Influence of soy lecithin and PGPR levels in chocolate crystallization behavior

Chocolates consist of a suspension of fine cocoa solids and sugar particles dispersed in a continuous lipid phase in a process assisted by emulsifiers, usually a combination of lecithin and PGPR. In the conventional process, the tempering is a pre-crystallization step in which the melted mass is cooled at a controlled rate of temperature decay under continuous shearing action in order to organize molecular packing. Melted chocolate behaves like a pseudo-plastic fluid and as crystallization progresses, the mass thickens. The soy lecithin added reduces the plastic viscosity and PGPR (polyglycerol polyricionleate) minimizes yield stress. The amphiphilic nature of these additives, however, has been shown to affect the crystallization behaviour of model lipids. The present work investigated a possible similar action during the dark chocolate mass crystallization process. Chocolate mass containing different levels of both emulsifiers (up to 0.92% of lecithin and 0.58% of PGPR) was produced and physical evaluations were performed, before and after tempering, and storage using a rheometer, a low resolution NMR, a tempermeter and a texturometer. The results confirmed the conflicting effect of large amount of emulsifiers on the rheological behaviour and indicate a weak but consistent influence of the emulsifier composition on the crystallization kinetics, affecting mainly the kinetic constant of crystallization.