Cross-linking of wheat starch and hydroxypropylated wheat starch in alkaline slurry with sodium trimetaphosphate

• Published in: Carbohydrate polymers Vol. 33; no. 4; pp. 263 - 271
• Main Authors: Woo, Kyungsoo, Seib, Paul A.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1997; Elsevier Science
• Subjects: alkalinity; Applied sciences; Biological and medical sciences; chemical reactions; cross-linked starches; Exact sciences and technology; Food industries; Fundamental and applied biological sciences. Psychology; kinetics; metaphosphates; Natural polymers; pasting properties; phosphoryl chloride; Physicochemistry of polymers; propylene oxide; starch; Starch and polysaccharides; Starch and starchy product industries; Pulping; Sodium Trimetaphosphates; Hydroxyalkylation; Experimental study; Chemical modification; Medium effect; Sodium sulfate; Oxirane(methyl); Crosslinked polymer; Oside polymer; Basic medium; Kinetics; Starch derivative; Wheat starch; Aqueous dispersion
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/S0144-8617(97)00037-4

Wheat starch was cross-linked at 40 °C and pH 11.0 by slurrying the starch (30% solids) in a solution of sodium trimetaphosphate (STMP), sodium hydroxide, and sodium sulfate. The extent of cross-linking was determined by an increase in alkaline fluidity or by a decrease in alkaline clarity. Response surface analysis showed that cross-linking increased with increasing levels of STMP (0.5-1.5%, based on starch, bos) and sodium sulfate (0–4.0%, bos) over a reaction period of 120–720 min. A regression equation with first and second order terms showed that STMP and sodium sulfate concentrations and the reaction time accounted for 99% of the variability in alkaline fluidity. Wheat starch (37% slurry) was hydroxypropylated by reaction with propylene oxide (8%, bos) for 24h at 45 °C in alkali (pH 11.5) containing 16.0% sodium sulfate (bos). The hydroxypropylated (4.5wt%) wheat starch (DS 0.12-0.13) was not isolated but was cross-linked with STMP (0.1-0.5%, bos) over a 10–40 min reaction period. A comparison of pasting curves at pH 3.5 showed that some of the cross-links produced by STMP were less stable than those produced by phosphoryl chloride, indicating a low level of pyrophosphate as well as monophosphate cross-links. The less stable cross-links were diminished by changing reaction conditions with STMP.