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Study On Preparation And Property Of Hydroxypropyl Oxidized High Amylose Corn Starch

Posted on:2016-12-02Degree:MasterType:Thesis
Country:ChinaCandidate:K PanFull Text:PDF
GTID:2181330467983541Subject:Chemical processes
Abstract/Summary:PDF Full Text Request
In order to improve the property of high amylose corn starch and enlarge its application field,the high amylose corn starch was modified by the oxidized and hydroxypropylated compositemethod. The preparation of the hydroxypropyl oxidized high amylose corn starch was studied byusing the high amylose corn starch as material, the sodium hypochlorite as oxidant, the propyleneoxide as ether reagent, the sodium hydroxide as catalyst, the sodium sulfate as swellinginhibitor in this paper. The effect of factors such as amount of sodium hypochlorite, reaction time,reaction temperature, pH, amount of propylene oxide, amount of sodium hydroxide and amount ofsodium sulfate on the oxidized reaction and etherization reaction were investigated respectively.The carboxyl content were measured by hot paste titration and the degree of substitution weremeasured by spectrophotometry.The optimum conditions for preparing oxidized high amylose corn starch and hydroxypropyloxidized high amylose corn starch were obtained by Design-Expert software. For the oxidizedmodification, the best conditions were as follows:amount of sodium hypochlorite50%, reaction time2h, reaction temperature40°C and pH9, respectively. The results showed that the best reactionconditions for preparing the hydroxypropyl oxidized high amylose corn starch were:amount ofpropylene oxide10%, reaction temperature42℃, amount of sodium hydroxide1.3%, reactiontime17.5h and amount of sodium sulfate9.0%.The physicochemical properties of corn starch, high amylose corn starch, oxidized highamylose corn starch, hydroxypropyl high amylose corn starch and hydroxypropyl oxidized highamylose corn starch were compared. The results showed that the swelling power, stability of coldand hot viscosity and alkali resistance were improved, while the retrogradation were weakened byoxidizing and etherization reaction. The hydroxypropyl high amylose corn starch had betterproperties in acid resistance, conversely, the oxidation decreased the properties of acid resistance.The blue value decreased obviously after hydroxypropylation.The granular structure, thermal property and microcrystalline structure of thehydroxypropyl oxidized high amylose corn starch were characterized by the infraredspectrogram, thermol gravimetric analyzer, differential scanning calorimetry and X-raydiffraction. At the same time, the particle morphology of the high amylose corn starch, oxidized high amylose corn starch and hydroxypropyl oxidized high amylose corn starch wereobserved by a polarizing microscope. The main results were as follows: a new absorption peakon the infrared spectroscopy of oxidized high-amylose corn starch was at wave number1735.6cm-1, which belonged to the stretching vibration of the C=O group. The onset decompositiontemperature and the conclusion decomposition temperature decreased in turn after oxidationand hydroxypropylation according to the TGA curves. The order of thermal stability wereoxidized high amylose corn starch, hydroxypropyl oxidized high amylose corn starch, highamylose corn starch.The DSC curve of high amylose corn starch a, oxidized high amylosecorn starch and hydroxypropyl oxidized high amylose corn starch showed the endothermicpeak at a span of20~200℃, the melting enthalpy of oxidized high amylose corn starch andhydroxypropyl oxidized high amylose corn starch were decreased in order, which suggestedthat the hydrogen bonds between the molecules of starch in the amorphous regions wasweakened owing to introduction of the carboxyl and hydroxypropyl group. The polarizationcross of high amylose corn starch was obvious, the starch granules was usually in ovoid shape.The structure of high amylose corn starch belonged to a B-type.
Keywords/Search Tags:high amylose corn starch, oxidation, hydroxypropyl, property
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