METHOD FOR ENCAPSUITING FLAVORS AND FRAGRANCES BY TRANSPORT OF CONTROLLED WATER IN MICROCAPSULESFIELD OF THE INVENTION This invention relates to a method for encapsulating flavors and fragrances in microcapsules having a hydrogel coating and an oil core.
BACKGROUND OF THE INVENTION Microcapsules that incorporate a compound with flavors or fragrances are useful to provide controlled release of the contained flavor or fragrance. Such products can be used in the food processing industry, where the encapsulated flavor particles can provide an explosion of flavor after chewing the food. Such products can also be used in the cosmetics and toiletries industries, where the encapsulated fragrance particles can provide an odor explosion after fracture of the capsule. The capsule may comprise a coating surrounding a core material in which the compound is contained with flavor or fragrance. The microcapsules can be formed by a process of coacervation or cross-linking, in which the lipids are coated by small drops of proteins, carbohydrates or synthetic polymers suspended in water. The coacervation process is, however, difficult to control and depends on variables such as temperature, pH, agitation of the materials, and the inherent variability introduced by a protein or natural carbohydrate. In the manufacture of microcapsules containing a compound with flavor or fragrance, several characteristics are desirable. It is desirable to produce microcapsules that have strong walls and do not agglomerate. It is desirable that the compound be easily charged into an oily microparticle, that is, that it be readily absorbed into the oily core of the microcapsule. Once absorbed, it is also desirable that the compound be irreversibly retained in the oily core of the microcapsule, i.e., that it be absorbed into the microcapsule. The amount of compound that can be encapsulated depends on several factors, including its water solubility, partition coefficient, molecular weight, water content, volatility and the ratio of empty capsule to water amounts. The flavors and fragrances can be mixtures of hundreds of components, each of which can vary widely in those properties. A flavored and fragranced compound that is lipophilic can easily be contained in an oily core of a microcapsule, while a flavored and fragranced compound that is hydrophilic can be less easily contained in an oily core. For example, the flavored compound, diacetyl (DA) is from about 20% to about 30% soluble in water. For diacetyl the typical maximum absorption in an oil is only up to 55%. A highly water soluble compound such as diacetyl is also more difficult to retain in the oil core once charged. The solubility of a compound in an aqueous phase versus an oil phase is determined by its partition coefficient, abbreviated as K. The partition coefficient of a compound is the ratio of the concentration of the compound in a liquid phase to the concentration of the compound in another liquid phase. The partition coefficient in this way is an inherent property of the compound with two given liquid phases, such as a liquid phase and an aqueous phase, and reflects the distribution of the compound at equilibrium between the aqueous phase and the lipid phase. Any means that decreases the water solubility of a compound will deviate the equilibrium of the compound and in this way, will deviate the distribution between an aqueous phase and a lipid phase. For example, the addition of a salt will decrease the solubility in water of a compound and increase its distribution to the lipid phase. Similarly, the cross-linking of a protein membrane to strengthen the membrane and physically decrease the amount of water or remove water from the environment, will cause the wall of the capsule or membrane to contract, decreasing the solubility in water of a compound and increasing its distribution to the oil phase. Flavors or fragrances that are soluble in water can interfere with the encapsulation of an oily particle. For example, compounds with flavor or fragrance that are soluble in water can not be encapsulated using gelatin coacervation. This is because for coacervation to occur there must be a drop to be coated, and for those water-soluble materials there are no drops to be coated. In addition, the water soluble flavor or fragrance can be partitioned so that the flavored or fragranced compound is located in an aqueous environment outside the encapsulated oil particle, rather than within the oil particle. If a flavored or fragrant compound is too soluble in water, the coacervation process stops working, because the colloid becomes too thick or too thin. A colloid that is too thick does not flow, and thus can not properly coat the oily surface. A colloid that is too thin is not retained on the oily surface. At the end, a water-soluble flavor or fragrance compound can fully solubilize the colloid, leaving the material without a wall to deposit on the oil surface. In addition to water solubility, a flavored or fragranced compound containing fatty acids affects the pH of a coacervation reaction. If a base is added in an attempt to adjust the pH, the fatty salts produced in the reaction impart an undesirable soap flavor. If a flavored or fragranced compound