CHAPTER 1: Nanotechnologies in Food: What, Why and How?
Published:17 May 2017
This first chapter sets the scene for subsequent chapters on various aspects of nanotechnologies in food written by acknowledged experts in their respective fields. It describes and defines the relevant materials, products and applications of nanotechnologies and highlights the distinctive chemical and physical attributes of nanomaterials that make them so attractive for applications in the food sector. This chapter presents an overview of the outlook for the applications of nanotechnologies in food and opens up a discussion on the different issues that have arisen from such applications. It highlights both the anticipated benefits and concerns, emphasizing that public perception and the ultimate acceptance or rejection of nanotech food products hinges on what benefits they may bring, to whom, and whether they may pose a risk to consumers. In this regard, it discusses the question of whether the novel chemical and physical attributes of some nanomaterials may also give rise to hitherto unrecognized health hazards. It also touches on the current frameworks for risk assessment and the regulation of nanotechnologies in food.
The possibility of controlling and manipulating certain properties of materials and substances by reducing their particle size to very small scales has been hypothesized since 1959.1 The term ‘nanotechnology’ has been coined in the past few decades to encompass different processes, materials and applications derived from a wide range of fields in the physical, chemical and biological sciences and in electronics and engineering with the common theme of the manufacture and use of materials on a nanometre size scale. One nanometre is one-billionth of a metre (1 × 10−9 m). The advent of modern analytical tools that can detect and characterize the various physicochemical aspects of materials at the nanoscale has further boosted developments in this field and nanotechnology has started to provide a systematic method for the study and fine-tuning of material properties to suit specific applications. This has inevitably attracted much interest from virtually all industrial sectors for the development of new or improved products and applications based on nanomaterials. Of particular interest in this regard are engineered nanoparticles (ENPs), which are manufactured specifically to achieve a certain composition or material property or composition for a particular purpose.
Like any new emergent field of science and technology, nanotechnology has brought both the promise of a number of new prospects and applications and new challenges. For example, it has not been easy to provide an exact definition of a nanomaterial. Despite several proposals, an internationally agreed definition is not yet on the horizon (see Chapter 2). Nevertheless, as a result of the commonality between different facets of nanotechnology in terms of a nanoscale particle size, there is a broad understanding that a typical nanomaterial could be characterized as having one or more external dimensions in the size range 1–100 nm.2 Nanomaterials can be in the form of nanoparticles, where all three external dimensions are at the nanoscale; nanorods or nanotubes, where two dimensions are at the nanoscale; and coatings or sheets, where only one dimension is at the nanoscale (Figure 1.1).
The chemical nature of the substances that can be used to manufacture ENPs is very diverse. In theory, any particulate material can be produced in nanoform either by a top-down (i.e. grinding down larger materials to the nanoscale) or a bottom-up (i.e. the upwards assembly of atoms/molecules to build nanoscale particles) approach. A nanomaterial can therefore be inorganic, organic or hybrid in nature. In addition to manufactured nanoparticles, some nanomaterials can be derived from natural sources—for example, montmorillonite is a clay obtained from volcanic ash or rocks. It has a natural nanoplate structure and has been used as a nanofiller in food packaging applications.
Nanomaterials are generally produced in the form of primary particles with nanoscale dimensions. However, most nanoparticles have a tendency to stick together to form larger agglomerates and/or aggregates during subsequent processing, formulation or storage. Unlike aggregates in which the primary particles are strongly bound together, these agglomerates only hold the primary particles together through weak van der Waals forces. The agglomerates can therefore de-agglomerate with changes in certain conditions, such as pH or ionic strength. Nanomaterials may be present as free particles in some applications, such as cosmetics and personal care products, but in other applications they are present as fixed, bound or embedded forms in a matrix, such as food packaging materials. Thus a nanomaterial may be present in a product in the form of free (separate from each other) nanoparticles and as larger sized clusters depending on the type of product or application.
