Encapsulation of active ingredients

Details Encapsulation of active ingredients Encapsulation of active ingredients

2000-06-29

2002-11-19

Spear, James M. (Department: 1615)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Tablets, lozenges, or pills

C424S439000, C424S484000, C424S485000, C424S488000, C424S489000, C514S773000, C514S777000, C514S778000, C514S782000, C514S783000, C514S951000

Reexamination Certificate

active

06482433

ABSTRACT:

This application claims priority to European Patent Application Serial No. 99112446.2 filed Jun. 30, 1999.
BACKGROUND
There exists a demand for encapsulating active ingredients, which are food, feed, beverage or pharmaceutical additives, especially vitamins and more specifically flavors. Among them, the need for dry versions of liquid flavors is important. Particularly, dry versions of liquid flavors are needed for flavoring dry food and beverage products such as, for example, tea, instant coffee, instant soups and desserts, dry beverage powders, effervescent tablets and pharmaceutical products.
Several techniques have been developed for producing dry flavors. Among them, the techniques of plating on a carrier and spray drying are most widely used. These methods are simple and cost saving. However, both techniques have the serious disadvantage of providing no protection or only limited protection of the flavor against heat, moisture, and oxidation. Hence the appropriate encapsulated flavors have poor shelf life stability. Therefore, these methods are not suitable for use in combination with flavors sensitive to oxidation such as, for example, citrus flavors.
In this respect, one of the most successful approaches to produce dry flavors, and especially to improve the shelf life stability of dry flavors, is their encapsulation in a glassy sugar matrix. The preferred technology for producing glassy encapsulated flavors is extrusion. Products of extrusion technology are very stable against oxidation and show high retention of volatiles during storage. However, extruded flavors are considerably more expensive than spray dried flavors because of the relatively low flavor load and the need of using a multi-step and multi-component process consisting of at least a heating, an extruding, a washing (usually with isopropanol), a drying and a grinding step. Moreover, a solvent recovery step normally has to be included as well. Another drawback of encapsulation of flavors by the extrusion technique is that the flavor is subjected to high temperatures, which might induce decomposition of sensitive flavor constituents. Hence, there exists a need to keep the melt temperature as low as possible, but this limits the choice of carrier materials. Low molecular weight carbohydrates, in combination with plasticizers such as glycerin and water, are used to keep the melt temperature as low as possible. However, a high content of low molecular weight carbohydrates and glycerin increases the hygroscopicity of the resulting powder which, in turn, results in a non-free-flowing, sticky product with a high risk of lump formation. Increase of water content is also problematic because of the enhanced flavor losses at the exit of the extruder and/or subsequent drying step.
U.S. Pat. No. 3,971,852 describes microparticulate compositions with flavor oil encapsulated in a glassy matrix that consists of a mixture of a polysaccharide with emulsifying properties and low molecular weight polyhydroxy compounds such as sugars or sugar alcohols. Standard spray drying is used to produce spherical particles having a flavor oil content of up to 80% by volume and an extractable oil of not more than 5%. The stability of the resulting dry flavors is claimed to be better than spray dried flavors prepared according to prior art methods.
U.S. Pat. No. 3,314,803 describes a method for encapsulating volatile flavor compounds in a glassy mannitol matrix by spray drying.
U.S. Pat. No. 3,554,768 describes a method for fixing acetaldehyde in selected carbohydrates by drying an aqueous solution of acetaldehyde and selected carbohydrates.
One of the drawbacks of the above mentioned methods is the high hygroscopicity of the matrix materials. To achieve good stability these products require storage under exclusion of ambient moisture and air. Thus, antioxidants have to be added to prevent oxidation of the flavors fixed in the matrix.
U.S. Pat. No. 4,532,145 describes a spray drying method for encapsulating volatile flavor compounds in a spray dried, moisture-stable matrix consisting of 10-30% low molecular weight carbohydrate such as maltose and at least 70% high molecular weight materials such as maltodextrin. Spray drying is carried out at relatively low temperature, i.e. the inlet temperature ranging from 100-180° C. and the outlet temperature ranging between 50-80° C.
U.S. Pat. No. 5,124,162 describes a method to prepare a moisture and oxygen stable, antioxidant free, fixed flavor having a free flow bulk density of at least 0.5 g/ml and a void space of less than 20% of the spray dried solids, comprising a flavorant encapsulated in a carbohydrate matrix consisting of 22-45% of mono- and disaccharides wherein at least 50% of the mono- and disaccharides is maltose, from 25-50% maltodextrin and from 10-35% high molecular weight film forming carbohydrate. The encapsulated flavor is said to be stable against oxidation for one year at 70° F. The products are obtained at moderate inlet and outlet temperatures of 100-180° C. and 70-100°C., respectively.
In all above mentioned spray drying techniques the thermoplastic nature of glassy matrices pose significant processing problems, especially sticking of the thermoplastic particles to the wall of the dryer. Moreover, loss of volatile flavor compounds is still substantial and the resulting powders have relatively small particle size, resulting in dust formation during handling.
With a multi-stage spray drying method, detrimental effects of particle expansion are avoided by spraying at high air temperature to create particles having a semi-solid surface in the form of a quickly built skin, and subsequent continued drying at lower air temperature in a fluid bed or moving belt dryer. The positive effect of two-stage spray drying on aroma retention has been confirmed experimentally by W. J. Coumans, P. J. A. M. Kerkhof and S. Bruin, Drying Technol. 12 (1 and 2), 99-149 (1994). According to the described process it is not possible to produce particles having high shelf life stability, i.e. having oxygen stability and/or low or no active ingredient diffusing out.
French Patent 2,686,486 discloses a method for drying honey using a multistage spray dryer. The advantage of this drying process is said to be the minimum decomposition of sensitive ingredients like vitamins and flavor compounds due to the low temperature during drying. No attempts have been reported to encapsulate flavors.
PCT publication WO 91/1782 discloses a method for preparing microcapsules encapsulating flavorants by multi-stage spray drying. An emulsion, a suspension or a solution of flavorant and matrix material is sprayed into a spraying tower in a cloud of simultaneously introduced fine particles of starch at 50-120° C. The emulsion drops, having freshly solidified surfaces, were then transferred to a fluidized bed and maintained fluidized for several hours at 30° C. The particles were more dense and larger than prior art microcapsules, contributing to reduced exposure to oxygen. But a drawback of this process is the long drying time in the fluid bed dryer and the need for introducing a second carrier or coating. The long resting time in the fluidized bed is necessary because the already solidified surface of the particles derived from spray drying hinder the water content inside the particles to migrate out easily, especially to diffuse out of the central part of the particles, thereby also losing sensitive fragrant materials.
From the above description of the prior art it results that there exists a need for a process which overcomes most of the aforementioned disadvantages or which at least improves an already known process.
SUMMARY
The invention is directed to a method for encapsulating an active ingredient in a matrix to form a free flowing particle that is dust free during handling. In the method, a suspension or emulsion of the active ingredient, such as a flavor, fragrance, or vitamin, is prepared in an aqueous solution of matrix material. The particles formed are dried, for example in a fluid bed or moving belt dryer, at a

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