contains water soluble esters, the coacervation temperature is affected and consequently the final gelation temperature is altered. Although it is desirable, therefore, to limit the compounds containing fatty acids or water-soluble esters, there is a relationship in the potency and the resulting profile of the encapsulated compound. This limits the range of formulations that can be encapsulated effectively. Currently, compounds with flavor or fragrance, which are difficult to encapsulate, are diluted with oil such as vegetable oil or mineral oil. This alters its coefficient of distribution of oil to water, in which the compound tries to reach a balance between the oil and water phases. The oil serves to reduce the natural solubility in water of most compounds, and as in many cases, it is reduced below the level at which it interferes with coacervation. A compound with flavor or fragrance that is highly soluble in water, however, does not have this effect. A compound having a solubility in water greater than 25% prefers partition in an aqueous phase, and a ratio of lipids: water greater than 90% is needed to encapsulate those compounds. The coacervation process, however, is generally limited to approximately 22% lipid. Thus, this technique is only of limited application for compounds with flavored or water soluble fragrances. Various methods are known in the art for absorbing compounds in a microcapsule, such as trapping cyclodextrin or electrocoating with silica. The disadvantage of the cyclodixtrin trapping technique is that the binding effect varies widely depending on the compound with particular flavor or fragrance. A disadvantage of the technique of electrocoating with silica is that there is no barrier that protects the compound with flavor or fragrance from evaporation. Thus, there is a need for an efficient method to absorb the many types of compounds with flavor and fragrance at the desired level of charge in an encapsulated oil. There is also a need for an efficient method to absorb compounds with flavor and fragrance once they have been encapsulated.
BRIEF DESCRIPTION OF THE INVENTION This invention relates to a method for encapsulating a flavored or fragranced compound by controlled transport of water of the compound to a capsule having an oil core. The method comprises preparing a microcapsule having a hydrogel coating and an oil core, and then adding a flavor or amphiphilic fragrance compound in the presence of water to the microcapsule to transport the compound through the hydrogel coating and into the oil core. The compound is transported to the core by aqueous diffusion through the hydrogel coating. The oil core is retained in the hydrogel coating during aqueous diffusion. A flavored or fragranced compound is thus encapsulated in the hydrogel coating containing the retained oily core. The coating may consist of a carbohydrate or a protein, which may be crosslinked or non-crosslinked, or a synthetic polymer, such as polyvinylpyrrolidone or methylcellulose. The oily core may comprise, for example, vegetable oil, mineral oil, benzyl alcohol or mixtures thereof. In a preferred embodiment, the oil is a short chain triglyceride of distilled coconut oil. As defined more particularly hereinafter, "oil" means that it includes a wide range of substances that are dispersible in water, due to their hydrophobic nature. In an alternative embodiment of the invention, the microcapsule can be prepared in dry form. A flavor or fragrance amphiphilic compound is added, in the presence of a controlled volume of water, to a substantially dry microcapsule having a hydrogel coating surrounding an oil core. The compound is transported through the hydrogel coating by aqueous diffusion to the oil core and is retained in the core. The microcapsule having the flavor or fragrance compound retained in the oil core is then dried. In a preferred form of the invention, a fragrance-flavored compound is encapsulated by preparing a microcapsule of a coacervate of an oil core and a hydrogel coating, adding the flavored or fragranced compound in the presence of water to the microcapsule for transport of the compound to the oil core, transport the compound through the hydrogel coating by aqueous diffusion, and retain the oil core in the hydrogel coating during transport to provide the encapsulated flavor or fragrance and the oil core retained in the hydrogel coating. The invention is also directed to the products produced by the methods of the invention. An advantage of the invention is that the microcapsule can contain a concentration of flavor or fragrance that has not been feasible until now. A second advantage is that the walls of the empty microcapsules have a substantially uniform thickness, strength, and elasticity. Another advantage is the higher yield of the encapsulated flavor or fragrance, since essentially no compound with flavor or fragrance is lost to the environment. Yet another advantage, is the economics of manufacturing the flavored or fragranced compounds of the invention, since the same technology is used for all flavors and fragrances. The objects and other advantages of this invention will be further understood with reference to the following detailed description and examples.
