Saturday, September 16th, 2017
Growing demand for sustainable production, increasing competition and consideration of health concerns have led the meat industries on a path to innovation. Nanotechnology can have a significant impact on the meat processing industry through the development of not only novel functional meat products, but also novel packaging for the products. By Karna Ramachandraiah and Chin Koo Bok, Chonnam National University, and Han Sung Gu, Konkuk University
With consumers demanding higher quality meat products at affordable prices and growing competition, the meat production sector has witnessed an exceptional change in not only the ingredients, but also the processing system.
The demand for sustainable production of meat products and emphasis on human health and wellness has further led to the growth of innovation in the meat product industry. Therefore, expectations have risen regarding the use of ingredients and additives with improved functionality to enhance the quality and image of muscle foods.
Some of the most commonly used additives in meat and poultry are antioxidants, binders, thickeners, humectants, curing agents, flavour enhancers, tenderising enzymes and sweeteners.
Although they are still widely used, growing health concerns has caused a shift in the focus towards the development of novel meat products with reduced amounts of saturated fats, sodium salts, colour fixatives and cholesterols, along with increased use of ingredients which have positive effects on health.
It is also expected that novel products developed with new ingredients and processing systems should possess similar gustatory, visual and aromatic effects as traditional meat products.
As a result, bioactive materials providing health benefits are increasingly added to foods in order to treat or prevent diseases. However, there are impediments in the production, storage and distribution of foods with incorporated bioactive components.
Owing to the range of traditional meat products, the impediments are likely far bigger in the meat industry. A significant challenge is the low bioavailability of bioactive components when included in meat products, mainly due to relatively elevated levels of proteins, fats, and minerals.
Consequently, modifications have been attempted to the formulations of meat products, but these have often led to unfavourable effects, such as poor organoleptic quality, lowered capacity to retain water and poor resistance to the growth of microbes.
Therefore, the meat industry needs to implement and support an innovation agenda to address such challenges and ultimately improve the quality experienced by consumers. Nanotechnology is one such process-based innovation that could have a significant impact on the food industry.
Ingredients produced by nanotechnology can be utilised to improve the taste and texture of food, and to increase the bioavailability of bioactive compounds and nutrients. They can also be used to mask unpleasant flavours and doors.
Dry and wet milling of organic materials may result in the production of nano-sized or ultrafine powders (sizes of 100 nm to 1 μm) which can be utilised in food manufacturing at a low cost.
An example is nanotea (green tea), which was shown to have increased antioxidant activity due to its reduced particle size. Other examples include ultrafine milled antimicrobial chitosan nanopowder, with increased hypolipidemic activity, and wheat bran, with improved bioactivity.
Reducing ginger, which is sometimes used in meat as a tenderiser and extender, to micro-sized powders, was found to improve its penetrability, while also making it more soluble and dispersible than native ginger.
If such ingredients were further reduced to nanopowders, they may exhibit novel physical and chemical properties. Although powders with particles in nanometre range may have enormous potential, further improvements in understanding of the nature of raw materials and advancements in equipment are required for successful application.
Most ingredients meant to serve special functions in food are not incorporated in their original form, making it necessary to modify these materials prior to use with suitable delivery systems.
For instance, many bioactive compounds are sensitive to temperature, oxidation, and lack of solubility in water along with the preference for loci in the gastrointestinal tract for entry into the blood stream through absorption. Therefore, a delivery system must transport the functional ingredient to its target while simultaneously protecting it from oxidative degradation.
Furthermore, the release of functional ingredients can be regulated by the strength of ions, as well as the surrounding temperature and pH. It is also important that the ingredients be compatible with the qualitative aspects of foods, such as colour, texture and taste etc.
Although several delivery systems exist, only a few systems are likely to have a broad impact on food production. Association colloids are a stable system with well-dispersed nanoparticles in the product.
