Differential scanning calorimetry and real-time X-ray diffraction using synchrotron radiation were used to study the isothermal crystallization formation mechanism of lard at 18, 20, 22 and 24°C. At 18°C, lard crystallized in three steps. A potential mechanism for these three steps was proposed. In the first step, part of the melt (the trisaturated triacylglycerols (TAGs)) crystallized in α crystals adopting a double length structure (2L), while the second step consisted of a polymorphic transition of these 2Lα crystals to β' crystals with a triple length structure (3L). Extra 3Lβ' crystals consisting of monounsaturated TAGs were also formed directly from the melt. In the third and last step, β crystals were formed due to a second polymorphic transition of trisaturated 3Lβ' crystals to β crystals adopting a 2L structure.Above a cut-off temperature of 20°C lard crystallized in two steps: no formation of α crystals could be observed and 3Lβ' crystals (trisaturated and monounsaturated TAGs) were formed directly from the melt. This proposed mechanism implies that lard crystallization is characterized by an overlap of fractionated crystallization and polymorphic transitions.

Differential scanning calorimetry and real-time X-ray diffraction using synchrotron radiation were used to elucidate isothermal cocoa butter crystallization at 17 and 20 °C in the absence and presence of different limonene concentrations. At 17 °C, a three-step crystallization process was visible for pure cocoa butter, whereby first an unknown structure with long spacings between a 2L and 3L structure was formed that rapidly transformed into the more stable α structure, which in turn was converted into more stable β' crystals. At 20 °C, an α-mediated β' crystallization was observed. The addition of limonene resulted in a reduction of the amount of unstable crystals and an acceleration of polymorphic transitions. At 17 °C, the crystallization process was accelerated due to the acceleration of the formation of more stable polymorphic forms, whereas there were insufficient α crystals for an α-mediated β' nucleation at 20 °C, resulting in a slower crystallization process.

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 a polymorph followed by a polymorphic transition to b 0 . 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 a crystallization with addition of lecithin, while rheology measurements demonstrated the reverse effect. However, both measuring techniques evidenced a faster polymorphic transition to the b 0 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.

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The objective of this study was to investigate the influence of commercially available monoacylglycerol (M), polyglycerol esters (P), and sunflower lecithin (L) on the onset of crystallization of bulk fat as a function of the added concentration. Not only a single type of emulsifier, but also binary and ternary mixtures of M, P, and L were added to the two different "host" fats using a statistically sound mixture design. The obtained mixtures were analyzed for their non-isothermal crystallization behavior by differential scanning calorimetry. If a single type of emulsifier was added, the nucleation was accelerated when adding M or P, while L addition had no significant effect. Furthermore, it was shown that the minimum concentration necessary to provoke a nucleation accelerating effect is lower for P than for M. Antagonistic effects between M and L (and not between P and L) were suggested by the coefficient estimates of the special cubic model.Practical applications: Palm oil (PO) is one of the most consumed vegetable oils in the world because of its unique physical properties. It imparts a very high stability to the b 0 crystal form, yielding relatively small crystals which give a smooth texture to e.g., margarines and shortenings. Because PO is semi-solid at room temperature, it forms an ideal hard stock to be used in trans free food products. However, PO has a slow crystallization rate and an unusually long a-lifetime. These disadvantages can be overcome by the addition of an emulsifier acting as crystallization modifier (e.g., monoacylglycerols and diacylglycerols) [1]. Furthermore, from a nutritional point of view, the saturated fatty acids present in PO [2], are among the factors contributing to cardio-vascular diseases [3]. When using more unsaturated fats as hard stock, the use of additives in order to avoid compromising the functionality of the food product should be further investigated.