Recent innovations in nanotechnology have transformed a number of scientific and industrial areas including the food industry. Applications of nanotechnology have emerged with increasing need of nanoparticle uses in various fields of food science and food microbiology, including food processing, food packaging, functional food development, food safety, detection of foodborne pathogens, and shelf-life extension of food and/or food products. This review summarizes the potential of nanoparticles for their uses in the food industry in order to provide consumers a safe and contamination free food and to ensure the consumer acceptability of the food with enhanced functional properties. Aspects of application of nanotechnology in relation to increasing in food nutrition and organoleptic properties of foods have also been discussed briefly along with a few insights on safety issues and regulatory concerns on nano-processed food products.
Over the past few decades, nanotechnology has increasingly been considered as to be attractive technology that has revolutionized the food sector. It is a technology on the nanometer scale and deals with the atoms, molecules, or the macromolecules with the size of approximately 1–100 nm to create and use materials that have novel properties. The created nanomaterials possess one or more external dimensions, or an internal structure, on the scale from 1 to 100 nm that allowed the observation and manipulation of matter at the nanoscale. It is observed that these materials have unique properties unlike their macroscale counterparts due to the high surface to volume ratio and other novel physiochemical properties like color, solubility, strength, diffusivity, toxicity, magnetic, optical, thermodynamic, etc. (Rai et al., 2009; Gupta et al., 2016). Nanotechnology has brought new industrial revolution and both developed and developing countries are interested in investing more in this technology (Qureshi et al., 2012). Therefore, nanotechnology offers a wide range of opportunities for the development and application of structures, materials, or system with new properties in various areas like agriculture, food, and medicine, etc.
The rising consumer concerns about food quality and health benefits are impelling the researchers to find the way that can enhance food quality while disturbing least the nutritional value of the product. The demand of nanoparticle-based materials has been increased in the food industry as many of them contain essential elements and also found to be non-toxic (Roselli et al., 2003). They have been also found to be stable at high temperature and pressures (Sawai, 2003). Nanotechnology offers complete food solutions from food manufacturing, processing to packaging. Nanomaterials bring about a great difference not only in the food quality and safety but also in health benefits that food delivers. Many organizations, researchers, and industries are coming up with novel techniques, methods, and products that have a direct application of nanotechnology in food science (Dasgupta et al., 2015).
The applications of nanotechnology in food sector can be summarized in two main groups that are food nanostructured ingredients and food nanosensing. Food nanostructured ingredients encompass a wide area from food processing to food packaging. In food processing, theses nanostructures can be used as food additives, carriers for smart delivery of nutrients, anti-caking agents, antimicrobial agents, fillers for improving mechanical strength and durability of the packaging material, etc. whereas food nanosensing can be applied to achieve better food quality and safety evaluation (Ezhilarasi et al., 2013). In this review, we have summarized the role of nanotechnology in food science and food microbiology and also discussed some negative facts associated with this technology.
Nanotechnology in Food Processing
The nanostructured food ingredients are being developed with the claims that they offer improved taste, texture, and consistency (Cientifica Report, 2006). Nanotechnology increasing the shelf-life of different kinds of food materials and also help brought down the extent of wastage of food due to microbial infestation (Pradhan et al., 2015). Nowadays nanocarriers are being utilized as delivery systems to carry food additives in food products without disturbing their basic morphology. Particle size may directly affect the delivery of any bioactive compound to various sites within the body as it was noticed that in some cell lines, only submicron nanoparticles can be absorbed efficiently but not the larger size micro-particles (Ezhilarasi et al., 2013). An ideal delivery system is supposed to have following properties: (i) able to deliver the active compound precisely at the target place (ii) ensure availability at a target time and specific rate, and (iii) efficient to maintain active compounds at suitable levels for long periods of time (in storage condition). Nanotechnology being applied in the formation of encapsulation, emulsions, biopolymer matrices, simple solutions, and association colloids offers efficient delivery systems with all the above-mentioned qualities. Nano polymers are trying to replace conventional materials in food packaging. Nanosensors can be used to prove the presence of contaminants, mycotoxins, and microorganisms in food (Bratovčić, 2015).
