Influence of Free Fatty Acids as Additives on the Crystallization Kinetics of Cocoa Butter

In this study, the influence of free fatty acids as additives on the crystallization kinetics of cocoa butter (CB) and the industrial tempering was considered for the first time. Different concentrations (0.5 %-5.0 %) of stearic, palmitic and oleic acid were added to CB and crystallized at isothermal temperatures between 18-28 °C. To imitate the industrial tempering, β-crystals were actively formed using a temper. The solid fat content (SFC) was determined by pulsed NMR with data fitted to the Gompertz equation and melting temperature and polymorphic behaviour were analysed by DSC. With an increase in temperature of 2-5 °C a reduction in crystallization rate of 40-80 %, lower solid fat contents and 1,5-6 times longer induction times occur. The SFC of tempered blends are significantly lower (P < 0.05 %) than their non-tempered counterparts independent of the crystallization temperature. At higher temperatures, palmitic acid and especially stearic acid act as a crystallization initiator due to their higher melting point of 63 and 69 °C, indicating shorter induction times with increasing free fatty acid content. Although pure CB crystallizes fastest, an increasing stearic acid content leads to higher crystallization rates. In contrast, palmitic and oleic acid have retarding effects. Thus, while under spontaneous conditions a temperature dependence was ascertained, after pre-crystallization the free fatty acid concentration could be identified as the driving force in terms of crystallization rate.