Optimization of nanoemulsion formulations using saponin from quillaja bark, a natural surfactant
Conference Paper
Overview
Overview
abstract
Nanoemulsions are systems comprising three constituents, hydrophilic, lipophilic and amphiphilic compounds, forming a single macroscopic phase with reduced particle size. Nowadays, an important topic under study is the introduction of natural products as surfactants. This is partly motivated by consumer’s demands for more sustainable products, leading industry and researchers to search for alternatives with natural-friendly connotation, avoiding the large utilization of the synthetic forms. In this context, recent studies have focused the use of saponins, highlighting its physicochemical properties, and commercial potential for the development of natural-based emulsions [1,2]. Thus, the objective of this work is to optimize a nanoemulsion formulation incorporating saponin as surfactant, through response surface methodology (RSM).
The systems were formed with the natural surfactant, pure saponin from Quillaja Bark, and glycerol as co-surfactant. Sweet almond oil was used as the lipophilic component. To produce the nanoemulsions, a high energy technique was chosen, namely high-pressure homogenization (HPH). The produced emulsions were characterized by measuring the zeta potential, droplet size (by laser diffraction) technique), pH and viscosity. In order to select the best formulation, a 2k full-factorial design with 3 factors and 3 replicates at the central point was implemented. The chosen parameters were oil/water ratio (10/90, 20/80, 30/70, w/w), surfactant content in the mixture (0.5, 1 and 1.5%, w/w) and the surfactant/co-surfactant ratio (50/50, 75/25, 100/0, w/w). The results obtained with the produced formulations showed zeta potential to vary between -40.3 and -46.0 (evidencing high stability) and a particle size in volume comprised in the range 111.9-431.4 nm. These two parameters were selected to perform the experimental design to find the most stable systems.
Nanoemulsions with pure saponin were successfully produced, where the formulations with better long term stability were those prepared with the lower amount of oil, which is 10%. It is important to point out that taking into consideration final product applications, to have less than 10% of the lipophilic component it is not suitable. Regarding the amount of surfactant, smaller droplet sizes, and consequently lower zeta potentials, were achieved at its highest content. The co-surfactant glycerol showed to have no significant impact in zeta potential, even it showed to slightly increase droplet’s size.
This work is financed by POCI-01-0145-FEDER-006984 (LA LSRE-LCM) and UID/AGR/00690/2013 (CIMO), funded by FEDER, through POCI-COMPETE2020 and FCT; Project NORTE-01-0145-FEDER-000006, funded by NORTE2020 under PT2020.
