2
Application of Nanotechnology to Food Products

This chapter summarizes the presentations and discussions of the first session of the workshop. All three presentations revolved around the question: How can nanotechnology be applied in the food industry? The first presenter, José Miguel Aguilera of Universidad Católica de Chile, Santiago, discussed how nanotechnology will provide new ways of controlling and structuring foods with greater functionality and value. But first, he talked about how “nano” has, in fact, been part of food processing for centuries, since many food structures naturally exist at the nano-scale. Until very recently, however, most of what has been done with nano-sized food materials has occurred in a largely uncontrolled way, and there is still a lot to be learned about the natural nano-structure of foods (e.g., how foods are constructed and how they break down during digestion). Until and unless these gaps in knowledge are filled, scientists could miss opportunities to apply some of the new nanotechnologies being developed. The second presenter, Frans Kampers of Wageningen UR, Wageningen, The Netherlands, argued that nanotechnology holds forth tremendous promise to provide benefits not just within food products but also around food products. In other words, not only can nanotechnology be used to structure new types of food ingredients, it can also be used to build new types of food packages, food quality detection tools, and other types of measurement and detection systems. He described some of the work that Wageningen UR scientists and others are doing in the areas of volatile sensing, microorganism detection, and food labeling. Kampers stated that these types of applications are arguably noncontroversial, or at least less controversial than some of the food ingredient applications of nanotechnology, and as such could serve as a “stepping stone for the general public to appreciate



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 21
2 Application of Nanotechnology to Food Products This chapter summarizes the presentations and discussions of the first session of the workshop. All three presentations revolved around the question: How can nanotechnology be applied in the food industry? The first presenter, José Miguel Aguilera of Universidad Católica de Chile, Santiago, discussed how nanotechnology will provide new ways of controlling and structuring foods with greater functionality and value. But first, he talked about how “nano” has, in fact, been part of food processing for centuries, since many food structures naturally exist at the nano-scale. Until very recently, however, most of what has been done with nano-sized food materials has occurred in a largely uncontrolled way, and there is still a lot to be learned about the natural nano-structure of foods (e.g., how foods are constructed and how they break down during digestion). Until and unless these gaps in knowledge are filled, scientists could miss opportunities to apply some of the new nanotechnologies being developed. The second presenter, Frans Kampers of Wageningen UR, Wageningen, The Netherlands, argued that nanotechnology holds forth tremendous promise to provide benefits not just within food products but also around food products. In other words, not only can nanotechnology be used to structure new types of food ingredients, it can also be used to build new types of food packages, food quality detection tools, and other types of measurement and detection systems. He described some of the work that Wageningen UR scientists and others are doing in the areas of volatile sensing, microorganism detection, and food labeling. Kampers stated that these types of applications are arguably noncontroversial, or at least less controversial than some of the food ingredient applications of nanotechnology, and as such could serve as a “stepping stone for the general public to appreciate 21

OCR for page 21
22 NANOTECHNOLOGY IN FOOD PRODUCTS what nanotechnologies can offer to the food industry and where benefits for consumers can be derived from these technologies.” The third presenter, Jochen Weiss of the University of Massachu- setts, Amherst, provided an overview of how nanotechnologies are being developed to add novel functionalities to food products. He described several different nanomaterials currently being explored for their poten- tial applications in food products, including microemulsions, liposomes, solid lipid nanoparticles (SLNs), and nanofibers. He also described some of the research that he and his colleagues have been conducting with each of these types of materials, emphasizing the variety of ways one can build nanostructured materials with potent, long-lasting antimicrobial capacities. In fact, scientists are beginning to construct all sorts of differ- ent types of microscopic structures with varying functionalities (not just antimicrobial capacities) using nanomaterials as their building blocks. What scientists don’t fully understand yet, however, is how these struc- tures will function once inside actual food systems. The session ended with a 20-minute question and answer period, with most of the discussion revolving around the commercial availability of these various applications and products, the definition and history of nanotechnology, and regulatory uncertainty. The last topic—regulatory uncertainty—would re-emerge in later sessions as a major overarching theme of the workshop dialogue. There was also some discussion on the issue of palatability and nutrient delivery and whether nanotechnology offers any solutions. APPLICATIONS OF NANOSCIENCES TO NUTRIENTS AND FOODS 1 Presenter: José Miguel Aguilera 2 Aguilera began with some introductory remarks about his work as a food microstructure engineer and how, in the past, the focus of his research was on larger food structures (i.e., “micron-size”). Now, he is trying to extrapolate what he has learned about the structure of foods at that micro-level to a smaller scale. He provided a brief outline of his presentation, with a reminder that “we already have a lot of nanotech in 1 This section is a paraphrased summary of Jose Miguel Aguilera’s presentation. 2 José Miguel Aguilera, PhD, is a Professor in the Department of Chemical and Biopro- cess Engineering, Universidad Católica de Chile, Santiago, Chile.

