Food & Beverage

UTG optimizes chocolate mass process by applying patented Sigma technology

Vertical tank mixing solution prevents temperature gradients from destroying chocolate


  • Cocoa mass and liquid chocolate are challenging media to agitate due to their high viscosity, non-Newtonian behavior and sensitivity to local overheating.

  • Completely blended ingredients, maintaining a truly homogeneous mixture and good heat transfer are essential for the quality of the end product.

  • Patented Sigma technology enables short homogenization times with lower power consumption.

Applying patented Sigma mixing technology for cocoa mass and liquid chocolate


The operating temperature had to be very close to the critical point that would have destroyed the quality of the product.

A major raw chocolate producer needed to develop their mass standardization process.

To achieve high homogenization of the cocoa mass concentration, the operating temperature had to be very close to the critical point that would have destroyed the quality of the product.

This set extra high requirements for efficient heat transfer from the vessel wall into the bulk mass in order to avoid temperature gradients destroying the chocolate.

Customers in the chocolate processing industry usually use top entry agitators or even more often horizontal blenders consisting of plough impellers or a combination with helical ribbon impellers.

The installed mixers/blenders have several disadvantages. In particular, the extremely high power consumption of the blenders has a negative impact on the overall energy balance of the process. Furthermore, these units have an enormous space requirement that leaves no space in the halls for expansions.

The top entry units installed in some chocolate processes mainly consist of anchor or complex frame-type impellers with additional elements in the center.

All of these constructions are complicated to clean.


UTG Mixing Group has applied its patented Sigma impeller series widely in the chemical industry and for special food industry applications for decades already. In 2015, this patented technology was introduced successfully also to the chocolate industry.

UTG Mixing Group’s experts designed with the customer a special modification of Sigma technology that allowed a vertical tank mixing solution. The solution was tested with the customer’s product and quality control methods at the UTG Mixing Technology R&D Center in Germany.

  • Sigma technology generates forced counterflow circulation with good wall velocity.
  • Sigma offers superior vertical blending compared to an anchor blade; the equivalent blending time can be achieved with less power due to more efficient circulation.
  • Forces impacting on the agitator and drive are smaller than with an anchor impeller, allowing a lighter construction.


After successful piloting, the solution was scaled up to industrial scale and the customer built their new line based on the new vertical solution.

Stelzer started by running base tests with all kinds of white and brown chocolate qualities. Especially chocolates with a higher cacao content (>70%) require high temperatures to mix the product well. This introduces the danger of overheating at the vessel walls.

Stelzer developed a combined solution with smooth overall tank mixing utilizing their specially shaped SIGMA elements plus close-to-the-wall running frames. The units are welded completely inside the tanks, are easy to clear and run at low circumferential speeds, creating a maximum damping effect on possible air drag-in, which is not
appreciated in production.


According to customer feedback, the industrial reference fulfilled all their expectations and they have specified this new solution for all of their new production lines.

We have the required theory, measurement data and experience to design optimal impeller setups and process parameters for all sizes and shapes of vessels.

Benefits of a vertical mixing solution compared to horizontal technology:

  • Same homogenization time at lower power consumption
  • Smaller footprint
  • More efficient mixing volume

Contact person from UTG for further information:

Arthur Binfet
Sales Manager

+49 5641 903-43 / Mob. +49 152 54524308


Stelzer Rührtechnik International GmbH
Visiting address:
Speckgraben 20,
34414 Warburg, Germany

Target group of the story:
Chocolate producers, Engineering companies, vessel manufactures

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