Lecture XXXIX 3.2 NANAOBIOTECHNOLOGY IN FOOD PRESERVATION

Transcription

1 Lecture XXXIX 3.2 NANAOBIOTECHNOLOGY IN FOOD PRESERVATION The use of nanotechnology principle in food packaging also led to the focus being shifted towards the preservatives of packaging used for food stuff. Food preservation has been defined as the process of treating and handling food to stop or greatly slow down spoilage in order to prevent loss of quality, edibility or nutritive value that are caused or accelerated by microorganisms which aim to prevent the growth of microorganism such as bacteria and fungi. 16 The main aim of the modifications in food preservation is to improve the food products but keeping the consumers requirements in mind. Their requirements have been encompassed desires for food that provide convenience in storage and use, besides, the food products should be fresher, healthier and must be of a higher quality than the previous ones. Nanotechnology here plays a central role by using its quick detection methods to identify viruses, bacteria and other pathogens in the food materials and thus preserve the food for a longer duration. a) Nanosensor The requirements on the food preservation has led to researchers being driven to conduct new research in order to develop better and efficient methods to preserve food for a longer time without using any sort of special containment. The principle of nanotechnology enables the development of such devices which are able to detect the spoilage of foods. This device is known as Nanosensor. Nanosensor was earlier used in crop and animal genetic but now has found its way into food preservation. Nanosensor is a device that consists of an electronic data processing part and sensing layer or part which is able to respond to environmental change and can translate a signal such as light, humidity of storage room, or the presence of an organic substance or gas into an electronic signal. 17 The sensitivity of nanosensor at both atomic and molecular level detects even extremely small contaminants. By embedding a nanosensor in the food packaging, it can be analysed whether the food has rotten or not and its nutritional information could also be calculated. This kind of nanosensor would serve as an electronic nose or an electronic tongue.

2 An electronic nose functions like a human nose; it identifies the odorant by estimating its concentration and characteristics. Similarly is the electronic tongue which was mimicked by observing human tongue. It is made from silicon chip that has an array of micro beads on its surface that respondss to different analyses. Both of the above two nanosensorss are able to alert the consumer whether the food is contaminated or not either by triggering an alarm or by displaying a colour change in the packaging. Brief History of Nanotechnology applications (UK). Despite first being referred to nearly 40 years ago, the world of nanotechnology particularlyy in relation to food is still a long way from being part of mainstream b) Nano silver

3 Silver nano particles are being extensively researched for food preservation. Silver nano particles are added in the food packaging that is functioned for food preservation as well. An active packaging an aseptic food containers based on silver ions are particularly promising because the ionic form of silver functions as a powerful antimicrobial agent (Miller G. & Senjen R.). 18 Nano sized silver particles have greater effectiveness than silver particless due to their greater surface area. The use of packagingg or coating films that contain antimicrobial agents can improve the safety of food as it is able to slow down the migration of the bactericidal agent from the carrierr film structure to the food surface. Thus nano silver is more chemically reactive and is highly ionisable, as a result, guarantees high antimicrobial activity. (Credits: Image courtesy, Retrieved from Website: //theholisticdentist.wordpress.com) The current researches suggest that incorporating silver nano particles in food preservation extends the shell life of food products by preventing the growth of post processing microorganisms and thus improving the quality of the food. Finally, there are still other nanoparticle devices being developedd for food preservation and research is being carried out all across the globe to incorporate these devices in our current food preservation techniques. 3.3 FOOD PACKAGING Food packaging is the packaging of food products in a way so as to deliver the products to the consumer in the best possible condition. Food packaging is considered as one of the most crucial aspect of successful consumer products. Nano technology enables the scientists and allows designers to alter the structure of packaging materials on a molecular scale in order to give materials desired properties. 19 Thus nanotechnology has proved to

