Experimental Studies on the Carboxymethylation of Arrowroot Starch in Isopropanol-Water Media
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English Slovak |
| Online Access: | http://www.viks.sk/chk/star_11_03_495_503.doc |
| Abstract: | Summaries. The reaction between granular arrowroot starch and sodium monochloroacetate (SMCA) in isopropanol-water mixtures has been studied in a systematic way using experimental design strategies. The effect of six factors, i.e. the theoretical degree of substitution (DSt), reaction time, weight fraction of water in the mixture, NaOH/SMCA ratio, temperature and weight fraction of starch on three responses, i.e. the degree of substitution (DS), the conversion of SMCA and the selectivity of SMCA towards car-boxymethyl starch, has been determined in a systematic manner. Granular car-boxymethyl arrowroot starch with a maximum DS of 1.4 could be prepared in a single-step procedure. The results are compared with data obtained for potato starch. Similar trends for all responses were observed, suggesting close similarities between the chemical composition and the topochemistry of granular arrowroot- and potato-starch. Conclusions. The effect of process conditions such as temperature, starch loading, reaction time and solvent composition, as well as reagent intakes on the carboxymethylation of arrowroot starch have been assessed quantitatively using experimental design strategies. The results provide valuable insights in the carboxymethylation process of arrowroot starch and allow optimization of the process conditions to prepare carboxymethyl starch with a desired DS. A key issue is the selectivity of the process. Data analyses were performed to obtain information on the selectivity of the process and to determine conditions to suppress the undesired side-reaction to glycolate. It turns out that the selectivity towards carboxymethyl arrowrootstarch decreases when increasing the DSt, and the NaOH/SMCA ratio. Temperature and reaction time only have a minor effect whereas optimum values were observed for the water content and the starch loading. The results obtained in this study will be valuable input for the development of kinetic models for the carboxymethylation process of arrowroot starch and other tropical starches. These activities are currently being undertaken and will be reported in due course. The results obtained for arrowroot starch closely mimic those obtained earlier in our laboratory for potato starch, suggesting strong similarities in composition and topochemical features between both types of starches. |
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| ISSN: | ISSN 0038-9056 |
