Multi-scale simulations of wax dissolution and crystallization in oil

Wax esters are common food-grade oil-structuring agents, exhibiting high oil-binding capacity and versatile textural and thermal characteristics, marking them as promising candidates for food applications. The ability of wax esters to structure oil has been intensively studied, while their dissolution and crystallization behavior still lack comprehensive understanding.

In the current research, the interactions between wax esters and triacylglycerols were investigated using molecular dynamics simulations at both atomistic and coarse-grained scales. Specifically, simulation boxes composed of 10% stearyl palmitate wax ester and 90% of the triacylglycerol (TAG) 1,2-dioctanoyl-3-decanoyl glycerol were constructed. Additionally, pure wax and pure TAG simulation boxes were used as controls. The atomistic resolution of all-atom simulations was initially employed to study the tendency of wax ester molecules to interact with other wax ester molecules and TAG molecules. Analysis of the interactions between the methyl ends of the molecules showed that the fatty alcohol side of the ester bond tends to form more interactions with a shorter characteristic distance compared with the methyl end of the fatty acid side. Evaluating the interactions formed by the ester carbon of the wax esters with the central carbon on the glycerol group of the TAGs revealed a mild preference for wax-wax interactions over wax-TAG interactions. Interestingly, the preference for wax-TAG interactions was slightly higher than that for TAG-TAG interactions. These observations suggest a possible deviation from ideal dissolution behavior. The atomistic simulations were further utilized to modify and validate a coarse-grained simulation model. These coarse-grained simulations were then used to study systems with much larger simulation boxes and longer simulation periods, providing insights into the larger-scale molecular organization.

Overall, this work employs multi-scale molecular dynamics simulations to study the mixing behavior of wax esters in oil, providing a fundamental scientific basis for the implementation of wax esters in fat-containing foods.