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P.84 right column:"A method using dilution of a high molecular weight dye is presented, whereby the hydrated density of starch granules in aqueous suspension may be determined precisely, accurately, and rapidly. Results for intact wheat starch granules of different cultivars and seasons suggest a value of 1.35±0.02 g/cm^3 at 20°C, which corresponds to a moisture content about 45% dry basis. Both mechanical damage to the starch granules and increased temperature lower the hydrated density. Treatment with toluene - acetone and dry heating both had very significant effects on the densities of granules that were mechanically damaged but not on intact granules. The method also allows determination of the anhydrous density of the granules, the sorption of dye by the granules, and the concentration dependence of the sorption. It should have wide application to other biological materials and
solvent systems. [Investigators] conclude that approximate densities of wheat starch are 1.6 g/cm^3 for dry granules, 1.5 g/cm^3 for air-equilibrated granules, and 1.3 g/cm^3 for hydrated granules. The latter figure varies with the degree of mechanical damage." |