Nanoparticles have better properties for encapsulation and release efficiency than traditional encapsulation systems. Nanoencapsulations mask odors or tastes, control interactions of active ingredients with the food matrix, control the release of the active agents, ensure availability at a target time and specific rate, and protect them from moisture, heat (Ubbink and Kruger, 2006), chemical, or biological degradation during processing, storage, and utilization, and also exhibit compatibility with other compounds in the system (Weiss et al., 2006). Moreover, these delivery systems possess the ability to penetrate deeply into tissues due to their smaller size and thus allow efficient delivery of active compounds to target sites in the body (Lamprecht et al., 2004). Various synthetic and natural polymer-based encapsulating delivery systems have been elaborated for the improved bioavailability and preservation of the active food components (Table 1). Further, the importance of nanotechnology in food processing can be evaluated by considering its role in the improvement of food products in terms of (i) food texture, (ii) food appearance, (iii) food taste, (iv) nutritional value of the food, and (v) food shelf-life. It is a matter of fact that surprisingly nanotechnology not only touches all the above-mentioned aspects but has also brought about significant alterations in food products providing them novel qualities.
Texture, Taste, and Appearance of Food
Nanotechnology provides a range of options to improve the food quality and also helps in enhancing food taste. Nanoencapsulation techniques have been used broadly to improve the flavor release and retention and to deliver culinary balance (Nakagawa, 2014). Zhang et al. (2014) used the nanoencapsulation for the highly reactive and unstable plant pigment anthocyanins which have various biological activities. Through, encapsulating cyanidin-3-O-glucoside (C3G) molecules within the inner cavity of apo recombinant soybean seed H-2 subunit ferritin (rH-2) improved the thermal stability and photostability. This design and fabrication of multifunctional nanocarriers for bioactive molecule protection and delivery. Rutin is a common dietary flavonoid with great important pharmacological activities but due to poor solubility, its application in the food industry is limited. The ferritin nanocages encapsulation enhanced the solubility, thermal and UV radiation stability of ferritin trapped rutin as compared to free rutin (Yang et al., 2015). The use of nanoemulsions to deliver lipid-soluble bioactive compounds is much popular since they can be produced using natural food ingredients using easy production methods, and may be designed to enhance water-dispersion and bioavailability (Ozturk et al., 2015).
As compared to larger particles which generally release encapsulated compounds more slowly and over longer time periods, nanoparticles provide promising means of improving the bioavailability of nutraceutical compounds due to their subcellular size leading to a higher drug bioavailability. Many metallic oxides such as titanium dioxide and silicon dioxide (SiO2) have conventionally been used as color or flow agents in food items (Ottaway, 2010). SiO2 nanomaterials are also one of the most used food nanomaterials as carriers of fragrances or flavors in food products (Dekkers et al., 2011).
Nutritional Value
A majority of bioactive compounds such as lipids, proteins, carbohydrates, and vitamins are sensitive to high acidic environment and enzyme activity of the stomach and duodenum. Encapsulation of these bioactive compounds not only enables them to resist such adverse conditions but also allows them to assimilate readily in food products, which is quite hard to achieve in non-capsulated form due to low water-solubility of these bioactive compounds. Nanoparticles-based tiny edible capsules with the aim to improve delivery of medicines, vitamins or fragile micronutrients in the daily foods are being created to provide significant health benefits (Yan and Gilbert, 2004; Koo et al., 2005). The nanocomposite, nano-emulsification, and nanostructuration are the different techniques which have been applied to encapsulate the substances in miniature forms to more effectively deliver nutrients like protein and antioxidants for precisely targeted nutritional and health benefits. Polymeric nanoparticles are found to be suitable for the encapsulation of bioactive compounds (e.g., flavonoids and vitamins) to protect and transport bioactive compounds to target functions (Langer and Peppas, 2003).