Micelles and reverse micelles are good examples of this type of colloidal system. In the colloidal system, the novel properties of particles (5 to 100 nm) can be delivered through the use of materials that may be polar, nonpolar and amphiphilic, thereby, improving the shelf life of the food along with providing other benefits.
Biopolymers in a nanometer scale can also be utilised to improve the shelf-life of foods. An example of a food-grade synthetic biopolymer is polylactic acid (PLA), which is used as a delivery system.
It was found that the fish fingers with chitosan or chitosan edible coating showed decreased bacterial counts compared to the uncoated fish fingers and those with commercial coating, suggesting a potential extension of the shelf-life.
Functional compounds can be included in a droplet or any other phase of nanoemulsions, such as the continuous and interfacial phases. These systems can provide a vehicle for more than one material, with activities such as antimicrobial and antioxidant functions.
An example of a nanoemulsion is the nanostructured multilayer emulsion, in which the release of active ingredients is dependent on external stimulus. However, the inclusion of emulsions in meat systems remains a challenge.
Nanotubes & Nanofibers
The idea of using nanotubes in food originates from carbon nanotubes (CNTs), which have numerous potential applications in materials, other than food.
CNTs (single-walled or multiple-walled) can be used in the detection of pathogens in food due to their ability to immobilise antibodies, along with other benefits. The large surface area of the nanotubes can be exploited to increase the sensitivity of immunosensor by up to six-fold thereby reducing the detection limit of staphylococcal enterotoxin B.
CNTs with allyl isothiocyanate in cellulose-based food packaging have been shown to have antimicrobial effects. This type of packaging inhibited the growth of salmonella in shredded cooked chicken for up to 40 days due to the inclusion of CNTs.
The milk protein α-lactalbumin, which assembles itself as a nanotube under certain conditions, has been exploited in food nanotechnology. Encapsulation of functional ingredients becomes easier with increased surface to volume ratio of the materials, along with additional nutritional benefits.
These nanotubes are resistant to heat and mechanical stress, and also possess improved ability for storage, gelation and viscosity. Electrospinning of gelatine results in the production of gelatine nanofibers, which can be used as a more effective thickening agent in lower amounts when compared to bulk gelatine.
Improved, Active & Smart Packaging
Food packaging materials should possess proper mechanical, thermal, and optical properties for foods. Antimicrobial and barrier functions against gases, vapour and aroma are also important as food packaging materials.
The materials currently used for the packaging of food are not biodegradable, and hence cause environmental concerns. On the other hand, environment friendly packaging made of biopolymers may not have optimal mechanical and barrier properties.
Major advantages of using nanotechnology for packaging include enhanced barrier, mechanical and heat-resistant properties, along with improved biodegradability and flame retardancy in comparison with conventionally used polymers. Nanomaterials can also be used in packaging to provide enhanced antimicrobial effects, and allow the detection of spoilage through nanosensors.
In comparison to molecular antimicrobials, inorganic nanoparticles can be incorporated into polymers without much difficulty, making them suitable for packaging with improved functionality. However, the suitability for packaging depends on the chemical nature of nanoparticles as seen with silver nanoparticles which possess excellent antimicrobial effect whereas no such effect is seen with gold nanoparticles.
The mechanisms for the antimicrobial effect of silver nanoparticles reported are cellular damage by silver atoms released from the surface of nanoparticles, toxicity caused by silver ions released from inside of the nanoparticles and structural destruction of cellular membranes by bound nanoparticles.
Due to the wide spectrum of antimicrobial action even at small concentrations (2 to 4 μg/mL), including activity against microbes that are resistant to conventional chemical antimicrobials, silver nanoparticles (45 to 50 nm) can effectively improve the shelf-life of foods.
TiO2 nanoparticles are also known for their antimicrobial properties, along with the protection of packaged food from UV damage and being optically clear. Apart from the type of nanoparticles, size, shape and surface charge are also known to determine the antimicrobial effect of nanoparticles.
