Optimisation of the carvacrol encapsulation method into PHBV nanoparticles

• Emulsification and low surfactant concentration increased the carvacrol recovery. • Nanoprecipitation and high surfactant concentration increased PHBV recovery. • Emulsification and high carvacrol/PHBV ratio increased the loading capacity. • Low carvacrol/PHBV and aqueous/organic ratio increased the process efficiency. • Emulsification induced more spherical and separated nanoparticles. The need of sustainable food packaging preserving food from degradation conducted to increase research on active packaging using essential oil, as carvacrol, for their antimicrobial and antioxidant properties. The encapsulation of this kind of volatile molecules is necessary and nanoencapsulation into biopolymers, as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) showed an increasing interest as a green solution, although this method again need to be improved. In this study, a full experimental design was developed to select the best method (nanoprecipitation and emulsification) and operating conditions (PHBV molecular weight, surfactant concentration, carvacrol/PHBV ratio and Aqueous/Organic phase volume ratios) to encapsulate carvacrol into PHBV. In this purpose, for each tested conditions, encapsulation efficiency (process efficiency, carvacrol recovery, PHBV recovery and loading capacity), as well as nanoparticles’ morphology and size were estimated, and statistically analysed. Carvacrol recovery and loading capacity were significatively highest (61 % and 100 % respectively) using emuslification method, low surfactant concentration, high carvacrol/PHBV ratio (for loading capacity) and low PHBV molecular weight (for carvacrol recovery). To the contrary, PHBV recovery increased (93 %) using the nanoprecipitation method, a high surfactant concentration and a low carvacrol/PHBV ratio, while process efficiency increased (73 %) with a low carvacrol/PHBV ratio and a low aqueous/organic phase volume ratio. Moreover, small spherical-shaped and separated nanoparticles were obtained using emulsification method, high surfactant concentration but low carvacrol/PHBV ratio. Therefore, including all the aspects of carvacrol nanoencapsulation into PHBV (shape and encapsulation efficiency) using emulsification method, with a low level for all parameters except the surfactant concentration are the most suitable strategy.