Preservation or Shelf-Life
In functional foods where bioactive component often gets degraded and eventually led to inactivation due to the hostile environment, nanoencapsulation of these bioactive components extends the shelf-life of food products by slowing down the degradation processes or prevents degradation until the product is delivered at the target site. Moreover, the edible nano-coatings on various food materials could provide a barrier to moisture and gas exchange and deliver colors, flavors, antioxidants, enzymes, and anti-browning agents and could also increase the shelf-life of manufactured foods, even after the packaging is opened (Renton, 2006; Weiss et al., 2006). Encapsulating functional components within the droplets often enables a slowdown of chemical degradation processes by engineering the properties of the interfacial layer surrounding them. For example, curcumin the most active and least stable bioactive component of turmeric (Curcuma longa) showed reduced antioxidant activity and found to be stable to pasteurization and at different ionic strength upon encapsulation (Sari et al., 2015).
Nanotechnology in Food Packaging
A desirable packaging material must have gas and moisture permeability combined with strength and biodegradability (Couch et al., 2016). Nano-based “smart” and “active” food packagings confer several advantages over conventional packaging methods from providing better packaging material with improved mechanical strength, barrier properties, antimicrobial films to nanosensing for pathogen detection and alerting consumers to the safety status of food (Mihindukulasuriya and Lim, 2014).
Application of nanocomposites as an active material for packaging and material coating can also be used to improve food packaging (Pinto et al., 2013). Many researchers were interested in studying the antimicrobial properties of organic compounds like essential oils, organic acids, and bacteriocins (Gálvez et al., 2007; Schirmer et al., 2009) and their use in polymeric matrices as antimicrobial packaging. However, these compounds do not fit into the many food processing steps which require high temperatures and pressures as they are highly sensitive to these physical conditions. Using inorganic nanoparticles, a strong antibacterial activity can be achieved in low concentrations and more stability in extreme conditions. Therefore, in recent years, it has been a great interest of using these nanoparticles in antimicrobial food packaging. An antimicrobial packaging is actually a form of active packaging which contacts with the food product or the headspace inside to inhibit or retard the microbial growth that may be present on food surfaces (Soares et al., 2009). Many nanoparticles such as silver, copper, chitosan, and metal oxide nanoparticles like titanium oxide or zinc oxide have been reported to have antibacterial property
Nanotechnology is the understanding and control of matter at the nanoscale, at dimensions between approximately 1 and 100 nanometers, where unique phenomena enable novel applications. Matter can exhibit unusual physical, chemical, and biological properties at the nanoscale, differing in important ways from the properties of bulk materials, single atoms, and molecules. Some nanostructured materials are stronger or have different magnetic properties compared to other forms or sizes of the same material. Others are better at conducting heat or electricity. They may become more chemically reactive, reflect light better, or change color as their size or structure is altered.
Although modern nanoscience and nanotechnology are relatively new, nanoscale materials have been used for centuries. Gold and silver nanoparticles created colors in the stained-glass windows of medieval churches hundreds of years ago. The artists back then just didn’t know that they were using nanotechnology to create these beautiful works of art!
Nanotechnology encompasses nanoscale science, engineering, and technology in fields such as chemistry, biology, physics, materials science, and engineering. Nanotechnology research and development involves imaging, measuring, modeling, and manipulating matter between approximately 1–100 nanometers.
What is nanotechnology?
The SCENIHR opinion states:
Nanotechnology is the term given to those areas of science and engineering where phenomena that take place at dimensions in the nanometre scale are utilised in the design, characterisation, production and application of materials, structures, devices and systems. Although in the natural world there are many examples of structures that exist with nanometre dimensions (hereafter referred to as the nanoscale), including essential molecules within the human body and components of foods, and although many technologies have incidentally involved nanoscale structures for many years, it has only been in the last quarter of a century that it has been possible to actively and intentionally modify molecules and structures within this size range. It is this control at the nanometre scale that distinguishes nanotechnology from other areas of technology.
Clearly the various forms of nanotechnology have the potential to make a very significant impact on society. In general it may be assumed that the application of nanotechnology will be very beneficial to individuals and organisations. Many of these applications involve new materials which provide radically different properties through functioning at the nanoscale, where new phenomena are associated with the very large surface area to volume ratios experienced at these dimensions and with quantum effects that are not seen with larger sizes. These include materials in the form of very thin films used in catalysis and electronics, two-dimensional nanotubes and nanowires for optical and magnetic systems, and as nanoparticles used in cosmetics, pharmaceuticals and coatings. The industrial sectors most readily embracing nanotechnology are the information and communications sector, including electronic and optoelectronic fields, food technology, energy technology and the medical products sector, including many different facets of pharmaceuticals and drug delivery systems, diagnostics and medical technology, where the terms nanomedicine and bionanotechnology are already commonplace. Nanotechnology products may also offer novel challengies for the reduction of environmental pollution.
