Effect of microwave heat-moisture and annealing treatments on buckwheat starch characteristics

Abstract

Buckwheat is a non-glutinous pseudo-cereal that has a long and traditional history as a food source in Asia, Europe, and the United States and has many beneficial health aspects but has suffered from declining production within the past years. In order to prevent further decline of buckwheat production new products will need to be developed for the consumer market and more research will need to be conducted to study the effect of different processing parameters on buckwheat characteristics. This study focused on the effect of microwave heat-moisture and annealing processes on buckwheat starch that had been dried to three moisture levels: 32.3%, 40.0%, and 44.4%. Starch samples were analyzed using a differential scanning calorimeter, a colorimetric amylose leaching tests, and an x-ray diffractometer. Additional moisture levels starch treatment groups, 13.2% and 26.8%, were produced for the x-ray diffraction test. Differential scanning calorimetry (DSC) and colorimeter amylose leaching tests were analyzed on SPSS 11.0 for Windows. DSC data indicated that moisture level had a significant effect on onset melting temperature (p < 0.01), peak melting temperature (p < 0.01), and enthalpy of fusion (p < 0.05). In addition, heat treatment (p < 0.01) and interaction of moisture with heat treatment (p < 0.05) both had a significant effect on amylose leaching results. Significant differences within each test were found mainly at the 44.4% moisture level. X-ray diffraction readings showed a stable d-space placement for all treatment groups. Intensity visibly increased with decreased moisture level and with heat treatment for the 40.0% and 44.4% moisture level starches. Resistance to amylose leaching and melting at higher temperatures for higher moisture level buckwheat starch was attributed to increased networking among amylose and amylopectin components in the buckwheat starch.