Phospholipase D catalyzed synthesis and characterization of novel phosphatidyl caffeoyl glycerol and synergetic interactions with soy protein isolates in stabilizing oil-in-water emulsions

This work presents an efficient enzymatic synthesis of a novel phosphatidyl caffeoyl glycerol (PA-CG) via phospholipase D (PLD)-catalyzed transphosphatidylation of phosphatidylcholine (PC) with caffeoyl glycerol (CG). Under optimized conditions (CG/PC 4:1 mol/mol, water/methyl tert-butyl ether (MTBE) 0.15:1 V/V, PLD 30 U/mL, 40 °C, 3 h), the yield exceeded 95% (HPLC mol% relative to PC), and the product was confirmed by NMR and ESI-MS. PA-CG exhibited additive antioxidant activity over PC and CG in DPPH, ABTS, and FRAP assays. When combined with soy protein isolates (SPI), PA-CG outperformed SPI or SPI+PC in stabilizing oil-in-water (O/W) emulsions, evidenced by the highest emulsifying activity index, smallest and most homogeneous droplets, and lowest creaming index, attributed to its excellent amphiphilic interfacial properties. Moreover, SPI+PA-CG emulsion displayed the slowest increase in peroxide value (POV) and thiobarbituric acid reactive substances (TBARS) over time. Collectively, PA-CG is a promising dual-function antioxidant and emulsifier for food, cosmetic, and pharmaceutical applications.