The cooling rate effect on the microstructure and rheological properties of blends of cocoa butter with vegetable oils

The elasticity (G′) and yield stress (σ∗) of blends of cocoa butter (CB) in vegetable oils (i.e., 30% CB/canola and 30% CB/soybean oil) crystallized at temperatures (TCr) between 9.5 °C and 13.5 °C and two cooling rates (1 °C/min and 5 °C/min) were determined, evaluating their relationship with parameters associated with the formation and structural organization of the crystal network [i.e., solid fat content (SFC), Avrami index, crystallization rate, fractal dimension (D)]. The results showed that TCr and cooling rate had a different effect for each blend on the three-dimensional organization of the crystal network, and on the proportion and size of β′ and β crystals. Thus, under low supercooling conditions at both cooling rates, the crystallized CB/canola oil blend was formed by a mixture of small β′ and large β crystals that provided high G′ and σ∗ at low SFC (i.e., 20.5–20.9%) and D (i.e., 1.66–1.72) values. The CB/soybean oil blend achieved similar G′ and σ∗ independent of cooling rate only at high supercooling. In this case, the crystal network was formed mainly by small β′ crystals with SFC (i.e., 25.4–26.3%) and D (i.e., 2.86–2.79) values higher (P < 0.05) than in the CB/canola oil blend at low supercooling.