Chemistry Reference
In-Depth Information
with low levels of oil. This is very effective in reducing any materials which may become
airborne.
The spray-dried powder can also be incorporated into other product forms. These can be
as simple as agglomerated powders or more sophisticated as structured particles. The powder
can be agglomerated to form larger particles and reduce dust. This is done by putting the
powder into mixing equipment and adding a binder material while mixing, which results in
binding the powder together and forming larger particles. The agglomeration process can
also be carried out in a fluid bed granulator. In this process, the powder is suspended in an
air stream and, while suspended, an atomized spray of binder is applied through a nozzle.
As the particles pass through the atomized liquid they will become wet, stick together and
then dry in that form. This process is carried out multiple times, thus resulting in larger and
larger particles. Both of these methods are somewhat uncontrolled and the resulting product
has a broad size distribution.
In specialized equipment, such as multi-stage driers, the spray drying and agglomeration
processes can be carried out simultaneously. In this process, the enzyme concentrate and any
added stabilizers are atomized though a nozzle similar to a standard spray drier. However,
any fine powders are evacuated from the drying chamber and subsequently re-introduced
into the drying chamber near the point of liquid atomization. This results in the dry particle
rewetting and agglomerating with other nearby particles. By controlling the airflows in the
system, it is possible to target a narrow size distribution of the final agglomerated particles.
The spray-dried powders can also be incorporated into more structured particles such
as extrudates, high shear granules or spray-chilled particles. These particles can offer other
advantages including improved stability and particle integrity. They also have the possibility
of including other food use agents and customized enzyme release mechanisms. In the
extrusion process, the spray-dried powder is mixed with other materials such as sugars,
starches, buffers and binders. The materials are mixed together to create a dough-like material.
This mixture is pressed through a perforated plate and the resulting 'noodles' are either cut-
off at regular intervals or allowed to fall-off on their own. There is also the possibility of
converting these cylindrical particles into spheres via a device known as a marumerizer.
Finally the particles are dried in a fluid bed drier. In the high shear process, dry ingredients
including the enzyme powder are added to the process bowl. While being mixed with a
plough shear mixer and a high-speed chopper, wet binding materials can be added. The
shearing action generates small particles which can be dried similarly to the extrusion
process. Finally, the spray-dried powder can be incorporated into a molten fat or wax. This
mixture is then atomized through a rotary nozzle into a cooled chamber essentially equivalent
to a spray-drier tower. The particles cool and harden as they fall, resulting in very spherical
particles.
3.5.1.2
Encapsulation
Finally, solid enzyme products can be further encapsulated to customize delivery of the
enzyme. By creating a core-shell particle where the enzyme is included in the core, a
functionalized coating can be added. These coatings can not only further improve the stability
of the enzyme product, but can also be triggered to release the enzyme under desired
conditions. These triggers could include pH, heat, shear or water activity just to name a few.
The enzyme core unit can be those already described, such as agglomerates, extrudates, high
shear granules or spray-chilled particles. Additionally, the enzyme core may be generated
using a fluid bed coater. In the fluid bed process, an inert carrier is suspended in a hot air
