Investigation On Sugar Based Surfactant: Sucrose Esters

Sucrose stearates with the different proportion of monoesters were prepared by reacting sucrose and alkyl searate (AS) in the presence of alkali catalyst by "methanol process", "low soap solvent-free process" and " medium soap solvent-free microemulsion process". The influences of molar ratio of AS to sucrose, reaction temperature, the amount of catalyst and soap, and residual pressure etc. on the conversion of AS, the yield of sucrose esters and the proportion of mono-, di-and polyesters were investigated. On the basis of comparison of superiority of these three processes, the medium soap solvent-free microemulsion process was opted as the final process for producing sucrose esters. Sucrose palmitates, sucrose laurates and sucrose oleates were also prepared form the solvent-free process. In addition, changes in the proportion of mono-, di- and polyesters in reaction process were monitored by HPLC-ELSD.Some analytical techniques, such as TLC, HPLC-ELSD, ESI-MS, HPLC-MS, were applied for the analysis of sucrose stearates, sucrose palmitates and sucrose laurates. The qualitative and quantitative results of the sucrose esters, soap, fatty acid, sucrose and fatty acid ester in crude and purified products were obtained by using TLC and TLC scanner and different separate agents. HPLC-ELSD was also used for the separation of sucrose monoesters, diesters and polyesters. Pure sucrose palmitates were prepared and used for the identification of mono-, di- and polypalmitates in sucrose stearates and sucrose palmitate. Commercial and synthesized sucrose esters containing mono-, di-, tri- or higher esters were qualitatively analyzed using electrospray ionization-mass spectrometry (ESI-MS). Sucrose esters were also analyzed by high-performance liquid chromatography (HPLC) in combination with electrospray ionization mass spectrometric detection in positive ion mode.Relationships of the composition and structure of sucrose esters to interfacial properties were investigated. A two-dimensional model of solubility parameters was established by simplifying the Hansen's three-dimensional model. The model comprises three areas corresponding to solubility parameter and solubility of different sucrose esters. According to the interaction R, interfacial phenomena of different sucrose monoesters, diesters, triesters and some commercial sucrose esters and synthesized sucrose esters at oil-water interface can be interpreted logically.Some physiochemical properties of sucrose esters, such as foamability and form stability, stability in hard water and emulsifying power were investigated. The synergism of sucrose esters with other surfactants and effect of sucrose ester coating on storage life and quality of litchi was evaluated.