Nano - A technology for food flavouring?
I was privileged to be given the opportunity to talk at the the British Society of Flavourists in June. My musings on the "Innovative Uses of Nanotechnology in Flavourings and Food" was well received, stimulating some interesting discussions. I thought others may like to have a look...
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.
Amoabediny G, Naderi A, Malakootikhah J, Koohi MK, Mortazavi SA, Naderi M, and Rashedi H (2009). Guidelines for Safe Handling, Use and Disposal of Nanoparticles. Nanosafe 2008: International conference on safe production and use of nanomaterials. J. Phys.: Conf. Ser. 170.
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.
Bishop J R P, Nelson G and Lamb J (1998). Microencapsulation in yeast cells. J Microencapsul; Vol. 15, (6) 761-73.
Han NS, Basri M, Abd Rahman MB, Abd Rahman RN, Salleh AB, Ismail Z (2012). Preparation of emulsions by rotor-stator homogenizer and ultrasonic cavitation for the cosmeceutical industry. J Cosmet Sci. Vol. 63, (5) 333-44.
Higashi T, Nishimura K, Yoshimatsu A, Ikeda H, Arima K, Motoyama K, Hirayama F, Uekama K, Arima H (2009). Preparation of four types of coenzyme Q10/gamma-cyclodextrin supramolecular complexes and comparison of their pharmaceutical properties. Chem Pharm Bull; Vol. 57, (9) 965-70.
Howlett J (2012). Practical guidance for the safety assessment of nanomaterials in food. Summary report of workshop held in April 2011 in Cascais, Portugal, organised by the ILSI Europe novel foods and technology task force. pp16.
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.
Munin A and Edwards-Lévy F. (2011). Encapsulation of Natural Polyphenolic Compounds: a Review. Pharmaceutics Vol. 3, 793-829.
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.
Ostiguy C, Roberge B, Woods C, Soucy B (2010). Engineered Nanoparticles Current Knowledge about OHS Risks and Prevention Measures. Chemical Substances and Biological Agents: Studies and Research Projects IRSST Report number R-656. pp143.
Weiss J, Takhistov P and McClements D J. (2006). Functional Materials in Food Nanotechnology. J Food Sci; Vol. 71, (9) 107-16.
The use of nanomaterials in novel food and beverage applications
As with all novel developments most companies like to keep things under the radar until ready for product launch. A number of companies have at least hinted that nanotechnology plays a part in their NPD strategy. The German company Aquanova AG uses a polysorbate micelle carrier technology to solubilize a range of poorly soluble ingredients for incorporation into clear beverages. Their product range includes isoflavones, natural colours, antioxidants, vitamins and coenzymes such as CoQ10. Their technology is exemplified in the international patent WO2004002469. These micelle systems have a particle size that typically ranges from around 20 nm to 200 nm.
Creating fine dispersions of poorly soluble natural fat soluble colourings to formulate clear beverage products is one area where the technology has been applied. Casein micelles are being investigated for their ability to carry functional ingredients including Vitamin D2 and for use in clear beverages and sports drinks. International patents have been filed by the Technion Research and Development Foundation Limited, Israel; for example “Casein Micelles for Nanoencapsulation of Hydrophobic Compounds” (patent number WO2007122613).
Nanodispersions of particles of around 100 nm can remain stable for longer than conventional emulsions or dispersions and can form clear pseudo-solutions. These properties have been exploited by companies such as Food Ingredient Solutions Limited (www.foodcolor.eu) who use a protein matrix system to formulate natural colours such as astaxanthin for use in beverages. Compass Foods have developed Habo Monoester P90, a monopalmitate sucrose ester surfactant to prepare micellar dispersions of 20-80 nm particles (http://bit.ly/1emuNNV). They propose the option of using nanocapsules containing antioxidants to stabilize the co-encapsulated natural colours. Incorporating colours into nano- and microcapsules to stabilise them may have an impact on their light scattering properties, as the phenomena of Rayleigh scattering and Mie scattering come into play. This means that additional development work may be required to achieve the desired colour outcome. A number of companies have addressed the challenges of formulating natural flavours and are regularly demonstrating their innovative products at the various global ingredients business exhibitions.
