Characterization and response surface optimization driven ultrasonic nanoemulsification of oil with high phytonutrient concentration recovered from palm oil biodiesel distillation

[Display omitted] Nanoemulsions are kinetically stable colloidal systems with low viscosity. They are generally prepared using oil and a surfactant in an aqueous medium by dispersion, producing nanometer sized droplets. Nanoemulsions often have a higher load capacity for active lipophilic ingredients than those of microemulsions, which is vital for various applications. In this study, nanoemulsions based on oil‒in‒water (O/W) were obtained using ultrasonication (US) assisted by microwaves (MW), using oil with high phytonutrients concentration (OHPC) recovered from the distillation of palm oil biodiesel, diluted in high oleic palm olein (HOPOo) (2–6 % w/w) in the oily phase, with soy lecithin (1.0–2.0 % w/w), gelatin (1.5–2.5 % w/w), and gum Arabic (1.5 to 2.1 % w/w) and Milli‒Q water as the aqueous phase were used for the preparation of various nanoemulsions. Three experimental designs based on the response surface methodology (RSM) were used for optimizing the process. The physical stability of the optimized nanoemulsion was assessed at 4 and 20 °C during 4 days of storage by monitoring the average particle size and color of the nanodispersion. The effect of the techniques used for nanostructuring over the molecular components and phytocompound contents in the oily phase was assessed by FTIR, GC‒FID, GC‒MSD and HPLC‒FLD/DAD analyses, respectively, before and after processing the nanoemulsion. In the OHPC, the estimated average concentrations were found to be 17,584 mg·kg−1 of vitamin E, 155464 mg·kg−1 of phytosterols, and 5675 mg·kg−1 of squalene. The optimal conditions for producing emulsions with higher stability were 2.0 % w/w of the oily phase, 1.998 % w/w of soy lecithin, 1.596 % w/w of gelatin, and 1.564 % w/w of gum Arabic in the aqueous phase, and three cycles of US‒MW treatment. The average particle size in the optimized nanoemulsion was 83.1 ± 0.5 nm, which remained almost constant during storage at 4 °C and increased gradually during storage at 20 °C. No substantial differences in the molecular composition and phytocompound contents in the oily phase were found before and after processing the nanoemulsion. This study aims to highlight the benefits of OHPC as a new raw material for the utilization of phytonutrients of nutritional and functional value, in addition to displaying the optimal conditions for the production of OHPC in HOPOo nanoemulsions by US–MW via statistical experimental design. Finally, OHPC nanoemulsions could be used in the for