Lecithin influences cocoa butter crystallization depending on concentration and matrix
Authors: Rigolle Annelien , Gheysen Lore , Depypere Frédéric , Landuyt Alex , Van Den Abeele Koen , Foubert Imogen 
Published: May 2015

The isothermal crystallization at 20°C of cocoa butter (CB) or milk chocolate (MC) with addition of two different sunflower lecithins and one soy lecithin in different concentrations was investigated by differential scanning calorimetry (DSC), oscillatory rheology and a dynamic experiment. A two‐step crystallization process was observed with first formation of an unstable α polymorph followed by a polymorphic transition to β′. In the CB matrix, different measuring techniques led to distinct observations by addition of 1.5% lecithin on a fat base. DSC showed a faster α crystallization with addition of lecithin, while rheology measurements demonstrated the reverse effect. However, both measuring techniques evidenced a faster polymorphic transition to the β′ polymorph in lecithin enriched samples. Between the different lecithins no large differences could be detected by the static measuring techniques, while the dynamic experiment exhibited a clearly lower crystallization rate for lecithin B, which was even lower than the pure CB. A remarkable concentration effect was visible in the CB matrix with in general a reduced effect at higher lecithin concentrations. Finally, a different behavior was observed in the MC matrix compared to the CB matrix, presumably by the interaction of lecithin with sugar.

Practical applications: Lecithin is added to chocolate formulations to control the flow properties. The handling and processability of the chocolate is improved by a proper viscosity and the perception of flavor by the consumer is also affected by the viscosity (Beckett, 2009, Industrial chocolate manufacture and use, Blackwell Publishing Ltd, Oxford, United Kingdom, pp. 224–246). The effect of lecithin on the rheology of chocolate has been extensively studied, but the effect of lecithin on the crystallization behavior has received much less attention in literature. This is true despite the fact that the crystallization process determines to a large extent the quality of the end product and the addition of minor components such as lecithin can modify the crystallization behavior. As lecithin is a natural product, different lecithins could demonstrate different effects and even different concentrations could show different behaviors (Smith et al., 2011, J. Am. Oil Chem. Soc. 88, 1085–1101). As such, the addition of lecithin should be optimized in chocolate recipes to compromise between flow properties and crystallization behavior.

In this work two sunflower lecithins and one soy lecithin were chemically characterized and subsequently their effect (by addition of 1.5%) on the crystallization behavior of cocoa butter was studied by DSC. Thereafter, the concentration effect was examined by varying the added concentration of lecithin between 1, 1.5, and 2%. By using a cocoa butter and milk chocolate matrix, the matrix effect was investigated. Finally, addition of 1.5% lecithin to cocoa butter was also studied with rheology and a dynamic experiment. In general, we can state that the observed effect depends on the concentration, matrix, and measurement technique used, which explains contradictory results in the literature.