Ultrasound-based systems for tempering and monitoring chocolate production

Chocolate quality is highly dependent on a stage of the manufacturing process known as tempering. Tempering is critical for reducing processing failures and ensuring a quality end product. Incorrect tempering makes the chocolate become dull, susceptible to fat bloom, soft in texture and warm in the mouth, as well as difficult to de-mould with a greater probability of mould marks on the surface.

Tempering is a highly complex process, affected by many raw material and processing factors, whereby the specific tempering conditions required will depend on the cocoa butter used, the type of product being made and the subsequent processing. Solid Fat Content (SFC) is crucial to the quality of chocolate and may change during manufacturing and storage. SFC in chocolate is related to crystallization of cocoa butter during tempering. Cocoa butter has six polymorphic forms (I-VI), with form V being the most desirable form in chocolate, giving a glossy appearance, pleasant texture, good snap, contraction, good de-moulding properties, stable shelf-life and resistance to bloom. The key goal in conventional tempering processes is to achieve 1-2% of solid fat content (SFC) in the tempering machine at a temperature where mostly Form V cocoa butter crystals can survive. Traditional methods of SFC determination are slow, irreproducible, require additional chemicals and are based on off- line sampling.

ULTRACHOC project aims to control the crystallization of cocoa butter into the most desirable form (V) by low frequency ultrasound (high power ultrasound, HPU) and to develop a low cost on-line sensor system (Ultrasound Velocity Profile Pressure Difference + Ultrasound Attenuation, UVPPD+USA) capable of measuring with precision and in real-time chocolate SFC and changes in the chocolate melt during tempering. The ULTRACHOC project builds on the results of past research that demonstrated the benefits of HPU to improve crystal purity and reduce crystallization time, and the usefulness of UVPPD+USA to characterize particulate fluids and monitoring the crystallization process. The use of this system will result in a better control of the complex tempering process, while improving the quality of final chocolate products.

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