OCR for page 21
23 APPLICATION OF NANOTECHNOLOGY TO FOOD PRODUCTS our foods.” The focus of his talk, he said, would be on how foods are structured today, how they could be structured in the future by reducing the scale of intervention, and the implications of the latter for adding unique value to foods with respect to nutrition/health and gastron- omy/pleasure. The smallest food microstructure that can be controlled with current processing technologies is probably only about 5–10 µm, which is about 100 times larger than the upper limit of nanotechnology. So there is a big gap between what current technologies can do and the promise that nanotechnology holds forth. Introduction: The Food Industry and the Role of Nanosciences The food industry is the largest manufacturing sector in the world, with an annual turnover approximating US $4 trillion. But it presents a very different innovation scenario than the chemical and pharma indus- tries do, and introducing new processing technologies (e.g., high hydro- static pressure [HHP] technology, -ohmic heating, irradiation) has been challenging. Globally, a large proportion of foods are consumed after only minimal processing (e.g., fresh fruits, vegetables, nuts, some cereals) and with high post-harvest losses (particularly with fruits and vegetables). In most places worldwide, particularly in urban centers, food is abundant and relatively cheap. Moreover, except for large multination- als, most food companies are relatively low-tech, small/medium enterprises (SMEs) where traditional technologies are geared to local tastes and traditions. The Two Axes of Today’s Food Industry Aguilera described two axes, or dimensions, of the food industry of today and the food industry of the future (see Figure 2-1): 1. The “food chain” axis, which extends from production to pack- aging and distribution (and includes raw materials, processing, and all of the various environmental and technological factors that contribute). 2. The “consumer” axis, which extends from the brain to the mouth on one end (and includes things like food perception and

OCR for page 21
24 NANOTECHNOLOGY IN FOOD PRODUCTS pleasure) and from the mouth to the body on the other end (affecting things like bioavailability of nutrients, weight control, and satiety). He remarked that the second axis has been part of the food industry for only the last 10–15 years, and it will probably play an even more prominent role in the future. Foods of the future will be built to meet consumer demands and desires around food perception, sensations of wellness and pleasure, texture and flavor, gut health, nutrient bioavail- ability, vitality, etc. Food chain Consumer The environment: Energy, water and waste Food perception Wellness Brain Pleasure Ethical issues Texture Processing Packaging/ Raw Production Flavor distribution Mouth materials Eating quality More foods Safety Preservation Delivering safe foods Gut health More nutrients Quality Structuring Convenience Satiety More “natural” Int’l trade Bioactives Information Gut Bioavailability of nutrients Right molecules Ingredients Traceability Ethical issues S&T: Biotechnology, nanotechnology, -omics Nutrition & health Vitality Body Weight control Analytical technologies and tools Assessment of quality and safety FIGURE 2-1 The two dimensions, or axes, of the food industry of the future: the “food chain” axis and the “consumer” axis. Image courtesy of José Miguel Aguilera. Where Is the Nano in Foods? Aguilera remarked that “nano” must exist naturally in food since even in natural foods (e.g., fresh fruits) structural components are built from molecules and, during digestion, break down into molecules. These molecules form ordered sructures like cells, fibers, gels, emulsions,

OCR for page 21
25 APPLICATION OF NANOTECHNOLOGY TO FOOD PRODUCTS foams, and liquids, which give foods their various properties (e.g., texture, flavor, shelf-life, nutritional value). Aguilera showed a variation of the “Scale of Objects” image that Yada showed during his presentation of the micro- vs. nano-scale worlds (see Figure 2-2 and Figure 1-1 for comparison), with pictures and illustrations of “things natural” vs. “things in foods” along a size scale, ranging from 0.1 nm to 1 cm. He agreed with Yada that it is a good visual to present to people as a way of explaining the sizes involved with the “microworld” [“microstructure”] versus the “nanoworld” [“nanotechnology”]. Food microstructures include things like plant cells, starch granules, meat fibers, and chloroplasts. Food nanostructures include things like crystalline blocklets of amylopectin molecules (which serve as building blocks for starch granules) and clusters of chlorophyll molecules embedded in lipid bilayers (which serve as building blocks for chloroplasts). Aguilera identified the cow udder as the most interesting “natural” microdevice (i.e., device for producing micro-sized food ingredients). He explained how a cow udder cell produces casein micelles and fat globules, both key ingredients of milk, with casein micelles ranging in size from 300–400 nm and fat globules ranging in size from 100 nm to 20 µm. Fat globule membranes have a thickness of 4–25 nm. All structured dairy products (e.g., butter, whipped cream, ice cream, milk, cheese, yogurt) are composed of these two ingredients plus an even smaller ingredient, the whey proteins, which ranges in size from 0.001– 0.01 µm. So, in fact, dairy technology is not just a microtechnology but also a nanotechnology, and it has existed for a long time. The dairy industry utilizes these three basic micro- and nano-sized structures to build all sorts of emulsions (butter), foams (ice cream and whipped cream), complex liquids (milk), plastic solids (cheese), and gel networks (yogurt). 3 But much of what has been done in the past with natural micro- and nano-sized structures, not just in the dairy industry but the food industry in general, has been largely uncontrolled. The first comprehensive scientific perspective on a micro-structural view of food was not published until as recently as 1987. 3 See JM Aguilera and DW Stanley. 1999. Microstructural Principles of Food Processing and Engineering, 2nd Edition. Heidelberg, Germany: Springer.

