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Study On Preparation, Properties And Applications Of Cross-linked Hydropropyl Carboxymethyl Starch

Posted on:2014-08-06Degree:MasterType:Thesis
Country:ChinaCandidate:Q X GuoFull Text:PDF
GTID:2251330401954586Subject:Sugar works
Abstract/Summary:PDF Full Text Request
Crosslinked hydroxypropyl carboxymethyl starch (CHMS) was synthesizedthrough cross-linked hydroxypropylation carboxymethylation based on tapioca starch.In this study, the carboxymethylation process of cross-linked hydroxypropyl starch(CL-HPS) was studied. The physicochemical properties of CHMS and the particlestructure, as well as application in ketchup as thickener were tested.Firstly, effects of ethanol concentration, NaOH and chloroacetic acid (CA)dosage, reaction temperature and time on carboxymethylation were studied. From theperspective of increasing viscosity, the optimal conditions for preparing CHMS wereobtained by single factor experiments as follows: ethanol concentration was92%,NaOH﹕AGU (molar ratio) was1.6﹕1, CA﹕AGU (molar ratio) was0.8﹕1,reaction temperature was55°C, reaction time was2.5h.Secondly, the whiteness, viscosity, transparency, salt tolerance, and freeze-thawstability of CHMS were tested. Results indicated that: the viscosity of starch pasteincreased, the transparency was enhanced, the freeze-thaw stability and salt toleranceof starch were also improved. Rheological properties of CHMS were tested byrheometer and texture analyzer. Effects of modified methods on rheological propertiesshowed that: with degree of cross-linking increasing, the consistency coefficient Kincreased firstly and then decreased; with degree of hydroxypropylation increasing,the consistency coefficient K increased consistently; with degree ofcarboxymethylation increasing, the consistency coefficient K increased rapidly. Theeffects of modified methods on thread length of starch paste were as follows: thethread length of starch paste increased with lightly cross-linking, and decreased withhigher cross-linking; the degree of hydroxypropylation had no obvious effect on thethread length; the thread length significantly increased with carboxymethyl groups.Thirdly, the structure of CHMS was characterized by IR spectroscope, XRD,SEM, and Polarizing microscope. The IR spectrogram demonstrated that:characteristic absorption peaks at1611cm-1,1452cm-1appeared, proving thatcarboxymethyl groups linked with starch molecule. X-ray diffraction results showedthat the relative crystallinity was reduced from33.67%to22.32%aftercarboxymethylation, proving the crystalline regions of starch granules were destroyed.SEM graphs illustrated CHMS still remained particles, but the surface had becomevery rough, with particles stripes breakage increasing, many particles surface were recessed into small hole or even burst shape. These changes showed that thecarboxymethylation occurs not only in the surface, also in the interior of the starchparticles. Polarizing microscope graphs showed polarization cross of particles becomeweaker or even disappeared, indicating that the carboxymethylayion reaction hadcaused damage to the crystallization region of the starch granules.Lastly, CHMS as thickener and stabilizer in ketchup was studied, includingsensory evaluation, rheological and textural properties. Results showed that, theapplication value of this compound modified starch had been greatly improved.Results above showed, the preparation of CHMS could help to improve the value oftapioca starch in the industry.
Keywords/Search Tags:cross-linked, hydroxypropyl, carboxymethylation, preparation, properties
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