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The Study Of Glutaric Acid Starch Ester And Its Crosslinked Composite Modification

Posted on:2016-01-15Degree:MasterType:Thesis
Country:ChinaCandidate:Y N ZhengFull Text:PDF
GTID:2191330479494231Subject:Sugar works
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In this study, glutaric acid starch ester was obtained by the modifications of native corn starch with glutaric anhydride in aqueous phase and alcohol phase, respectively. Furthermore, cross-linked starch ester was also prepared in aqueous phase with epichlorohydrin. The physical and chemical properties of different starch esters were investigated and the detailed results were showed as follows:1. Glutaric acid starch ester was prepared in aqueous phase. The effects of reaction conditions such as starch concentration, reaction time, temperature and p H value on the degree of substitution(DS) were studied by the single factor analysis and orthogonal test. The optimum conditions for the preparation of glutaric acid starch ester in aqueous(AGAS) were starch concentration of 40%(w/w), reaction time of 2 h, temperature of 35℃ and reaction p H of 8.5. When adding glutaric anhydride content of 4% in the optimum reaction system above, the DS of AGAS was 0.0230.2. The study on physicochemical properties of AGAS. After modification, the peak viscosity of starch had greatly improved. And with the increase of DS, this trend became more obvious. Compared with native corn starch, the viscosity and transparency of AGAS with DS 0.0356 had been significantly improved with an increasement of 400% and 2900%, respectively. Meanwhile, the viscosity and transparency were 88.2% and 117% that of native potato starch. There were new absorption peaks appeared in the FTIR spectrogram of AGAS. The surface of starch granules had changed little. AGAS was still A-type crystal structure and the gelatinization enthalpy decreased slightly. In addition, the AGAS was superior to the native corn starch in terms of freeze-thaw stability and anti-shearing force, but the hot paste stability and salt tolerance were both decreased.3. Preparation and properties of dual-modified starch which was cross-linked by epichlorohydrin and esterified by glutaric anhydride were investigated. The effect of modification sequences on the DS and cross-linking degree was studied. The crosslinked- esterification was proved to be the most efficient method. The hot paste stability of starch had enhanced because of the composite modification. The peak viscosity of dual-modified starch was deeply related with cross-linking degree. When the cross-linking degree was at a low range, it was positively correlated with peak viscosity, otherwise, they were negatively correlated. Among them, the viscosity of dual-modified starch with DS 0.0247 and μ 2.75 m L had increased 627% and 21.7% compared with native corn starch and native potato starch, respectively. From FTIR, we determined that the glutaric acid groups were successfully bonded with starch; XRD showed that the dual-modified starch was still A-type crystal structure. The freeze-thaw stability of dual-modified starch was significantly improved. Transparency was negatively correlated with the cross-linking degree.4. The study on preparation and properties of glutaric acid starch ester in alcohol-phase(EGAS). The optimum conditions obtained by single factor experiments and orthogonal test were showed as follows: starch concentration was 35%, reaction temperature was 35℃, reaction time was 3 h and reaction p H was 8.5. Under such conditions, adding glutaric anhydride content of 4%, we obtained the product with DS 0.0252. New absorption peaks were appeared in the FTIR spectra. There was no much difference with native corn starch on granules surface and it also belonged to A-type crystal structure. The gelatinization enthalpy of EGAS decreased. But the completed temperature of gelatinization increased, which was different from AGAS. After a comparative study on the native corn starch and EGAS, we found the peak viscosity of EGAS improved and the gelatinization temperature decreased. Compared with AGAS, the hot paste stability of EGAS had an evident improvement. Characters including freeze-thaw stability, shearing and salt resistance of EGAS were all much better than those of the native corn starch and AGAS. The transparency of EGAS was higher than the native corn starch but lower than AGAS. EGAS not only had a higher peak viscosity but also showed excellent hot paste stability. According to the comparison of EGAS and AGAS, we concluded that both esterification and cross-linking occurred in alcohol-phase, while.only esterification occurred in aquous-phase.
Keywords/Search Tags:Corn starch, Esterification, Cross-linked, Glutaric anhydride
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