Fast-Spoiling Pear Mystery Solved

Pears spoil more quickly than apples because they're out of breath, according to European researchers.

The finding could lead to new ways of storing pears to prevent them from rotting on the way to the fruit bowl.

Pieter Verboven and his colleagues from the Catholic University of Leuven in Belgium and the European Synchrotron Radiation Facility (ESRF) have published the findings in the journal Plant Physiology.

After being picked from the tree, apples and pears continue to 'breathe.' To keep the fruit healthy, a minimum level of oxygen must be supplied to all of its cells. If this does not happen, the fruit turns brown.

To understand why pears spoil more quickly than apples, Verboven and his team placed samples of each fruit in the path of a synchrotron beam. The beam was used to create 3D images that have a resolution of one thousandth of a millimeter.

Researchers have hypothesized that apples and pears contain microscopic pathways between each cell, thereby allowing oxygen to pass into the fruit.

The synchrotron images revealed that apples contain large, irregular cavities between cells, while in pears the cavities have the shape of tiny, interconnected channels.

They found the voids in apple were often larger than the surrounding cells, and some cells were not connected to voids.

In comparison, the voids inside pears were smaller than the cells. Each cell was surrounded by a tight and continuous network of voids.

"It is still unclear how airways in the fruit develop and why apples have cavity structures and pears micro-channel networks," said Verboven.

"The micro-channels are so small that oxygen supply to the fruit core is very limited, and cells are quickly 'out of breath' when oxygen levels fall below the safety threshold," he added.

The researchers believe their results provide a better understanding of how the fruit degrades after harvest and explain why pears are more susceptible to decay during storage.

It is hoped the research can also be used in computer models to calculate oxygen concentration in individual cells of fruit tissues.