OCR for page 21
26 NANOTECHNOLOGY IN FOOD PRODUCTS Things natural Things in foods FIGURE 2-2 Similar to the image that Yada showed (see Figure 1-1), this image more clearly represents the difference in scale between nano-sized vs. micro-sized materials and structures in foods. Image courtesy of José Miguel Aguilera and the U.S. Department of Energy. 4 The Scales of Food: Length and Time Aguilera showed a graph illustrating the range of the length scales of food elements that already exist (either in nature or as a result of process- ing), emphasizing again that in fact many elements that play very impor- tant structural roles in foods that we already eat exist on the nano-scale (see Figure 2-3). We don’t notice them because not only are they invisi- ble to the naked eye (most things smaller than about 80 µm cannot be seen by the human eye), they are imperceptible by taste as well (most 4 This image is a modification of “The Scale of Things” chart developed by the Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy. The original can be viewed online at http://www.er.doe/gov/bes/scale_of_things.html.

OCR for page 21
27 APPLICATION OF NANOTECHNOLOGY TO FOOD PRODUCTS things smaller than about 40 µm cannot be sensed in the mouth). In fact, some of food’s most important raw materials—proteins, starches, and fats—undergo structural changes at the nanometer and micrometer scales during normal food processing (see Figure 2-4): 1. Proteins: Food proteins (e.g., native beta-lactoglobulin, which is about 3.6 nm in length) can undergo denaturation (via pressure, heat, pH, etc.) and the denatured components reassemble to form larger structures, like fibrils or aggregates, which in turn can be assembled to form even larger gel networks (e.g., yogurt). Protein-polysaccharide mixed solutions can spontaneously sepa- rate into a phase with nano- or micro-sized droplets dispersed in a continuous phase. 2. Starch: Starch granules expand when heated and hydrated releas- ing biopolymers that can be recrystallized into nano-sized struc- tures (e.g., recrystallized amylose regions may be about 10–20 nm); dextrins and other degradation products of extrusion can be used to encapsulate bioactive substances in micro-regions, etc. 3. Fats: While many people think of fats as being homogeneous liquids or solids, in fact some fats have a lot of structure. Monoglycerides, for example, can self-assemble into many mor- phologies at the nanoscale level, and hierarchically structured into tryglicerides can be crystallites (10–100 nm), followed by arrangment into large clusters, then flocs, and finally, fat crystal networks. Fat crystal networks give foods spreadability, texture, and other similar properties. Aguilera emphasized that all foods, at one stage or another, become dispersions of these multiple interacting components not only with each other but also with water and air. For example, proteins interact with polysaccharides to form mixed polysaccharide gels, starches and proteins interact to form starch-protein complexes, and emulsions and food foams have interfaces that are stabilized by small molecules (surfactants), bio- polymers or even small particles.

OCR for page 21
28 NANOTECHNOLOGY IN FOOD PRODUCTS Food product physics Colloidal science Polymer science Resolution “Nano” sciences of the eye Detection Chemistry in the Digesta mouth Gluten Microbial Powder Water network FOOD PRODUCTS cells Cocoa particles 0.3 nm particles Fiber Flavors Crystals Lipid micelles Ice crystals CHO Microbubbles Bubbles in icecream polymers Micro Plant cell droplets Fat droplets Proteins walls Emulsifiers Plant Grains Particle Network cells gels gels Cooked Casein Starch starch micelles Casein nanoparticles 10 µm 100µm 1 mm 10 mm µ1m 1 nm 10 nm 100 nm FIGURE 2-3 The length scales of food elements that already exist. Structures to the left of the right dotted line (“Resolution of the eye”) are invisible to the naked eye, and structures to the left of the left dotted line (“Detection in the mouth”) are imperceptible to taste. Image courtesy of José Miguel Aguilera. Length is just one scale of measurement for food. Another is time. In order to interact, different components of a food structure must come into position at the right time. The structuring of a foam for example, requires that certain structural components and processes happen not only at spe- cific length scales but also within specific time scales. The beginning of foam formation occurs at the nm-length scale within milliseconds (e.g., adsorption of emulsifier molecules at the air-water interface), whereas later phases of the process occur at larger length scales and longer time scales (e.g., drainage of liquid lamellae occurs at the µm-length scale and within minutes).

