Determination of the maximum water solubility of eight native starches and the solubility of their acidic-methanol and -ethanol modified analogues

The maximum water solubilities of eight native starches from potato, shoti, tapioca, maize, waxy maize, amylomaize-7, wheat, and rice and their acid–methanol and acid–ethanol modified analogues have been determined. Maximum solubilities of 18.7 and 17.4 mg/mL were obtained for waxy maize and tapioca and 12.4 mg/mL for potato and maize starches by autoclaving 220 mg/10 mL at 121 °C; 8.7 mg/mL was obtained for shoti starch by stirring in 85:15 (v/v) Me2SO–H2O at 20 °C; and 7.0 and 5.2 mg/mL for rice and amylomaize-7 starches by stirring in 1 M NaOH at 20 °C. The acid–alcohol treated starches were 4–9 times more soluble than their native starches. The compositions of the solubilized starches had, in general, much higher ratios of amylose to amylopectin than the ratios in their native granules. A major exception to this was the acid–methanol treated potato, shoti, and rice starches that had much lower ratios of amylose to amylopectin than the ratios in their granules.

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