Extraction and identification of rice, maize, wheat, sweet potato and potato starch granule surface protein
2016
Shiono, K. (Tokyo University of Agriculture, Setagaya-ku, Tokyo (Japan). Faculty of Applied Bioscience, Department of Applied Biology and Chemistry) | Tsujii, Y. | Noguchi, T. | Sato, H. | Takano, K.
Starches are a major commercial food source, and different starches have distinct properties that result in part from their associated proteins. We examined the starch surface proteins (SSPs) of rice, maize, and wheat, sweet potatoes and potatoes. We identified a strong correlation between the color (bsup*) of various starches stained with Coomassie Brilliant Blue (CBB) and their protein content (r = 0.965). Protein was extracted from various starches using 0.1 % sodium hydroxide. The percentage of the decreased protein using this procedure differed depending on the source: Rice, maize, wheat, sweet potato, and potato yielded 71.6, 29.8, 21.6, 60.0, and 40.0 % of their SSP, respectively. The SSPs were separated to 19 protein bands by gel electrophoresis, and we successfully identified 16 of the 19 proteins. A granule-bound starch synthase or precursor was identified from each starch. The wheat SSPs included an alpha-amylase inhibitor. The potato SSPs included aspartic proteinase inhibitor homologue and cysteine protease inhibitor 7. Furthermore, several storage proteins were identified among the SSPs, including glutelin and prolamin from rice, gamma zein from maize, globulin from wheat, and sporamin from sweet potato. Since storage proteins are commonly hydrophobic, we suggest that these proteins affect the pasting characteristics of various starches.
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