The effects of pH and iron ions on the mechanical properties of pea starch hydrogels

In this study, the network strength of starch hydrogels was improved by adjusting the pH value (3-11.5) and adding iron ions (Fe3+), and the mechanical properties and swelling properties of the hydrogels were improved. The complex modulus of the starch hydrogel with a pH value of 11.5 and containing Fe3+ was above 3400 Pa. SEM showed that the hydrogel structure became more compact with the increase of pH value. In addition, the hardness of the hydrogel increased from 50.29 g at pH 3.0 to 215.1 g at pH 11.5, while the addition of 0.5 mol/L Fe3+ at pH 11.5 promoted a further hardness increase to 301.8 g. Moreover, the swelling rate of the hydrogel decreased from 670.2 % at pH 7.0 to 464.4 % at pH 11.5, and the addition of 0.5 mol/L Fe3+ further decreased the swelling rate to 191.8 %. Overall, the results indicate that the mechanical properties of starch hydrogels can be improved by making simple adjustments to the pH and the iron ion concentrations.

Automated summary

The network strength of starch hydrogels was enhanced by adjusting the pH value and adding iron ions, leading to improved mechanical and swelling properties. The starch hydrogel with a pH value of 11.5 and containing Fe3+ exhibited a complex modulus above 3400 Pa, and its structure became more compact with increasing pH value. Moreover, the hardness and swelling rate of the hydrogel increased with pH value and addition of 0.5 mol/L Fe3+, indicating that simple adjustments to pH and iron ion concentrations can improve the mechanical properties of starch hydrogels.