Additionally, sialic acid is an important component of gangliosides in the animal brain, which is related to memory ability and intellectual development, and is related to neonatal liver function.

Sialic acid usually binds to the non-reducing ends of the sugar chains of glycolipids and glycoproteins and plays the role of receptor ligands in fertilization, immunity, differentiation, information transmission, and other activities. Under physiological conditions, sialic acid has a negative charge, is easy to combine with positively charged minerals and some vitamins (B 12), and improves their absorption efficiency.

Sialic acid has been proven to take part in a variety of physiological functions on the cell surface and plays a very important role in regulating human physiological and biochemical functions. Sialic acid, which was isolated from mucin of the submandibular gland early in 1957, is an acidic aminosaccharide (5-acetamido- 3,5-dideoxy-D-glycerol-D–galacta-nonyl ketone sugars) with nine pyranose structures. A suitable emulsifier is very important for the establishment of stable oil-in-water emulsions. It is used to reduce the viscosity of chocolate products. PGPR, which is an oligomeric nonionic surfactant formed by esterification of castor oil fatty acids and polyglycerol, is an extremely strong lipophilic emulsifier. It is also insoluble in water but can be highly dispersed in water.

Although lecithin is soluble in mineral oil, it cannot be dissolved in unheated vegetable oil. The principal components of Lecithin include phosphoric acid, choline, fatty acid, glycerol, glycolipid, triglyceride, and phospholipid. Lecithin is the only natural emulsifier at present, mainly from soybeans and eggs. Įmulsifiers that can form W/O emulsions need a low HLB. The stability of water-in-oil emulsion depends on the composition of the emulsion and various process parameters, including the type and concentration of hydrophobic emulsifier, nature of the oil phase, homogenization parameters, the ratio of oil phase to water phase, and homogeneous technology. The high fluidity of water droplets will promote the instability of W/O emulsion through precipitation flocculation, polymerization, and Ostwald ripening. The W/O emulsion is a thermodynamically unstable system because of the high interfacial area of the dispersed phase. The dispersion system of emulsion is formed by the dispersion of a liquid as droplets in another liquid that is immiscible with it, and the stability of the emulsion system can be enhanced by using surfactants with proper hydrophilic and lipophilic balance (HLB).

The excellent properties of emulsion determine its bright application prospect in the fields of food, medicine, and cosmetics. These results indicated that the W/O emulsions could effectively co-load and protect sialic acid and chitosan and thus could be a novel method for increasing the stability of these water-soluble bioactive compounds. Moreover, the storage stability showed that there was no significant change in droplet size distribution and Sauter mean diameter of the emulsions at room temperature (25 ☌) for 30 days. Initial droplet size distribution curves of the two stable emulsions displayed unimodal distribution, and the rheological curves displayed the characteristics of shear thinning and low static shear viscosity. Two stable W/O emulsions that were olive oil-based with 1.5% ( w/ v) PGPR+ 0.5% ( w/ v) LE and maize oil-based with 2% ( w/ v) PGPR+ 0% ( w/ v) LE were obtained. Increasing the concentration of PGPR and LE presented different effects on emulsion formation between olive oil-base and maize oil-base. The results revealed that the aqueous phase of 5% ( w/ v) SA and 2% ( w/ v) chitosan could form a stable complex and make the aqueous phase into a transparent colloidal state. Emulsions were prepared using two different oils (olive oil and maize oil) and polyglycerol polyricinoleate (PGPR) alone or in combination with lecithin (LE) as emulsifiers. This study was designed to co-load sialic acid (SA) and chitosan in a water-in-oil (W/O) emulsion and investigated its characterization and stability.

Water in oil emulsion base water