Modulation of the retrogradation kinetics of sweet potato starch by the addition of pectin, guar gum, and gallic acid

Abstract

The effects of the addition of pectin (P), guar gum (GG), and gallic acid (GA) on the pasting properties and retrogradation kinetics of sweet potato starch (SPS) during storage at 4 °C were evaluated by whiteness, as a measure of turbidity, molecular mobility, and differential scanning calorimetry analysis. The incorporation of GG increased the peak, hot paste, breakdown, and final viscosities of the systems, while the opposite resulted with the addition of P and GA. Gallic acid was particularly effective in delaying the progress of SPS retrogradation, since lower whiteness and retrogradation degree and kinetic parameters were obtained throughout the storage assay. Proton population and relaxation times analysis confirmed higher water molecules retention in the presence of GA, which limited hydration and swelling of SPS, thus reducing its posterior retrogradation. Besides, its low molecular weight and high polarity could have hindered starch molecules' reassociation through non-covalent interactions. A concentration-related effect was observed for P, since 1% addition delayed retrogradation, but it was accelerated when 2% were added due to changes in inter and intramolecular interactions between pectin and SPS. Finally, GG promoted SPS retrogradation, which could be explained by the breakage of the structure of swollen starch granules that facilitated ulterior reorganization. Results confirmed that SPS retrogradation can be successfully modulated by the incorporation of pectin, guar gum, or gallic acid for different gluten-free industrial applications.