanotechnology. Nanotechnology is not a discrete area, but rather a broad spectrum of applications concerned with the rational modification of food structures at the molecular or macromolecular level, or the introduction of nanoparticles or nanostructures into foods.

The opportunity to design foods, ingredients or food contact materials at the molecular level suggests new ways to reduce food waste, to improve authenticity, to maintain and enhance microbiological safety, to protect against the onset of chronic diseases and to optimise personal nutrition and individual lifestyles. For industrialists, the decision to use nanotechnology will depend on the value of the final product, the costs of development and clearance and ultimately consumer opinion. For the consumer, the decision to buy nanoproducts will depend on the benefits and perceived risks. It is possible to regulate nanoproducts that are produced and, to some degree, imported into Europe. European law requires that food producers are ultimately responsible for the safety of their products. Hence, all applications of nanotechnology are likely to require clearance as novel foods, additives or ingredients, and there are tried procedures to evaluate the products. Presently, the EU regularity authorities are considering each new product and only modifying procedures when or if there is a need.

Different countries have different attitudes to regulation and there are a growing number of products becoming available worldwide through the internet. A perusal of databases shows the types of products emerging and provides an opportunity to consider the likely benefits, risks and consumer reactions.

The main products which have started to appear are food supplements, nanoceuticals and a variety of anti-microbial and/or smart food contact materials.

Nanoparticles and food supplements

The area that has engendered the most debate is the introduction of manufactured nanoparticles into foods. Worldwide consumer product databases show examples of food supplements containing nanosilver or other metal nanoparticles. Metal oxides (e.g. TiO2 and SiO2) are available commercially as nanoparticles and the patent literature suggests potential food applications. Bioaccumulation of these minerals within the body will depend on the level of consumption and the rate of excretion. Many of these materials are cleared for food use in their macroscopic form. The proposed use of nanoparticles implies that a reduction in size generates novel functionality and a compelling need for incorporation into foods. These nanoparticles are thus novel ingredients or additives and need separate food clearance.

Clearance of nanoparticles requires new information on bioaccumulation and the consequences of the particles penetrating regions where normal sized particles cannot reach. Prolonged consumption of colloidal silver leads to slow accumulation within the body. Colloidal silver particles are excluded from cells but nanosilver may enter cells, enhancing bioaccumulation. The long-term consequences of bioaccumulation of nanosilver need to be established and similar considerations apply to other mineral nanoparticles. Nanosilver is marketed as an anti-microbial agent but at present, there appears to be no published data on the effects of ingestion on natural microbial populations present in the mouth and gut. Are the effects broad spectrum or specific, and will the systems readily recover?

Manufactured nanoparticles will be expensive and use may be limited. However, consumers may want the opportunity to exercise choice and there does seem to be a need to consider product labelling. Presently, there is no definition of the term ‘Nano’ that enables consumers to assess health and safety claims. If nanoparticles of food-approved additives or ingredients are used in food, there is a potential difficulty with labelling. Nanoparticles of allowed ingredients or additives that induce unique functionality would need to be indicated on a label. If this is done using an E-number, or by naming the material, then this would imply safety data and an annual daily intake (ADI) derived for the ‘native’ material. This could be misleading for the nanoform. Thus, there may be a need to use modified E-numbers or to consider restrictions on the use of nanoparticles in certain foods.

Nanoencapsulation

There is a growing interest worldwide in using nanotechnology to package molecular components to improve incorporation into food matrices, to change, enhance or disguise taste and appearance and to optimise bioavailability. Carriers currently available include mineral-based nanocages, nanosomes, nanodrops, nanoemulsions and stabilised nanocrystals. Nanoencapsulation claims advantages over microencapsulation. Nanosized containers scatter less light, allowing the dispersion of materials in clear or coloured products. Nanodrops, nanoemulsions or nanosomes claim to enhance delivery, particularly at interfaces such as membranes. Currently, there are cholesterol-lowering nanoproducts designed to deliver phytosterols directly to bile salt micelles.