To help visualize nanomaterials in context, organic life is carbon-based and the C–C bond length is about 0.15 nm. Thus, when placed in a food context, most ENPs are larger 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 drivers at the heart of most nanotechnology applications are the potential for improvement in material properties, the development of new functionalities and/or a reduction in the amount of (chemical) substances needed for a function. This is because, on an equivalent weight basis, the nanoforms of a material will have a much larger surface to mass ratio than their conventional bulk equivalents. Thus a much smaller amount of an ENP could, in theory, provide the level of functionality that would otherwise require a much greater amount of the same material in conventional form. The notion ‘a little goes a long way’ is probably the single most powerful reasoning behind many nanotechnology applications. Other benefits have also been attributed to the very small dimensions of ENPs—for example, nanosizing may allow the conversion of water-insoluble substances to forms that are dispersible in aqueous formulations. This may make it possible to reduce the need for solvents in certain consumer products, such as cosmetics, paints and coatings. The similar processing of water-insoluble food additives, such as colours, flavours and preservatives, may improve their dispersion in low-fat products. Nanoforms of various nutrients and supplements have also been claimed to have a greater uptake, absorption and bioavailability in the body than their bulk equivalents. This aspect alone has attracted a lot of interest in the use of nanosized ingredients in supplements, nutraceuticals and (health) food applications.3
The current applications of nanotechnology span a wide range of sectors, predominantly cosmetics and personal care, health care, paints and coatings, catalysts, agri-food, packaging and electronics. Nanotechnology applications have also been widely regarded to have the potential to revolutionize the whole of the agri-food sector, from production, processing, packaging and transportation to storage. Examples may include greater nutritional/health benefits, new or improved tastes, textures and flavours and also food products with lower amounts of additives, such as sugar, salt, fat, and artificial preservatives, colours and flavours. Nanotechnology applications for food packaging have also enabled the development of lightweight yet strong packaging materials that are able to keep foodstuffs secure during transportation, fresh for longer and safe from pathogens. Innovative smart labels incorporating ENPs are being developed to provide warnings to the consumer when a packaged food has started to deteriorate. Another emerging R&D and application area relates to the use of nanosized carriers for the enhanced delivery of nutrients and other bioactive substances in supplements, nutraceuticals, cosmeceuticals and health food products.4 Such formulations are generally derived from the nanoscale processing of food materials to form micelles or liposomes, or encapsulating bioactive supplements in natural or synthetic biodegradable polymeric materials. Any enhancement in uptake and bioavailability, or targeted release in the body, of certain poorly absorbed minerals and other health-promoting supplements may benefit consumers in general and certain population groups—such as elderly people, patients, and sportspersons—in particular.
Nanotechnology has emerged as one of the major converging technologies, offering the potential for further new developments through integration with other scientific and technological disciplines. There are already examples where the integration of nanotechnology with biotechnology and information technology has enabled the development of miniaturized sensing and monitoring devices, such as nanobiosensors. Such developments can be expected to enable the detection of pathogens and contaminants in food during processing, transportation and storage, and to enhance the safety and security of food products. In view of the known and envisaged technological developments, it is not surprising that the food industry is among those sectors eagerly seeking ways to realize the potential benefits offered by nanotechnology.
This book aims to provide an impartial view of the prospects and benefits that nanotechnology can be expected to bring to the food sector, the potential risks associated with these new materials and applications, and questions about the relevant societal and regulatory issues. This first chapter sets the scene for the subsequent chapters on different aspects of nanotechnologies in food, with each chapter written by experts acknowledged to be leaders in their respective fields.
1.2 Technological Advances in the Food Sector
The main driver that has shaped the present day food industry is the continuous basic human quest for a sustained supply of safe, nutritious, diverse, affordable and enjoyable foodstuffs. Our food has gone through a long history of transformations over the centuries, from hunting and gathering to highly mechanized farming and technologically advanced methods for processing and preservation. Agricultural food production during early human settlements is known to have started with instinctive knowledge and elementary tools and was at the mercy of the climate, pests and pathogens. Knowledge and experience gained over generations enabled different civilizations to live off the land and paved the way for more systematic farming and animal breeding. However, our basic food production methods seem to have remained more or less unchanged over the millennia. Until the early 1900s, agriculture was still run as a family-controlled or community-owned affair in most parts of the world. The norms of food production, transportation and trade started to transform in the 20th century with the introduction of mechanized farming, high-yielding crop varieties and, later, with the availability of synthetic fertilizers, pesticides and other agrochemicals (e.g. antibiotics and hormones). The so-called ‘green revolution’ of the mid-20th century succeeded in substantially increasing global food production. As the production of global food reached industrial scales, new ways had to be found to transport, store and preserve foodstuffs. This laid the foundations of the modern day food industry. In recent decades, advancements in DNA technology have led to a better understanding of the fundamental biological principles and genetic mechanisms involved in food production, which has enabled further large leaps from protracted conventional breeding methods to faster, knowledge-based improvements in crops and farm animals.
