Abstract
The sago palm (Metroxylon sagu) can accumulate 200 kg or more of starch per palm in its trunk. The characteristics of sago starch are different in the growing stages, portions of trunk, and cultivars. The differences between starch grains of non-spiny and spiny sago cultivars have not yet been fully characterized. In this study, an optical and scanning electron microscope, X-ray diffraction (XRD), and 13C cross-polarization/magic angle solid-state nuclear magnetic resonance (13C CP/MAS NMR) were used to analyze the structure of sago starch. The grain size of non-spiny sago starch was slightly smaller than that of the spiny one. The heated non-spiny sago starch samples showed that heating from 40 to 80°C resulted in the combining of 4a and 4b X-ray diffraction patterns, changing the reflecting face of the starch with a distance of 0.52 nm. The difference between non-spiny and spiny sago starches was not remarkable in 13C CP/MAS NMR spectra. The NMR signal peak of C1 at 102 ppm increased with increasing heat temperature up to 80°C and decreased with increasing heating temperature after 80℃. It is concluded that the crystalline structures of non-spiny and spiny sago starches are affected by temperatures above 60°C based on the X-ray diffraction pattern and the fact that the conformation flexibility of the sago starch structure by heating was limited to the surface portion from the X-ray diffraction patterns and NMR spectra.
https://ror.org/00b45dj41 
