Nanocomposites, nanostructures or nanoparticles incorporated in packaging materials enhance their performance, but potential health effects remain unclear due to inconsistent testing methods and a lack of global regulatory standards for their use.
The objectives of food packaging technologies are to preserve food quality, ensuring product integrity and consumer safety. One of the most promising approaches consists in integrating nanomatierals into food packaging. Nanotechnology involves the design, characterization, and application of structures that have at least one dimension in the range of 1 to 100 nm. Numerous studies are exploring nanomaterials in food packaging to create better storage conditions. Nanocomposites, nanostructures or nanoparticles can be incorporated into packaging materials to improve, for example, mechanical properties, gas barrier functionality and UV resistance.
Application of nanotechnology in food packaging
Nanotechnology is transforming the food packaging industry by introducing innovative materials, techniques, and functionalities that improve food quality, safety, and shelf-life, as well as minimize environmental impact. The increasing applications of nanotechnology in food sciences represent a unique advancement with far-reaching implications. From improving nano-food packaging and shelf-life to assisting efficient storage and contamination detection, nanotechnology has become a crucial strength in food engineering. Its use extends beyond packaging to the introduction of health supplements and nutrients into food products.
The nanoscale alteration and production of materials results in small particles with high surface area to volume ratio. Optical, mechanical, electrical and practical characteristics of matter have improved and are the reason for the effective present and the future applications of this modern technology. The use of nanosensors, in conjunction with active and smart packaging systems, is a fast method for detecting food pathogens, heavy metals, contaminants and maintaining food safety. Nanosensors are useful in the storage, packaging and transportation of food products, because they are able to detect and report information about quality, freshness, chemical, physical and microbiological changes, all of which are essential parameters in preventing food spoilage from moisture, light, off-flavours and off-odours.
Nanotechnology allows the modification of the structure, properties and interactions between different food materials, allowing the development of novel foods with enhanced taste, texture, colour, freshness and stability. Several studies have shown that nanoparticles like gold and silver increase the food packaging life as they can inhibit and reduce microbial contamination. Zinc, titanium, copper, gold and silver are emerging metal nanoparticles with biocidal characteristics used in food packaging. Polymers with renewable and biodegradable properties, such as polysaccharide HPMC with silver nanoparticles, can be used as food packaging nanomaterials.
Developments in the preparation of nanoparticles, which integrate food-safe ingredients, have allowed researchers to study edible film functional modifications which involve nanoemulsions, nanoparticles, polymeric nanoemulsions, solid lipid nanoparticles, nanofibers, nanotubes, nanocrystals, nanostructured lipid carriers, or blends of nanoscaled organic and inorganic components. These nanoparticles are typically composed of protein or polysaccharide known as “nanocomposites”, i.e. materials composed of two or more phases, where at least one constituent phase has at least one dimension (length, width, thickness) in the nanometer range. In order to enhance conservation, nanocomposites allow for the adoption of edible coatings such as “temporal distribution systems” that transfer active chemicals from a reticular layer to the food.
Nanomaterials and edible coatings containing nanoparticles outperform traditional packaging materials in terms of food preservation and quality maintenance. Thin edible nano-coatings (∼5 nm) can be used as moisture and gas barriers in fruit, meat, cheese, vegetables, bakery goods and confectionery products. There are a variety of bakery goods available that are coated with edible antibacterial nanocoatings. Nanostructured gelling agents have been used as edible coatings to keep fresh food freshness for longer periods of time. Examples include edible coatings formulated with gelatine nanoparticles and cellulose nanocrystals, coatings made of nanosilice and chitosan, film made of chitosan and silicon dioxide nanoparticles, nanolaminate coatings made of lysozyme and alginate.
Non-edible packaging in the form of nanocomposites is widely used in packaged food because it is biodegradable and environmentally friendly. Active nanomaterials, such as oxygen absorbers, and antimicrobials are also used. Such nanomaterials are advantageous for interacting directly with food, providing better protection for food products. Some nanomaterials have antimicrobial potentials that can be added to food packaging. Nanosilver, nano-magnesium oxide, nano-titanium dioxide, carbon nanotubes, nano-copper oxide, and other materials are examples.
