Insights into the effects of fucoidan and caffeic acid on pasting, thermal, rheological, freeze-thaw and structural properties of cassava starch

Abstract

Fucoidan (FU) and caffeic acid (CA) can modify the physicochemical properties of starch and confer various health-beneficial functional characteristics to cassava starch (CS) products. This study utilized Rapid Visco Analyzer (RVA), Differential Scanning Calorimetry (DSC), rheometer, Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) to investigate the effects of FU andCA on the gelatinization, rheological properties, freeze-thaw stability, and structural characteristics of CS. Results from RVA showed that FU boosted the free expansion, shear resistance and gel thermal stability of CS while reducing their gel formation capacity and delaying short-term retrogradation. CA decreased the free expansion, shear resistance and gel formation ability of CS while delaying the short-term retrogradation of CS. The analysis of DSC showed that FU and CA could decrease the gelatinization enthalpy of CS. The rheological results revealed that each gel system was typical weak gel and pseudoplastic fluid. Both FU and CA weakened the relative motion of amylose molecules and reduced the energy required to disrupt the CS gel system. FU significantly enhanced the pseudoplasticity of CS gel (upward: 0.48 to 0.44; downward: 0.566 to 0.488, p < 0.05), whereas CA significantly decreased the thickening ability in the upward stage. FU and CA increased the hardness of CS gel (except 2.5 % CA). Furthermore, the addition of FU and CA was not conducive to the improvement of freeze-thaw stability of CS gel. FT-IR and XRD analyses exhibited that non-covalent bond mediated the effect of FU and CA on CS gel. SEM observations showed that FU and CA induced the formation of denser “honeycomb” pores in the CS gel. Both FU and CA were found to effectively retard the short-term retrogradation of CS, while enhancing the microstructural integrity of the gel network. These findings suggested that the incorporation of FU and CA could be utilized as a means to modulate the quality attributes of cassava starch-based products.