Effect of metal ions on physicochemical and rheological properties of octenyl succinate starches

Functionality differences between esterified and pregelatinized esterified starches simultaneously prepared by octenyl succinic anhydride modification and its application in dough

Octenyl succinic anhydride (OSA)-modified starches have gained widespread interest, but the modification can produce two starches with different states ignored. Herein, the two types of starches, esterified starch (ES) and pregelatinized esterified starch (PES), prepared by OSA modification were separated, and their structural and functional characteristics were comprehensively explored. Results showed that compared with native starch (NS), ES and PES exhibited high water-holding capacity, solubility, and swelling power and significantly decreased pasting temperature and thermal stability. Dynamic rheological tests illustrated that OSA modification changed the rheological behavior of starches. Fourier transform infrared spectroscopy confirmed that PES with higher degree of substitution showed more obvious ester carbonyl and carboxylate groups than ES. Laser confocal micro-Raman spectroscopy revealed that the short-range molecular order of ES, especially PES, decreased after modification. X-ray diffraction indicated that OSA modification disrupted the crystalline structure of starch, and that more amylose-lipid complex was formed in PES. Scanning electron microscopy showed that OSA modification eroded starchs surface and reduced its smoothness, and significantly disrupted PES integrity. ES and PES could be developed as food additives for retrogradation inhibition of dough. These results provide new insights into OSA modification and expand its functional application in foods.

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.