Victor J. Morris Institute of Food Research Norwich, United Kingdom
In today’s competitive market technology is essential to keep leadership in the food and food processing industry. Consumers demand fresh authentic, convenient and flavourful food products. The future belongs to new products and new processes, with the goal of enhancing the performance of the product, prolonging the product shelf life and freshness, and improving the safety and quality of food. Nanotechnology is an enabling technology that has the potential to revolutionise the food industry. Nanotechnology can be applied to develop nanoscale materials, controlled delivery systems, contaminant detection and to create nanodevices for molecular and cellular biology.
Nanotechnology involves creating and manipulating organic and inorganic matter at the nanoscale. It promises to provide the means for designing nanomaterials; materials with tailor-made physical, chemical and biological properties controlled by defined molecular structures and dynamics. The present molecular biology techniques of genetic modification of crops are already forms of what has been termed nanotechnology. Nanotechnology can provide for the future development of far more precise and effective methods of, and other forms of, manipulation of food polymers and polymeric assemblages to provide tailor-made improvements to food quality and food safety. Nanotechnology promises not only the creation of novel and precisely defined material properties, it also promises that these materials will have self-assembling, self-healing and maintaining properties.
NANOTECHNOLOGY IN FOOD MICROBIOLOGY
Detection of very small amounts of a chemical contaminant, virus or bacteria in food systems is another potential application of nanotechnology. The exciting possibility of combining biology and nanoscale technology into sensors holds the potential of increased sensitivity and therefore a significantly reduced response-time to sense potential problems. Nanosensors that are being developed by researchers at both Purdue and Clemson universities use nanoparticles, which can either be tailor-made to fluoresce different colours or, alternatively, be manufactured out of magnetic materials. These nanoparticles can then selectively attach themselves to any number of food pathogens. Employees, using handheld sensors employing either infrared light or magnetic materials, could then note the presence of even minuscule traces of harmful pathogens. The advantage of such a system is that literally hundreds and potentially thousands of nanoparticles can be placed on a single nanosensor to rapidly, accurately and affordably detect the presence of any number of different bacteria and pathogens. A second advantage of nanosensors is that, given their small size, they can gain access into the tiny crevices where the pathogens often hide.
The application of nanotechnologies on the detection of pathogenic organisms in food and the development of nanosensors for food safety is also studied at the Bioanalytical Microsystems and Biosensors Laboratory at Cornell University. The focus of the research performed at Cornell University is on the development of rapid and portable biosensors for the detection of pathogens in the environment, food and for clinical diagnostics. The bioanalytical microsystems use the same biological principles as were used in the simple biosensors, i.e. RNA recognition via DNA/RNA hybridisation and liposome amplification. The bioanalytical microsystems that are studied focus on the very rapid detection of pathogens in routine drinking water testing, food analysis, environmental water testing and in clinical diagnostics.
NANOTECHNOLOGY FOR CONTROLLED RELEASE
The ability to design materials at the atomic or molecular level is likely to impact on the food industry through the development of coatings, barriers, release devices and novel packaging materials. In the synthetic polymer field novel barriers are starting to be produced through the use of composite structures (fuzzy nanoassemblies) formed from successive molecular layers of different polymers, and this approach may be adapted to the food area. The drive to develop bio-compatible surfaces for medical or pharmaceutical applications may lead to novel surfaces or coatings that repel or combat bacterial adhesion and biofilm formation. Nanofabrication of surfaces allows imprinting methods to be used to create novel catalytic structures or alternatives to naturally occurring enzymes.
Nanotechnology also promises to provide a means of altering and manipulating food products to more effectively and efficiently deliver nutrients, proteins and antioxidants to precisely target nutritional and health benefits to a specific site in the human body or to specific cells to enhance their efficacy and bioavailability. Several of the groups are studying the use of nanotechnology to encapsulate certain nutrients, flavours and colours and release them upon need or over an extended period of time. Functional food will benefit firstly from the new technologies, followed by normal food, nutraceuticals and others.
Self-assembled colloidal composite structures, colloidosomes, micron-sized hollow spheres with selectively permeable membranes that allow controlled release of the shell’s contents are being studied at Harvard1,2. The solid capsules are fabricated by the self-assembly of colloidal particles onto the interface of emulsion droplets. After the particles are locked together to form elastic shells, the emulsion droplets are transferred to a fresh continuous-phase fluid that is the same as that inside the droplets. The resultant structures, which are referred to as “colloidosomes,” are hollow, elastic shells whose permeability and elasticity can be precisely controlled. These self assembly shell structures can be utilised for the encapsulation of functional ingredients.
Salvona Technologies developed a multicomponent delivery system3,4,5. This system, MultiSal™, delivers multiple active ingredients that do not normally mix well, such as water-soluble and fat-soluble ingredients, and releases them consecutively. It enhances the stability and bioavailability of a wide range of nutrients and other ingredients, controls their release characteristics and prolongs their residence time in the oral cavity, and thus prolongs the sensation of flavours in the mouth. The system consists of solid hydrophobic nanospheres composed of a blend of food-approved hydrophobic materials encapsulated in moisture-sensitive or pH-sensitive bioadhesive microspheres. A proprietary suspension technology generates nanospheres with a diameter of about 0.01-0.5 microns. The nanospheres are then encapsulated in microspheres of about 2050 microns in diameter. The nanospheres are not individually coated by the moisture-sensitive microsphere matrix, but are homogeneously dispersed in it. When the microsphere encounters water, such as saliva, it dissolves, releasing the nanos-pheres and other ingredients (Figure 1). Various ingredients can be incorporated into the hydrophobic nanosphere matrix, the water-sensitive microsphere matrix, or both matrices.
