Starch Stearate Prepared By Extrusion And Its Application

To solve the high cost of production and poor food safety of starch searate, an extruder was used as a dry reactor to prepare starch stearate under solvent-free conditions. The effect of screw speed, moisture content, barrel temperature and adding form of stearic acid on properties of starch stearate were studied. And the efficiency mechanism was revealed by XRD, SEM and FT-IR. In addition, the starch stearate was applied to quick-frozen dumplings, aiming at solving some problems of quick-frozen dumplings, such as cracking, muddy soup and cooked adhesion when boiling. The main results were as follows:(1) The stearic acid which was crushed to 80 meshes was mixed with native starch. A dry reactor was used to prepare starch stearate. On the basis of single factor experiment, the optimum conditions of producing starch stearate were determined by the orthogonal experiment: speed 900 r/min, moisture content 22%, and barrel temperature 140 ℃.(2) Under solvent-free conditions, the quality of starch stearate was better when stearic acid was crushed before adding. Results of XRD and SEM showed that high temperature and high shear of the extruder destroyed the crystal and granular structures of starch. So stearic acid could enter the inside of starch granules and react with starch molecules, which improved reaction uniformity and efficiency. Infrared spectra showed characteristic absorption peaks with ester bond. It meaned that stearic acid was esterified with hydroxyl groups on starch molecules.(3) With addition increase of starch searate, cracking rate and losing water of dumplings declined, transmittance of soup after cooling and sensory quality increased, hardness and chewiness decreased. In result, the optimum adding amount of starch stearate was 4%, and stearate starch should be gelatinized before adding.