THE PHENOMENON OF TOMATO BRUISING: WHERE BIOMECHANICS AND BIOCHEMISTRY MEET

Tomatoes are a commercially important vegetable worldwide.
Tomato fruit quality is substantially reduced by bruise (i.e. impact) damage.
The occurrence of bruising depends on two main factors: the direct mechanical damage of the tomato, and the presence and subsequent action of unregulated cell wall-modifying enzymes.
Bruising is considered to be a two-step process, in which mechanical damage occurs first and then enzymatic degradation of the affected tissue, including cell walls, takes place.
This could result in a rapid enzymatic breakdown of the cell wall polysaccharides, observed as soft spots (bruises) on the fruit.
To discover the bruising mechanism in tomatoes, the mechanical and biochemical properties of the pericarp tissue were investigated.
At first, a logistic regression was established between impact energy and the resulting bruise damage.
Results suggested that the fruit’s characteristics could not be neglected.
A new logistic regression was established, expressing the probability to develop bruises as a function of the energy absorbed and the specific fruit properties.
In addition, a comparative biochemical analysis of the bruised and intact tissue of green, pink, light red and red tomatoes, showed that a mechanical impact results in an immediate loss of cell wall material for the riper fruit only.
This study revealed that, in the case of mechanically damaged fruit, polysaccharide-digesting enzymes are responsible for the rapid breakdown of the cell wall.
This action results in soft spots on the fruit.
No bruises will form without the enzymatic digestion of the cell wall.

V International Postharvest Symposium

V. Van Linden, J. De Baerdemaeker

cell wall, pericarp, hemicellulose, mechanical damage, logistic regression, Lycopersicon esculentum Mill.

https://doi.org/10.17660/ActaHortic.2005.682.120