Facile lipase-catalyzed synthesis of a chocolate fat mimetic

Abstract

A cocoa butter equivalent (CBE) was synthesized enzymatically from readily available edible fats with fatty acid and triacylglycerol compositions that closely resemble the fat present in chocolate, cocoa butter. A commercially available immobilized fungal lipase, Lipozyme RM IM, was used as the reaction catalyst. Reaction parameters were a temperature of 65 °C, water activity of 0.11, a 4 h reaction time, and a substrate mass ratio of a commercial enzymatically synthesized shea stearin (SS) to palm mid-fraction (PMF) of 6:4 (w/w). Fractionation was also used after reaction completion to further approach the triacylglycerol composition of cocoa butter by removing trisaturated and unsaturated triacylglycerols. The yield of the triglyceride 1-palmitoyl-2-oleoyl, 3-stearoyl-glycerol (POS) produced was 57.7% (w/w). The amounts of 1,3-dipalmitoyl-2-oleoyl-glycerol (POP), (POS) and 1,3-stearoyl-2-oleoyl-glycerol (SOS) in the final CBE were 11.2%, 36.3%, and 34.8%, respectively. In comparison, the amounts of POP, POS and SOS in the cocoa butter used in this study were 15.2%, 38.2%, and 27.8%, respectively. No significant differences (P > 0.05) in melting point and enthalpy of fusion between CB and the CBE were observed. In comparison, a non-interesterified blend of SS and PMF (60:40 w/w) showed significantly (P < 0.05) higher melting point and lower enthalpy of fusion compared to CB. The crystal polymorphic form V of CB (β2-3L) was similar to that of CBE and SS/PMF (60:40 w/w). The solid fat content (SFC) vs. temperature profile of the CBE generally resembled that of CB, except that the CBE had significantly (P < 0.05) higher SFCs at 5, 10, 15, 20 and 25 °C compared to both CB and SS/PMF (60:40 w/w). Addition of 15% (w/w) CBE to CB did not cause any changes in physical properties (melting point, SFC and crystal polymorphic forms) of the CB. This study demonstrates the potential for synthesizing a CB-like CBE using a green, rapid, straightforward one step enzymatic conversion followed by fractionation from widely available edible fats.