Eui-Seok Lee

Ostwald Ripening Stability of Curcumin-Loaded MCT Nanoemulsion: Influence of Various Emulsifiers

Curcumin is a flavonoid found in the rhizome of the turmeric plant (Curcuma longa L.) and has recently attracted interest because it has numerous biological functions and therapeutic properties. In the present study, we attempted to incorporate curcumin into medium-chain triglyceride (MCT) nanoemulsions (0.15 wt% curcumin, 10 wt% MCT oil, and 10 wt% emulsifiers) with various emulsifiers [polyoxyethylene (20) sorbitan monolaurate (Tween-20), sorbitan monooleate (SM), and soy lecithin (SL)]. The physicochemical properties of the nanoemulsions including the Ostwald ripening stability were investigated. The initial droplet size was found to be 89.08 nm for the nanoemulsion with 10 wt% Tween-20 (control), and when Tween-20 was partially replaced with SM and SL, the size decreased: 73.43 nm with 4 wt% SM+6 wt% Tween-20 and 67.68 nm with 4 wt% SL+6 wt% Tween-20 (prepared at 15,000 psi). When the nanoemulsions were stored for 28 days at room temperature, the droplet size increased as the storage time increased. The largest increase was observed for the control nanoemulsion, followed by the 4 wt% SL+6 wt% Tween-20 and 4 wt% SM+6 wt% Tween-20 systems. The Turbiscan dispersion stability results strongly supported the relationship between droplet size and storage time. The time-dependent increase in droplet size was attributed to the Ostwald ripening phenomenon. Thus, the Ostwald ripening stability of curcumin-loaded MCT nanoemulsions with Tween-20 was considerably improved by partially replacing the Tween-20 with SM or SL. In addition, curcumin may have acted as an Ostwald ripening inhibitor.

Studies on the preparation of Rice Bran Protein Concentrate by Ultrafiltration

In this study, ultrafiltration with a membrane of molecular weight cut off (MWCO) 50 kDa or 100 kDa was applied to produce rice bran protein concentrate and influence process variables such as operation pressure, time, and volume concentration ratio (VCR) on the composition of rice bran protein concentrate and changes in permeation flux were investigated. An increase in permeation flux was observed in accordance with increasing operation pressure, while it decreased with operation time, possibly due to concentration polarization. In addition, the permeation flux was observed to be higher when a membrane with larger MWCO was used and a maximum permeation flux (32 L/m·h) was observed with an operation pressure of 2 kgf/cm 2 and a 100 kDa membrane. Protein content in the concentrate rose with increasing VCR, and also with membranes of smaller MWCO (i.e, 50 kDa). It was found at VCR 8 and with an operation pressure of 2 kgf/cm 2 that total processing time decreased by 40% and average permeation flux increased by about 2 times, when a membrane with 2 times larger MWCO (i.e., 50 kDa→100 kDa) was used.