The history of food processing is as old as that of food production. Through the centuries, foodstuffs have been processed and treated in various ways and blended with different ingredients and additives to kill pests and pathogens, to enhance nutritional value, taste, flavour and texture, and to keep and store foodstuffs for longer periods of time. In that respect, many of the processes used by the modern day food industry—for example, heat treatment, fermentation, acid hydrolysis, kilning, curing, smoking and drying—are not new. However, the present day consumer-driven food industry has to constantly look for innovation and to develop new products that not only offer new tastes, textures and flavours, but are also wholesome, nutritious and better value for money for consumers. The present day food sector is a gigantic and complex web of subsectors and branches spanning from farm to fork. The global food retail market alone was estimated to be worth US$5.8 trillion annually in 2014.5 With the globalization of trade and industry worldwide, the rigid national boundaries that existed to protect local food production and supply are gradually becoming obscure and the supply and demand of foodstuffs is now increasingly influenced and determined by global market forces. In this context, the introduction of nanotechnology is likely to make new waves in the already very competitive and technologically advanced food industry. These aspects are discussed in more detail in subsequent chapters.
1.3 Public Consent for Technological Innovation
Before becoming established, any new technology has to cross a number of technological, societal and regulatory barriers, especially when it is applied to a sensitive area such as food. The applications of nanotechnology to food are facing this challenge. Despite the new emergent nature of nanotechnology applications to food, there have already been calls for clarity on whether and how the new technological developments would bring any real benefits for consumers and not just for the industry alone, and whether the benefits outweigh any risk to consumer health and the environment.
The early stages of any new technology are generally associated with a high level of uncertainty. Building consumer confidence and trust to encourage acceptance of the novelty determines the ultimate success or failure of the technology. Food products derived from nanotechnology are currently unfamiliar and unknown to the public at large, and it remains to be seen how such developments will be viewed by consumers. Uncertainties due to a lack of knowledge, or a lack of clear communication, are known to raise concerns over real as well as perceived risks. This is evident from the recent debacle over genetically modified foods. Despite the lack of analogy with genetically modified foods, nanofood applications seem to have opened up a similar debate among stakeholders, with calls for a moratorium or an outright ban on the use of nanotechnologies in food.6,7 Surveys of public opinion in the European Union have shown that, although consumer opinion is conducive to other applications of nanotechnology, it may not be entirely favourable to applications to food.8,9 This seems to contrast with public opinion in the USA. A survey carried out in 2008 for the Woodrow Wilson Institute for Scholars10 showed that, although the majority of American respondents had little or no knowledge of nanotechnology, they expressed positive expectations when told about the potential benefits and risks of the technology.
Gauging public perception of a new emerging technology is fraught with difficulties as it may be influenced by a multitude of factors. For example, with food security in mind, in developed countries where food is currently plentiful and affordable, there is a degree of public scepticism towards food products that are (or are perceived to be) unduly overprocessed, or that lack wholesomeness, freshness or ‘naturalness’. However, consumer perceptions of nanofood1 in less well-off parts of the world, where food security is a problem, may be different from those in the developed world. It also appears that, although food production is becoming increasingly globalized, public perceptions and priorities of food quality and safety have more of a national characteristic, partly due to economic and cultural reasons. Thus, even within a single trading block such as the European Union, consumer priorities differ from country to country, with some countries placing pesticides at the top of the agenda and some animal welfare, while others consider genetically modified organisms to be more worrying. A similar heterogeneity in the perception and acceptance of nanotechnology is likely and it remains to be seen how developments in food nanotechnology will be perceived on their own merits by the general public. However, it is logical to think that some applications of nanotechnology will be seen as less acceptable than others. These important aspects of public perception are discussed in detail in Chapters 3 and 4, where analogies have been drawn from experience with technologies previously introduced into the food sector.
1.4 Potential Benefits and Market Drivers for Nanotechnology
Like any other sector, the food industry is driven by innovation, competitiveness and profitability. The industry is therefore always seeking new technologies to offer products with improved taste, flavour, texture, longer shelf lives, better safety, traceability and competitive costs. Increasing health consciousness among consumers and tighter regulatory controls are also constantly driving the industry to look for new ways to reduce the amount of certain additives in food products, such as salt, sugar, fat, artificial colours and preservatives. Other societal and regulatory pressures are forcing the industry to address certain food-related ailments, such as obesity, diabetes, cardiovascular disease, digestive disorders, certain types of cancer (e.g. bowel cancer) and food allergies. Food packaging has also transformed over time, from wood, cardboard, paper and glass to stronger, but lightweight, recyclable and functional packaging materials. Food labels have been transformed to provide much more information than a mere list of ingredients and cooking instructions, and smart labels have been predicted to find increasing use in ensuring the quality, safety and security of food products in the supply chain. With the increasing global movement of food commodities, there are newer societal and technological pressures on the food industry to ensure the control of pathogens, toxins and other contaminants in foodstuffs, and to reduce the amount of packaging, food waste and the carbon footprint over the whole lifecycle of food products. In this context, the advent of nanotechnology has raised new hopes that it can address many of these needs (Figure 1.3). These aspects are discussed in more detail in subsequent chapters.
