Temper temper!

25 January 2021

Find out how and why one chocolate producer has employed heat transfer technology to help it improve on the traditional tempering process and increase throughput.

Tempering – the controlled heating and cooling of chocolate – is an essential step in the manufacturing of chocolate. Today this task is often still carried out in batches using technology and equipment that has changed little in hundreds of years.

Tempering is vital to produce consistently small crystals of cocoa butter. Without this strict temperature control stage, the crystals formed will be of different sizes and the resulting chocolate will ‘bloom,’ having a matt appearance and waxy texture.

Improving on tradition

One forward-thinking UK chocolate supplier, wanted to improve on the traditionally time-consuming and slow batch tempering process to speed up the process and increase its capacity.

The client processes chocolate from a number of suppliers which is generally delivered in bulk. Historically the tempering process was achieved manually, tempering its chocolate using a traditional method of heating the chocolate using a large bain-marie and then cooling it on a marble table until it reached the right temperature. The chocolate manufacturer had tried tempering the chocolate in specialist vessels but found that this was still quite a slow process. Another issue is that tempered chocolate solidifies quickly as it cools, so it is important to maintain a working temperature until it has been moulded or poured into the final shape.

The company turned to HRS to see if it could offer a better tempering solution, using heat transfer technology. Trials were arranged using an HRS R series heat exchanger which confirmed that the technology was suitable for the tempering purpose. The company then worked with HRS to develop a solution which could be mounted on a process skid. The result comprises three R Series rotary scraped surface heat exchangers in series – the first raises the temperature by 19°C, and the second then cools is back down by 2°C before the final heat exchanger raises the temperature to a level that allows the chocolate to be transported and worked on elsewhere in the factory. The new heat exchangers have significantly speeded up the tempering process, increasing the volume of product that the factory can handle.

The heat exchangers specified for use in this application feature a helical scraper bar design which prevents the build-up of viscous products, such as molten chocolate, on the tube surface to maintain efficient heat transfer. The scrapers also help to mix the product in the tube, improving the homogeneity and effectiveness of heat transfer. The design also helps to reduce the pressure drop along the length of the heat exchanger, reducing energy and running costs.

Another advantage of the system is that it allows small solids, such as pieces of nuts or honeycomb, to be included in the molten chocolate without damaging them or the integrity of the product.