The phenomenon of tomato bruising: where biomechanics and biochemistry meet.
Van linden V., De Baerdemaeker J.
5th International Postharvest Symposium . Volume of Abstract . Verona, Italy 6-11 June 2004,p 43.
2004
บทคัดย่อ
The phenomenon of tomato bruising: where biomechanics and biochemistry meet.
Tomatoes are a commercially important vegetable worldwide.The fruit quality is substantially reduced by bruise damage.Tomato bruising is not well understood and the main responsible parameters for bruise damage are not yet entirely known.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 on the fruit.Bruises would probably not develop if the direct and immediate mechanical damage were the only damage the fruit experienced.This research aims to (i) determine the factors that are responsible for bruising of tomatoes and (ii) elucidate the bruising mechanism.Fruit mechanical and physical parameters were characterized in relation to impact loading.Fruits of 3 ripening stages and at 2 temperatures were subjected to 3 levels of impact energy (0.020J, 0.087J & 0.260J) by means of a pendulum.Fruit biochemical properties were characterized by monitoring the changes in the cell wall composition of the pericarp tissue after bruising.Tomatoes of distinct ripening stages were impacted and incubated for 3 hours, while stored at 12 °C or at 22 °C.Then, bruised areas and non-bruised control areas of the same fruit were collected.Cell walls were extracted and assayed for pectin and hemicellulose content.This study revealed that, in the case of mechanically damaged fruit, polysaccharide-digesting enzymes are responsible for the rapid breakdown of the cell wall, resulting in soft spots on the fruit.No bruises will form without the enzymatic digestion of the cell wall.