Nanoencapsulated Additives in Food ProductsMary SmithAbstractBy utilizing the self-assembly mechanisms of many nanomaterials, and applying them to nanoencapsulation it is possible to create super foods. These super foods will be able to alter texture, nutritional content, shelf life and many other aspects of food without comprising the taste. Nanoencapsulation is achieved using many different methods such as coacervation, spray drying, electrospinning, and supercritical fluid. The appropriate method depends on the properties of the encapsulated compound such as solubility, and thermal sensitivity. Nanoencapsules need to be reduced in size, as well as have more uniform size. The applications are also not currently wide spread due to the capsules only applying to Prior to the commercialization of nanofoods the long term effect of nanomaterials in the human body, and the environment must be studied. It is also necessary to establish regulatory bodies and develop an appropriate way to label foods containing nanomaterials. IntroductionIn this paper the term nanomaterials will refer to materials that are on the nanoscale (10-9 meters, or one billionth of a meter). Nanomaterials are desirable because of the differences in properties between the nanoscale and their bulk components. As the size of the particles gets reduced to nanoscale range, there is an immense increase in the surface to volume ratio which increases reactivity and changes the mechanical, electrical, and optical properties of the particles. [3] In the food industry alone nanotechnology can be used for biosensors, bio packaging, smart foods, and nanoencapsulation. This paper will discuss a few of the ways in which nanomaterials are synthesized, how nanocapsules are formed, and the potential issues associated with nanomaterials in foods.Many major food companies have products on the market containing nanomaterials, or are funding research related to nanomaterials. Nestle, and Unilver are reported to be developing a nanoemulsion based ice cream that would have a lower fat content without sacrificing the creamy texture, [1] and Kraft is collaborating with universities to develop interactive foods. [2] Interactive foods are an example of smart foods utilizing nanoencapsulation in order to control the taste profile and nutritional content of a food. However, interactive foods are currently little more than science fiction. [3]Nanoencapsulation has the potential to create foods that cater to an individuals tastes and nutritional needs. Many foods either have good nutritional content or a pleasing flavor. Nanoencapsulation has the potential to combine the two. For example omega3 fatty acids are good for the heart, but they are found in fish oil and often leave a fishy taste or smell. Nanocapsules would be able to deliver the beneficial nutrients to stomach without releasing an unpleasant taste or odor. SynthesisOne of the most important aspects of nanomaterials is how they are grown. Neethirajan, Sanguransri, and Sozer, all agree that nanomaterials unique properties arise from their large surface area to volume ratio. Nanomaterials in general are created using either a top-down or a bottom-up method. Top down is where a physical process is used to take a bulk material and make it much smaller. Bottom-up is where the nanomaterials are grown often using self-assembly methods. Most commercially available nanomaterials are produced using top-down methods, but the prevalence of self-assembly methods are expected to grow. [4] The importance of the growth method is that controlling the size and uniformity of the nanomaterials is essential for better control of functionality and product quality. [4] Dry MillingDry milling is the most common method of synthesis for the food industry. [4] Dry milling is a top-down processes in which a material is ground into a very fine powder. This process can be used to produce wheat flour that has a high water binding capacity. [5] This same process has been used to create a green tea powder that has increased antioxidant activity. [6] The potential of nanomaterials is demonstrated in the green tea example. Relative to normal green tea there is a 100 fold increase in activity using the nano-green tea. [4]Self-AssemblyDespite the fact that top-down methods are the current fore runner, self-assembly methods have the most potential. Precise control of the environment (temperature, pressure, concentration, pH, ionic strength etc.) causes a large variety of ordered structures to be possible. [4] Not only are more structures possible, but being able to control the resulting structure by controlling the environment could lead to the development of nanomaterials more suited to food industry applications. Polyelectrolyte capsules are used to encapsulate nanoparticles such as neutraceuticals and are an example of self-assembly growth. The capsules are produced using layer-by-layer absorption of polyelectrolyte onto oppositely charged particles or onto a layer or polyelectrolyte particles. [4]There are many other ways to synthesize nanomaterials; however every method has its drawbacks. For example nanoemulsions are also commonly used, but not only does the environment need to be precisely controlled, but the emulsions have to be stabilized using electrostatic stabilization, steric stabilization or static stabilization by solid particles at the interface or by increasing the viscosity of the emulsion. All synthesis methods have their pros and cons. Top-down methods are simpler, but do not have the same potential of the harder to produce self-assembled nanomaterials. Table (1) goes into detail about other modes of synthesis.