Some nanocomposite materials have been used to prevent the passage of oxygen, carbon dioxide, and water into food. Metal-based nanosensors (platinum, gold, and palladium) can detect gas production and colour changes in food due to spoilage, any change in humidity, heat, light, gas, and toxins, like aflatoxin B1 in milk. Nanosensors are created for smart packaging in order to identify food spoilage and also to release nano-antimicrobials as needed to prolong the shelf-life of food. Nanosensors alert consumers to contamination or food spoilage by detecting pesticides, toxins and microbial contaminants and converts them into observer readable signals, like colour formation.
Nanosensors are also used to establish the shelf-life of food. For example, gold nanoparticle incorporated enzymes are used in the detection of microbes, nanofibrils of perylene-based fluorophores signal meat rotting by sensing gaseous amines. Other uses include nanocomposites of titanium and zinc monoxide for detecting volatile organic compounds. Nanobarcodes are used for both labelling and safety measures. The concept of “Smart Packaging” is becoming a reality. Research is being conducted on the development of antigen-specific biomarkers in food packaging and on the incorporation of nanoparticles to produce films of nanocomposite polymers.
Antigen-specific biomarkers will help in detecting the presence of the organism responsible for food spoilage. Nanotechnology is also employed to develop the barrier properties of plastics (mechanical, chemical, thermal and microbial) and improve heat resistance and mechanical characteristics. Various biodegradable nanocomposites with desired properties have been developed for a wide variety of products. Starch derivatives, polylactic acid (PLA), polybutylene succinate (PBS), aliphatic polyester polycaprolactone and polyhydroxybutyrate (PHB) are currently the most commonly used biodegradable nanocomposites for packaging.
Safety issues and challenges
Different authors’ conclusions about whether nanoparticles can migrate out of polymers are inconsistent and even conflicting. This raises concerns about the possible implications for health and safety. Approval to adopt nanocomposites in packaged food could be based on the results of tests on the migration of nanoparticles from the nanocomposite system to the packaged food. In fact, when packaging materials are in contact with food, metals typically migrate. The migration process consists of 3 stages: diffusion of the migrant nanoparticle, the dissolution of the nanoparticle, and the dispersion of the nanoparticle in food.
There are various approaches to detect, study and characterize nanoparticles and nanomaterials in food. Microscopy (e.g. AFM, SEM, TEM) and spectroscopy (e.g. Raman, FT-IR, DLS) techniques have proven to be the most popular and effective. Understanding the migration of nanoparticles is critical for determining the possible health implications of these compounds when they come into contact with food. The rate of migration for nanoparticles is influenced by several factors. It has been found that time and temperature significantly increase the level of nanoparticles migration from packaging to food. Nanoparticles toxicity is also influenced by their solubility.
Understanding the molecular activities through which nanoparticles and nanomaterials come in contact with food products and within living organisms is critical. Due to their size, nanomaterials can easily pass through the cell membrane to accumulate in the cytosol, affecting the cell viability. Moreover, nanomaterials can travel deeper into the cell nucleus and damage the DNA, causing DNA breaks or potentially carcinogenic mutations. Taking cognisance of the level of exposure to nanoparticles is essential for determining the shape and nature of injuries they could cause to a variety of cells and tissues. Dermal, respiratory and digestive nanoparticle exposure are the three primary routes of nanoparticle exposure. Foods and materials containing nanoparticles have the potential to enter the human body through any of these routes.
Some organs, like the liver, lymph nodes and spleen, absorb nanomaterials significantly faster than others. Despite promising innovations in food nano-packaging, there numerous gaps in research that require targeted attention. Studies are needed to investigate the long-term health effects of nanoparticle migration from packaging to food products. Understanding the potential toxicity and bioaccumulation of these nanoparticles is important to ensure consumer safety. Furthermore, the lack of standardised testing methods for the identification and characterisation of nanoparticles in food matrices and packages, and for a toxicological assessment, makes it difficult to carry out an acceptable risk assessment and enact clear and unambiguous regulatory frameworks.