According to a study, zinc oxide (ZnO) can be a potent antimicrobial along with silver (Ag) in a nanocomposite with low density polyethylene. Pathogens in meat, such as escherichia coli, pseudomonas aeruginosa and listeria monocytogenes, were inhibited by this type of packaging, based on a study on chicken breasts.
In another study, the inclusion of silver nanoparticles in a sausage casing made of cellulose and collagen film had strong antibacterial and antifungal effects.
Food packaging consisting of polymers in conjunction with nanodevices is referred to as smart packaging. Smart packaging can be used to monitor food or the environment around it during storage and transit.
In addition, smart packaging ensures the authenticity of the food product, providing protection against counterfeiting. Furthermore, smart packaging was originally developed with the intention of checking the integrity of the food package.
The inclusion of devices is also able to track the history of time -temperature and expiration date. Devices such as nanosensors are able to detect microbes, toxins and chemicals while being incorporated in the packaging.
Nanosensors have great potential to hasten the speed of detection, identification and quantification of pathogens, spoilage substances and proteins that cause allergies.
Therefore, nanosensors have the potential to significantly impact many sectors including food. Generally, nanosensors are placed in food packages to monitor the internal and external conditions of the food. An example of a nanosensor can be seen in a study where oxygen indicators were employed in the packaging of uncooked bacon under carbon dioxide. The change in colour of the sensor inside the package was designed to indicate exposure of the food to oxygen.
The spoilage of food could be detected in the early stages, and thereby, avoid several problems for food businesses and consumers. Nanosensors that employ CNTs with antibodies against Salmonella attached can be applied to detect food pathogens on the surfaces of foods, such as chicken.
Another application is to detect the freshness of canned tuna, by examining the presence of indicator chemicals such as xanthine and hypoxanthine. Nanotechnology based devices are projected to have a brighter future in many areas including food although challenges in fabrication, integration and mass manufacture of such devices exist.
Nanolaminates: Edible coatings
Nanolaminate used to cover food consists of more than one layer, and the materials are in the nanoscale. Layer by layer (LbL) deposition techniques could be used to cover food which has surface charges. An advantage of the LbL technique is that the thickness of the coating can be regulated with precision (1 to 100 nm).
Due to the extreme low thickness, it is better suited to be coated on food than as freely standing coatings. Along with serving as a barrier for gas or moisture, they can also carry antioxidants and antimicrobials. However, it is important to note that the properties of these edible coatings depended on the characteristics of the nanomaterials used in the layers.
Proteins, polysaccharides, and lipids are currently being used in the layers. Depending on the type of biopolymeric nanoparticles included in the coating, different functionality could be observed. Layers made of lipids act as barriers to moisture, but are not efficient to block gases and lack mechanical strength.
On the other hand, protein and polysaccharide-based layers offer effective barriers against gases, but not moisture. As a result, nanolaminates can be used as natural edible barriers for the simultaneous extension of shelf-life and nutrition.
Since the production and use of engineered nanomaterials can lead to human exposure, hazards of the nanoparticles have to be controlled to reduce personal exposure. Nanotracers have the ability to monitor potential risks of exposure, thereby benefiting food safety and biosecurity.
Nanotracers and nanomonitors can have diverse applications such as air quality monitoring, environmental monitoring and nanoparticle exposure assessment. However, devices that monitor the release of nanomaterials in different environments such in places of nanomaterial production or reuse are limited.
Nonetheless, a nanoparticle monitor such as aerasense is able to detect and quantify the concentration, surface area and size of nanoparticles in real-time. Exposure assessments on a personal level, monitoring of nanoparticle pollution at workplaces and tracing of particles sources can be achieved through the use of such devices. Therefore, nanotracers and nanomonitors can be applicable to assess the risks at every level of meat chains.
Potential Risks In Processing
Although there are many potential benefits, concerns over the potential risks of using nanotechnology in the food industry have also been raised.
For example, it has been found that cytotoxicity, genotoxicity, oxidative stress, inflammation and other influences may be induced by the use of some nanomaterials in food applications.
