Pectin is composed of polymers of galacturonic acid. During senescence polygalacturonic acid
can be degraded by enzymes that fragment large pectin polymers. In order to monitor pectin
breakdown the uronic acid content was monitored during storage. A high level of uronic acid is
an indication that pectin polymers are being broken down into smaller fragments. This
fragmentation of high molecular weight polygalacturonic polymers leads to fruit softening.