Rheometry and polymorphism of cocoa butter during crystallization under static and stirring conditions

Abstract

In this work the association between polymorphism and the crystal network structure developed by the TAG of cocoa butter (CB) was investigated under static and stirring crystallization conditions using a dynamic mechanical spectrometer. The results obtained showed that parameters obtained through oscillatory rheometry (i.e., phase shift angle, δ) followed the polymorphism of CB during static crystallization. Although standard DSC was not capable of differentiating the α to β′ phase transformation from the direct β′ crystallization from CB melt, δ rheograms measured these two processes separately. Additionally, through oscillatory rheometry, we followed the dimensionality of the crystal network during CB crystallization. Within this context, the pre-exponential term (ln γ) from the weak-link regime equation for colloidal dispersions was much more sensitive than the fractal dimension (D) to differences in crystal size, spatial distribution of the crystal network, and melting temperature of the β′ phase of CB. On the other hand, torque measurements obtained during CB crystallization under stirring conditions showed a shear rate effect that favored TAG development in the β phase at temperatures of 19, 22, and 26.5°C, particularly at shear rates of 120 and 400 rpm. In contrast, under static conditions CB did not develop in the β phase at any of the crystallization temperatures investigated (i.e., 18 to 26.5°C).Paper no. J10685 in JAOCS 81, 195-202 (February 2004). KEY WORDS:Avrami index, cocoa butter, fractals, stirring crystallization.Crystallization of cocoa butter (CB) provides unique characteristics of texture, mouth feel, and flavor release to chocolate and other confectionery products. Although CB is composed of various TAG, more than 75% exhibit a symmetrical conformation with oleic acid in the sn-2 position. Because of this homogeneity in TAG conformation and composition, polymorphism in CB is quite complex, i.e., at least six polymorphic forms have been observed. According to Wille and Lutton (1), each polymorph has a unique m.p. and crystal structural properties. These authors named the polymorphs from I to VI in increasing order of m.p. However, a study with real-time Xray diffraction by van Malssen et al.(2) showed that forms III and IV according to the Wille and Lutton nomenclature exist as a range of β′ polymorphic phases rather than as two separate polymorphic phases. This property may be ascribed to cooperative interactions among the three major TAG of CB, i.e., StOSt, POSt, and POP, where St = stearate, O = oleate, and P = palmitate. Accordingly, TAG in CB crystallizes in the β′ phase as a distribution of crystallites with a particular TAG composition, providing a distribution of individual melting temperatures and diffraction patterns, all of them characteristic of the β′ polymorph (2). CB is used as the main lipid phase in chocolate manufacture, but it is also used in combination with other vegetable oils, such as hydrogenated soybean oil and palm oil, in the elaboration of confectionery products. I...

Influence of shear flow on polymorphic behavior and microstructural development during palm oil crystallization

“…At both temperatures, the major increase in complex modulus occurred earlier in time when a higher shear rate was applied during the shear step, indicating that the sample crystallized faster and with a higher level of crystallinity. The effect of a shear step on the crystallization kinetics, evaluated by rheological measurement, corresponds to the findings of Sonwai and Mackley [10], Dhonsi and Stapley [12] and Toro-Vazquez et al [13], who all studied the effect of continuous shear on the crystallization kinetics of cocoa butter. They reported an increase in rheological parameter (viscosity or torque) at the crystallization onset and a shorter crystallization induction time when higher shear rates were applied.…”

“…Sonwai and Mackley [10] and MacMillan and Roberts [11] used the same technique to elucidate the effect of various shear rates on the polymorphic transitions in cocoa butter. Dhonsi and Stapley [12] and Toro-Vazquez et al [13] used a rheological approach to study cocoa butter crystallization under continuous shear, while Garbolino et al [14] equipped a rheometer with ultrasonic sensors to asses the effect of shear on crystallization of a confectionery fat. These experiments were all carried out with continuous shear throughout the whole experiment, except for the study of Sonwai and Mackley [10].…”

Rheological of chocolate-flavored, reduced-calories coating as a function of conching process

“…weakly structure) and in the solid part (more organized structure). This behavior is usually found in systems with high lipid content in liquid state (Toro-Vazquez et al 2004) and in cocoa butter (Vaeck 1960;Landfeld et al 2000). This coating showed an improved rheological behavior as compared to the that of the commercial brand, that is to the crossover point of the xantham gum chocolate coating lies at lower which means that this coating has a better mechanical response (higher solid behavior at 25°C and stability) and also better flow behavior at high temperatures with both modules having lower values as those of the commercial brand indicating a lower viscosity, which is possibly due to the coating composition (due to the enhanced fatty acid chain mobility).…”

Avaliação De Propriedades Térmicas De Manteiga De Cacau E Gorduras Alternativas

“…Conforme a legislação brasileira, até 2003, só podia ser denominado de chocolate o produto composto unicamente por manteiga de cacau como fase gordurosa, além da gordura do leite, presente nos chocolates ao leite e branco. Quando se acrescentavam outras gorduras vegetais o produto era denominado de "chocolate composto" ou "chocolate fantasia", ou MIQUEL et al, 2001;VAZQUEZ et al, 2004;MARTÍNEZ et al, 2007). A manteiga de cacau possui três principais triacilgliceróis simétricos, POP (1,3-dipalmito-2-óleo triacilglicerol), POS (1-palmito-2-óleo-3-estearo triacilglicerol) e SOS (1,3-diestearo-2-óleo triacilglicerol), os quais, somados, podem representar mais de 75 % da composição da gordura.…”

“…Este trabalho teve como objetivo avaliar as propriedades térmicas (temperatura de fusão e entalpia) de amostras cristalizadas de manteiga de cacau com gorduras alternativas para futuras aplicações em chocolates. Os resultados mostraram que o maior decréscimo no ponto de fusão das misturas ocorreu a partir da incorporação de MIQUEL et al, 2001;VAZQUEZ et al, 2004;MARTÍNEZ et al, 2007). A manteiga de cacau possui três principais triacilgliceróis simétricos, POP (1,3-dipalmito-2-óleo triacilglicerol), POS (1-palmito-2-óleo-3-estearo triacilglicerol) e SOS (1,3-diestearo-2-óleo triacilglicerol), os quais, somados, podem representar mais de 75 % da composição da gordura.…”