Many approaches have been used to encapsulate volatile flavours but one of the more unusual approaches is the incorporation of food flavours within baker’s/brewer’s yeast cells (Bishop et al. 1998). This approach has been adopted by FlavArom International Limited (http://www.flavarom.com/) and Firmenich SA (http://www.firmenich.com/) to produce stable spray dried flavour products (Normand et al. 2005). Yeast cells have a size of typically 5-7 microns in diameter and can absorb food flavours such as limonene which are stabilized internally as small droplets ranging in size from below 100 nm to around 4000 nm. Flavour loading of 20 to 40% on a dry weight basis (200-400 g/kg powder) can typically be achieved. Inclusion of nanomaterials within microcapsules, matrix particles or agglomerates that will disperse at the point of use is one means of improving the stability and handling properties of these products.
Spray drying is a common way of generating dry powders of encapsulated ingredients and particle sizes achieved are as low as 2 micron at laboratory scale or around 20-50 micron at production scale. There are now lab scale spray driers available that can produce powders with a particle size ranging from around 300 nm to 5 micron, for example the B-90 Nano Spray Dryer from BÜCHI Labortechnik AG (http://bit.ly/17OheHJ). As these systems are scaled up, the usual hazards associated with powder handling and dust in the workplace will have to be considered with a view to the challenges presented by the smaller particles that are potentially entering the atmosphere. The key is in the design and engineering controls that need to be incorporated from the outset and examples and guidance can be found from a number of sources including publications from Ostiguy et al. (2010) (http://bit.ly/1bI2Tbi) and Amoabediny et al. (2009) (http://bit.ly/1bI3fPr). A recent workshop was held by the International Life Sciences Institute and a summary report, by Howlett (2012), considered the need for providing practical guidance for the safety assessment of nanomaterials in food (http://bit.ly/17USBJe).
The production of stable emulsions with very small droplet sizes, often known as sub-micron-emulsions or nano-emulsions, is well established. Typically high-pressure homogenization is used to form lipidic bodies stabilized with an encapsulating phospholipid monolayer suspended in an aqueous environment. Alternatively, liposomes have an aqueous core enveloped by a lipid-bilayer membrane. More commonly used in cosmetics, personal care and medicinal products, they are typically unstable in most food processing environments. Ultrasound is being used to generate oil in water (O/W) and more complex double emulsions, for example water in oil in water (W/O/W), for NPD. These techniques can be used to generate stable emulsions with little surfactant with very small droplet sizes. Trials, using a rotor-stator homogenizer and ultrasonic cavitation, produced emulsions of palm oil esters with particle sizes around 63 nm (Han et al. 2012).
Many applications involve the production and use of nano-particles, nano-tubes or fibres as dispersions in liquids or as powders. Monitoring these materials has presented a number of technical challenges. There are now tools available for routinely measuring particle numbers, size, size distribution, shape and charge characteristics (zeta potential) using a variety of technologies provided by companies such as Malvern Instruments, Beckman-Coulter and Micromeritics; some companies have adopted advanced particle tracking systems to improve the quality of particle characterization, for example NanoSight Limited. However, for the very smallest of particles or droplets in the 1-10 nm range and for characterising nanostructured materials within a matrix, advanced microscopy techniques are required such as atomic force microscopy (AFM), field emission-scanning electron microscopy (FE-SEM) and cryogenic-transmission electron microscopy (cryo-TEM).
Process scale up provides a number of challenges in this area. Some companies have developed micropore membrane filtration systems, e.g. Micropore Technologies Limited (www.micropore.co.uk/). However, microfluidic technologies that could be more suitable for large scale processing typically operate at the micron scale. Scale up of nanomanufacturing is a rapidly developing field and new materials and processes are needed; we should expect to see them appearing in ever greater frequency in the near future.
Increasing the surface area by reducing particle or droplet size is one strategy for improving dissolution rates, stabilizing emulsions and improving bioavailability through increased uptake by the digestive tract. There are however some shortcomings in this approach. Increasing the surface area also increases the potential for chemical reactivity, for oxidation and other undesirable chemical interactions. Nano scale encapsulation through the use of micelles and inclusion complexation can overcome some of these limitations but will incur additional costs. Thus the potential benefits of using nanotechnology in developing novel food ingredients and products may be in niche, high value areas. This is particularly pertinent when taking into consideration the additional costs of manufacturing and process controls that may need to be implemented to ensure safe production and handling of ENMs.
There are clearly many opportunities when working with nanomaterials in the food and beverage industry particularly, in the area of natural product formulation, particularly when low fat, sugar, salt and low surfactant use are targets for novel foodstuffs development. Opportunities for modifying food structure have yet to be fully explored and the use of ENMs in beverage development continues in support of the growing use of natural colours. The influence of micellar flavour formation in aroma delivery in food and beverage systems is also the subject of a growing number of studies (e.g. Aznar et al. 2004). The greater understanding of how nanostructured materials affect the sensory impact of food and beverage ingredients will hopefully lead to new tools becoming available for NPD in the near future.
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Aznar M, Tsachaki M, Linforth RST, Ferreira V, Taylor AJ (2004). Headspace analysis of volatile organic compounds from ethanolic systems by direct APCI-MS. Int J Mass Spectrom; Vol. 239, (1) 17-25.
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Lucas-Abellán C, Fortea I, Gabaldón JA, Núñez-Delicado E (2008). Encapsulation of quercetin and myricetin in cyclodextrins at acidic pH. J Agric Food Chem; Vol. 56, (1) 255-9.
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Normand V, Dardelle G, Bouquerand PE, Nicolas L, Johnston DJ (2005). Flavor encapsulation in yeasts: limonene used as a model system for characterization of the release mechanism. J Agric Food Chem; Vol. 53, (19) 7532-43.
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Craig is a consultant, a flavour enthusiast and an unapologetic analytical chemistry geek.