Comparison of the molecular structure of heat and pressure-treated corn starch based on experimental data and molecular dynamics simulation

The effect of high hydrostatic pressure (HHP) and heating on the molecular structure of corn starch were firstly studied using classical experimental methods and molecular dynamics (MD) simulation. Heat-treated (HT) starches showed more amorphous content further than pressure-treated (PT) starches at similar DGs, further confirming that a higher level of gelatinization occurred after heating. Compared with PT starches, longer external B2 and B3 chains (DP > 25) degraded more into A chains (DP 6–12) in HT samples at a similar degree of gelatinization (DG). Heating increased the breakage of α-1,4-glycosidic bonds and significantly reduced molecular weights even one third of the native corn starch at 100% DG. On the other hand, MD results showed that HHP triggered a greater number of amylose-water inter-molecular hydrogen bonds which agreed well with the higher the freedom degree of water molecules in PT starches. Regarding to various energy changes, PT starches exhibited lower bonding-related energies, but higher Van der Waals and electrostatic forces than HT ones. This study adds to understanding of the different molecular features of heating and HHP gelatinization and provides a molecular tool to assist the starch industry in selecting better modification parameters.