A number of reports and reviews have identified the current and short-term projected applications of nanotechnology in the food sector.3,4,11–17 These include the use of engineered nanomaterials as well as nanostructured or nanoencapsulated food ingredients and additives. A current niche for such applications is in the intersecting areas of the food, medicine and cosmetic sectors, where products are marketed as a means to enhance nutrition for different lifestyles and age groups or as an aid to health, wellbeing and beauty. The first examples of nanotechnology derived products appeared in the form of supplements, health foods, nutraceuticals, cosmeceuticals and nutricosmetics, with a slower progression to applications in mainstream food and beverage products. However, although many of the nanotechnology applications for food are still relatively new and emerging, they have been widely regarded to have the potential for making a major impact on the whole food chain. A major area of current application for ENPs is in food packaging, where innovative ENP–polymer composites with improved mechanical and barrier properties and/or antimicrobial activity have been developed.
It has been estimated that between 200 18 and 400 19 companies are undertaking research and/or using nanotechnology for food applications. These are most likely to include some major international food and beverage firms. However, despite much commercial interest, accurate information on the true scale of industrial activity in this area is difficult to gauge because of certain commercial and other sensitivities. A number of food corporations, which had been at the forefront of R&D in food nanotechnology, have gradually disassociated themselves from open involvement in this area. The absence of any quality scheme for nanofood products has made it even harder to segregate real nanoproducts from those that may have been based on unsubstantiated claims to project the ‘magic’ of nanotechnology for short-term commercial gain. This has also raised concerns that at least some, if not many, of the products claimed to have been derived from nanotechnology may in fact not have been so. Conversely, some products may contain a nanocomponent, but may not have declared its presence. In this context, the market forecasts for a dramatic future growth in the nanofood sector need to viewed with a degree of caution. It is nevertheless noteworthy that the number of nano(health)food products has been steadily increasing over the past few years and it is likely that many more products and applications that are currently in the R&D pipeline will appear on the market in coming years. The commercial exploitation of nanotechnology was almost concurrent with the start of the online marketing of consumer products. This new phenomenon has enabled consumers anywhere in the world to buy a nanotechnology derived product online.
The available reports suggest that the current nanofood sector is led by the USA, followed by Japan and China.20 Despite the infancy of the nanofood sector, the overall size of global market in 2006 was estimated at between US$410m19 and US$7 billion.20 Estimates have also varied between US$5.8 billion in 2012 19 and US$20.4 billion in 2010.20 Despite such anomalies, it appears that the upwards trend in nanofood applications will continue and may gather pace in the coming years.12,19
1.5 Nanotechnology Applications in the Food Sector
Nanotechnology applications in the (health) food sector are potentially numerous and are discussed in detail in the following chapters. The main focus of recent R&D and product development has been on food packaging, smart labels, nanosized ingredients and additives, and nanoscale carriers for the delivery of nutrients and supplements.12
1.5.1 Nanostructured and Nanoformulated Food Products
A key application area of nanotechnology in food processing is the development of nanostructured (also termed nanotextured) foodstuffs, such as spreads, mayonnaises, creams, yoghurts and ice creams. Nanoscale processing that produces nanostructured food products has been claimed to develop new tastes, textures, consistency and emulsion stability compared with conventional processing methods. A typical example of a nanostructured food is a low-fat product that is as ‘creamy’ as the full-fat alternative, and offers the consumer a ‘healthy’ option without compromising taste or texture. One such example is a mayonnaise composed of nanomicelles containing nanodroplets of water. The mayonnaise offers taste and texture attributes similar to the full-fat equivalent, but with a substantial reduction in the amount of fat.21
Another major area of nanotechnology applications is the use of nanosized or nanoencapsulated food additives and supplements. This involves the formulation of additives into liposomes or encapsulates with phospholipids, proteins or other degradable/digestible polymers. Nanoencapsulation is a technological next step from microencapsulation, which has been used by the food industry for certain ingredients and additives for many years. Nanoencapsulation is claimed to be more effective in preserving additives during processing and storage, masking undesirable tastes and flavours, controlling their release and enhancing uptake in the body. Other benefits claimed for nanosizing or nanoencapsulating include the better dispersibility of water-insoluble substances in foodstuffs without the need for additional fat or surfactants, and enhancing tastes and flavours due to the greater surface areas available at the nanoscale. This area of application is expected to exploit a much larger segment of the (health) food sector because it can encompass food colours, preservatives, flavourings and supplements. A wide range of products is already available in the form of supplements, nutraceuticals and (health) food products containing nanoforms of minerals, vitamins, antioxidants and other health-promoting supplements and antimicrobials.