However, just as phenomena taking place at the nanoscale may be quite different to those occurring at larger dimensions and may be exploitable for the benefit of mankind, so these newly identified processes and their products may expose the same humans, and the environment in general, to new health risks, possibly involving quite different mechanisms of interference with the physiology of human and environmental species. These possibilities may well be focussed on the fate of free nanoparticles generated in nanotechnology processes and either intentionally or unintentionally released into the environment, or actually delivered directly to individuals through the functioning of a nanotechnology based product. Of special concern would be those individuals whose work places them in regular and sustained contact with free nanoparticles. Central to these health risk concerns is the fact that evolution has determined that the human species has developed mechanisms of protection against environmental agents, either living or dead, this process being determined by the nature of the agents commonly encountered, within which size is an important factor. The exposure to nanoparticles having characteristics not previously encountered may well challenge the normal defence mechanisms associated with, for example, immune and inflammatory systems. It is also possible for there to be an environmental impact of the products of nanotechnology, related to the processes of dispersion and persistence of nanoparticles in the environment.
Wherever the potential for an entirely new risk is identified, it is necessary to carry out an extensive analysis of the nature of the risk, which can then, if necessary, be used in the processes of risk management. It is widely accepted that the risks associated with nanotechnology need to be analysed in this way. Many international organisations ( e.g. Asia Pacific Nanotechnology Forum 2005), governmental bodies within the European Union (European Commission 2004,), National Institutions (e.g. De Jong et al 2005, Roszek et al 2005, US National Science and Technology Council 2004, IEEE 2004, US National Institute of Environmental Health Sciences 2004), non-governmental organisations (e.g.UN-NGLS 2005), learned institutions and societies (e.g. Institute of Nanotechnology 2005, Australian Academy of Sciences 2005, METI 2005, UK Royal Society and Royal Academy of Engineering 2004) and individuals (e.g. Oberdörster et al 2005, Donaldson and Stone 2003) have published reports on the current state of nanotechnology, and most draw attention to this need for a thorough risk analysis.
The European Council has highlighted the need to pay special attention to the potential risks throughout the life cycle of nanotechnology based products and the European Commission has signalled its intention to work on an international basis towards establishing a framework of shared principles for the safe, sustainable, responsible and socially acceptable use of nanotechnologies.
3.2 Definitions and Scope
There are several definitions of nanotechnology and of the products of nanotechnology, often these been generated for specific purposes.
In this Opinion, the underlying scientific concepts of nanotechnology have been considered more important than the semantics of a definition, so these are considered first. The Committee considers that the scope of nanoscience and nanotechnology used by the UK Royal Society and Royal Academy of Engineering in their 2004 report (Royal Society and Royal Academy of Engineering 2004) adequately expresses these concepts. This suggests that the range of the nanoscale is from the atomic level, at around 0.2 nm up to around 100nm. It is within this range that materials can have substantially different properties compared to the same substances at larger sizes, both because of the substantially increased ratio of surface area to mass, and also because quantum effects begin to play a role at these dimensions, leading to significant changes in several types of physical property.
The present Opinion uses the various terms of nanotechnology in a manner consistent with the recently published Publicly Available Specification on the Vocabulary for Nanoparticles of the British Standards Institution (BSI 2005), in which the following definitions for the major general terms are proposed:
Nanoscale: having one or more dimensions of the order of 100 nm or less.
Nanoscience: the study of phenomena and manipulation of materials at atomic, molecular and macromolecular scales, where properties differ significantly from those at a larger scale.
Nanotechnology: the design, characterization, production and application of structures, devices and systems by controlling shape and size at the nanoscale.
Nanomaterial: material with one or more external dimensions, or an internal structure, which could exhibit novel characteristics compared to the same material without nanoscale features.
Nanoparticle: particle with one or more dimensions at the nanoscale. (Note: In the present report, nanoparticles are considered to have two or more dimensions at the nanoscale).
