COVER STORY
‘HOW TO’ BENEFIT FROM HIGH SHEAR MIXING
struggles with higher viscosity mixes and for this reason it is practically impossible to create high percentage gum solutions using these methods. Once viscosity increase has started, agitation of the solution and therefore powder incorporation becomes increasingly difficult. When using conventional equipment to try to avoid this, the powder must be added to the vessel in a careful, controlled manner, relying on the operator to try and reduce the formation of agglomerates. This increases the chance of operator error and there is no way to keep batches consistent. Using a high shear mixer for the dispersion
of gums and thickeners can reduce process times by up to 90% and achieve consistent, repeatable results batch-after-batch. Gums can be added directly into the vessel
Silverson Machines offers a range of High Shear mixers from laboratory to full scale production which are ideal for hydrating gums and thickeners. Pictured is the FMX with suction wand
The Silverson 'how to' video series now features over 25 videos on applications across a range of industries, demonstrating how high shear mixing can be beneficial in these applications
T
he latest addition to the series focuses on CMC, or Carboxymethyl Cellulose, a hydrocolloid derived from cotton or
wood pulp. This video joins 'how tos' on Xanthan Gum, Pectin, Gelatine, Guar Gum and Starch, as each thickening agent has its own unique processing challenges, but the effective, homogeneous dispersion of these functional ingredients into liquid is one of the most difficult of all mixing tasks... unless you're using the right mixing equipment. Gums and thickening agents are widely
used in many industries including food and pharmaceuticals. These functional ingredients are notoriously difficult to disperse and hydrate, and these problems can often be exacerbated by the wrong type of processing equipment being used. For example, conventional agitators and stirrers do not produce the high shear necessary to hydrate gums and thickeners quickly and efficiently without forming agglomerates. This can lead to very long mixing times while the powder slowly hydrates as the agitator simply moves the contents of the vessel around. Even after a long period of mixing there is
still often the need for a filtration stage to remove any undispersed gum the agitator has failed to hydrate. This further increases the processing time and costs. Many formulations contain unnecessarily high
16 OCTOBER 2021 | PROCESS & CONTROL
levels of gum to compensate for the poor yield achieved when using conventional agitators as they cannot disperse agglomerates once they have been formed, wasting expensive raw material. Any unhydrated gum that remains in the mix could gradually hydrate during storage, leading to undesired changes in viscosity and inconsistency between batches. Some conventional mixing equipment also
and the gum does not need to be pre-mixed with other powders to aid wetting out or try to prevent agglomerates from forming. The high speed rotor/stator workhead of a
high shear mixer creates a powerful suction which draws the gum and liquid into the workhead, eliminating rafting on the surface of the vessel. The powder and liquid are intensely mixed inside the workhead and then forced out through the holes in the stator. Any agglomerates which may have formed are broken down. The mixture is then projected back into the body of the mix. In a short mixing cycle all of the material
passes many times through the workhead, progressively reducing the particle size and exposing an increasing surface area to the surrounding liquid, accelerating the hydration process, maximising yield of the raw materials and eliminating the filtration stage. Using this method of mixing many products can be reformulated with reduced gum content, cutting raw material costs. The Silverson Ultramix has a single-piece
dynamic mixing head which creates a powerful vortex in the vessel, ideal for incorporating large volumes of powders. It can maintain excellent in-tank movement, even when processing higher viscosity mixes. For larger batches, the Silverson Flashmix is
capable of incorporating large volumes of powder and a laboratory scale version of this mixer, the FMX5, is now available and is ideal for R&D and small scale production. The Flashmix is also available with a suction wand attachment, this enables the machine to suck powdered ingredients into the mix straight from their original containers, minimising handling requirements. To find out more, visit the Silverson YouTube
channel where you'll find the 'how to' series:
www.youtube.com/user/silversonmixers
E:
sales@silverson.co.uk www.silverson.co.uk
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