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ARS Home » Midwest Area » Peoria, Illinois » National Center for Agricultural Utilization Research » Plant Polymer Research » Research » Publications at this Location » Publication #139021
Title: RAPID PREPARATION OF STARCH ESTERS BY HIGH TEMPERATURE/PRESSURE REACTION

Author
item Shogren, Randal

Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2002
Publication Date: 2/10/2003
Citation: SHOGREN, R.L. RAPID PREPARATION OF STARCH ESTERS BY HIGH TEMPERATURE/PRESSURE REACTION. CARBOHYDRATE POLYMERS. 2003. v. 52. p. 319-326.

Interpretive Summary: Corn starches which are highly modified by certain chemical reactions (starch esters) can have very different properties from the parent starch and have many potential practical applications. However, current commercial methods for the preparation of starch esters are slow, expensive and sizeable quantities of byproduct and wastewater are produced. In this study, starch esters were prepared rapidly and efficiently by simply heating starch with the reactant in a non-toxic solvent (acetic acid) at elevated temperatures and pressures. Little or no byproduct was formed and the acetic acid solvent could be easily removed after reaction by heating under vacuum. These findings should allow the chemical industry to prepare starch esters more efficiently and for lower cost, thereby expanding markets for corn. The findings could also be useful to academic, government and industrial scientists developing methods for preparing new modified starches.

Technical Abstract: This study was undertaken to determine if starch esters of moderate to high degree of substitution (D.S.) could be prepared more rapidly, efficiently and with fewer byproducts. The method selected was to heat mixtures of dry corn starch, glacial acetic acid and anhydrides under pressure in small (60 micro liters) stainless steel sealed pans. Starch acetates of D.S. 0.5-2.5 were prepared at temperatures of 160-180 degrees C in 2-10 min. Reaction efficiencies were essentially 100%. Reaction rates increased with increasing acetic acid concentration and decreased with increasing acetic anhydride concentration. The acetic acid remaining in the samples could be completely removed by vacuum stripping at 120-190 degrees C. Starch succinates of D.S. 1.0-1.5 were prepared at temperatures and times similar to those for starch acetates above. Longer reaction times (20-60 min.) were required for the preparation of starch octenylsuccinates and dodecenylsuccinates having moderate D.S. values (about 0.5). Significant acetylation due to esterification of starch with acetic acid also occurred in these systems for long heating times (more than 20 min.). This results in release of water and probably accounts for some of the apparent degradation (reduction in viscosity, browning) seen at long heating times.