1.5.2 Engineered Nanomaterials in Food
The available information suggests that nanomaterials used in (health) food applications consist of inorganic, organic and hybrid materials. Examples include: metals (e.g. iron and silver); metal oxides (e.g. titanium dioxide); the alkaline earth metals (e.g. calcium and magnesium); non-metals (e.g. selenium and silicates); organic materials (e.g. a wide range of vitamins, antioxidants, colours, flavours and preservatives in nanostructured or nanoencapsulated forms); and hybrid or surface-functionalized nanomaterials (e.g. with enzymes or binding moieties attached to the surface). In particular, certain approved food additives, such as titanium dioxide (TiO2, E171) and silica (SiO2, E551), are known to contain nanoscale particles.
1.5.3 Engineered Nanomaterials in Food Packaging
Among all the known products and applications of nanotechnology, food packaging currently forms the largest area of application in the food and related sectors. Examples include: thermoplastics formulated with nanoclay additives as a gas barrier; nanoparticles of silver, zinc oxide and magnesium oxide for antimicrobial packaging; nanoparticles of titanium dioxide for UV protection; nanoparticles of titanium nitride as a processing aid; and nanoparticles of silica for surface coatings.
Although only a few nanotechnology applications for mainstream food and beverage products are currently known, nanotechnology enhanced food packaging is now a commercial reality.12,19 A factor contributing to rapid commercial development in this area appears to be the expectation that, due to the fixed or embedded nature of the ENPs in plastics, they are unlikely to migrate into packaged foodstuffs and pose a risk to consumers. Nanotechnology applications for food contact materials (FCMs) already make up the largest share of the current and short-term predicted nanofood market.19 It was estimated that nanotechnology enhanced packaging (including food packaging) would make up 19% of the share of nanotechnology products and applications in the global consumer goods industry by 2015.22 The main developments in the area of nanotechnology enhanced FCMs include the following.
Improved FCMs in terms of flexibility, gas barrier properties and temperature/moisture stability. Typical examples include polymer composites with nanoclay (gas barrier), silicon dioxide (abrasion resistance), titanium dioxide (UV absorption) and titanium nitride (processing aid). Also under research are nanocomposites of biodegradable polymers, such as nanoclay composites with polymers of starch and polylactic acid, to improve mechanical and moisture barrier properties.
Active FCMs incorporating metal or metal oxide nanoparticles (e.g. silver, zinc oxide or magnesium oxide) for antimicrobial properties. They are claimed to prevent microbial growth on the surface of plastics and hence to keep the food within fresher for longer periods of time. Other active functions include nanoadditives or nanocoatings for FCMs to give antimicrobial properties, such as self-cleaning surfaces that help to maintain hygienic conditions in food processing facilities such as abattoirs.
Intelligent and smart packaging incorporating nanosized sensors that can monitor the condition of food during transportation and storage. Of particular interest in this regard are the safety and quality indicators that can be applied as labels or coatings to add an intelligent function to food packaging—for example, to monitor the integrity of packages sealed under vacuum or an inert/modified atmosphere by detecting leaks, freeze–thaw–refreeze scenarios by detecting variations in time–temperature, or microbial safety and/or quality indicators by detecting the deterioration of foodstuffs.
The available examples of nanotechnology enhanced FCMs include multi-layered PET bottles containing a layer of nanoclay composite to provide an effective gas barrier. This technology is understood to already be used by some large breweries. Other examples include food containers made of plastic–nanosilver composites and wrapping film containing nanoparticles of zinc oxide for the antimicrobial protection of food. Market estimates for the current and short-term predicted applications suggest that nanotechnology enhanced food packaging materials already make up the largest share of the overall nanofood market.19 Chapter 7 covers the nanotechnology processes, products and applications of food packaging materials in detail.