Table 1, Structured materials for food and related industries. [4]Nanoencapsulation MethodsNanoencapsulation is the process of encapsulating a bioactive compound within another material in order to make the compound easier to handle, more stable, protect the material from oxidation, improve retention of volatile ingredients, mask undesirable flavors, control the release of the material, and/or improve the bioavailability and efficacy. [3] In food flavor masking, odor masking, controlled release of materials, and an extended shelf life are the most beneficial. The best materials for nanocapsules are biocompatible, biodegradeable, and the material must be able to be modified to satisfy the needs of the capsule. [7] Some of the most common methods to create nanocapsules are discussed below. It is also possible to note that most of the research into nanoencapsulation has been for the pharmaceutical industry, but parallels may be drawn for food. [4] Table 2 lists some common methods of nanoencapsulation.CoacervationCoacervation is a method of encapsulation that utilizes electrostatic forces between oppositely charged molecules. The charge can be induced in a bioactive compound and an oppositely charged polymer. If multiple polymers are used it is referred to as complex coacervation, where as if only one polymer is used its a simple coacervation. [8] The performance of the capsule is dependent on both the chemical and physical properties. For example the higher the opposing charges the better the encapsulation. pH, ionic strength, concentration, and other properties also affect the nature of the complex formed. [8] This method has been used to encapsulate capsaicin (the chemical that makes food spicy) inside of gelatin (the base for jello). [8] Many people are not fond of spicy foods, but by encapsulating it in gelatin consumers are able to gain the health benefits of the chemical without the pain. The benefits of this method are that it is fairly easy to implement, and it has been applied to both non-polar and polar bioactives. [7] The major issue for this method arises with commercialization. Often this encapsulation is achieved using glutaraldehyde, which is a regulated substance and most be handled according to the countrys legislation. [8]

Table 2- Common methods for nanoencapsulation [7]

Spray DryingIn the spray drying technique the core material of the nanocapsule is dissolved into a liquid, and then turned into droplets where it is quickly dried. The droplets can be formed using several methods such as a rotating spray jet, or a vibrating mesh. [7] Both methods create very uniform spherical particles which ensure that the core is completely protected. However, at this time the normal size of these nanocapsules is in the range of 300 nm to 1200 nm. [7, 8] It is also important to note that this method has some limitations for volatile or thermo-sensitive bioactives. [7] Despite the large size this method has many positives. Its relatively inexpensive and its been proven to be reproducible. [7] To date this method has been used to encapsulate flavors, vitamins, minerals, colors, fats and oils in order to protect them from their surroundings, environment and extend their shelf life and stability during storage. [9]ElectrospinningElectrospinning, like coacervation, utilizes the electrostatic forces between molecules. In electorspinning a high voltage source generates a charge in a polymer solution. The solution is then extruded into a wire (Figure 1b-d) and a grounded collector collects the nanoparticles (Figure 1a). [7] This method can also be used to create nanotubes. An important application of this method is in the production of the biopolymer zein (maize protein). [10] Zein nanoparticles can be used as edible carriers for flavor compounds or for the encapsulation of nutraceuticals such as beta-carotene. [3, 11] Nutraceuticals are foods or food ingredients that contain health benefits. This technique is also commonly used in encapsulating supplements like epigallocatechin-3-gallate. Epigallocatechin-3-gallate is a compound found in tea that has high potential for health benefits, but is greatly reduced in boiling. [7] The potential for this method lies in its high encapsulation efficiency and the possibility of production in one step. [12, 13] Supercritical Fluid (SCF)A supercritical fluid is a gas or liquid that is above the fluids critical heating and pressure point. These fluids exhibit properties between those of liquid and gasses. To create a nanocapsule using this method the bioactive compound and the polymer shell are solubilized and then the solution is expanded in a nozzle. [8] The expansion is similar to the spray drying process and the spray will eventually precipitate. [14] The main benefit of this method is that thermally sensitive compounds can be encapsulated using this method, [8] and the size of the nanocapsules are reported to range from 163 nm to 219 nm, [15] which is significantly better than the spray drying technique. However, this method does require the use of organic solvents [7], and has a very high initial cost due to the high pressures under which the capsules are formed. [8] Overall the method of encapsulation is highly dependent on the bioactive compound used in the core. The core must be protected from its surroundings and environment as well as being able to activate when needed. Shefer described an invention where one day food will be able to be personalized by the activation of different flavors, nutrients, and active ingredients due to nanoencapsulation of different bioactive compounds. [16] A lot must happen in order for this prediction to come true, but by continuing to improve the production of nanocapsules, both by size, and efficiency personalized foods are not too lofty of a goal.

