Inactivated mechanisms of high pressure processing combined with mild temperature on pectin methylesterase and its inhibitor

High pressure processing (HPP) of orange juice faces storage issues due to refrigeration need and cloud loss caused by pectin methylesterase (PME). Our previous research indicated that HPP conjunction with pectin methylesterase inhibitor (PMEI) enhanced juice stability, but not fully inactivated PME. This study explored the effectiveness of HPP with mild temperature treatments to fully inactivate PME and sterilize microorganisms in juice, using experimental analysis and molecular dynamics simulation. The findings revealed that PME activity was reduced by 94 % at 600 MPa and 60 °C, with completely inactivating at 80 °C. Conversely, PMEI exhibited resistance to pressure and temperature. Following processes at 600 MPa and above 60 °C, the tail-end helix structure of PME destabilized, with α-helices converting to β-sheets and disrupting hydrogen bonds within molecular chain. Conversely, the structure of PMEI was stable. Additionally, the combination of HPP and temperature treatment enhanced the binding affinity between PME and PMEI.