1.5.4 Other Applications
The apparent benefits of substituting food ingredients and supplements with nanosized equivalents or the use of nanoscale carriers has opened up a new door for research into the development of nanoforms of pesticides, veterinary medicines and other agrochemicals, such as fertilizers and plant growth regulators. For example, the use of active ingredients formulated or encapsulated at the nanoscale has been explored for the delivery of pesticides and fertilizers. The anticipated benefits driving R&D in these areas include the potential for reductions in the amount of agrochemicals used and better control of their application and dosage in the field. However, despite the growing industrial interest in R&D, there is no example of a nanoproduct available in this area. Some R&D has been reported in the published literature suggesting the potential benefits of the use of nanoemulsions, micronized (volcanic) rock dust and nanosilica as a delivery system for pesticides, fertilizers and growth regulators.12
In theory, nanosized supplements, e.g. vitamins and minerals, developed for human use can equally be used for fortifying animal feeds. Some feed-grade nanovitamin mixes are available for use in poultry and livestock feeds. Examples of R&D into nanosized additives for animal feeds include a natural biopolymer from yeast cell walls intended to bind mycotoxins to protect animals against mycotoxicosis and the possible use of an aflatoxin binding nanoadditive for animal feed derived from a modified nanoclay.23 Another interesting example of R&D in this area is ‘intelligent chicken feed’, which is reported to contain polystyrene nanoparticles coated with host proteins to mimic the host cell surface. When used in chicken feed, these nanoparticles are reported to offer large surface areas for binding and purging the animal of feed-borne pathogens without the use of antibiotics.24
1.6 Potential Safety Concerns
The gradual progression of nanotechnologies to food applications has raised some safety concerns for consumers.12,25,26 Many of these concerns, however, seem to stem from uncertainties relating to the properties and effects of ENPs and the perceived lack of regulatory controls for risks to consumers and the environment. Aspects relating to consumer safety are discussed in detail in Chapter 10.
It is known that conventional physicochemical rules are generally not fully applicable at the nanometre scale and that there can be some fundamental shifts in the physicochemical properties, behaviour and biological interactions of ENPs compared with their bulk equivalents. For example, quantum effects may have a much greater influence on the properties of nanoscale particles, especially those in the lower nanometre size range. In some cases, such changes in physicochemical properties could lead to changes in biokinetic behaviour, biological interactions and biological effects. Studies have suggested deviations in the toxicity profiles of some ENPs compared with their conventional equivalents. The use of insoluble and non-degradable ENPs in food applications, especially those that are not degraded inside or outside the gastrointestinal tract, can raise consumer safety concerns. The potential translocation of such ENPs with large and potentially reactive surface areas to cells and tissues in various parts of the body may pose a risk to consumer health. Thus although a relatively small amount of an ENP can provide a similar level of functionality to a much greater amount of the bulk equivalent, by the same token it may also have a proportionately greater impact on consumer health and/or the environment. ENPs are also known to adsorb or bind various compounds and moieties on their surfaces and may act as carriers of potentially harmful contaminants and foreign substances into the blood circulation and thus facilitate their distribution to different organs in the body.
Another important aspect to consider in relation to the potential harmful effects of ENPs is their ability to penetrate cellular barriers. This aspect has added another dimension to considerations relating to the biokinetics and toxicology of particles because ENPs may penetrate through membrane barriers and reach new targets in the body where the entry of larger sized particles is restricted.
Depending on the surface chemistry, ENPs may also interact with a variety of chemical and biological entities and this may have a substantial effect on the absorption, distribution, metabolism, elimination (ADME) profile. In this regard, there is evidence to suggest that ENPs may become surface coated with certain biomolecules, especially proteins, and this can alter their distribution profile in the body.27 This suggests that ENPs can undergo complex interactions in biological environments. It is therefore likely that ENPs added to food products will undergo certain transformations, which may affect their translocation, bioavailability and eventual biological effects. Although nothing can be generalized due to the limited nature of the available knowledge, a common manifestation of the exposure of in vitro biological systems to ENPs has been an increase in the generation of reactive oxyradicals. Depending on the level and duration of exposure, this may lead to oxidative stress and inflammatory reactions. A greater uptake and bioavailability of even useful substances may also lead to negative health consequences. For example, continued exposure to ENPs with a strong antimicrobial activity via food and drinks might be harmful to the natural microflora of the gastrointestinal tract.
