High Viscosity Mixing: Processing Honey with High Shear Technology

Coming soon: High Viscosity Mixing – Honey applications

• High viscosity products such as honey can present significant challenges for conventional agitators and stirrers.
• Silverson Machines’ high shear rotor/stator mixers are designed to handle demanding high viscosity mixing applications.
• A specially developed pumping rotor increases the capacity of Silverson’s High Viscosity In-Line mixer and enables self-pumping operation.
• High shear mixing can help incorporate ingredients such as spices, seasoning and cocoa powder into honey while also helping to refine crystallised honey.
• The positive mixing action helps prevent stratification and localised mixing while reducing processing times and the risk of unwanted temperature increases.

High viscosity mixing challenges

While there are many designs of agitators and stirrer/scrapers capable of handling high viscosity products, the low shear nature of these machines can limit their effectiveness to relatively simple mixing tasks. These can include blending liquids with similar viscosities and maintaining uniformity within a vessel.

When processing products with significantly different viscosities or attempting to incorporate solid ingredients into a highly viscous liquid, conventional agitation can struggle to generate sufficient movement and shear throughout the vessel.

Honey is a particularly challenging example.

Its highly viscous and ‘sticky’ characteristics can make it difficult to process efficiently using conventional mixing equipment. Where additional ingredients such as spices, seasoning and cocoa powder need to be incorporated, achieving a uniform mixture can be extremely difficult. Similarly, refining honey that has crystallised can require lengthy processing times and significant energy input.

Silverson Machines has developed high shear rotor/stator mixing technology specifically suited to demanding applications such as these. The company’s high viscosity mixing technology is designed to provide the intensive mixing action required to process difficult, viscous products efficiently.

Silverson’s existing honey application information highlights a number of challenges associated with conventional processing, including localised mixing, the difficulty of incorporating low-density powders and the potential for stratification when liquids with significantly different viscosities are combined.

High shear mixing for honey applications

Silverson’s specially designed High Viscosity In-Line mixer features a unique and innovative ‘pumping rotor’ design which provides increased capacity.

The pumping rotor is located within the precision-machined workhead and plays a key role in maintaining the flow of high viscosity products through the mixer. It forces liquid and solids into the rotor/stator assembly, helping to maintain the mixer’s flow rate even when processing products with higher viscosity.

As material enters the workhead, it is subjected to the intense mixing action generated by the high-speed rotor and stator. Material is then forced out through the holes in the stator and pumped back towards the vessel as fresh material is simultaneously drawn into the workhead.

This creates a continuous circulatory pattern of mixing in which the contents of the vessel are repeatedly passed through the workhead.

The result is a positive mixing action that helps ensure ingredients are uniformly dispersed throughout the product rather than remaining concentrated in isolated areas of the vessel.

The self-pumping action is also an important feature for high viscosity processing. Because the mixer can handle the recirculation itself, additional pumping equipment may not be required. 

Silverson states that its High Viscosity In-Line mixers are designed to provide high flow rates when processing higher viscosity products and can eliminate the need for an additional feed pump in many applications.

How rotor/stator mixing works

The rotor/stator workhead is central to Silverson’s high shear mixing process.

As the rotor rotates at high speed, it creates a powerful suction which draws liquid and solid materials into the workhead. Centrifugal force then drives the material towards the periphery of the workhead where it passes through the precision-machined clearance between the rotor blades and the stator wall.

The material is then subjected to intense hydraulic shear before being forced at high velocity through the perforations in the stator.

At the same time, fresh material is continuously drawn into the workhead. This maintains the mixing and pumping cycle and helps ensure that material throughout the vessel is processed rather than only the product immediately surrounding the mixer.

For high viscosity products such as honey, this continuous circulation can be particularly important. Rather than simply moving a viscous product around the vessel, the rotor/stator mixer repeatedly brings material into the high shear zone where it can be subjected to the mixing action.

More efficient processing of viscous products

For food manufacturers processing honey and honey-based products, achieving consistent dispersion can be challenging when conventional mixing equipment is used.

Additional ingredients may have substantially different physical characteristics from the honey itself. Powders can be particularly difficult to incorporate and may remain on the surface or form agglomerates rather than becoming evenly distributed throughout the product.

Silverson’s high shear rotor/stator technology is designed to overcome this problem by drawing the ingredients directly into the high shear zone of the workhead.

Any powder agglomerates that form can be subjected to the intense shear generated between the rotor and stator, helping to break them down and disperse them throughout the honey.

Silverson’s honey application data also identifies the processing of crystallised honey as a potential application. Conventional approaches can involve heating and holding honey at temperature to reduce viscosity and process crystallisation. However, excessive heating can be undesirable because it may affect flavour and functional properties.

The ability to combine high shear mixing with continuous circulation therefore provides an alternative approach for demanding honey processing applications.

Preventing stratification and localised mixing

Another important consideration when mixing high viscosity products is stratification.

When materials with significantly different viscosities are combined, conventional mixing equipment can struggle to keep the entire contents of the vessel moving uniformly. This can result in different phases remaining separated or poorly dispersed and can increase processing times.

Silverson’s positive mixing action is designed to minimise this problem by continually drawing fresh material into the rotor/stator workhead and returning processed material to the vessel.

This avoids the problem of stratification and helps create a more consistent final product.

The continuous circulation can also reduce the time required to achieve a uniform mixture. Faster processing reduces the risk of an unintentional temperature rise caused by prolonged mixing times, an important consideration when processing temperature-sensitive food products.

Silverson’s wider high shear mixing technology is designed to reduce processing times while improving product quality and consistency, with its batch mixer range stating that processing times can be reduced by up to 90% in suitable applications.

High viscosity in-line mixing

The High Viscosity In-Line mixer is particularly suited to applications where high viscosity materials need to be continuously recirculated through a mixing system.

Silverson’s HV In-Line mixers use the specially developed pumping rotor to increase self-pumping capacity. The technology is available for production-scale equipment as well as laboratory-scale development work, allowing processors to evaluate applications before moving to production scale.

The company also offers small-scale high viscosity in-line equipment for development and smaller-batch applications. Its 150 UHS-HV, for example, incorporates the same pumping rotor principle as the production-scale UHS-HV In-Line mixer and is designed to process higher viscosity products.

This ability to trial and scale mixing technology can be particularly valuable for food processors developing new honey-based products or looking to improve existing production processes.

High shear technology for honey processing

Honey represents just one example of where high viscosity mixing technology can be applied. Silverson’s high viscosity equipment is designed for a range of demanding products and industries, including food, pharmaceutical, cosmetic and chemical processing.

For honey processors, potential applications include blending different grades of honey, incorporating powders and other ingredients, processing honey-based products and helping to decrystallise honey.

The precise mixer configuration will depend on factors such as the application, ingredients, batch size and position of the mixer within the processing vessel. Silverson also operates a trial programme allowing customers to test specific applications and identify a suitable mixer for their product.

Watch the honey mixing demonstration

Silverson Machines will soon be releasing a ‘How to’ video demonstrating its high viscosity mixing capabilities with honey.

The video will provide a practical demonstration of how high shear rotor/stator technology can be applied to one of the more demanding high viscosity food products and will highlight the principles behind Silverson’s approach to honey mixing.

To watch the video, visit the Silverson website. Alternatively, contact sales@silverson.co.uk to discuss a specific application or arrange a trial.

Silverson’s high viscosity mixing technology provides processors with another option when conventional agitators and stirrers are unable to achieve the required level of dispersion, circulation and product consistency.