Research Of The Supercritical CO₂ Treatment On Cassava Starch And The Synthesis Of Octenyl Succinate Anhydrate Modified Starch

The technology of chemical synthesis and the extraction in supercritical carbon dioxide fluid is a green chemical technology that has broad application prospects. This paper combines the supercritical technology with the technology of starch modification. We discussed the effects of supercritical CO2 treatment on properties of cassava starch and the process parameters of the synthesis of octenyl succinic anhydride modified starch in supercritical CO2. Meanwhile, we studied the application performance of the octenyl succinic anhydride modified cassava starch.Firstly, cassava starch was extracted in different conditions with supercritical carbon dioxide. The effects of supercritical CO2 treatment on properties of cassava starch were evaluated by using scanning electron microscope, X-ray diffraction analyzer, Brabender visco-analyser, or other methods. The results showed that the morphology of the treated starch was not obviously changed, but the swelling degree decreased and the crystallinity increased. It also could be obtained that the anti-precipitability of the treated starch’s gel was strengthened and the freeze-thaw stability reduced. Meanwhile, Brabender viscosity analysis suggested that the gelation temperature of the treated starch could be slightly raised, the peak viscosity of the treated starch’s gel decreased and the thermal stability little changed.Secondly, using supercritical carbon dioxide as reaction medium, cassava starch as raw material, octenyl succinic anhydride(OSA) as esterifying agent, sodium hydroxide as catalyst to synthesis octenyl succinic anhydride modified starch(OSAS). On the base of the best single factors, the suitable parameters of the preparation conditions were selected as follows: 0.6%NaOH concentration (in proportion to starch, w/w), reaction time 3h, reaction temperature 90 ℃, pressure of 15MPa, amount of OS A,6%(in proportion to starch, w/w). Under these conditions, DS was 0.0103. The highest RE(31.07%) was obtained by changing the amount of OSA to 4%. And the structures of the samples were tested by FTIR, NMR, XRD, SEM, et al.Finally, the OSAS had been processed by multiple charged metallic salt solutions like calcium chloride solution, barium chloride solution, ferric chloride solution and so on. Emulsification ability and emulsion stability of different ionic starch ester were investigated. The results showed that emulsion stability of the emulsion of OSAS that processed by multiple charged metallic salt solution were decreased when the OSAS concentration was 0.4%, oil/water ratio was 1:10 and homogeneous time was 8 min. However, the study of lemon oil microcapsules preparation by spray-drying showed that the embedding rate of OSAS that processed by multiple charged metallic salt solution was higher than unprocessed when the wall material concentration was 5%, the core wall ratio was 1:3 and the homogeneous time was 8 min, and the embedding rate of the microcapsule that prepared by ferric ion starch ester was as high as 86.64%.