Study on effect and mechanism of high pressure processing on hardness of fresh-cut carrot

Processing methods always cause damage to fresh-cut fruits and vegetables. High pressure processing ( HPP) is promising a technology for protecting the quality of fresh-cut fruits and vegetables. In order to explore the hardness change of fresh-cut fruits and vegetables with the increased pressure and the corresponding internal mechanisms.This study was designed to evaluate the effect of high pressure processing ( 100 ~ 600 MPa, 5 min) on the changes in hardness, cell membrane, pectin methylesterase ( PME) and cell wall pectin fraction of fresh-cut carrot.The results showed that there was no significant change in carrot hardness after 100 MPa treatment, and the relative conductivity and the hardness of carrots increased significantly with the increase of pressure.When the pressure reached 300 MPa, the relative conductivity and hardness no longer alter significantly even if increased pressure.Meanwhile, increase in sodium carbonate soluble pectin ( NSP) and decrease in water soluble pectin ( WSP) fraction at all pressure levels were observed.However, complete inactivation of pectin methylesterase activities could not be fulfilled by HPP. Hardness change of fresh-cut carrot processed by HPP was attributed to changes of cell membrane permeability and cell wall pectin components profile.