4 be as of a significant commercial success in food packaging. Currently the employment of nanotechnology in food packagingg has made it the largest category of food sector that uses such technological advancements. Such packaging methods have led to smart, active and intelligent packaging that responds according to environmental change and provides better food products qualitativelyy along with high safety standards. Most of the materials that are used for food packaging are produced from fossil fuels and are practically non-degradable. The use of these nonwaste degradable materials in foodstuff has generated a serious global environmental problem. 20 Before the advent of nano technology, bio-based materials were used as replacement to these non-degradable materials in orderr to increase the shelll life and enhance the food products. Now theses bio based packagingg materials comprised of edible and bio-degradable films which were made from renewable resources. a) Nano composites The most common particles used for nano reinforcementt in food packaging are clay and silicates to produce polymer composites due to their availability,, low cost, significant enhancements and relatively simpler processing ability (de Azeredo, 2009). Nanoclays and nanofilms have been used as barrier materials to prevent spoilage and preventt oxygen absorption. Toyota was the first company to experiment with nanocomposi ites at a commercial level by using clay/nylon-6- nanocomposite as the timing belt covers for their car products. Nanocompositess found their way into food sector in the late 90 s. These nanocomposites were able to increase the shell life of the food products by acting as a physical barrier to slow down the diffusion of gases such as oxygen across the packaging layer.

5 These nanocomposites were a grade much higher than their predecessors and significantly improved the fundamental properties of food packaging materials such as strength, barrier properties, antimicrobial properties, and stability to heat. Meanwhile, they not only improved the poor properties of existing materials but also offered extra benefits such as low density, transparency, good flow, better surface properties and recyclability. 22 A successful packaging material encompasses the ability to control gas composition and water loss in packaging. For instance, the shell life of the vegetables was increased by one week when nanocomposites were used for packaging. The researches and efforts to modify the food packaging have led to the advent of new polymeric materials and composites with inorganic nanoparticles such as nanoclay. b) Nanoclay The clay nanoparticles were the first nanocomposites to be used at a global scale. Polymer-clay nanocomposite is the nanocomposite that is based on organic polymers and inorganic clay minerals consisting ofsilicate layers (de Abreu et. al., 2007). 23 The addition of clay to polymers enhanced their properties at nano scale level by reducing the gas permeability by increasing the gas barrier properties. The clay layer acts as a barrier to gases and water which forces them to follow a winding path. This led to noticeable effects such as increase in strength of polymer, lower thermal expansion coefficient while increasing the thermal stability, higher conductivity and improved mechanical properties. c) Edible Nanocomposite-based material These relate to the materials such as edible films and coatings. They have been defined as a thin continuous layer of edible materials which are transformed into a film and placed between food components so as to prevent any mass transfer between them. These materials are comprised of two modes namely the application and formation mode.

6 In the application mode of these two kinds of edible materials, the edible films are free standing structures which are formed first and then applied to foods later, whereas, edible coatings are applied and formed directly on the food whereas in the formation mode, edibles films are formed by casting or by traditional plastic processing techniques, while, edible coatings are formed either by addition of a liquid film-forming solution or by molten compounds on the food product and as an integrated part of thefood. d) Nanofilm Nanofilms are films which have been incorporated by nanoparticles such as clay in order to enhance the physical properties of films. The nanoparticles ameliorate the barrier effects of the films but still maintaining transparency and thus improve the development in hot packaging process. Nanoparticles characteristics namely it being glossy, transparent and completely edible led to its huge commercial success and was applied in food packaging in a number of ways. Nano films have been used as non-sticky films for the lining of bottles in case of mayonnaise and tomato sauce. The contents of these bottles are difficult to remove out and there are left overs in the bottles due to their sticky nature. Successful trials of application of nano films in the inside of these bottles with a width of approx. 20 nm have been conducted. Although this concept has not been commercialized but awareness is being spread regarding these films as how they reduce the leftover and is environmental friendly in nature. e) Nanocoatings The rapid advancements in nanofilms lead to the development of nanocoatings. Coating is a partly polymerized mixture which is applied over surfaces such as in the food paper that could be made impermeable to water or the tin cans that can be rendered ineffective against corrosion. Nano particulates coatings are the coating added with nano crystalline powders which are able to improve strength and hardness of the material. Currently edible nano coatings are being developed which can be used in confectionary products, dairy products, bakery products, fruits and vegetables as they increase the shell life of the products while also being edible in nature.

7

8