Impacts of high hydrostatic pressure processing on the structure and properties of pectin

To understand the impacts of high hydrostatic pressure (HHP) processing on the microstructure and properties of pectin, an aqueous solution of apple pectin (50 g/L) was treated at 200, 400, and 600 MPa for 30 min. The chemical structure and properties of resultant pectin were characterized and compared with those of native pectin (0.1 MPa). The contents of α-1,4-linked d-galacturonic acid and reducing sugar in pectin did not change after HHP, whereas the degree of esterification of pectin increased slightly. Fourier transform infrared spectroscopy showed that no chemical conversion of pectin occurred during HHP process. For the first time, molecular dynamics simulation revealed that the hydrophobic hydration of the methyl group dramatically improved under HHP, thereby enhancing pectin dissolution in water. In turn, this result increased the aqueous pectin solution's apparent viscosity and stability, which are very important for fruit- and vegetable-based products containing pectin.