Patent DE-19750679-A1 (DE)
Title: Freeze dried microcapsules
Inventor: WINDHAB ERICH J
IPC: A23L27/00
Filed: 1997-11-15
Abstract: To produce microcapsules, emulsions or suspensions are delivered in the finest jet sprays into a cold chamber in a temp. of 10-15 deg C below the setting temp. of the outer fluid phase of the microcapsules and at a pref. temp. of  <= -50 deg C.  The droplets in the spray are cooled at a rapid rate such as \-1000  deg C/sec. and the water content, in one case, forms the solid phase to encapsulate the added content components.  The glass transition temp. of the matter of \- -15 deg C and pref. \- -5 deg C forms a glassy barrier layer to prevent the diffusion of water mols. and sintering between the frozen powder particles and also there can be no diffusion of the encapsulated particle contents.  The molten fats, in another case, are selected to form the continuous solid phase which are physiologically compatible and, during storage, contain less than 10% of molten fat matter. The spray is a stable fat and water emulsion, where the structure of the emulsion is unchanged in the sprayed droplets, so that the continuous water phase hardens in a glass structure round the droplets.  The fat phase contained in the water droplets has dissolved or undissolved suspended components with specific characteristics to prevent reduction of the glassing temp. or dispersion into the outer water phase. When using a double emulsion of water/fat/water, the dispersed fat droplets form a second dispersed water phase to form a skin for frozen and separated microcapsules.  During storage, the second water phase is in a liquid or part-frozen state.  The second water phase can contain an active ingredient. A starch syrup with low dextrose equivalents is used to raise the glassing temp., or other polysaccharides or their derivatives, proteins and/or dried milk materials free of lactose and/or a sweetener such as Aspartame (RTM). When for use in a sweet dessert, the powder particles are formed in a single water phase, or in further inner phases if required. The stable fat/water emulsion is structured so that, when the microcapsules are stored, there is a max. liquid fat content of 10% at the storage temp.  The microcapsules can be formed in a double structure where the outer system remains solid and the inner system is liquid at storage temps. The droplets are sprayed into the cold zone, to freeze as they drop to the base of the zone. An Independent claim is included for an apparatus to produce the microcapsules.  It has an upright freezing tower (12) where the water and components are delivered to the upper side by at least one spray jet (10,11).  A number of jets (16), at different levels, deliver a coolant as a liquid gas such as nitrogen, helium or carbon dioxide.  The interior temp. is dropped to 0 deg C to -50 deg C and pref. \- -50 deg C to freeze the sprayed droplets in their free fall.  The tower has an outlet opening (21) at the base to take off the particles. Preferred Features: The assembly has an arrangement of pumps and pipelines with jets and mixing vessels, together with an emulsifier/disperser system (4,6,7) to produce single- or multiphase fluid systems to be sprayed as droplets into the freezing zone.