Firm, fresh tomatoes are less prone to damage and have a longer shelf life. Higher levels of calcium in the cell wall will improve fruit firmness and as a result, transportation and storage characteristics.
When used for canning, the tomato fruit must have a thick, firm wall so that they retain their shape when cooked. The peduncle must also be easy to remove from the fruit.
Firmness decreases during fruit maturation. The use of calcium will help minimize breakdown of pectins by holding the pectic matrix together, maintaining the cell wall strength. Tomato firmness is assessed by pressure load or shear press tests. Tomatoes with a Durofel rating of >75 are described as firm, 60 - 70 are soft, and <60 limp.
Tomato quality and the shelf life suffer as a result of using excessive ammonium forms of nitrogen. Fruit is firmer and more marketable where nitrate forms (calcium nitrate, potassium nitrate) are used.
Calcium is needed to maintain good fruit structure and quality. Adequate supplies improve tomato firmness.
Boron has a positive influence on the level of cracking and shelf life of the tomato fruit. Any cracks on the fruit shoulder increases water loss and susceptibility to pathogen attack.