Banana disorders and diseases
Good quality bananas are free from diseases and disorders. Customers are not willing to purchase fruit presenting rots or damaged skin. Furthermore, fruit that looks good on the outside but presenting brown flesh on the inside will not lead to happy customers. There are dozens of different diseases and disorders, which are not always easy to recognize. A good diagnosis of the fruit’s health is important. By recognizing the symptoms of a disease or disorder, it can be linked to the cause. If you know the cause, you know what measures can be taken to prevent the disease or disorder in the future.
Identification of banana disorders and diseases usually takes place by carefully looking at the symptoms. Some symptoms are visible from the outside, while others can only be found internally after peeling. It is important to detect the quality issues as early as possible in the supply chain to reduce further incidence. Retailers can also benefit from knowledge about disorders they may encounter. For them, it is important to know whether the cause lies at a previous stage in the supply chain or is due to their own operations. Disorders and diseases can lead to significant post-harvest losses. Common causes of deterioration of bananas are chilling injury and skin bruises..
Frequently occurring disorders and diseases
Bananas with symptoms of chilling injury visible when removing part of the peel. Photo by WUR.
Chilling injuryChilling injury can occur both at green and ripe fruits, when exposed to low temperatures, indicatively below 13 °C. The skin of green bananas on the inside may be discoloured. Peeling can reveal this underpeel discoloration visible as brown and black streaks. It leads in the more advanced ripening stage to a dull grey appearance. Symptoms appear especially after
transfer to higher temperatures: fruits can turn black, have an off-taste and are very sensitive to handling damage.
Grey colouration of banana resulting from high desiccation. Photo by WUR.
DesiccationDesiccation of green bananas can lead to loss of skin glossiness and in severe cases to a grey colour. This under-skin discoloration resembles the symptoms of chilling injury. Relative humidity during transport and controlled ripening must be high to slow down desiccation, also using perforated bags. Desiccation of yellow bananas can promote skin browning triggered by handling
Bananas with bruises. Photo by WUR.
Bruises and injuriesRough handling can easily lead to mechanical damage to the banana skin, at any stage of the supply chain. Scuffing of bananas against each other during transport can cause skin abrasions with brown or black discolorations. Dropping of bananas can lead to internal bruises. Bruises are usually soft with discoloration of the underlying flesh.
Latex stains on banana. Photo by WUR.
Latex stainsWhen banana bunches are separated from the banana plant, latex comes out of the cut wound. Later in the supply chain, latex can also flow out of the wound. The latex leads to dried latex stains and can even cause latex burn on the banana peel. Measures during harvesting and washing in the packhouse can help prevent stains. Traces of latex stains can be found on bananas on the shelf.
Banana artifically split into ripe (left) and more senescent side (right). Photo by Elena Zajchikova/Shutterstock.com
SenescenceSenescence is the natural development stage that follows the eat-ripe stage. Senescent spots (sugar spots) appear on the skin surface during the last stage of ripening. Eventually, the banana peel turns brown. The pulp loses its firm texture and becomes brown and possibly gelatinous. Senescence is enhanced by higher temperatures. The bananas with senescence symptoms may have been stored under suboptimal conditions such as too high temperature or were simply stored for too long.
Premature ripened bananas triggered by some rotten bananas in the box. Photo by WUR.
Premature ripeningPremature ripening can be the result of too advanced harvest maturity, too warm temperature or the presence of ethylene somewhere in the preceding chain. The more mature bananas then ripen first, causing differences in colour stage. Banana hands can start ripening during long-distance transport or will ripen faster later in the chain after artificial ripening. The presence of rotten bananas (ethylene) can trigger ripening in the complete box.
Bananas with splitted skin. Photo by WUR.
SplittingSplitting of the skin is caused by ripening at high temperature under moist conditions. It may develop at the end of the supply chain after the controlled ripening, when bananas are still under moist conditions inside polyethylene bags. Premature ripening during shipment can also lead to this splitting of the skin. The open wound leads to moisture loss and is susceptible to moulds and rots.
Tip end rot on a banana. Photo by WUR.
Moulds and rotsAnthracnose infection of wounds can lead to large dark brown to black lesions. Cigar-end rot is a tip-end rot that can lead to dry tissue, which resembles the ashy end of a burnt cigar. Crown mould, crown rot and finger-stalk rot are caused by fungi on the cut surface of the crown growing into the fingers. In general, the development of rot can often be controlled by careful handling to prevent injury and cool down quickly after harvest.