Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/16/2011
Publication Date: 10/19/2011
Citation: Byars, J.A., Fanta, G.F., Kenar, J.A., Felker, F.C. 2011. Thickeners from normal and high amylose corn starch with sodium palmitate. AACC Annual Meeting.
Technical Abstract: Our previous studies have shown that materials with applications as thickeners can be formed from aqueous dispersions of amylose helical inclusion complexes obtained from high amylose corn starch and sodium palmitate. In order to prepare less expensive materials, to broaden the range of possible materials, and to examine the role of amylopectin in gel formation, dispersions were prepared containing normal corn starch. The starch was jet cooked under excess steam conditions and blended with aqueous solutions of sodium palmitate to form helical inclusion complexes with the amylose component of the starch. As prepared, the charged amylose complexes remained in solution and did not retrograde. However, upon lowering the pH by adding acid, the charge was partially neutralized, decreasing intermolecular repulsion and allowing junction zones to form and create a gel network throughout the sample. The rheological properties of these gels were measured to determine the effects of starch concentration, amylose content and pH. The maximum storage modulus was observed at a pH of about 6.3 for each sample. For 5% normal corn starch (1.25% amylose), the storage modulus at a frequency of 1 rad/s was 90 Pa, whereas for 2% high amylose corn starch (1.4% apparent amylose) it was 300 Pa, indicating that the presence of amylopectin inhibited effective gel formation. At lower pH, the amylose interacts even more strongly and eventually precipitates from solution. For normal starch, 83% of the total starch solids were precipitated, suggesting that the amylopectin was part of the gel network. Samples were also prepared from blends of high amylose, normal and waxy corn starch to obtain a range of amylose/amylopectin ratios and gel properties.