Exploratory Studies on the Carboxymethylation of Cassava Starch in Water-miscible Organic Media
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English Slovak |
| Online Access: | http://www.viks.sk/chk/star_3_4_04_100_107.doc |
| Abstract: | Conclusions. We have performed an exploratory investigation in a batch set-up to gain insights in the Carboxymethylation of cassava starch using SMCA to obtain granular carbox-ymethyl cassava starch. Solvent screening studies indicate that higher alcohols like isopropanol and te/t-butanol give the best results provided that 10 wt% of water is present in the reaction mixture. The DS is rather insensitive to the starch loading, in a range of 4-8 wt%. The highest DS obtained in a single step was about 1.4, for a DSt of 2.5, a reaction temperature of 55°C and a reaction time of 300 min. Higher reaction temperatures were not applied to prevent degradation of the granule and subsequent gelatinization. The observed trends for cassava starch closely mimic those reported for the Carboxymethylation of potato and arrowroot starch. The results obtained in this study will serve as valuable input for subsequent kinetic studies and reactor models to assess the effects of all variables in an integrated way. Summary. The Carboxymethylation of cassava starch using sodium monochloroacetate (SMCA) as an etherification agent was investigated. Mixtures of water and water-miscible organic liquids were selected as Carboxymethylation reaction medium to obtain a high degree of substitution (DS) without changing the granular form and to prevent gelatinization. Factors that affect the process of chemical modification of cassava starch, including the type of solvents, the mass percentage of water in the reaction medium, the mass percentage of starch, the molar ratio of NaOH to SMCA, the theoretical DS (DSt ), and the temperature were investigated experimentally. Isopropanol and fert-butanol appear to be the best solvents for the Carboxymethylation process of cassava starch, and the optimum condition for this etherification reaction are a reaction medium consisting of about 10 wt% water, a reaction temperature between 50 and 55°C and a starch mass percentage between 4-8 wt%. When applying these conditions in combination with a DSt of 2.5, granular modified cassava starch with a DS of 1.4 can be obtained. The experimental results will be compared with those reported for other types of granular starches. |
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| ISSN: | ISSN 0038-9056 |