OCR for page 21
29 APPLICATION OF NANOTECHNOLOGY TO FOOD PRODUCTS PROTEINS STARCH FATS 10 nm 1 µm 10 µ m 100 nm FIGURE 2-4 A schematic of the structural changes that proteins, starch, and fats naturally undergo during normal food processing. Many of these changes occur at the nano-size scale. Image courtesy of José Miguel Aguilera. How Are Foods Structured Today, and How Should They Be Structured? Today, foods are structured using a formulation, or recipe, with structure formation (i.e., biopolymer transformation, phase creation, reactions) and stabilization (i.e., vitrification, crystallization, network formation) occurring at the same time. The end result is a metastable structure. In the future, with nanotechnology, foods will be structured from the bottom up. Rather than using a recipe, food structure engineers will use molecules as their starting material, modifying those molecules and building interactions in order to get the desired properties. The process will be more akin to engineering design than recipe-reading, much like how computers and cars are assembled. By building foods from the molecule up, rather than relying on a coupled structure- formation-structure stabilization process, food engineers will utilize an uncoupled “matrix precursors/structural elements” paradigm. That is, microstructural elements will be engineered separately and then

OCR for page 21
30 NANOTECHNOLOGY IN FOOD PRODUCTS dispersed into a matrix precursor, which will have been developed independently. The end product will be a more functional product. As Aguilera said, “the beauty that I see in going down[ward] on the size scale is that we can control and really design and assemble new foods.” Also in the future, not only will food structural engineers be follow- ing this architecture-like paradigm, they will be utilizing new tools. Right now, traditional food processing relies on equipment that is capable of intervening at only the microscale (i.e., 10 µm–1 mm), not nanoscale (with some exceptions). Even then, it’s like “hammering a nail with a bulldozer,” Aguilera said. Emulsification, for example, involves manipu- lating structural elements that are about 10 µm in length, using a device with an opening of 1 mm—that’s two full orders of magnitude differ- ence. As another example, shaping (molding), involves manipulating structural elements that are about 20–30 µm in lengthsize (e.g., bubbles), using a device with an opening devices of 10 cm—that’s four orders of magnitude difference. In the future, the scale of intervention will be reduced to the size of the elements being manipulated. Reducing the Scale of Food Design: Four Examples Aguilera gave four examples of reduced scale food design, or “controlled structuring” (in each case, the device/method that enables controlled structuring is italicized). The descriptions below accompany the images in Figure 2-5: 1. Architectures of foams made in a 250 µm coaxial capillary tube by varying the ratio of gas/liquid flow rates. 5 Here, a microflu- idic device (i.e., the capillary tube) is used to vary the gas to liq- uid ratio and thereby build different types of foam architectures inside a capillary. The capillary tube gives the food engineer control over the architecture of the foam. 5 O Skurtys, P Bouchon, and JM Aguilera. 2008. Formation of bubbles and foams in gelatine solutions within a vertical glass tube. Food Hydrocolloids 22:706-714.

OCR for page 21
31 APPLICATION OF NANOTECHNOLOGY TO FOOD PRODUCTS Architectures of foams made in a 250 µm coaxial capillary capillary tube by varying the ratio gas/liquid flow rates (from Skurtys, Bouchon and Aguilera, 2007). Oil droplets in an O/W emulsion after passage through a stack of layers of etched channels of a microfluidic device made m icrofluidic from a silicon chip (from van der Zwan et al., 2006). Evolution of a 2% potassium kappa- carrageenan particle subjected to capillary shearing flow during g elation gelation (from Walther et al., 2004). Different shapes of ice crystals made in: (A) Tris buffer; (B) Buffer and 400 mM of a polypeptide of an ice ice nucleating protein, and (C) Buffer and 50 mM of an anti- anti-freeze protein (from Kobashigawa et al., 2005). FIGURE 2-5 Four examples of reduced-size controlled structuring. For each example, the method or device that enables the controlled structuring is in bold. SOURCE: Reprinted from Food Hydrocolloids, Volume 22, Issue 4, O Skurtys, P Bouchon, and JM Aguilera, Formation of bubbles and foams in gelatine solutions within a vertical glass tube, pp. 706-714, Copyright (2008), with per- mission from Elsevier. E van der Zwan, K Schroën, K van Dijke, and R Boom, Visualization of droplet break-up in pre-mix membrane emulsification using microfluidic devices, pp. 223-229, Copyright (2006), with permission from Elsevier, Reprinted from Food Hydrocolloids, Volume 17, L Hamberg, M Wohlwend, P Walkenström, and A Hermansson, Shapes and shaping of bio- polymer drops in a hyperbolic flow, pp. 641-652, Copyright (2008), with per- mission from Elsevier, Reprinted from FEBS Letters, Volume 579, Y Kobashigawa, Y Nishimiya, K Miura, S Ohgiya, A Miura, and S Tsuda, A part of ice nucleating protein exhibits the ice-binding ability, pp. 1493-1497, Copy- right (2005), with permission from Elsevier; Reprinted from Colloids and Sur- faces A: Physicochemical and Engineering Aspects. 2. Controlling a uniform size of oil droplets in an oil/water emul- sion after passage through a stack of layers of etched channels of a microfluidic device made from a silicon chip. 6 Again, use of the micro-fluidic device gives the food engineer capacity to 6 E van der Zwan, K Schroën, K van Dijke, and R Boom. 2006. Visualization of droplet break-up in pre-mix membrane emulsification using microfluidic devices. Colloids and Surfaces A: Physicochemical and Engineering Aspects 277:223-229.