DETAILED DESCRIPTION In a preferred practice of the invention, microcapsules are formed which contain a compound with desired flavor or fragrance by a coacervation process. In coacervation there is separation of a colloid in a phase rich in colloid (the coacervate) and an aqueous solution of the coacervating agent (the equilibrium liquid), forming an oil coated with protein, carbohydrate or polymer drops to suspend the oil in the coacervation. Water. In the process, two lipid phases and an aqueous phase in a lipid phase and an aqueous phase are finally absorbed. The first lipid phase forms the core of the microcapsule. The nucleus is surrounded by a hydrogel capsule, defined here as a colloid in which the dispersed phase (colloid) has been combined with the continuous phase (water) to produce a viscous product similar to a jelly. The nucleus consists of an oil, which is a term that is used here to define a wide range of substances that are very different in their chemical nature. The oils can be classified by any type and function and include mineral oils (petroleum or petroleum products), vegetable oils (mainly seeds and nuts), animal oils (which are usually found as fats); liquid types include fish oils), essential oils (volatile liquids derived from flowers, stems, leaves, and often the whole plant), and edible oils (mainly vegetable oils, as well as some special fish oils). The oils derived from living organisms are chemically identical to fats, the only difference being that of the consistency at room temperature. In one embodiment, the oil may be mineral oil, vegetable oil or benzyl alcohol. In a preferred embodiment, the oil is a short chain triglyceride of distilled coconut oil, available under the trade names of Migylol "(Huís Corp., Piscataway, NJ) or Captex® (Abitec Corp., Janesville, Wl). Hydrogel coating can be a carbohydrate, protein or a synthetic polymer, such as polyvinylpyrrolidone or methylcellulose In a preferred embodiment, the oil is Migylol® or Carpex® and the coating is gelatin.The second lipid phase is the flavored compound or desired fragrance, which to some degree is soluble in water and soluble in lipid, ie, which is amphiphilic, which is the term used here to define its dual solubility properties.The aqueous phase is used to transport, by means of the equilibrium of the partition coefficient, the compound with flavor or fragrance slightly soluble in water towards the oily core of the microcapsule by aqueous diffusion.The balance dynamics continues until the three phases(two lipid and one aqueous) are absorbed in two phases(one lipid and one watery). For some water-soluble compounds, less water is required for absorption or distribution in the oil phase. On the other hand, for some highly lipid-soluble compounds, more water may be required for the distribution to the oil phase. In this way, by temporarily varying the amount of water that is available to a compound, taking into account the partition coefficient of the compound, a compound can be absorbed through the coating of the hydrogel into an oil. The adsorption of the compound in the oil can be controlled. Dehydration of the microcapsule or crosslinking of the capsule coating encloses the flavor or fragrance compound within the microcapsule. In dehydration, a substantial volume of the water is removed from the capsule, thereby reducing the loss of the partially flavored or fragranced compound in water from the oil core to an aqueous environment. Alternatively, the crosslinking of the hydrogel coating of the coacervate returns the encapsulated thermoset oil, since a capsule containing crosslinks is a stable structure. The use of known chemical crosslinking agents, such as formaldehyde or glutaraldehyde, to irreversibly crosslink the oil-containing capsule is known. Other crosslinking agents such as tannic acid (tannin) or potassium aluminum sulfate (alum) are also known. An optional hardening step of the capsule, as described in Patents No. 2,800,457 and 2,800,458, consists of adjusting a suspension of capsular material of pH 9 to 11, cooling from 0 C to 5 C, and adding formaldehyde. Formaldehyde and glutaraldehyde are also effective chemical crosslinking agents. For the food industry and the cosmetics / toiletries industries, suitable crosslinking agents can be selected depending on the specific application. Certain enzymes found in nature are also good crosslinking agents. Cross-linking using enzymes, such as transglutaminase, is described in copending application Serial No. 08 / 791,953 entitled Enzymatic Encapsulation of Oil Particles with Protein by Complex Coacevation. Enzymes work by catalyzing the formation of bonds between certain amino acid side chains in proteins. In addition, because the enzymes are found in nature, encapsulated oils that are enzymatically crosslinked do not suffer from the inherent problems with crosslinking with formaldehyde and glutaraldehyde, and consequently, can be ingested or applied without concern of toxicity of the crosslinking agent. Because cross-linking is an enzymatically catalyzed reaction, however, appropriate environmental conditions must exist for optimal enzymatic activity. For compounds with high water solubility, defined herein as at least about 20% water soluble, it is preferable to concentrate the microcapsule to 55% solids or start with the dried microcapsules and gravimetrically add water and mix to obtain the desired results. For compounds with low water solubility, defined herein as less than about 20% soluble in water, a hydrated microcapsule preparation can be used.
