Case Study: Fat-Conscious Online Viscometer Watches the Chocolate

On-line viscometers from Hydramotion Ltd are helping to ensure that the chocolate melts in your mouth, not in your hand. Chocolate is a dispersion of finely-divided sugar, milk protein and cocoa in a continuous fat phase, generally cocoa butter or cocoa butter equivalent. During production, molten chocolate must be cooled in a controlled way in order to promote the formation of small, stable fat crystals, a process known as “tempering”. Stable cocoa butter crystals provide the right qualities of texture, surface gloss and melting behaviour in the finished product. If the crystals are small enough the chocolate will taste smooth and melt just where it should, in the mouth (at a temperature of about 35°C) but not in the hand (at about 20°C).

The viscosity of melted chocolate depends directly on its fat content and the degree of tempering, so monitoring viscosity gives an immediate window into the production process. With this in mind, a leading UK manufacturer of chocolate products recently installed Hydramotion XL7 online viscometers on pipelines leading to its mixing tanks as part of a global automation project. By continuously monitoring the viscosity of the liquid chocolate its fat content could be adjusted automatically in real-time, maintaining product quality and reducing wastage.

The benefits have been immediate. “The viscometer is a godsend,” commented the production manager. “We feel totally comfortable using it for process control.”

The XL7 is a field-proven device with high immunity to plant noise and vibration providing continuous, reliable and accurate viscosity measurement regardless of variations in fluid condition. It has high sensitivity and excellent repeatability. Measurements are unaffected by stirrers, agitators, changes in flow rate or the presence of bubbles or solid particles.

The sensor is a clean-in-place all-welded 316 stainless steel construction capable of withstanding hostile process conditions. It has a truly hygienic crevice-free design, minimizing the risk of fouling or material entrapment. Suitable for pipe or tank mounting in any orientation, the instrument can be supplied with any size or type of sanitary fitting, including quick-release tri-clamp mountings, RJT, IDF or DIN. The dedicated readout unit can be located up to 1000 metres from the sensor.

Outputs include a 4-20 mA analogue viscosity signal and a more comprehensive RS232 serial data link for remote monitoring or viscosity control.

Factory-calibrated using certified viscosity standards traceable to NIST, the XL7 viscometer requires no field calibration. With no moving parts, seals or bearings it is virtually maintenance-free, giving a very low total life-cycle cost.

So successful were the initial results in the UK that the company has now gone on to install further XL7s in its plants around the world, including a major new facility in Asia. “The Hydramotion viscometers are making a significant contribution to our product quality,” commented one production engineer. “We could not do without them.


Our Hydramotion Viscometers are the ideal solution for the Food & Beverage Industry.  You can find out more by visiting our brand page or calling to speak to a technical representative at 1-800-912-9262.