It is worth stressing that any risk to consumers from nanofoods would depend on a number of factors, including the concentration of ENPs in a given food product, the amount and frequency of consumption of the product and, more importantly, the physicochemical nature, level of uptake, translocation and bioavailability of the ingested ENPs. There are currently significant knowledge gaps with regard to the behaviour, interactions, fate and toxicological effects of ENPs inside and outside the gastrointestinal tract. It is important to note that many of the current studies indicating the harmful effects of some ENPs either relate to inhalation exposure or are based on studies using in vitro models that have as yet unproved biological relevance. They may therefore be an early alert for potential hazards, but not necessarily for risk. It is possible that ENPs added to food will lose their nanostructure as a result of dissolution on reaction with stomach acids or digestive enzymes, or as a result of transformation in the gastrointestinal tract, such as agglomeration or binding with other food components, and will not be available for translocation in particle form. As such, the full extent of the fate and behaviour of nanoparticles entering the body through food and drinks has not yet been fully characterized. In anticipation of the likely developments in the nanofood sector, it is imperative that the safety of nanotechnology derived products is adequately addressed.
1.7 Potential Health Risks
The most likely route of entry for micro- or nanosized particles to the gut is through the consumption of food and drinks, although some entry through lung clearance is also possible. A healthy digestive system allows the absorption of nutrients from the gut only after the digestion of foodstuffs. The gut wall is thus designed to ensure the passage of dietary nutrients, but to prevent the uptake of larger materials. There is a concern that the very small size of nanoparticles may give insoluble and biopersistent particles the ability to cross the gut wall. This may lead to an increase in their absorption and bioavailability, which could give rise to higher internal exposure with higher plasma concentrations (from a higher absorption rate) or a higher area under the curve exposure (from a higher uptake efficiency). From this, various possible consumer health implications may be envisaged. For example, it may lead to an altered nutrient profile in the body due to the greater absorption of certain nanoingredients, or particular health consequences due to the greater absorption of certain nanosized substances.
It is well documented that the gastrointestinal uptake of exogenous nanoparticles is greater than that of microparticles.28 Translocation through the gut epithelium is dependent on the physiochemical properties of an ENP, e.g. its size, surface charge, hydrophobicity and surface chemistry. The process is also affected by the physiology of the gastrointestinal tract. For example, the translocation of nanoparticles may be different in a diseased versus a normal healthy gut.28 It has been speculated that the presence of particulate materials in the diet can exacerbate certain aliments, such as Crohn’s disease and irritable bowel syndrome. Trials carried out so far to test whether a reduction in microparticles in the diet can reduce the symptoms of these diseases have, however, produced contradictory results. It is therefore unclear whether the presence of micro- or nanoparticles is unequivocally linked to these diseases. These aspects are discussed in detail in Chapter 10.
There are other aspects that need consideration in relation to the assessment of the risk of nanomaterials in food. Although nanotechnology has provided a systematic method for the nanoscale formulation of food products to develop new tastes and textures, it is known that our foodstuffs are naturally composed of nanostructures. For example, certain proteins, carbohydrates and fats exist as natural structures on a nanoscale. Even the larger sized food materials are broken down to smaller sizes during the digestion process. Although proteins, carbohydrates and lipids are each digested in a different way, in theory they are all broken down to nanostructures in the gastrointestinal tract before being absorbed and assimilated in the body. It has therefore been argued that our body is already used to dealing with nanostructures and that foods processed at the nanoscale would be more readily digested, absorbed and bioavailable in the body. Although this is a valid argument for food materials that are naturally digestible/degradable, it remains to be seen whether the nanoscale processing of the same materials can make them any different and whether they will be handled in the body in a different manner from the food nanostructures generated during digestion. These aspects are discussed in more detail in Chapter 10.
The concept of nanodelivery systems seems to have originated from research on the targeted delivery of drugs and therapeutics. However, the use of similar technology in foodstuffs is interesting in the sense that, although it can offer increased absorption, uptake and bioavailability, it also has the potential to alter the tissue distribution of substances in the body. For example, a water-soluble compound can be rendered fat-dispersible through nanocarrier technology and, vice versa, a fat-dispersible compound can be rendered water-dispersible. It is hoped that such nanocarriers will be broken down completely with the release of the contents within the gastrointestinal tract. In such an example, the encapsulated compounds will not be any different from the conventional equivalents. However, where a nanocarrier system can deliver the encapsulated substance to the bloodstream, its absorption, tissue distribution and bioavailability may become drastically different from the conventional equivalent. This has raised the concern that some nanocarriers may act as a Trojan horse and facilitate the translocation of encapsulated substances or other foreign materials to unintended parts of the body. Also, where a nanocarrier as such, or in a partially degraded form, can carry a bioactive substance from the gastrointestinal tract to the circulatory system, its subsequent absorption, tissue distribution and bioavailability may be different from those expected from the conventional equivalent. Knowing the fate of nanocarriers is therefore crucial for the assessment of safety. Although enhancement in the uptake and bioavailability of certain poorly absorbed nutrients and supplements could provide positive health benefits, it may also give rise to an atypically high level of these, which, for some substances, may bring about harmful consequences that may not be foreseen for conventional forms of the same substance.29
The risk to consumers from the use of food or drinks packaged in nanotechnology enhanced FCMs is dependent on the migration of ENPs into foodstuffs. Such migration data have so far been very limited, but model estimates and studies have shown insignificantly low levels of migration of ENPs in FCMs.30 The presence of ENPs does not seem to affect the migration of other non-nanoscale components. Thus although more testing is needed to ascertain the migration patterns in ENP–polymer composites, it seems that this application area of nanotechnology may not carry a significant risk of ENP exposure for consumers.
