The effect of supercooling on crystallization of cocoa butter‐vegetable oil blends

Abstract

AbstractThe solid fat content (SFC), Avrami index (n), crystallization rate (z), fractal dimension (D), and the pre‐exponential term [log(γ)] were determined in blends of cocoa butter (CB) with canola oil or soybean oil crystallized at temperatures (TCr) between 9.5 and 13.5°C. The relationship of these parameters with the elasticity (G′) and yield stress (σ*) values of the crystallized blends was investigated, considering the equilibrium melting temperature (TMo) and the supercooling (i.e., TCro−TMo) present in the blends. In general, supercooling was higher in the CB/soybean oil blend [TMo=65.8°C (±3.0°C)] than in the CB/canola oil blend [TMo=33.7°C (±4.9°C)]. Therefore, under similar TCr values, higher SFC and z values (P<0.05) were obtained with the CB/soybean oil blend. However, independent of TCr TAG followed a spherulitic crystal growth mechanism in both blends. Supercooling calculated with melting temperatures from DSC thermograms explained the SFC and z behavior just within each blend. However, supercooling calculated with TMo explained both the SFC and z behavior within each blend and between the blends. Thus, independent of the blend used, SFC described the behavior of G′eq and σ* and pointed out the presence of two supercooling regions. In the lower supercooling region, G′eq and σ* decreased as SFC increased between 20 and 23%. In this region, the crystal network structures were formed by a mixture of small β′ crystals and large β crystals. In contrast, in the higher supercooling region (24 to 27% SFC), G′eq and σ* had a direct relationship with SFC, and the crystal network structure was formed mainly by small β′ crystals. However, we could not find a particular relationship that described the overall behavior of G′eq and σ* as a function of D and independent of the system investigated.