Agriculture Reference
In-Depth Information
Physiological disorders
Chilling injury
The maximum storage life of pineapple at 7°C is about 4 weeks; however, when
removed, chilling injury develops within 2-3 days. The symptoms of chilling
injury (CI) include: (i) wilting, drying and discoloration of crown leaves; (ii)
failure of green-shelled fruit to yellow; (iii) browning and dulling of yellow
fruit; and (iv) internal fl esh browning (Paull and Rohrbach, 1985). Preharvest
shading and pre- and postharvest low temperatures are the major factors
increasing CI symptom intensity. CI symptoms have been called endogenous
brown spot, physiological breakdown, blackheart and internal browning.
Postharvest CI symptoms develop after fruits are returned to physiological
temperatures (15-30°C). Susceptible fruits are generally lower in ascorbic acid
and sugars and are opaque (Teisson, 1979a,b). Partial to complete control of
CI symptom development has been achieved by waxing, polyethylene bagging,
heat treatments, controlled atmospheres and ascorbic acid application.
Flesh translucency
Flesh translucency increases fruit sensitivity to mechanical injury. This
condition begins before harvest and continues after harvest. TSS, fl esh
pigments and palatability increase to a maximum at about 60% translucency,
then decrease in fruit with greater translucency. Translucency is more severe
and has a higher incidence when maximum and minimum temperatures
3 months before harvest are both low, less than 23 and 15°C or, to a lesser
extent high, greater than 29 and 20°C, respectively. Fruit with a larger crown
has a lower incidence and severity of translucency (Paull and Reyes, 1996).
Bruising
Fruit bruising is a major problem during harvesting and packing. Bruising can
be caused by impact damage, a 30 cm drop causing signifi cant damage. This
injury is normally confi ned to the impact side of the fruit. The damaged fl esh
appears slightly straw-coloured. Mechanical injury of translucent fruit can
lead to leakage of fruit cell contents and loss of marketable fruit.
Sunburn
Sunburn is common during hotter periods (>35°C) of the year, when the fruit
is not shaded by leaves and especially in ratoon crops. The condition is more
prevalent in the outer rows and when fruit is lodged. Sun-scorched fruit fi rst
show a bleached yellow-white skin, which turns pale grey and brown, with
damage to the fl esh underneath. These damaged areas are more susceptible to
disease organisms, particularly yeasts and bacteria.
