Preparation of Glyceroglycolipids from Pumpkin and Their Effects on Polymorphic Transformation of Cocoa Butter

Abstract

Monogalactosyldiacylglycerol (MGDG), diagalactosyldiacylglycerol (DGDG) and trigalactosyldiacylglycerol (TGDG) were extracted from pumpkin, then hydrolyzed to the corresponding galactosylmonoacylglycerols by 1, 3-specific lipase from Rhizopus arrhizus; MGDG was then hydrolyzed to diacylglycerol (DG) by β-galactosidase from Aspergillus oryzae. The kinetics of polymorphic transformation on cocoa butter and the effect caused by the addition of these seven glyceroglycolipids were investigated. Each glyceroglycolipid could be incorporated at the level of 5% into the cocoa butter without changing the crystal lattice. The polymorphic transformation on cocoa butter was induced by continuous temperature cycling between 32 and 20°C at 12 h intervals and monitored with a differential scanning calorimeter. The result indicated that MGDG, DGDG, TGDG and DG significantly retarded the polymorphic transformation from Form V to VI of cocoa butter compared to the control, while the other glyceroglycolipids had no effect. The addition of MGDG was the most effective. These results indicate that the number of the acyl chain and galactose of glyceroglycolipid strongly influence the polymorphic transformation of cocoa butter.