Pectins are complex polysaccharides found in the cell wall of fruit. These polysaccharides include homogalacturonan, located in the so called smooth zone of the pectin molecule and the hairy zone is composed of rhamnogalacturonan I (RGI), and rhamnogalacturonan II (RGII).
The hairy zone is highly branched containing arabans, galactans and arabinogalactans of various configurations and sizes are attached to the rhamnosyl units ofRG. The Degree of Methylation (“DM”) depends on the fruit variety and maturity.
In apple and pear, the DM is between 65 to 92 %. The insoluble pectin, protopectin, is slowly transformed to soluble pectin by the action ofendogenous pectinases present in fruit. Apple and pear juice can contain anywhere from 2 to 5 g/L of pectins after pressing. Duringearly season harvest, apple and pear juice contains starch and pectin.
Pectinases and amylases must be added simultaneously after aroma recovery and pasteurization when the temperature reaches 45 to 60°C. These characteristics must be taken into consideration when choosing the correct enzyme balance for superior juice clarification, increased stability, prevention of browning and no production of methanol resulting from enzyme treatment.