OCR for page 21
44 NANOTECHNOLOGY IN FOOD PRODUCTS The next step with microemulsions is to build even more complex structures, for example by combining charged binary microemulsions with charged food polymers, such as pectins, and creating stable microemulsion-polymer clusters with potentially improved function- alities) (see Figure 2-9). Weiss and his colleagues are experimenting with these more complex structures in an effort to make a palatable antimicrobial microemulsion (which would otherwise be too bitter to ingest). + + + Charged Binary + Microemulsion ++ + Mixing at appropriate + + + + + conditions and + concentrations + + + + + + + + Stable Cluster with Potentially Improved Functionalities (Antimicrobial, Sensory) Inappropriate Charged Food conditions Aggregation & Precipitation Polymer (e.g. Pectin) FIGURE 2-9 The next step for microemulsion nanotechnology is the creation of composite microemulsion-polymer clusters with novel functionalities, such as antimicrobial potency or palatability. Image courtesy of Jochen Weiss. Liposomes Liposomes are another type of nanostructure being used to add func- tionality to food. Liposomes are spherical bilayer membrane structures with aqueous cores, so unlike lipophilic-containing microemulsions, they can be used to contain and deliver hydrophilic, or water-soluble, ingredi- ents. Moreover, their internal pH is adjustable, so they can contain ingre- dients that otherwise would not be stable under certain circumstances. As with microemulsions, there is a lot of engineering that can be done and

OCR for page 21
45 APPLICATION OF NANOTECHNOLOGY TO FOOD PRODUCTS different materials that can be used, leading to a range of differently shaped and sized final products. For example, depending on how the phospholipids base materials are put together, one could form either mul- tiple vesicular structures or single onion-shaped vesicles. Also as with microemulsions, Weiss and his colleagues have been experimenting with liposomes as a way to encapsulate antibacterials, in this case nisin, and they have shown that encapsulated microemulsions are better than free nisin at inhibiting growth over a longer period of time, partly as a result of a more controlled and long-term sustained release. Liposomes are, however, extremely fragile. A liposome is basically just a shell with water inside, and it leaks over time. In fact, this is why industry hasn’t really been that interested in liposomes until now. Weiss and his colleagues have shown that it is possible to engineer leak- resistant liposome surfaces by surrounding the liposomes with polymeric layers and forming double-layered, or two-layer, liposomes. Two-layer liposomes are significantly more stable to long-term storage than single- layer liposomes, and they have greater controlled release possibilities (see Figure 2-10). Primary Secondary Nisin, Lysozyme Liposomes Liposomes Phospholipid & Buffer Ultrafiltration Microfluidize Add Protein or Carbohydrate Isotropic Solution Two Layers Nisin or Lysozyme Decreased Leakage Unilamellar Improved salt stability Liposomes Controlled Release FIGURE 2-10 Next steps for nanoliposomes include forming double-layered liposomes (“secondary liposomes”) that are more stable and leak-resistant than single-layer liposomes (“primary liposomes”) and that have greater controlled release capabilities. Weiss and colleagues have been studying the capacity of liposomes to encapsulate and deliver antibacterials (i.e., nisin, lysozyme). Image courtesy of Jochen Weiss.

OCR for page 21
46 NANOTECHNOLOGY IN FOOD PRODUCTS Biopolymeric Nanoparticles Biopolymer nanoparticles are highly bioactive solid particles with diameters of 100 nm or less. They are already heavily used in the drug delivery industry, where they serve as the basis of modern anticancer drug delivery systems. Weiss and his colleagues have demonstrated that the particles can also serve as carriers of antimicrobial components, with nicin-containing biopolymeric nanoparticles exhibiting much more potent activity against E. coli O157:H7 than particles without nicin. The application of biopolymeric nanoparticles in the food industry is precluded however by the fact their manufacture requires the use of organic solvents. While alternative methods of assembly could be pursued, as of yet biopolymeric nanoparticles do not have any direct applications in food systems. Solid Lipid Nanoparticles (SLNs) An alternative to the biopolymer nanoparticle approach is the actual construction of solid particles using lipids as the base material. These so- called solid lipid nanoparticles, or SLNs, are basically crystallized emul- sions composed of a high-melting point lipid and a bioactive lipophilic component. SLNs are typically about 50–500 nm in diameter and can be either sprayed or applied as powder. Smaller SLNs (i.e., 120–130 nm or less in diameter) have crystal structures that exhibit very different behav- iors than those of larger SLNs because of surface-initiated crystallization. Because of these behaviors, smaller SLNs serve as highly effective car- rier systems for susceptible bioactive ingredients. Weiss and his col- leagues have demonstrated this fact by showing that SLN-encapsulated β-carotene lasts much longer than nonencapsulated β-carotene when stored at 20°C. Interfacial engineering is the key to success. When the interfaces of the SLNs are not engineered properly, the emulsions de- grade very rapidly and the β-carotene is lost very quickly over storage time. If, however, the engineering of the SLN interface is done properly (i.e., via surface-initiated crystallization using saturated lecithin as the surfactant), the resultant crystal structure readily entraps the β-carotene and with very little degradation over the time. The next step forward, Weiss said, is the creation of more complex structures. He pointed to the work of David Weitz, Harvard University, who has shown how SLNs can be used to form shells around emulsion

