Interactions between phospholipid head groups and a sucrose crystal surface at the cocoa butter interface

Lecithin is one of the most used food additives in a wide varying range of food products. It has great beneficial effects on rheological properties and prolongs the shelf-life of foods. Lecithins have a varying molecular composition due to environmental influences. To characterize the molecular components of lecithin, the interactions between different phospholipid head groups and a sucrose crystal surface were examined by performing non-equilibrium molecular dynamics simulations on the example of chocolate conching. Pulling simulations were used to detach six different lecithin molecules from a sucrose crystal. Forced detachment allows characterization of the strength of the interaction between the sucrose crystal and individual phospholipids, as it models the reversed process of lecithin adsorption during chocolate conching. The required work for the detachment of 1,2-dilinoleoyl-phosphatidylcholine (DLPC), 1-palmitoyl-2-linoleoyl-phosphatidylcholine (PLPC), 1,2-dilinoleoyl-phosphatidylethanolamine (DLPE), 1-palmitoyl-2-linoleoyl-phosphatidylethanolamine (PLPE), 1,2-dilinoleoyl-phosphatidylinositol (DLPI), and 1-palmitoyl-2-linoleoyl-phosphatidylinositol (PLPI) from the (1 0 0) sucrose crystal surface was calculated. Molecules with the phophatidylinositol head group (DLPI, PLPI) were shown to require the biggest detachment work, followed by phospatidylcholine molecules (DLPC, PLPC) with medium detachment work and phosphatidylethanolamine molecules (DLPE, PLPE) with the lowest detachment work. The different aliphatic chains seem to have no impact on head group detachment. Furthermore, the influence of different adsorption states of DLPC and PLPE molecules were examined. It was shown that the required detachment work correlates with the number of hydrogen bonds between the phospholipids and the sucrose.