L-Theanine improves emulsification stability and antioxidant capacity of diacylglycerol by hydrophobic binding β-lactoglobulin as emulsion surface stabilizer

Diacylglyceml (DAG) is commonly used as fat substitute in food manufacture due to its functional properties, but DAG has poor emulsification and oxidation stability, which limits its wide application in food industry. In this work, fluorescence quenching data and thermodynamic parameters were analyzed to investigate the interaction mechanism between L-theanine (L-Th) and beta-lactoglobulin (beta-LG). DAG emulsion was prepared by using beta-lactoglobulin-theanine (beta-LG-Th) as surface stabilizer, and its emulsification and oxidation stability were evaluated. The results showed that the hydrophobic interaction played an important role on the conjugate of beta-LG and L-Th due to the negative values for Delta G, positive values for Delta H and Delta S at pH 4.0, pH 6.0 and pH 8.0. The DAG has been better embedded by using beta-LG-Th as surface stabilizer, and the droplet size was about 0.2 mu m to 1.5 mu m when the pH was 6.0, the ratio of L-Th to beta-LG was 1:1. beta-LG-Th as surface stabilizer for DAG can increase the zeta-potential and emulsion index, make the emulsion droplet size distribution more uniform. The L-theanine was better to be used to improve the emulsification stability and antioxidant capacity of DAG by binding beta-LG as surface stabilizer.

Automated summary

The interaction mechanism between L-theanine and beta-lactoglobulin in the preparation of diacylglycerol (DAG) emulsion was investigated, showing that hydrophobic interaction played an important role. Using beta-lactoglobulin-theanine as a surface stabilizer improved the emulsification stability and antioxidant capacity of DAG.