CAPÍTULO 2. POSTURA TEÓRICA
2.3. ESCENARIOS PÚBLICOS
A number of organic nano-sized materials are used (or have been developed for use) in food products. These include supplements (e.g. vitamins, antioxidants), colours, flavours and preservatives. The main principle behind the development of nano-sized organic substances is the greater uptake, absorption and bioa- vailability in the body, compared to conventional bulk equivalents. However, a greater uptake and bioavailability of certain compounds, such as preservatives, could pose a greater risk to consumer health and this needs to be further investigated through research.
One example of an organic food additive is the synthetic form of lycopene, a carotenoid found in tomato that has very good colorant and antioxidant properties. A synthetic form of lycopene is reported to have a particle size in the range of 100 nm.13The insolubility of carotenoids in water, moderate solubility in fats and oils, and susceptibility to oxidation, impede the direct use of
relatively coarse particles, which also limits their colouring ability. The nano- particulate nature of the synthetic lycopene is intended to offer a wide diversity of colouring properties, with improved bioavailability. The possible foodstuff applications include soft drinks, baking mixtures and blancmanges but this is predicted to expand in scope significantly.
Also developed for use in food products are nano-sized carrier systems for nutrients and supplements. These are based on nano-encapsulation of the substances both in liposomes and micelles, as well as protein-based carriers. Such nanocarrier systems are used for taste masking of ingredients and addi- tives such as fish oils, and protection from degradation during processing. They are also claimed for enhanced bioavailability of nutrients, supplements, anti- microbial activity and other health benefits. There is a wide range of materials available in this category, for example, food additives (e.g. benzoic acid, citric acid, ascorbic acid), and supplements (e.g. vitamins A and E, isoflavones, b- carotene, lutein, omega-3 fatty acids, coenzyme-Q10). Examples include Novasols (Aquanovas, Germany), and ‘nano-sized self-assembled liquid structures (NSSL)’ (NutraLease Ltd., Israel). An example of NSSL-based product is ‘Canola Active Oil’ (Shemen Industries, Israel), which is fortified with supplements, such as phytochemicals. A similar technology is based on NanoClustert delivery system for food products (RBC Life Sciencess
Inc., USA). A number of products has been developed based on NanoClustert system, including ‘Slim Shake Chocolate’ that is reported to contain cocoa nanoclusters. The product is understood to incorporate nano-sized silica par- ticles that are coated with cocoa to enhance the chocolate flavour through the increase in surface area that hits the taste buds. BioDelivery Sciences Inter- national has developed Bioralt nanocochleate nutrient delivery system, for micronutrients and antioxidants. This phosphatidylserine based carrier system (B50 nm) is derived from soybean, generally regarded as safe (GRAS). The BioDelivery Sciences International’s Bioralt nanocochleate is a nutrient delivery system for protecting micronutrients and antioxidants from degrada- tion during manufacture and storage. The system is claimed to have enabled the addition of omega-3 fatty acids for use in goods that are then baked or cooked such as cakes, muffins, pasta noodles, soups and cookies. The company has also claimed to have added the Bioralt omega-3 formulation to soy milk, milk, liquid yoghurt, orange juice, smoothies, sports drinks, soft drinks, coffee, frappuccinos and other beverages without altering taste or odour.
Self-assembled nanotubes from hydrolysed milk protein a-lactalbumin with a good stability have recently been reported.14s-Lactalbumin is already used as a food ingredient, mainly in infant formula products. These food-protein derived nanotubes may provide a new carrier for nano-encapsulation of nutrients, supplements and pharmaceuticals.
The concept of nanodelivery systems has essentially originated from research into targeted delivery of drugs and therapeutics. The use of similar concepts in foodstuffs is interesting because whilst nanocarrier systems can offer increased absorption, uptake and bioavailability of a compound, it also has the potential in theory to alter tissue distribution of the substances in the body. For example, 77 Nanotechnology Applications for Food Ingredients, Additives and Supplements
the technology can turn water-soluble substances (such as vitamin-C) into fat- dispersible forms through nanocarrier technology, and vice versa, can turn fat- dispersible substances (e.g. vitamin A) into water-dispersible forms. If the nanocarrier is completely broken down and releases the contents in the GI tract, any risks posed by the encapsulated compound should not be any dif- ferent from the conventional bulk equivalent. However, if a nanocarrier system is capable of delivering the encapsulated substance to the bloodstream, its absorption, tissue distribution and bioavailability (and hence the health risk) might be very different from the conventional forms.
Current research is also aiming at the development of nano-structured (or nano-textured) food ingredients and additives to improve taste, colour, flavour, texture and consistency. For example, nano-structured mayonnaises, spreads and ice-creams may have a creamy texture with much less (or no additional) fat, and hence will offer a healthier option to the consumer. The processes com- monly used for producing nano-structured food products include nano-emul- sions, surfactant micelles, emulsion bilayers, double or multiple emulsions and reverse micelles.15 An important point to mention is that all foods contain nanoparticles and the processing of ingredients or foods themselves can change the structure so that the properties such as taste, texture and stability are improved. The changes need not necessarily involve a reduction in size to the nanoscale as it has been found that reduction to the microscale can also pro- duce large and improved changes to the functional properties of an ingredient. Changes to properties of all ingredients could be found by reducing the size to the micrometer or nanometer level and this could lead to a reduction in the need for current levels of certain ingredients or improvements to ingredient functionality generally. Two areas that have been found promising are the change in size or structure of salt to enable the industry to lower the salt levels in foods while maintaining taste, functionality and safety, all of which are actions of salt in foods; and the restructuring of water in emulsions to improve the properties of low-fat products such as dressings.
Figure 5.1 shows the surface of a potato chip with table salt added as usual by the consumer. Studies from a project on sensory properties of different salt sizes at Leatherhead Food International showed that reducing the size to 10– 40 mm increased the initial salt time and intensity. The micrograph illustrates that table salt with its large size does not cover much of the surface of the chip (or other product). The use of a smaller sized salt would give more salt particles on the product and allow the consumer to taste the salt more when added at a lower level.
In reduced-fat emulsion products such as salad dressings, the extra water needs to be stabilised with added ingredients such as modified starch to maintain stability and viscosity. Restructuring the water to enclose it within the fat droplets by manufacturing a water in oil in water (WOW) emulsion allows the lower fat product to maintain the higher stability and creaminess associated with a higher fat product. An example of the structure of the WOW emulsion is shown in Figure 5.2. In this confocal microscope image, the oil appears white and the water black. This work was produced in a LINK project between
Figure 5.1 Scanning electron micrograph of table salt on the surface of a potato chip.
Figure 5.2 Confocal scanning laser micrograph of a WOW emulsion: water¼ black,
oil¼ white, bar ¼ 2 mm.
79 Nanotechnology Applications for Food Ingredients, Additives and Supplements
Leatherhead Food International, Institute of Food Research, DEFRA and industry.16
Interesting developments might be seen if emulsions were produced with all nano-sized oil droplets. It is possible that they could be stable without the need for current emulsifiers.
It is also worth mentioning that many other nanomaterials are used in non- food applications, but they are unlikely to find applications in food or food packaging. Examples of these include carbon-based materials (such as full- erenes and carbon nanotubes). Recent studies have linked carbon nanotubes with potential harmful effects in biological systems.17However, they are highly unlikely to be used in food applications, because the functionalities they offer relate to enhanced tensile strength and electrical conductivity, which are of little benefit for use in food. Application of such materials in the packaging area is, nevertheless, a possibility.