OCR for page 21
47 APPLICATION OF NANOTECHNOLOGY TO FOOD PRODUCTS droplets, creating what are known as colloidosomes. As with simpler SLNs, colloidosomes can be loaded with bioactive compounds, which are released upon the application of mechanical or thermal stress. Nanofibers Finally, Weiss described some of the work he and his colleagues have been doing with nanofibers. He explained how the fibers are pro- duced through a process known as electrospinning, whereby an electric voltage is applied to a polymer solution, resulting in deposits of either microparticles or very ultra fine fibers. The fibers range in size from 30– 500 nm in diameter. The advantage to this technique is that a variety of morphologies of particles can be created, with different morphologies having different properties and textural attributes. As they have with other types of nanomaterials, Weiss and his colleagues have demon- strated that nanofiber technology can be used to create potent antimicro- bial systems that maintain their antimicrobial capacity for long periods of time. In collaboration with researchers at the University of Tennessee, Weiss and colleagues have also demonstrated how nanofibers serve as ideal materials for catalysis because of their extremely high surface-to- mass ratio and high reaction kinetics. By modulating the surface, some very unusual reactions can be run that would not be possible with larger structures. Future steps include combining nanofibers with other nano-scale systems, namely microemulsions, and building more complex structures with greater functionalities (see Figure 2-11). Weiss and his colleagues have demonstrated that the technique of co-spinning antimicrobial microemulsions inside the nanofibers can yield another type of highly active antimicrobial nanofiber system.

OCR for page 21
48 NANOTECHNOLOGY IN FOOD PRODUCTS Electrospinning Apparatus Fiber SEM Eugenol Fiber TEM PVA Surfynol Micelles Microemulsions were incorporated in solutions to produce spun fibers. Fibers were thus rendered antimicrobially active Packaging or ingredient system FIGURE 2-11 One of the next steps with nanofiber technology in food is to combine the nanofibers with others type of nanomaterials, in this case microe- mulsions, to form novel structures with new functionalities. Image courtesy of Jochen Weiss. The Future of Nanoscience: Playing Lego with Molecules In conclusion, Weiss said that it is difficult to predict the future direction of nanoscience, since many of these structures are being built faster than their new properties (and potential functionalities) can be determined. However, what we have learned so far has allowed us to begin experimenting with architectural design and creating new microscopic structures with this wide range of simple building blocks. The building blocks can be combined in various ways (e.g., microemulsions inside of nanofibers), giving us enormous control over how these systems are assembled. In contrast to how food structures have traditionally been constructed (i.e., from recipes), nanoscience enables a bottom-up design approach using molecules as the starting material: We then assemble these mole- cules and engineer their surfaces in ways that lead to new functionalities. We do not fully understand, however, how most of these structures are going to function within the food matrix where they will be applied. Many unanswered questions remain about their lifetime, mobility, and

OCR for page 21
49 APPLICATION OF NANOTECHNOLOGY TO FOOD PRODUCTS location inside actual food systems. Understanding this complex interac- tion between the nanostructures and the food products that contain them is critical to discussing safety. OPEN DISCUSSION 19 Following Weiss’s presentation, there was a 20-minute open ques- tion and answer period. While most of the questions revolved around the actual science and technology of nanostructured food, workshop partici- pants also asked about regulatory uncertainty around food nanotechnol- ogy. More specifically, questioners asked about when the potential applications of food nanotechnology will be realized and commercially available; whether and how regulatory uncertainty around food nanotechnology is impacting corporate investment and intention to bring these products to market; whether and how the definition and history of nanotechnology (-ies) play into some of the unanswered questions around regulation; whether and how nanotechnology is being used to address the palatability issues typically associated with nutrient delivery; and whether there are limitations to food nanotechnology such that smaller might not always be better. When Will These Opportunities Be Realized? Doyle opened the discussion with a question about the short-term opportunities among all of the various and very exciting applications that were described throughout the morning. Weiss, Kampers, and Aguilera all offered responses. Weiss stated that the applications revolving around the delivery of functional ingredients will be immediate and that, in fact, some of the simpler systems have been available for quite a while. He cited AQUANOVA’s encapsulated bioactive products as one example. However, some composite structures currently being researched and developed, such as those that he described during his presentation, are longer-term prospects. Kampers concurred that some encapsulated food nanotech products are already on the market. However, the food industry does not refer to these products as “nanotechnology,” even though scientists classify them 19 This section is a paraphrased summary of the open discussion that followed Weiss talk.