EXAMPLE 1 Empty capsules that are hydrated are prepared by preheating deionized water at 50 ° C ± 2 ° C. A gum solution is prepared by vigorously stirring preheated deionized water (87.2018 g), carboxymethyl cellulose, sodium salt (1.8447 g), and FCC powder of gum arabic SP Dri (0.1845 g). The solution is mixed until the solids are completely dissolved, then the solution is cooled from about 35 ° C to about 40 ° C. Prepare a gelatin solution by vigorously stirring preheated deionized water (163.0453 g) and gelatin type A 250 Bloom (18.4461 g) in a pre-emulsion tank until the gelatin dissolves completely, then the solution is cooled from about 35 ° C to about 40 ° C. Without stirring, the gum solution is added to the gelatin solution in the pre-emulsion tank and the foam is allowed to dissipate for about 15-20 minutes. The pH is adjusted to about 5.5 with a dilute solution of sodium hydroxide (50% w / w) or a diluted solution of citric acid (50% w / w). Vegetable oil (180.02 g of mixed triglycerides Captex "355 or Migylol®) is added with slow agitation, preventing the accumulation of the oil.The capsule size is adjusted from approximately 100 microns to approximately 400 microns and the size is verified microscopically. The solution is slowly cooled to approximately 1 ° C for 5 minutes until the solution reaches approximately 28 ° C. If the walls of the capsule are intact, as determined by the microscopic examination of the capsules, showing uniform protein deposition without free protein floating in the aqueous phase, the solution can be rapidly cooled down to about 10 ° C. If the walls of the capsule are thin, as determined by the microscopic examination of the capsules, showing non-uniform deposition of free protein and free protein floating from the aqueous phase, the solution is heated again from about 32 ° C to about The solution is mixed at about 5 ° C to about 10 ° C for 1 hour. The solution is then heated from about 15 ° C to about 20 ° C, fifty percent glutaraldehyde is added and allowed to mix for about 16 h. The stirring is then continued and the capsules are allowed to separate by flotation. About 48% to 50% (approximately 379 pounds to 395 pounds (172.1 kg to 179.3 kg)) of water is drained from the bottom of the tank into a separate container. If the capsules are present in the drained liquid, the draining stops and the stirring begins to resuspend the separated capsules in the solution. The separation step is then repeated. Once the separation is completed, stirring is started again to resuspend the capsules in the solution. Sodium benzoate (10% w / w) is added by mixing perfectly. If necessary, citric acid is added to adjust the pH to less than 4.0. The empty capsules, defined herein as encapsulated oil with no flavor or fragrance value, which are dry, were prepared by the following method. A siloid solution was prepared by mixing a powder of 244 grade 68 siloid silica compound (15.9497 g) with deionized water (143.5477 g) until the powder was completely dispersed and no lumps were present. The flavor was mechanically mixed until uniformly distributed, then the siloid solution was mixed with the flavor until it was completely dispersed without lumps, thinning after about 30 minutes of stirring. The product was concentrated by centrifugation to approximately 50% or more solids. The material was then dried in a vacuum oven dryer at about 80 ° C or in a fluid bed dryer at about 70 ° C. The dried crosslinked capsules (400 g) were placed in a stainless steel mixing tub (Hobart Lab Scale Mixer). The desired pure flavor (428.6 g) was mixed with deionized water (171.4 g) on a magnetic stirrer for 5 minutes. The dried capsules were mixed with water / flavor mixture in the Hobart Mixer at a power level of 1-2 for 5 minutes. The mixture was poured into a plastic storage container, using a rubber spatula to scrape the sides of the mixing tub, and the container was closed. The mixture was allowed to incubate for 24 hours for flavor absorption before the product was used.
