Research On Preparations Of Amphoteric Starch Using The Semi-dry Process

The preparation of amphoteric starch using semi-dry method was investigatedin order to provide valuble data for its industrialization.In addition,someproperties of amphoteric starch were discussed in this dissertation.Firstly, the cationic starch with low degree of substitution was preparedvia reacting starch with 3-chloro-2-hydroxypropyltrimethylammoniumchloride(CHPTMA) using the semi-dry process. Through single factor tests andorthogonal tests, it was concluded that under conditions that corn starch 50g,sodium/ amine molar ratios 1.6, temperature 100℃, reaction duration 3h, thecontents of water 25%,amine 1.7g,the optimized reaction efficiency wasobtained;under conditions that corn starch 50g, sodium/ amine molar ratios 1.6,temperature 100℃, reaction duration 2.5h, the contents of water 25%, amine3.75g,the optimized and relatively high DS was obtained.Immediately all sorts of factors that influencing reaction were investigatedduring the phosphorylation of starch.It attach much importance on the effectsof urea on the reaction.The urea was not only catalyst on the preparation ofstarch phosphate but also a composition of the reaction.The urea could have thestarch crosslinked, lower the maximum viscosity, increase the gelatinizationtemperature and influence the paste clarity, solubility and swellingability.Then the amphoteric starch was prepared by reacting with previously madecationic starch using STP. The results of orthogonal design of regressionindicated that the optimized condition was: ①cationic starch(DS=0.03812) 50g,STP2g, reaction temperature 128.2℃,reaction pH5.90,reaction durations 4.2h,anionic DS 0.0135,RE=70.32%;②cationic starch(DS=0.03812) 50g, STP1g, reactiontemperature 141.6 ℃ ,reaction pH5.61,reaction durations 2.6h, anionic DS0.0092020,RE=80.12%;③ cationic starch(DS=0.03812) 50g, STP0.5g, reactiontemperature 142 ℃ ,reaction pH5.72,reaction durations 3.65h, anionic DS0.006726,RE=83.12%.In the end,the properties of amphoteric starch with different DS preparedin the same conditions were discussed.From the Brabender viscosity curve, thepaste of amphoteric starch had higher pasting temperature,more stability andreduced tendency to retrograde comparing with cationic starch;Inaddition,sugars and sodium chloride had also some influence on the pasteproperties of amphoteric starch. IR spectrum of corn starch and amphoteric starchmade sure that the final products consisted of cationic and anionic groups.Thechemical reaction occured not only in the amorphous regions but also in thecrystalline through the SEM of amphoteric starch.