Purification, characterization, thermal and high-pressure inactivation of a pectin methylesterase from white grapefruit (Citrus paradisi)

The present works describes the combined thermal and high pressure inactivation of pectinmethylesterase (PME) from white grapefruit. White grapefruit contains two PME fractions with different process stability (both towards temperature and pressure), the stable fraction contributing to about 20% of the total PME activity. The results demonstrate that combined mild heat and high-pressure processing cannot be used to fully inactivate PME in grapefruit juice. However, by eliminating up to 80% of the PME activity (labile fraction), such treatment can probably contribute to a significant decay of the cloud loss defect observed in grapefruit juices, while allowing pasteurisation and good quality retention of the latter. Combining high pressure mild temperature processing with other non-thermal approaches (e.g. use of PME-inhibitor) could be of interest in creating juices with extended shelf-life.