Homogenisation with High Shear Mixers

Ensuring a homogeneous end product is an essential aspect of manufacturing for a wide range of products across many industries.

Homogeneity is important a variety of reasons - to improve the appearance and texture of a product such as cosmetic or pharmaceutical creams and ointments; to activate and maximise yield of functional ingredients; and to ensure shelf stability – especially with pharmaceutical suspensions such as vaccines, or to help increase the shelf life in products like sauces and flavour emulsions.

When most people think of homogenisation what comes to mind is high pressure homogenisers, which are powerful devices that use a piston pump to force product through a very small adjustable aperture at high pressure. Although these devices can ensure homogeneous products, they require a large amount of energy and capital expenditure.

However, what many people don’t realise is that for the vast majority of products a high pressure homogeniser isn’t actually required. Reducing the globule or particle size down to around 2 – 5 microns is a sufficient degree of homogenisation for products such as creams and ointments, suspensions, etc. A Silverson high shear mixer/homogeniser can achieve a globule or droplet size in this range of and in some cases, depending on the formulation, finer results down to 0.5 microns can also be obtained with a Silverson mixer, eliminating the need for expensive homogenisation equipment in the manufacturing process.

This is what happened recently when a flavouring manufacturer purchased a Silverson Batch mixer after successful trial results at laboratory scale. Before contacting Silverson the company were using a process that relied on mixing ingredients for a long time using a conventional agitator to form a pre-mix. This pre-mix was then fed through a high pressure homogeniser several times to obtain a uniform particle size of 5 microns.

After seeing the Silverson Mixing Science ‘What is homogenisation’ animation on the Silverson website, the company got in touch to find out the what particle size they could achieve using a Silverson High Shear mixer. A trial was arranged to test the companies application at laboratory scale.

For the trial, a Silverson Laboratory mixer fitted with a General Purpose Disintegrating Head was used. Keeping the ingredients and formulation the same as their current process, when using the Silverson Laboratory mixer the company were able to achieve a uniform particle size of around 1.5 microns after only five minutes of mixing. This was a huge reduction processing time compared to their previous mixer and the particle size had been reduced finely and uniformly enough that they could completely eliminate the high pressure homogenising step.

The company immediately scaled up and purchased a Batch mixer which has been added to the process line and has been able to produce high quality flavouring for them in a much quicker time. In most cases, the company now bypasses the high pressure homogenisation stage, but when used, the pre-mix created with the Batch mixer means it passes through at a much faster rate and in a single pass.

Silverson mixers are able to achieve these results due the precision engineered rotor/stator workhead which generates exceptionally high shear rates in a three stage mixing/homogenising process; firstly the high speed rotor draws materials into the workhead where they are intensely mixed. Centrifugal force then drives the materials to the periphery of the workhead and subjects them to mechanical shear in the precision gap between the rotor and stator. This is followed by intense hydraulic shear, as the product is forced through the stator screen at high velocity and circulated back into the mix. Fresh material is continually drawn into the workhead, progressively reducing particle size and quickly resulting in a homogeneous, uniform product.

The flavouring manufacturer was immediately able to scale up their application without the need for further trials or reformulation as all of Silverson high shear mixers are built to the same fine tolerances, demonstrating that results achieved at Laboratory scale can easily be replicated on larger scales. And with the largest capacity range from a single manufacturer, whatever your batch size, Silverson can help find the right mixer for your needs.

With over 70 years of mixing experience Silverson has an unmatched level of expertise and has helped thousands of companies meet their unique mixing requirements.