EXAMPLE 2 Empty capsules that are hydrated are prepared by preheating deionized water at 50 ° C ± 2 ° C. A gum solution is prepared by vigorously stirring preheated deionized water (87.2018 g), carboxymethyl cellulose, sodium salt (1.8447 g), and FCC powder of gum arabic SP Dri (0.1845 g). The solution is mixed until the solids are completely dissolved, then the solution is cooled from about 35 ° C to about 40 ° C. A gelatin solution is prepared by vigorously stirring preheated deionized water (163.0453 g) and gelatin type A 250 Bloom (18.4461 g) in a pre-emulsion tank until the gelatin is completely dissolved, then the solution is cooled to about 35 ° C until about 40 ° C. Without stirring, the gum solution is added to the gelatin solution in the pre-emulsion tank and the foam is allowed to dissipate for about 15-20 minutes. The pH is adjusted to about 5.5 with a dilute solution of sodium hydroxide (50% w / w) or a diluted solution of citric acid (50% w / w). Vegetable oil (180.02 g of triglycerides mixed Captex® 355 or Migylol) is added with slow agitation, avoiding the accumulation of the oil. The size of the capsule is adjusted from approximately 100 microns to approximately 400 microns and the size is verified microscopically. The solution is slowly cooled to approximately 1 ° C for 5 minutes until the solution reaches approximately 28 ° C. If the walls of the capsule are intact, as determined by the microscopic examination of the capsules, showing uniform protein deposition without free protein floating in the aqueous phase, the solution can be rapidly cooled to approximately 10 ° C. If the walls of the capsule are thin, as determined by the microscopic examination of the capsules, showing non-uniform deposition of free protein and free protein floating from the aqueous phase, the solution is heated again from about 32 ° C to approximately 33 ° C. The solution is mixed at about 5 ° C to about 10 ° C for 16 hours, then stirring is continued and the capsules are allowed to separate by flotation. About 48% to 50% (approximately 379 pounds to 395 pounds (172.1 kg to 179.3 kg)) of water is drained from the bottom of the tank into a separate container. If the capsules are present in the drained liquid, the draining stops and the stirring begins to resuspend the separated capsules in the solution. The separation step is then repeated. Once the separation is complete, stirring is started again to resuspend the capsules in the solution. Sodium benzoate (10% w / w) is added by mixing perfectly. If necessary, citric acid is added to adjust the pH to less than 4.0. The capsules are stored at about 5 ° C to about 10 ° C. The non-crosslinked hydrated beads (815.20 g) were added to a glass reactor at about 5 ° C to about 10 ° C. Stirring was started at about 95-100 rpm, while maintaining the temperature from about 5 ° C to about 10 ° C. The pure flavor or fragrance (181.8 g) was added to the glass reactor. The mixture was stirred for about 2 hours at about 5 ° C to about 10 ° C to allow the flavor or fragrance to be absorbed into the capsules. Fifty percent glutaraldehyde (3.0 g) was then added and allowed to mix at about 15 ° C to about 20 ° C for 16 hours. Sodium benzoate (10.25 g of a 10% solution) was added to the reactor. Citric acid (20%) was added to adjust the pH of the solution to 3.9. The capsules were stabilized by adding a mixture of well-mixed xanthan / propylene glycol gum (1 part xanthan to 2 parts propylene glycol). The mixture was stirred for approximately 30 minutes until the capsules were stabilized. Once the capsules are stabilized, they are ready for use.
EXAMPLE 3 Sodium alginate (8.22 g, type FD) was dissolved155, Grinsted Corp.) in deionized water (300 g). The solution was stirred until homogeneous. Microcapsules (3.75 g) were added with stirring until a homogeneous phase formed. Then Migylol (99.9 g) was added with vigorous stirring to form an oil-in-water emulsion. The emulsion was fed through a vibrating needle (with an inner diameter of 1.22 mm) which was placed about one inch above the lowest point of a vortex generated in a glass beaker by vigorous stirring of an aqueous solution of CaCl 2 at 4% w / w (150 ml). The flow velocity of the emulsion through the needle was adjusted to prevent the formation of a jet. The emulsion droplets, after introducing the CaCl2 solution, gelled immediately, producing particles with a diameter of approximately 80 μm. After the emulsion was added, the suspension of the beads was allowed to stand for about 30 minutes to allow migration of the calcium ions to the microcapsules. The microcapsules were dehydrated at room temperature either by centrifugation or by vacuum filtration, and subsequently dried by techniques known in the art, such as drying in a vacuum oven or fluid bed drying. The resulting microcapsules had a slight tendency to adhere together due to the presence of some surface oil. A fragrance or fragrance compound was obtained, encapsulated in dry, free-flowing alginate, by mixing the microcapsules (approximately 58%) and water (approximately 7%) with the compound with desired flavor or fragrance (approximately 35%). The optimum absorption time is between approximately one hour and 10 hours, depending on the partition coefficient of the compound with flavor or fragrance.
It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.