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Banana, Musa sp. / Musaceae
Postharvest Atmosphere Management
Banana
The optimal temperature for the storage and transport varies according to the cultivar but it ranges from 13 to 14ºC. Later on, it is raised up to 15-20ºC for bananas to mature and they usually need the application of ethylene and controlled atmosphere.

The bananas packed in cardboard boxes are transported to the markets in freezer ships. It is recommended to pre-cool the warehouses at 7ºC around two days before the load arrives, although nowadays in the modern banana ships they have great capacity for fast cooling and thus this operation is not so necessary.

The optimal temperature for storage and transport is between 13 and 14ºC, although it may vary according to the cultivar (for example:’Pequeño Enano’ 11-12ºC and’Gran Enano’ 12,8ºC).

The maturity stage of bananas at their place of destination is at present an automatic process that is carried out in isolated premises, with different capacity according to the amount of fruit. The optimal temperature of maturation is 15-20ºC.

Most of the commercial varieties of bananas require the application of ethylene (100-150 ppm, 24-48 hours at 15-20ºC and relative humidity of 90-95%) to obtain a uniform maturation. The CO2 concentration must be maintained below 1%. The use of maturation systems such as forced air implies a uniformity in the heating or cooling of bananas, according to their needs, and the ethylene concentration throughout maturation.

With the controlled atmosphere , at levels of 2-5% O2 and 2-5% CO2 during transport, the maturation may be delayed to supply bananas in satisfactory conditions. The respiration and the ethylene production of the fruit are also reduced.

For further information and recommendations to maintain the quality of bananas after harvesting, consult the Web page ( http://postharvest.ucdavis.edu/Produce/ProduceFacts/Fruit/banana.html )
Postharvest Problems
Physiological alterations and diseases that may affect bananas: Chilling imjuries, skin burning, bruise effect, rot of the crown or top, anthracnose, peduncle rot, cigar end, bad torulosa Deightoniella and Panama disease.

Bananas may undergo physiological alterations caused by unsuitable temperatures or relative humidity or because of unsufficient care during handling; or they may suffer from the symptoms caused by some fungi, causing different diseases.

1. Chilling injuries
Symptoms include a discolouration of the external part, pale colour peduncle, the tissue of subepidermis forms dark brown stripes, they drop when they mature, and, in some cases, the flesh is bronced. This is caused by the exposure of bananas to temperatures below 13ºC, from several hours to several days, depending on the variety, maturity and temperature. The damaged fruits are prone to suffer mechanical damages.

2. Skin burning
Caused by friction between fruits or against surfaces of the handling equipment. When they have been exposed to low relative humidity conditions (<90%), the fruit loses water through the bruises and the colour changes from brown to black.

3. Bruise effect
The fall of bananas may lead to flesh bronzing without any appreciation in the skin.

4. Crown rot
This disease is caused by one or more of the following fungi: Thielaviopsis paradoxa, Lasiodiplodia theobromae, Colletrotrichum musae, Deightoniella torulosa, and Fusarium roseum. They attack the hands’ cut surface. It begins with a softening of the fruit and from the rotten tissue of the hand the fungus grows and penetrates in the finger’s pedicel, and eventually, it affects the fruit. A meaningful characteristic of this disease is the presence of gray-whitish mycellium in the surface of the necrotic tissue.

The recommended practices to avoid the increment of this disease are for example, to maintain the vegetal health in the plantation, the hygiene in the handling premises, the fungicide treatment of the crowns and to use chlorinated water in the tanks of fruit selection.

5. Antracnosis
Caused by Colletrichum musae, it causes that bananas to ripen especially in the wounds and cracks of the skin. They are covered by an orange-salmon mycellium. Nevertheless, the flesh is not affected at all, unless the bananas are too ripe or bear high temperatures.

6. Peduncle rot
Caused by Lasiodiplodia theobromae and/or Thielaviopsis paradoxa, that penetrate through the peduncle or the’hand’s’ cuts. The affected part of the flesh becomes smooth and watery.

7. Cigar end
Caused by Verticillium theobromae and/or fructigena Trachysphaera. A necrosis in the end of the bananas takes place, resembling the ash of a pure cigar.

This disease is prevented by deflowering, cutting the pistiles of the flowers twelve or fifteen days after the’ bunch’ grows or the inflorescence takes place.
For a good control of the fungus, spray directly to the cluster with benomile 50%, to 60-80g/hl or thiabendazole 60%, 150g/hl.

8. Torulosa Deightoniella
Caused by the Deightoniella torulosa fungus that causes the development of spots of a dark green colour and oily appearance, 4mm of diameter, with a mark similar to an insect’s bite in the center, although it is not. It should not be confused, therefore, with the attack of trips or red spider, that happens frequently.

The young fruits, ten to thirty days mature, are more prone to fungus than when they are already older than seventy to one hundred days.

It seems that a bad drainage favours the development of the disease, a very narrow frame of plantation and an inadequate control of weeds. For their control, sprayings with copper, zineb, or maneb compounds are recommended, with a dose of 300g/hl of water, or benomile 50%, dose of 80g/hl.

9. Panama disease
Disease caused by the Fusarium oxysporum F. sp. cubense fungus, that affects all the plant, and in special commercial varieties like Gros Michel. The Pequeña Enana variety, produced in the Canary Islands, is considered quite resistant to the fungus. The affected plants produce late’ clusters’ or they do not get to produce them. Bananas do not fill up with normality since the tissues do not grow as they should. These bananas are also called’snap beans’ bananas. The fruit is not rotten but the’hands" produced are smaller than the normal ones, and therefore of smaller weight.

The best thing to prevent it is to carry out suitable agricultural practices during the culture.
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