Cationization of field pea starch in salt-free aqueous suspension

Abstract

Industrial production of cationic starches involves excessive amounts of costly and environmentally toxic salts (∼60%, starch dry weight basis) as swelling inhibitors. The present study investigated the preparation of cationic field pea starch using the reagent, 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC), substituting a commonly used salt, sodium sulfate, with natural sugars such as sucrose or glucose under alkaline conditions. The effects of sugar type and concentration on the degree of substitution were studied. At a concentration of 20% of the weight of starch solids both sucrose and glucose effectively prevented starch granule swelling. Under reaction conditions similar to those used in industrial processing, cationization of pea starch in the presence of sodium sulfate resulted in a degree of substitution and reaction efficiency approximately twice as high as sucrose and four times as high as glucose. For this reason, sucrose was investigated further as a more suitable alternative to sodium sulfate than glucose in the salt-free preparation of cationic starch. Optimization of reaction conditions such as temperature, pH, swelling inhibitor and cationic reagent concentrations using sucrose as the swelling inhibitor resulted in a cationic starch with a degree of substitution of 0.07, comparable to the 0.06 that was obtained using sodium sulfate. These results indicate that sucrose may be a viable alternative to sodium sulfate in the production of cationic pea starch.