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Distribution of Granule Channels, Protein, and Phospholipid in Triticale and Corn Starches as Revealed by Confocal Laser Scanning Microscopy

¹Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada. ²Corresponding author. Phone: 1-780-492-2898. Fax: 1-780-492-8914. E-mail: tv3@ualberta.ca

The morphology and microstructure of starch granules from two cultivars of triticale and from normal corn were characterized using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Compared to numerous pores distributed randomly on the surfaces of corn starch granules, markedly fewer pores were observed on the surfaces of starch granules isolated from Pronghorn triticale, and even fewer on the surfaces of starch granules isolated from Ultima triticale. CLSM with fluorescence staining revealed that starch-associated protein was predominately distributed on the granule surface and in the internal channels of both triticale and corn starches. However, after triticale starch was treated with SDS or SO₂, the radially oriented, protein-filled internal channels of the granules were observed more frequently and extended to the central region of granules. Phospholipid was located mainly on the granule surface but also in channels and throughout granules in triticale starches, whereas in corn starch granules, it was mainly in the channels. The amount of protein and phospholipid in chemically and protease-treated starches varied with starch source and treatment conditions. In treated triticale starches, the nitrogen content was positively correlated with the phosphorus content, indicating a close association between protein and phospholipid within starch granules. Starch-associated protein and phospholipid may play an important role in maintaining the structural stability of both the granule surface and the internal channels.