Synthesis of Carboxymethyl Starch

Abstract

The following types of starch were used for carboxymethylation: native starch, oxidized starch (Starch Industry, Zrenjanin, Serbia, starch oxidized by hypochlorite solution, content of carboxyl groups between 0.40-0.60 mass%) and starch enriched with amylose (BAGKF, Germany, 70% amylose).All the other chemicals used in this investigation (NaOH, Carboxymethyl starch (CMS) was obtained under heterogeneous conditions as a product of the reaction of starch and monochloroacetic acid (MCA) in the presence of sodium hydroxide. The influence of the composition of the reaction mixture, the reaction time and temperature and the type of starch being carboxymethylated on the degree of substitution, DS, and limiting viscosity number, [η], was studied. The reaction temperature influenced the DS values, the highest values of the DS being obtained when the carboxymethylation was performed at 58°C. Increase of the molar ratio of NaOH to anhydroglycose units leads to an increase in DS, but only to certain extent. The values of the DS and [η] of CMS increased almost linearly with increasing MCA amount in the reaction mixture. The reaction mixture changes caused by adding water to ethanol influenced the DS values of the obtained CMS samples, the maximum DS value being obtained for CMS sample synthesized in ethanol with 25% (v/v) water.

Preparation and Application of Carboxymethyl Yam (Dioscorea esculenta) Starch

“…Carboxymethyl starch is a popular chemically modified starch. It is prepared by a reaction of starch (St-OH) and sodium monochloroacetate (SMCA) (ClCH 2 COO − Na + ) in the presence of sodium hydroxide (NaOH) (2)(3)(4)(5). This is a two-step reaction that proceeds as…”

Synthesis of Carboxymethyl Flaxseed Gum and Study of Nonlinear Rheological Properties of Its Solutions

“…When the MCA concentration is below a certain threshold, the DS of CMFG does not increase with increase in reaction time. The above results are in agreement with the observations made during the carboxymethylation of starch [31]. Thus, the optimum reaction time for carboxymethylation of FG appears to be 60 min.…”

Radiation cross-linked carboxymethylated starch and iron removal capacity in aqueous solution

“…The CMS powder was dissolved with distilled water in separate containers maintaining at 15 and 50% (w/v) concentrations. Here, two concentrations of CMS solutions (15 and 50%) were selected to investigate the effect of concentration in cross-linking of CMS.…”

“…Back titration method 15 was followed to determine the degree of substitution (DS) of carboxyl group. The acid form of CMS (H-CMS, 0.5 g), obtained after treatment of sodium salt of CMS (Na-CMS) with HCl was dissolved in 20 mL of 0.2 M NaOH solution in a 100 mL volumetric flask.…”

“…Aqueous blank solution without sample was also titrated with standard hydrochloric acid solution and the DS was calculated using the following equation. 15 Here, 162 is the molar mass of anhydro-glucose unit (AGU) of starch in g/mol, V b and V are the volumes of HCl in mL consumed for titration of blank and sample. C HCl (M/dm 3 ) is the concentration of hydrochloric acid, m ds (g) is the mass of dry CMS estimated from known mass of sample, 58 (g/mol) is the increased mass of AGU for each carboxymethyl group substituted, and 4 is the ratio of total solution volume and the volume taken for titration (100/25 mL).…”