These products aim to deliver approved components in a novel way. If the components and the delivery systems are food-approved, then approval of the new products would mainly require a demonstration that delivery does not alter the metabolism of the components within the body. Enhanced delivery may result in over-consumption and labelling may be required to ensure optimum intake. These products use the term ‘Nano’ as a branding tool to imply a high-value product. Because ‘Nano’ is not defined or regulated, it is difficult for consumers to establish whether products are actually nanoproducts and whether ‘Nano’ reflects verifiable evidence for health or safety claims. Growing consumer awareness of nanotechnology means there may be a need for labelling to enable consumer choice, based on verified health and safety claims.

Food contact materials

There is considerable interest in using nanotechnology for developing novel packaging and contact materials. One successful approach designed to improve shelf-life is to incorporate nanoclays as layers into plastic containers and bottles to increase the time needed for gases to flow through the containers. There is also interest in developing smart packaging. Smart packaging could record the source of a product and track distribution and storage. Sensors may detect and report environmental changes that might adversely affect quality. Nanosensors could detect spoilage or microbial growth and even react to treat such events. Perhaps the largest growth area is in the development of an ever-increasing number of anti-microbial surfaces, packages, coatings and containers, mainly using nanosilver as an anti-microbial agent. Early detection or prevention of microbial contamination will lead to reduced waste and improved food safety.

Clearance of food contact materials containing nanoparticles requires a demonstration that there is no detectable leaching of nanoparticles into food. This would alleviate concerns about the ingestion or bioaccumulation of nanoparticles. Detection of leaching requires the definition of a suitable threshold level for measurement purposes. If ADIs have not been established for the safe use of nanoparticles in food, it is not clear how thresholds will be set. Many food contact materials use ‘Nano’ as a brand name. There may need to be a systematic labelling of food contact materials as nanoproducts, since consumers may be satisfied with their safety and advantages of their use, but may have concerns about their disposal and possible subsequent breakdown and release of nanoparticles into the environment, or even back into the food chain.

Nanoparticles could be incorporated into edible coatings or even into biodegradable containers or packaging. These products would raise new issues on regulation, clearance and labelling, related to the ingestion of nanoparticles or their release into the environment. Such issues will require joint consideration by several regulatory bodies. Another form of nanotechnology is the layer by layer assembly of molecular structures to form coatings, barriers or devices for encapsulation and release. The structures can be produced from conventional food-approved ingredients and formed by conventional chemical approaches. The major interest here is in the generation of environmentally-responsive release characteristics which could be used to target the release of flavours, colours, nutrients or bioactive agents within food. Such systems would be novel foods but may not need to be considered as nanoproducts.

Natural nanostructures

Carbohydrates and proteins are naturally occurring nanoparticles. Although their functionality is dependent on size, they are not engineered from any equivalent macro materials. Proteins and polysaccharides have been eaten safely for generations, or have undergone rigorous clearance procedures. They are safe not because all such biopolymers are inherently safe, but due to well-established procedures for their clearance for food use. Novel natural nanostructures present in raw materials or formed during processing provide opportunities for manipulating the food structure to enhance quality and nutritional value. Food scientists have been studying the molecular nature of food structure for many generations but new microscopic tools, spawned from the birth of nanoscience, such as atomic force microscopes (AFMs), provide new insights into food structure and provide the solution to previously intractable problems in food science. With these tools, we can visualise food structures under near-native conditions. We can see molecular networks in gels, understand the molecular origins of thixotropy, visualise interfacial networks that stabilise foams and emulsions or the molecular structures underpinning gelation and retrogradation of starches. Such understanding allows us to screen for better raw materials and to rationally manipulate food structures to control function. As well as enhancing appearance, texture and shelf-life, it is becoming possible to design novel nutritional attributes. For example, we can begin to identify starch structures with novel intrinsic ‘resistant starch’ characteristics or try to design emulsions to regulate fat metabolism. In addition to visualising molecular structures, we can directly feel the interactions between molecules. Emerging models for the bioactivity of certain plant polysaccharides suggest the importance of carbohydrate–mammalian lectin interactions. AFM allows us to test such models by measuring binding between molecules and identifying bioactive components. These approaches offer new avenues for the design of foods to promote health or to protect against the development or progression of long-term disease. Although based on nanoscience, these new foods will be produced by conventional technology and, although needing clearance as novel foods, are unlikely to be classified as products of nanotechnology.