Abstract
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.
Highlights
The optical quality of a product is one of the most important criteria in the consumer's purchasing decision
Pure cocoa butter (CB) crystallizes fastest, an increasing stearic acid content leads to higher crystallization rates
Our studies has shown that even the smallest amounts of minor components have a significant effect on the crystallization properties of fats
Summary
The optical quality of a product is one of the most important criteria in the consumer's purchasing decision. Crystallization can be affected by the minor components of CB, including monoglycerides- (MOG), diglycerides (DAG), free fatty acids (FFA), phospholipids, hydrocarbons, sterols and sterol esters, tocopherols and many others (Lipp & Anklam, 1998; Foubert, Vanrolleghem, Thas, & Dewettinck, 2004; Chaiseri & Dimick, 1989; Ziegleder, 1995). According to Smith, Bhaggan, Talbot and van Malssen (2011) there is no accepted concentration of components that influence crystallization. It depends on their structure, whether and to what extent the crystallization is influenced by the minor component. Herrera and Rocha (1996) showed that incorporation into the crystal requires a concentration of 0.5-5.0 % to affect crystallization; if the minor component is involved in nucleation, 0.1 % is sufficient to obtain significance. Crystal growth can be hindered by minor components blocking the growth sites on the crystal surface
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