OCR for page 21
50 NANOTECHNOLOGY IN FOOD PRODUCTS as nanostructure materials. Also, many of the measurement, sensor, and diagnostic applications currently in development, such as those that he described during his presentation, are very close to being market ready. Aguilera commented that those applications that can satisfy con- sumer needs unmet by traditional or conventional items would reach the market first. Weiss agreed with Aguilera, stating additionally that con- sumer benefit, not the potential to decrease company costs, company cost-cutting, “should be the main driver” of nanotechnology. This last comment prompted an unidentified audience member to state that a good business strategy should be able to balance consumer demand with com- pany cost-cutting efforts. Another unidentified audience member then asked Kampers about the time frame of commercialization for a specific application that Kampers described: the early detection of volatiles. Specifically, when will this technology be available for refrigerators and packaging? Kampers said that technologies are already available for the detection of volatiles in air and that nanotechnology is simply increasing the specificity and sensitivity of this type of detection. He predicts that these improvements will probably be achieved within the next five years. Corporate Intent and Regulatory Uncertainty An unidentified workshop attendee remarked that there has been “pull back” in industry because of high early expectations for nanotechnology that remain unmet. The questioner then asked, what is the current level of corporate investment and intention to bring these various applications to market, and how does regulatory uncertainty affect that? Weiss responded first by saying that the investment and intention still exist but that much of what happens in the food industry happens “behind closed doors.” There are a lot of intellectual property rights riding on many of these developments. Also, as with any emerging technology, these types of applications take many years of development before products are ready to enter the market. Moreover, also like any new technology, nanotechnology solves existing problems in many cases, but it also creates new challenges and requires optimizing. Kampers agreed with Weiss and added that regulation is definitely an issue since industry views regulation as something that limits the pos- sibilities. On the other hand, regulation is critical to building trust with consumers and ensuring that the public accepts the technology. With

OCR for page 21
51 APPLICATION OF NANOTECHNOLOGY TO FOOD PRODUCTS good regulation in place, consumers recognize the presence of an objec- tive body that is maintaining some sort of control over applications of the new technology. Without good regulation, consumers must rely on the industry itself. He said that this lack of regulation and absence of an ob- jective body responsible for maintaining control “might be the key ele- ment that is missing in the current situation.” Definition and History of Nanotechnology: More Questions About Regulatory Uncertainty Food Forum member Ned Groth commented on Aguilera’s discus- sion of the definition of nanotechnology. He said that food has been en- gineered for a long time in ways “involving molecules” and that the main difference between what has been done in the past and what is now being done with nanotechnology seems to be that the latter involves doing things on a “smaller scale.” Nanotechnology allows us to combine the natural components of foods in more useful ways than has been done in the past, but it is still part of a continuum of the engineering of compo- nents. In contrast, genetically modified foods created through recombi- nant DNA technology represented a sharp line between the “old, traditional science” and modern biotechnology. While societies have been cross-breeding and genetically improving animals and plants for a long time, genetically modified organism (GMO) technology enabled the introduction of genetic combinations, like salmon and tomato DNA, that do not naturally exist. Groth asked, “Can you draw such a line [with nanotechnology in food]? Is there a way to separate what would be a novel introduction of technology at a nano-level?” In particular, is there a way to delineate at what point the use of nanotechnology “might raise some concerns and therefore be subject to more intense regulatory over- sight” compared to the current standard for products derived from tradi- tional food science? Kampers replied that the definition of nanotechnology (in food) is “very, very difficult,” and yet a definition is necessary for regulation. Regulation, in turn, is necessary to control risks. Kampers identified persistent, non-dissolvable, non-biodegradable nanoparticles as the predominant source of food nanotechnology risks. He emphasized that most nanotechnology does not involve nanoparticles and that most nanoparticles are naturally existing, not synthetic, materials.

