Ethanol-soluble polysaccharide from sugar beet pulp for stabilizing zein nanoparticles and improving encapsulation of curcumin

Ethanol-soluble polysaccharide (ESP) is a highly ethanol-soluble (85% v/v) fraction from the precipitation process of sugar beet pectin and holds the potential to be utilized for food purposes. This study aimed to explore ESP as a coating polymer to stabilize zein nanoparticles against agglomeration via co-dissolving ESP and zein in an ethanol/water mixture (85% v/v) and subsequently dispersing into the water to form composite nanoparticles. Structural analyses showed that the ESP contained 28.3 wt% galacturonic acid, 45.7 wt% neutral sugar, and 17.6 wt% protein, and that its average molecular weight was 93,157 Da. In this study, we fabricated ESP-coated zein (zein-ESP) nanoparticles with a diameter of around 248 nm using the antisolvent co-precipitation method. These zein-ESP nanoparticles were stable over a wide pH range of 2.0–8.0 when the ESP:zein mass ratio was higher than 0.6:1. Additionally, the nanoparticles exhibited good stability in environmental stresses such as sodium ion concentrations of 400 mM and high temperatures of 90 °C (for 120 min). The encapsulation efficiency of Cur improved significantly, from 68.5% with the zein nanoparticles to 88.7% with the zein-ESP nanoparticles. When encapsulated by zein-ESP nanoparticles, Cur presented as an amorphous form and was released in a sustained and controlled manner after exposure to simulated gastrointestinal fluids, resulting in enhanced solubility and in vitro bioaccessibility, as compared with the free Cur. Altogether, ESP has great potential to stabilize zein nanoparticles-based delivery systems for hydrophobic bioactive compounds with enhanced water solubility and encapsulation efficiency for use in the food and pharmaceutical industries.