1.8 Regulation of Risks
Rapidly expanding nanotechnological applications in a wide range of industrial sectors have brought a new challenge to regulatory frameworks in relation to assessing and managing the associated risks. Questions have been raised about whether the current risk assessment paradigm, designed for conventional substances, is applicable and adequate for nanomaterials. There are certain knowledge gaps in relation to the toxicological hazard characterization of many ENPs, suitable metrics for hazard and exposure assessments, and validated methods for the characterization of ENPs in complex food matrices. Despite such uncertainties, the new nanotechnological developments are not taking place in a regulatory void. A number of regulatory gap reviews31–33 have shown that the existing regulatory frameworks are adequate to cover any risk arising from nanotechnology. Although highlighting the need for certain modifications in testing methodologies, the existing models for the risk assessment of chemical substances have been concluded to be equally applicable to nanomaterials. Within the past few years, more guidance has become available on the safety assessment of products and applications of nanotechnologies, including for food and animal feeds. In this regard, a number of cross-cutting horizontal regulations—as well as vertical regulations that relate to specific processes, materials and products—have been deemed to be relevant and applicable. For example, the European Food Information Regulation (EU) No 1169/2011, together with the new European Regulation on Novel Food (EU) No 2015/2283, provide a clear regulatory path for the safety assessment, pre-market authorization and labelling of nanomaterials used in food products. The regulatory aspects are discussed in detail in Chapter 11.
Like many other sectors, emerging technological advancements in the fields of nanoscience and nanotechnology have raised hopeful anticipation in the food sector for a new route to innovation that could bring wide-ranging benefits to the whole food chain. Examples of such innovations include: the development of new tastes, textures, mouth sensations and consistencies of food products; a potential reduction in the amount of fat and certain additives, such as salt; an enhancement in the absorption and bioavailability of nutrients and supplements; the preservation of food quality and freshness; and novel packaging solutions allowing better traceability and security of food products in the supply chain. It is also clear from the current and projected applications in the (health) food sectors that these have been on a slow, but steady, increase worldwide. Food packaging applications currently make up the largest share of the nanofood market, followed by nanosized and/or nanoencapsulated ingredients and additives for (health) food applications. A number of nanotechnology enhanced FCMs and (health) food products containing nanosized ingredients and additives are already available in some countries, although they are still new and scarce in Europe and other regions. However, considering the increasingly global nature of the current food business and active R&D in nanotechnology applications for food, it is not unreasonable to expect that such products will be available on the global market in increasing numbers and variety in the coming years. The market penetration of such products in different countries and regions will, however, depend on, among other factors, the price, quality and, above all, acceptance by consumers. This also means that there will be a growing need for strategies to regulate risks in a globally harmonized manner. This might pose a challenge to the regulatory authorities because food laws in different countries may not conform to each other. In due course, however, such issues will probably be resolved through the development of frameworks relating to key international trade agreements, such as those administered by the World Trade Organization.33
In brief, although nanotechnology applications for the food and health food sectors have undoubtedly opened up enormous opportunities for innovation and new developments, at the same time they have also raised new challenges with regard to ensuring safety and communicating the risks and benefits of this new technology without jeopardizing the pace of new developments. In this regard, the industry is likely to face several challenges. These include demonstrating the clear benefits of nanofoods for consumers, ensuring stringent quality control of the products, complying with regulatory standards and communicating health and safety assurance to the consumer. This book aims to provide much-needed insights into the various aspects and issues relating to the new and exciting developments that nanotechnologies are offering to the food and related sectors.
The recently coined term ‘Nanofood’ refers to the use of nanotechnology techniques, materials or tools for production, processing, or packaging of food.