February 2013.– 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. In simple terms, tempering involves mixing and cooling the liquid chocolate under controlled conditions to ensure that the fat phase in the chocolate composed mainly of cocoa butter, crystallises in its most desirable form, i.e. form V. Incorrect tempering makes the chocolate become dull, susceptible to fat bloom, soft in texture as well as difficult to de-mould. Thus, the physical and textural properties of chocolate are influenced by the microstructure formed during crystallization of liquid fat. The control of the molecular structure and polymorphic form of this fat is therefore particularly important in the manufacture of chocolate.
To this end, small, medium and large enterprises of the chocolate industry, as well as research centres from 8 different European countries will participate in the EU-funded project ULTRACHOC that aims to develop a low cost ultrasound-based system capable of controlling by real-time monitoring the tempering process during chocolate manufacture. The project Kick-Off meeting took place on the 18th and 19th of February in Castelldefels, Spain, at the headquarters of IRIS, project coordinator.
Cocoa butter as key factor
The key goal in chocolate conventional tempering processes is to achieve 1-2% solid fat content (SFC) in the tempering machine at a temperature where mostly Form V cocoa butter crystals can survive. Polymorphism is the ability of the cocoa fat to exist in more than one crystal form, and it is an important material characteristic in chocolate manufacturing as it is directly linked to product quality and processing performance. 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.
As SFC may change during manufacturing and storage, it is important to be able to measure this parameter to control the ingredients and manufacturing conditions for achieving optimum product quality. Traditional methods of SFC determination are slow, irreproducible, require additional chemicals and are based on sampling such as dilatometry. While dilatometry is an extremely precise technique, it is somewhat laborious and has been replaced in many applications by low resolution Nuclear Magnetic Resonance (NMR). While the NMR method is rapid and easy to use, it is poorly sensitive to low concentrations of solid fat and is expensive. An on-line sensor capable of measuring the SFC in the chocolate melt would allow automated control of the tempering process and would be of great value to manufacturers. Unfortunately, neither of these approved methods, which are based on sampling technique, is entirely appropriate for on-line application, thereby leaving a clear technological gap.
In view of this technological gap, the ULTRACHOC project will build on the promising results of past laboratory scale research that has revealed the strong sensitivity of cocoa butter shear crystallisation process to the Ultrasound Doppler-based velocity profile (UVP) and pressure drop (PD) technique, thereby practically providing a basis for an on-line temper meter. To this end, this project will aim to carry out further laboratory trials with the UVP-PD and Ultrasound attenuation (USA) technique, UVPPD + USA, in order to define the parameters required for the industrial system that can be used as a tool in commercial chocolate manufacturing facilities.
Ultrasound has long been a popular technique that is finding increasing use in the food industry for both the analyses (ultrasound of high frequency) and modification of food products (ultrasound of low frequency or high power ultrasound). Two possible methods for controlling the tempering process will be explored during the project based on the use of ultrasound: as a technology to control the fat crystal size during tempering (high power ultrasound), and ultrasound of low energy for the development of an on-line sensor capable of measuring the SFC (UVPPD and USA). The project coordinator, Dr Adriana Delgado, highlights that the combination of the two methods in a system that is readily integrated in chocolate tempering machines will represent a breakthrough for the EU chocolate industry.
Towards the end of the project, the system will be installed at the sites of the different end-user SMEs in the consortium, SKELLIGS in Ireland, and CARLA in the Czech Republic, and an additional test site will be set up at one of the European facilities of either NESTLE or VALOR. As for the role of the three research performers, SIK will carry out laboratory trials using high power ultrasound to tailor and control the fat crystal size, while ETH Zurich will perform laboratory trials with ultrasound of high frequency using ultrasound Doppler based velocity profile (UVP), pressure drop (PD) and ultrasound attenuation techniques (USA) to measure the solid fat content (SFC) on-line. Finally, IRIS will scale up the technology based on these laboratory results and build a precompetitive ULTRACHOC system able to measure in real time the SFC content of the chocolate and changes in the chocolate melt during tempering, and to assist and improve the crystallization process during tempering by using ultrasound technology.
IRIS R&D, a Barcelona-based company dedicated to advanced engineering and R&D solutions, will coordinate the international project from its branch office in Dublin, Irleand, whereby 9 other companies and research centres will also participate: Carla Spol Sro (Czech Republic), Seaclaidi Na Sceilge Teoranta (Ireland), Aktive Arc Sarl (Switzerland), Ubertone Sas (France), Prefamac Nv (Belgium), Nestec York Ltd (United Kingdom), Chocolates Valor SA (Spain), SIK-Institute foer Livsmedel Och Bioteknik AB (Sweden), and Eidgenoessische Technische Hochschule Zurich of Switzerland. The consortium of ULTRACHOC consists in 5 SMEs and 2 large companies, and 3 research centres. The two-year project will strength Europe’s reputation as a consistent supplier of superior quality chocolate.