OCR for page 21
52 NANOTECHNOLOGY IN FOOD PRODUCTS Aguilera reiterated some of the comments he had made during his presentation. He mentioned that he did not recall ever having read anything explaining to consumers that the food industry has been operating within the nano-range for a long time and that it would be interesting for consumers to realize this. He referred to the examples he described during his presentation (e.g., dairy technology revolves around the use of milk proteins, fat globules and casein micelles, all of which can be measured in nanometers). However, until recently, the food industry hasn’t actually targeted objects at the nano-scale when working with food structure since it was widely believed that most functionalities and properties of food were determined by objects within the 1–100 µm range (i.e., the micrometer, not nanometer range). Now, food scientists are realizing that the assembly of these smaller objects is important and that there is still a lot of work to be done with respect to understanding how even naturally existing nano-sized objects in conventional foods give foods their properties. Later during the discussion, there was another, related question about what the questioner said was a lack of clear distinction between nano and micro, especially in food, and whether and how the “infiltration” of “nano” can be detected. The questioner commented that manipulation at the micro scale is generally accepted (and implied that manipulation at the nano scale is not generally accepted). Kampers responded by saying that he, for one, is “not very particular” about the distinction since the goal is to create new functionality; whether that new functionality is created by manipulating below 100 nm (at the nano level) or above 100 nm (at the micro level) is not the issue. Palatability The discussion shifted back toward issues about the technology itself. Van Hubbard from the NIH commented that one of the reasons he and his group 20 were interested in this workshop was to gain a better understanding of how nanotechnology can be used to improve health. He mentioned that one of the issues addressed during the morning session, nutrient delivery, touched on this theme. One of the issues with nutrient delivery, in turn, is palatability. He asked the panel to comment on the 20 Hubbard is the Director of the NIH Division of Nutrition Research Coordination, which is housed within the National Institute of Diabetes and Digestive and Kidney Dis- eases, or NIDDK.

OCR for page 21
53 APPLICATION OF NANOTECHNOLOGY TO FOOD PRODUCTS use of nanotechnology to address the issue of palatability. Specifically, how can nanotechnology be used to introduce critical nutrients into the food supply in such a way that those ingredients are bioavailable and the foods still palatable? Weiss agreed that palatability is a major issue with nutrients. When nutrients are added to foods, the flavor or textural attributes of the food are often compromised. Weiss referred to the antimicrobial examples he gave during his presentation (i.e., adding antimicrobial components to various types of nanomaterials), commenting that adding antimicrobials to foods creates the same palatability problem. “While it’s a wonderful compound,” he said, “you can’t apply them in a product without the con- sumer rejecting them.” He said that efforts to engineer products with functionalities that change the way the products interact with the taste receptors on the tongue, for example, would have an impact on palat- ability. Kampers agreed with Weiss, stating that one of the new functional- ities that nanotechnology can deliver is the capacity to control where in the human body an encapsulate will fall apart and release its nutrient or other contents. In cases where the nutrient contents of the encapsulate do not taste good, the encapsulate could be engineered not to break apart until it reached the small intestine, for example, where it would have the greatest effect anyway. As a second example, Kampers mentioned that Nestlé has developed an encapsulated product filled with both vitamin A and iron and engineered so that both ingredients don’t become available until they reach the wall of the gastrointestinal (GI) tract, where their combined availability is necessary for absorption. He referred to studies in Morocco that have shown how the addition of nanoencapsulated iron to salt can reduce iron deficiency in children. Aguilera added that the issue of palatability is a difficult one, since it involves human biology of the brain as well as mouth, but that there have been reports linking the structure and shape of small particles to tongue sensation. He reiterated that correlating people’s responses to food manipulations at the nanoscale is a new area of study which scientists have been investigating for only the last 8–10 years. Is Small Always Better? Food Forum member Eric Decker of the University of Massachu- setts, Amherst, commented on the very exciting applications discussed

OCR for page 21
54 NANOTECHNOLOGY IN FOOD PRODUCTS throughout the morning. “I didn’t hear the other side of it. Are there some limitations?” he asked. “Is smaller always going to be better?” In particular, by manipulating at this very small scale, one dramatically in- creases bioavailability—is that a risk? Is there a risk to stability? Where is nanotechnology not going to work? Kampers agreed that, yes, there are risks, not just with the nanoparti- cles themselves but with other components of the system for which nanotechnology serves simply as “the deliverer.” Consider bioavailabil- ity. What if a consumer eats two or three different products, each with very high bioavailability of a given nutrient? What are the consequences of that? Those consequences would not directly be related to the nanotechnology, but nanotechnology makes them possible and therefore they are risks we must consider. Weiss agreed that Decker raised a very important point. He said, “I do not agree with the statement ‘small is always better’; definitely not.” He said that sometimes nanotechnology will improve food products, but other times it will not, and “we need to critically evaluate in which cases we gain clear benefits and derive clear new functionalities that are good. If we don’t see those benefits, we are much better off staying with the systems we have, which are microstructured systems where we have a lot of experience.” He urged everybody involved with food structure devel- opment to critically examine their structures and identify where and how those structures would be useful, recognizing that not all nanostructures will be “good.” Related to the issue of risk, Doyle asked whether the antimicrobial applications that Weiss and his colleagues were studying would impact the gut microflora once inside the human body. “What’s that going to do to the gut flora when you consume a long-lasting antimicrobial compo- nent?” Doyle asked. Weiss responded, “There is absolutely the possi- bility that you can impact the microflora.” Fortunately, he said, target specificity can be built into these systems, and that will likely be an area of active future research.