PARTIAL CHARACTERIZATION OF BUCKWHEAT (FAGOPYRUM-ESCULENTUM) STARCH

Laboratory-isolated buckwheat (Fagopyrum esculentum) starch was compar ed to commercial corn and wheat starches. Buckwheat starch granules (2 .9-9.3 mu m) were round and polygonal with some holes and pits on the surface. Buckwheat starch had higher amylose content, water-binding ca pacity, and peak viscosity, and it had lower intrinsic viscosity when compared with corn and wheat starches. Buckwheat starch also showed re stricted swelling power at 85-95 degrees C and lower solubility in wat er at 55-95 degrees C and was more susceptible to acid and enzymatic a ttack. Gelatinization temperatures, determined by differential scannin g calorimetry, were 61.1-80.1 degrees C for buckwheat starch compared to 64.7-79.2 degrees C and 57.1-73.5 degrees C for corn and wheat star ches, respectively. A second endotherm observed at 84.5 degrees C was an amylose-lipid complex attributed to the internal lipids in buckwhea t starch, as evidenced by selective extraction. The retrogradation of buckwheat, corn, and wheat starch gels was examined after storage at 2 5, 4, and -12 degrees C for 1-15 days. In general, buckwheat starch re trogradation was slower than that of corn and wheat starch, but it inc reased as storage time increased, as did that of the other starch past es. When the values of the three storage temperatures were averaged fo r each storage period analyzed, buckwheat starch gels showed a lower p ercentage of retrogradation than did corn and wheat starch gels. Buckw heat starch also had a lower percentage of water syneresis when stored at 4 degrees C for 3-10 days and had better stability to syneresis af ter three freeze-thaw cycles at -12 and 25 degrees C.