Abstract:

The granular properties of water caltrop starch from three varieties (Trapa acornis Nakano from Nanhu, Trapa quadrispinosa Roxb from Nanhu and Trapa biocornis Osbeck from Xichang) were investigated using scanning electron microscope, laser light scattering analyzer, X-ray diffraction and differential scanning calorimeter. Results indicated that most starch granules of water caltrop from three varieties were oval-shaped and some starch granules were round-shaped. The starch granules exhibited smooth surface with obvious birefringence phenomena and “X” polarized mode with the umbilical point close to the center of starch granules. The granular size of more than 85% of water caltrop starch from three varieties was ranged 7.96－ 63.37 μm. Average volume of water caltrop starch granules from Trapa acornis Nakano, Trapa quadrispinosa Roxb and Trapa biocornis Osbeck were 21.24, 19.67 μ m and 38.52 μ m, respectively. Starch from Trapa acornis Nakano and Trapa quadrispinosa Roxb displayed an A-type X-ray diffraction pattern with relative crystallinity of 39% and 28%, respectively. While starch from Trapa biocornis Osbeck displayed a Ca-type diffraction pattern with relative crystallinity of 40%. The initial, peak and termination temperatures for the gelatinization of water caltrop starch from three varieties were 75.2－78.1, 76.6－81.8 ℃ and 80.7 － 86.0 ℃, respectively. The enthalpy for the gelatinzation of three kinds of starch was 15.3 － 19.7 J/g.

Key words: caltrop, starch, granular property