Impact of pressure on physicochemical properties of starch dispersions

Effects of high hydrostatic pressure on the ordered structure including double helices and V-type single helices of rice starch

This study mainly aimed to investigate the influents of high hydrostatic pressure (HHP) on the ordered structures of starch, for this purpose, we compared the ordered structure of rice starch treated by HHP and heat, including long- and short-range ordered structures and thermodynamic properties at similar levels of gelatinization degree (DG). X-ray diffractometer, Fourier transform infrared spectrometer (FTIR), ¹³C cross polarization magic angle spinning/NMR, and Differential scanning calorimeter were used to detect crystal structure, band height ratio in FTIR spectra (R), double helix structure, and thermodynamic behavior. Results showed that HHP-treated rice starch (HHGS) had greater crystallinity, larger R, and more double helix and V-type single helix structures as compared to heat-treated rice starch (HGS) at a similar DG. The thermodynamic analysis illustrated that T_o of HHGS was lower as compared to HGS. The ordered structure of HHGS was close packaged. HHP simultaneously induced annealing and pressure-induced gelatinization until achieving a certain degree of gelatinization.

Potato Starch Hydrogels Produced by High Hydrostatic Pressure (HHP): A First Approach

Starch-based hydrogels have received considerable interest due to their safe nature, biodegradability and biocompatibility. The aim of this study was to verify the possibility of producing natural hydrogels based on potato starch by high hydrostatic pressure (HHP), identifying suitable processing conditions allowing to obtain stable hydrogels, as well as to characterize structural and mechanical properties of these products. Sieved (small size granules and medium size granules) and unsieved potato starch samples were used to prepare aqueous suspensions of different concentrations (10-30% w/w) which were processed at 600 MPa for 15 min at different temperatures (25, 40 and 50 °C). Products obtained were characterized by different techniques (light and polarized microscopy, Fourier transform infrared spectroscopy (FTIR), rheology and differential scanning calorimetry (DSC)). Results obtained so far demonstrated that potato starch suspensions (20% starch-water concentration (w/w)) with granules mean size smaller than 25 µm treated at 600 MPa for 15 min and 50 °C showed a complete gelatinization and gel-like appearance. Potato HHP hydrogels were characterized by high viscosity, shear-thinning behavior and a highly structured profile (G' >> G''). Moreover, their FTIR spectra, similarly to FTIR profiles of thermal gels, presented three absorption bands in the characteristic starch-gel region (950-1200 cm-1), whose intensity increased with decreasing the particle size and increasing the processing temperature. In conclusion, potato starch hydrogels produced by HHP in well-defined processing conditions exhibited excellent mechanical properties, which can be tailored according to the requirements of the different applications envisaged.