Crystallization and polymorphism of cocoa butter equivalents from blends of palm mid fraction and hard stearins produced by enzymatic acidolysis of high oleic sunflower oil

Cocoa butter equivalents (CBEs) are formulated by mixing palm mid fraction (PMF) with silica-treated hard stearin fractions produced via enzymatic acidolysis of high oleic sunflower oil with various mixtures of stearic and palmitic acids. The CBE blends always contain ≈30% 1,3-distearoyl-2-oleoyl-sn-glycerol, but vary in 1,3-dipalmitoyl-2-oleoyl-sn-glycerol (POP; 40–45%) and rac-1-palmitoyl-2-oleoyl-3-stearoyl glycerol (POSt; 10-16%) content. Overall symmetric disaturated monounsaturated (Sat-O-Sat) levels range from 81–86%. The effects of varying POP/POSt content on the non-isothermal and isothermal crystallization (at 20 °C) of the CBEs are then studied using differential scanning calorimetry (DSC), stop and return DSC, and X-ray diffraction (XRD), and compared with CB. Four polymorphs (I/sub-α, II/α, IV/β′, and V/β) are identified which appear at different stages. The addition of PMF (raising POP levels) slows crystallization rates compared to the original stearins, but higher levels of POP also produce a small amount of V/β in under 4 h at 20 °C via apparent transformation from II/α. This does not occur with (high POSt) CB samples. However, after storage at 20 °C for 7 days, CB demonstrates greater transformation to V/β (from IV/β′) as confirmed via XRD. Solid fat contents of CBE blends are higher than CB due to higher Sat-O-Sat levels. Practical applications: The paper demonstrates a new route for formulating CBEs. The relative proportions of StOSt, POSt and POP in the formulation can be controlled by changing the proportions of palmitic and stearic acid used in the enzymatic acidolysis and the blend ratio with the PMF. This can then be used to fine-tune the crystallization behavior.