As
opposed to fruits, which are generally picked when mature but unripe,
many vegetables (apart from legume seeds, tubers, bulbs and roots) are
picked and consumed when still immature, tender and succulent.
This
is largely due to the fact that while fruits generally soften on
maturation and storage, young vegetables become tougher when they age.
This toughening is due to the lignification of the primary cell wall and
formation of the secondary cell wall. When cucumbers are stored below
7°C, their texture breaks down due to excessive softening and exudation
of liquid as tissue undergoes a structural collapse. Tomatoes are also
susceptible to low-temperature injury.
Many of the form, structure and physiological considerations discussed in connection with fruit texture also apply to vegetable texture. The main difference is that, while on maturation the fruit tissue stops growing and suffers enzymatic degradation, the vegetable tissue proceeds to differentiate and cell growth and enlargement continue. The amount of fibrous tissue increases. Toughening may reach the point where the vegetable is no longer suitable for human consumption.
