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Morphological, Structural, and Thermal Properties of Starch Nanocrystals Affected by Different Botanic Origins¹

¹Journal Series No. 313. This study was conducted at the Agricultural Research Station, Virginia State University. ²Agricultural Research Station, Virginia State University, Petersburg, VA 23806, U.S.A. ³Corresponding author. Phone: (804) 524-5668. Fax: (804) 524-5186. E-mail: yixu@vsu.edu ⁴Nanomaterials Characterization Center, Virginia Commonwealth University, Richmond, VA, 23284, U.S.A. ⁵Department of Chemistry and Physics, Virginia State University, Petersburg, VA 23806, U.S.A.

Six types of starch nanocrystals were prepared from corn, barley, potato, tapioca, chickpea, and mungbean starches with an acid hydrolysis method. The yields and morphological, structural, and thermal properties of starch nanocrystals were characterized. Starch nanocrystals had yields ranging from 8.8 to 35.7%, depending on botanical origin. During acid hydrolysis, amylose was effectively degraded, and no amylose was detected in any starch nanocrystal. Shape and size of native starch granules varied between starches, whereas there was no obvious difference in shape among different types of starch nanocrystals. The average particle size of starch nanocrystals was mainly related to crystalline type of native starches. Compared with their native starch counterparts, changes in crystalline diffraction patterns of starch nanocrystals depended on the original botanical source and crystalline structure. Degree of crystallinity, melting temperature, and enthalpy of starch nanocrystals increased, whereas their thermal decomposition temperature decreased. Of six produced starch nanocrystals, potato starch nanocrystal had the lowest yield, degree of crystallinity, and onset and melting temperatures, the largest particle size, and obvious changes in crystalline diffraction pattern.