Cyclodextrins have been successfully used to encapsulate a wide range of fat soluble functional ingredients by forming molecular inclusion complexes. Cyclodextrins are a form of modified starch with a ring structure made up of glucose units. The most common ones in routine use comprise 6, 7 or 8 member rings and are termed alpha- beta- and gamma-cyclodextrin (figure 2). They have a small outer diameter of less than 2 nm. These molecules have a polar outer surface allowing them to dissolve quite well in water. Their inner core forms a non-polar cavity into which can fit small fat soluble molecules such as many food flavours, fat soluble vitamins and natural colours such as carotenoids. This enables them to be used to help to solubilise poorly soluble ingredients. The three main forms are now being used more widely in new product development (NPD) as approval for their use as a novel food ingredient proceeds through the US, Japan and Europe.
Figure 2. Simplified diagram of the chemical structure of alpha-, beta- and gamma cyclodextrin.
Cyclodextrins have been utilized by the UK company FlavorActiV Limited for over ten years to stabilise flavours, off-flavours and taints. The resulting powders are used for training sensory panels to recognise positive and negative attributes in products, for improved quality management and process control, in the brewing industry and in the wider food, beverage and water industries.
Cyclodextrins are being adopted in the pharmaceutical industry to improve the delivery and bioactivity of active ingredients and are also being used in food supplements and can be found for example in formulations of CoQ10. Tishcon Corporation in the US has commercialized this type of product with their HydroQSorb® product (http://bit.ly/19qpDLB). The performance of a number of different formulations of complexed CoQ10 has been reported by Higashi et al. (2009).
Cyclodextrins have also been investigated for a number of other applications, such as improving the stability of bitter tasting products containing compounds including flavonols (e.g. quercetin, and myricetin) by Lucas-Abellán et al. (2008); taste masking of ginseng and green tea (Wacker AG information sheet “Masking tastes and odors with CAVAMAX® cyclodextrins” (http://bit.ly/1acC16q). A more general review of polyphenol encapsulation has been recently published by Munin and Edwards-Lévy (2011) that details the range of techniques used to encapsulate these often unstable and unpalatable functional ingredients.
In Part 3 we consider what we might mean by the term "nanostructured materials" and is also where you can find further reading and a list of references.
Over the past few months I have attended several meetings where nanotechnology in the food and beverage industry was a key topic of interest. Frustratingly there was little practical detail available for those of us on the fringes of this emerging technology so I decided to have a look around to see what was going on. Thus the topic of my first blog is nanotechnology.
Nanotechnology is the manipulation, development and manufacture of materials typically in the size range 1-100 nm. At this size, particles can exhibit properties not necessarily observed at greater sizes in the nanometre (100-1000 nm) to micrometre range. Nanomaterials may be natural or specifically engineered nanomaterials (ENMs). They are all around us in our everyday lives. They are extremely mobile in their free state with a low sedimentation rate; they have large specific surface areas, and may demonstrate quantum effects. As a consequence, the physical and chemical properties of materials at the nano scale may differ from those at the micro and macro scale. These differences may include colour, melting point, crystal structure, reactivity, conductivity, magnetism and mechanical strength.
One of the simplest natural examples of natural nanomaterial is the presence of nanoparticles in milk. Milk comprises, amongst other components, an emulsion of small fat droplets and a suspension of milk proteins such as casein. A demonstration of the analysis of milk carried out by Malvern Instruments using laser diffraction illustrated that a higher proportion of smaller particles (less than 100 nm) was present in skimmed milk than was in full fat milk. These smallest particles comprise casein, present as micelles. Further information can be found on Malvern’s web site at http://bit.ly/19qa5aA.
Applications in the food ingredients industry
There are a large number of potential applications for nanotechnology in the wider food and beverage industry as illustrated in the diagram below (figure 1).
Figure 1. Potential applications for nanotechnology in the food industry (modified from Weiss, Takhistov and McClements 2006).
In Part 2 the blog will focus on the current and potential use of nanomaterials in novel food and beverage applications.
Craig is a consultant, a flavour enthusiast and an unapologetic analytical chemistry geek.