Nanocomposite: composite in which at least one of the phases has at least one dimension on the nanoscale.
Nanostructured: having a structure at the nanoscale,
It should be noted that nanoscience and nanotechnology have been emerging rapidly during recent years, and that the vocabulary used within the contributing disciplines has not been consistent during this time. Also, as this report notes, there have been, and continue to be, serious difficulties with the precise measurement of the parameters of the nanoscale, such that it is not always possible to have complete confidence in the data and conclusions drawn about specific phenomena relating to specific features of nanostructures and nanomaterials. This Opinion recognises the inevitability of this situation and has drawn some general conclusions in the knowledge that the literature may contain inconsistencies and inaccuracies. Whilst, therefore, this Opinion uses the definition that nanoscale should now be considered to involve dimensions up to 100 nm, it recognises that some of the literature will have represented nanoscale as having larger dimensions than 100 nm. Much of the literature related to particles, especially that concerned with aerosols, air pollution and inhalation toxicology, has referred to particles as either ultrafine, fine or conventional. This report has assumed that, unless otherwise stated, ‘ultrafine particles’ are essentially equivalent to nanoparticles.
Also, in relation to nanoparticles, it must be borne in mind that a sample of a substance that contains nanoparticles will not be monodisperse, but will normally contain a range of particle sizes. This makes it even more difficult to assess accurately the parameters of the nanoscale, especially when considering the doses for toxicological studies. In this Opinion reference is frequently made to studies of exposure and toxicology data concerned with particles and will quote the particle size given in the papers as either single figures (e.g. 40 nm) or ranges (e.g. 40 – 80 nm) recognising that these will be approximations.
Moreover, there will be a tendency in some situations for nanoparticles to aggregate. It might be assumed that an aggregate of nanoparticles, which may have dimensions measured in microns rather than nanometres, would behave differently to the individual nanoparticles, but at the same time there is no reason to expect the aggregate to behave like one large particle. Equally, it might be expected that the behaviour of nanoparticles will be dependent on their solubility and susceptibility to degradation and that neither the chemical composition nor particle size are guaranteed to remain constant over time.
With the above definitions and caveats in mind, it is clear that, as far as both intrinsic properties and health risks are concerned, there are two types of nanostructure to consider, those where the structure itself is a free particle and those where the nanostructure is an integral feature of a larger object.
In the latter group are nanocomposites, which are solid materials in which one or more dispersed phases are present as nanoscale particles, and nanocrystalline solids, in which individual crystals are of nanoscale dimensions. This group also includes objects which have been provided with a surface topography with features of nanoscale size, and functional components that have critical features of nanometre dimension, primarily including electronic components. . For medical purposes surface modifications can be obtained by using specific coatings composed of nanosized materials (Roszek et al 2005). This Opinion recognises the existence of such materials and products, and recognises that material features of nanoscale dimensions can influence interactions with living systems. However, although the science of interactions between biological systems and nanotopographical features is developing rapidly, very little is known of the potential of such interactions to induce adverse effects . The risk would be dependent on the strength of the adherence to the carrier material, and associated with the release during use or at the end of the life time of the product. As long as the nanomaterials are fixed on the surface of the carrier there is at the moment no reason to suppose that immobilized nanoparticles pose a greater risk for health or environment than the larger scale materials.
It is the former group, involving free nanoparticles, that provides the greater concern with respect to health risks, and which is the subject of the major part of this Opinion. The term ‘free’ should be qualified, since it implies that at some stage in production or use the substance in question consists of individual particles, of nanoscale dimensions. In the application of the substance, these individual particles may be incorporated into a quantity of another substance, which could be a gas, a liquid or a solid, typically to produce a paste, a gel or a coating. These particles may still be considered to be free, although their bioavailability will vary with the nature of the phase in which they are dispersed. Ultrafine aerosols and colloids, and cream-based cosmetics and pharmaceutical preparations would be included in this category, and it is with these examples that much of the recent work on nanotechnology health risks has been concerned.
This opinion essentially discusses the potential risks associated with the manufacture and use of products incorporating engineered nanomaterials. Nanostructures of biological origin such as proteins, phospholipids, lipids etc. are not considered in this context.
