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Native corn starch (NCS) is chemically modified by crosslinking with glutaraldehyde (GLU) at different concentrations of GLU (at constant reaction time) and different reaction times (at constant GLU concentration). Crosslinked corn starches with varying degree of substitution (DS) are produced in acidic (pH = 1.43 ± 0.01) and alkaline (11.04 ± 0.02) reaction mediums and DS values are determined. Thermal, structural, swelling, and solubility properties of the crosslinked starches are also investigated. The increase in DS become greater as the reaction pH increases to alkaline. Fourier transform infrared spectroscopy (FTIR) results indicate that hydroxyl band frequency values of crosslinked starches prepared in acidic medium shift to a higher frequency value as a result of the decrease in the number of hydrogen bonds in starch. However, no change in the frequency value of the hydroxyl band is observed in the FTIR spectrum of the crosslinked starch prepared in alkaline medium. Gelatinization temperatures of crosslinked starches produced in the acidic medium increase while gelatinization enthalpy, swelling power, and solubility considerably decrease. When the reaction medium is alkaline, crosslinked starches display slightly lower gelatinization temperatures and dramatically reduce gelatinization enthalpy values, although solubility does not change significantly compared to NCS. Swelling power decreases considerably when the starch is treated with 20% GLU in the alkaline medium. As a result, glutaraldehyde with different functional properties based on the pH of the reaction medium can be an effective crosslinking reagent for starch.
Gönenç et al. (Wed,) studied this question.