The active ingredients and sensory markers encapsulated in the nanospheres can be the same as, or different from, those encapsulated in the microspheres. The nanosphere surface can include a moisture-sensitive bioadhesive material, such as starch derivatives, natural polymers, natural gums, etc., making them capable of being bound to a biological membrane such as the oral cavity mucosa and retained on that membrane for an extended period of time. The nanospheres can be localised and the target ingredient encapsulated within their structure to a particular region, or a specific site, thereby improving and enhancing the bioavailability of ingredients which have poor bioavailability by themselves. Ingredients that have high water solubility, such as vitamin C, usually have low bioavailability. Enhancing the hydrophobicity of these ingredients enhances their bioavailability. In vitro tests have shown the ability of the nanospheres to adhere to human epithelial cells, such as those in the oral cavity. The encapsulation system has numerous benefits:
- Ease of handling. The system can be utilised to transform volatile liquids such as flavours into a powder, which are in many cases easier to handle.
- Enhanced stability. The system can be utilised to isolate active ingredients as well as flavours that may interact with the other food ingredients. This provides long-term product shelf life.
- Protection against oxidation. The microspheres have very low surface oil (less than 0.5%) at very high payloads (3040%) compared to conventional spray-dried particles utilising materials such as gum arabic or starch.
- Retention of volatile ingredients. The moisture-sensitive matrix provides excellent retention of highly volatile ingredients, such as flavours, over an extended period of time to reduce the flavour loss during the product shelf life.
- Taste masking. Unwanted taste can be masked by preventing interaction between the active molecule and the oral mucosal surface. The nanospheres are hydrophobic and can prevent bitter ingredients encapsulated within their structure from going into solution and interacting directly with taste receptors.
- Moisture-triggered controlled release. As discussed above, the microspheres dissolve in the presence of water or saliva to release the active ingredients or flavours, thereby providing a high impact flavour “burst.”
- pH-triggered controlled release. Ingredients can be encapsulated in the microspheres to enhance their stability during the product shelf life and to release them when needed or upon food consumption. For example, citral can be stabilised in a fruit juice at acidic pH and released in the mouth upon drinking. This pH triggered release was initially designed to deliver drugs to different regions of the gastrointestinal tract.
- Heat-triggered release. The hydrophobic nanospheres are temperature sensitive and can be utilised to release active ingredients and flavours at a certain temperature, e.g., upon heating in an oven or microwave oven or the addition of hot water for hot drinks and soups.
- Consecutive delivery of multiple active ingredients. Two or more ingredients that would react with each other if put together can be separated and provided consecutively by placing one in the nanosphere and the other in the microsphere. An example is encapsulation of folic acid and iron that work synergistically. Other examples would be the delivery of one flavour after another, or the delivery of a flavour or sensation (in the microsphere) to indicate that the active ingredient (in the nanospheres) has been delivered.
- Change in flavour character. Encapsulation of a flavour in the nanospheres that is different from the flavour encapsulated in the microsphere can provide a perceivable change in the organoleptic perception in response to moisture during the use of the product.
- Long-lasting organoleptic perception. As a result of the bioadhesive properties of the nanospheres and their residence in the oral cavity, flavour perception and mouth-feel can be extended over a longer period of time.
- Enhanced bioavailability and efficacy. As a result of their hydrophobic/lipophilic nature, the nanospheres can enhance the bioavailability of various active ingredients, such as vitamins, nutrients and other biologically active agents encapsulated within their structure.
Major potential product applications for the nanosphere/microsphere system are baked goods, refrigerated/frozen dough and batters, tortillas and flat breads, processed meats, acidified dried meat products, microwavable entrees, seasoning blends, confectionery, specialty products, chewing gum, dessert mixes, nutritional foods, products for well-being, health bars, dry beverage mixes and many others.
Some companies are already aware of the impact of nanotechnology in the food industry. Research facilities are established, potential applications are under study, although only a handful of nano food products are now available in the market. Nevertheless, the tremendous potential will attract more and more competitors into this still untapped field. ¦
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- Dinsmore A. D., Hsu M. F., Nikolaides M. G., Marquez M, Bausch A. R., and Weitz D. A., Science, Vol. 298, p. 906, 2002
- Shefer, A. and Shefer, S. 2003a. Biodegradable bioadhesive controlled release system of nano-particles for oral care products, U.S. patent 6,565,873 B1.
- Shefer, A. and Shefer, S. 2003b. Multi component biodegradable bioadhesive controlled release system for oral care products. U.S. patent 6,589,562 B1.
- Shefer, A. and Shefer, S. 2003c. Multi component controlled release system for oral care, food products, nutraceutical, and beverages. U.S. patent application 20030152629 A1.
Dr Adi Shefer A leader in the field of polymers and controlled delivery systems, Dr. Adi Shefer gained extensive experience in commercialisation of delivery systems. Adi Shefer holds a PhD. in Chemical Engineering and Polymer Physics from Ben-Gurion University with excellence. She completed her postgraduate experience at MIT and Harvard University in the field of controlled delivery and intelligent hydrogels. Dr. Adi Shefer has served on the directory committee of the Controlled Release Society since 1998. Prior to Salvona, Dr. Adi Shefer was involved with a global product development at the cooperate level at International Flavors and Fragrances Inc.,
Dr. Sam Shefer Dr. Sam Shefer gained a PhD in biochemical and Chemical Engineering and has developed various controlled release technologies for over 20 years. In 1999, Dr. Sam Shefer co-founded Salvona Technologies Inc. Dr. Sam Shefer established a career at MIT where he was involved in developing advanced drug delivery systems, bioreactors and artificial organs.