Fig. 1. Schematic representation of typical elctrospinning system. [7]Potential Issues/DiscussionAs with all things there are potential concerns with regards to nanomaterials, especially in the food industry. In fact the nature of nanomaterial properties being different from their bulk counterparts is a direct cause of one risk. It is possible that nanomaterials are toxic even if they are harmless in a bulk state. [17] The main concern is that once in the body the nanoparticles may cross biological barriers to reach those parts of the body which are otherwise protected from larger materials. [18] Another potential issue is that in some instances an improved bioavailability of vitamins and minerals may not always be beneficial for the consumer. [18] The last major concern for the nanomaterials themselves arise from the potential use of insoluble, indigestible, and biopersistent nano-additives. These additives have uses that are beneficial, such as silver particles used as an antimicrobial, but also by nature could cause some issues in the body. [18] Table 2 lists some current and projected nanofood applications and their risks. The general lack of knowledge and understanding of nanomaterials is an issue as well. Despite the fact that some nanofoods have already made it to the commercial market, such as iron in nutritional drinks, micelles that carry vitamins, and zinc oxide in breakfast cereals, [11] there are insufficient regulations that exist specifically to control, or limit the use of nanomaterials in food. [3, 11, 19] It is also necessary to inform the general populace. Similar to genetically modified food, most consumers cannot judge the benefits and risks of nanofood. [11] It is also difficult to appropriately label nanofoods for packaging purposes. [11] Sanguansri, and Sozer, both believe that creating awareness of nanofoods is essential to furthering the development of nanofoods. [4,11] To overcome these issues several steps will need to be taken. Firstly, research needs to be done into all aspects of nanomaterials. However a strong emphasis should be placed on the toxicity, and the long term effects on both humans and the environment. From this research regulatory bodies need to develop standards to protect the consumer and provide a consistent quality product. [3] The general public will need to be educated, and develop standards for labeling nanofoods. Once these issues are bridged there will be less to inhibit the continued growth of nanofoods.

Table 2-List of current and projected nanotechnology applications in the food sector-excerpt [18]ConclusionNanomaterials can be created using many methods. The nanomaterials can be synthesized using either top-down or bottom-up methods. The self-assembly properties of some materials should be utilized to create nanomaterials with desired properties. To create the nanocapsules the chosen method should take into account the needs of the bioactive core, and the purpose of the capsule. For example, a core that is sensitive to temperatures should not be encapsulated using a spray drying technique. It should be encapsulated using a super critical fluid technique. All encapsulation techniques have their benefits and their negatives, and all methods require highly regulated environments to ensure the uniform production of the capsules. Prior to commercialization more research into nanofoods must be completed. Despite not being toxic when in a bulk state there is concern that some materials may become toxic when reduced to the nanoscale. There are also concerns about nanomaterials being small enough to get into normally blocked off parts of the body where they will then cause issues. There are also no regulations that exist specifically for the use, and labeling of nanomaterials in foods. Regulating bodies need to be established to set clear rules for the use of nanofoods. The other major hurdle to be overcome is public perception. With the current trend of organic health foods it is possible that people will not accept nanofoods. This is especially true for the foods that contain nonorganic and nonfood grade materials despite their potential benefits such as using silver as an antimicrobial. The public will need to be educated in order for nanofoods to be a continually growing industry.The potential for nanomaterials in food products are staggering. Smart foods that can be personalized by the consumers taste and nutritional needs are not as crazy as they once sounded. Nanoencapsulation is a step in the right direction. Already companies are utilizing this technology to cover up the unpleasant taste of fish oils, and research is being done into ways to extend the shelf life of foods. The focus for further research should be both on the long term effect of nanomaterials on the body, and continuing to decrease the size of the capsules. Nanoencapsulation is the future of the food industry.

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