Metallic nanoparticles such as copper, zinc and titanium dioxides showed acute oral toxic effects in rodents at elevated dosage levels. The toxicity associated with biopolymeric nanoparticles such as PLGA was found to be minimal, but it lacked efficiency due to decreased loading capacity and increased burst release.
It is important to note that the differences in toxicity originating from free nanomaterials, biodegradable, or bound nanomaterials needs to be understood. Liposomes, which vary from micro to nanometers in size, are known to be biodegradable, and the association of toxicity with its use is uncommon. However, the cost of production, complicated preparation methodologies, and stability problems has impeded their utilisation in foods.
Potential Risks In Packaging
The area of food production wherein nanotechnology can have a great impact is in food packaging. Studies have indicated that consumers are more willing to accept the presence of nanomaterials in packaging than in food.
However, the nanomaterials in food packaging may potentially migrate to food, which in turn can be ingested or inhaled, or even be transferred through skin contact.
Studies on nanoparticles of titania, silver and CNTs have shown that these materials could enter blood circulation, and their insolubility may cause accumulation in organs.
The result of another study has shown that only a small amount of particle migration from nanocomposites to foods was seen during food packaging. This migration was within the limits prescribed by the European Commission (EC) for silica nanoparticles in clay nanocomposites.
Similarly, studies on Ag and ZnO also showed particle migration to be well below the limits set by the EC. On the other hand, a report shows that nanoparticles of ZnO may potentially lead to genotoxicity in epidermal cells at very less concentration.
In another study, the temperature at which the packaging was stored and the time were identified as two factors which influenced the amount of nanoparticle migration from the packaging. In addition, the use of some nanocomposites has raised concerns about environmental contamination, as they may not be bio-degradable.
Eco-toxicity studies on such nanoparticles would significantly improve the acceptability of nanotechnology to consumers. Even when some countries permit the release of compounds from packaging, the long term effects of some nanomaterials are not yet known.
Regulation Of Nanotechnology
The US, Japan, Germany, and China are currently leading the development of food products which apply nanotechnology. Countries such as China may provide better open markets due to their underdeveloped regulatory systems.
In the US, the challenges in regulation due to complexities in nanotechnology are further exacerbated by the lack of a single comprehensive regulatory framework (ensuring consumer safety).
The impediments in the analysis of risk originating from nanoproducts are limited information, insufficient models (reflecting real world) and uncertainties with respect to oversight by government agencies. The pace of risk assessment research is also making the regulation of nanomaterials a difficult undertaking.
In addition, the safety assessment of food packaging has become essential to ensure safety, due to the potential migration of nanoparticles. Furthermore, with growing interest in nanotechnology, the development of nanoproducts has not kept up with the expectations of consumers about the safety of such products.
Nonetheless, the effectiveness of regulation in food depends on the comprehensiveness of definitions, and liabilities of products and applications that possess nanomaterials with novel and varied properties as well as the proper permitted levels pertaining to the nanomaterials.
Public acceptance is imperative for the commercial success of any product. As seen in the case of genetically modified foods, acceptance can be hindered by concerns over health and environment.
Consumers are expected to purchase products which are low-priced and offer more benefits, but reluctance was also seen towards the use of nanotechnology in food.
Using the the willing to buy (WTB) model to explain the factors influencing the acceptability of nanotechnology in food, it was found that affect heuristics played an important role in the perception of benefits and risks of novel products.
Therefore, gaining social trust and improving the perception of naturalness of nanoproducts could positively affect the WTB of such products. According to a study on the public acceptance of nanotechnology in the US, consumers were found to have limited knowledge about this technology, but an optimistic perception.
Studies in Europe were less positive, while results in Taiwan were more positive when the perception of benefits was higher. Therefore, improving the knowledge and social trust among consumers could improve the public perception regarding the use of nanotechnology in food.
In order to improve the public acceptance of food nanotechnology, major efforts to ensure the safety of nanofoods need to be undertaken by governments, manufacturers and concerned authorities.
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