Introduction Name, Taxonomy, Botany
Nutritional Value
Common Varieties
Agronomy
Pest & Disease
Post-harvest & Processing
Market and International Trade
Research and Development
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Harvesting:
Stalks of bananas are usually formed in the late summer and then winter over. In March they begin “plumping up” and may ripen in April. Occasionally, a stalk will form in early summer and ripen before cold weather appears. The bananas are harvested at a specific maturity, relating to the number of days from flowering, the angularity of the fingers in cross section, the size of fingers, and distance to market. Skilled teams harvest the bananas, using specialized equipment to cut stems and support cut bunches. Where flat land allows, wire and pole systems suspend and transport the bunches from the field to the packing shed.
Fruit should be harvested early in the day, when the temperature is low. The fruit can be harvested by cutting the stalk when the bananas are plump but green. For tree-ripened fruit, cut one hand at a time as it ripens. If latter is done, check stalk daily as rodents can eat the insides of every banana, from above, and the stalk will look untouched. Once harvested the stalk should be hung in a cool, shady place.
Maturity Indices:
The plant has six or less functional leaves.
Fruits are full, plump, round and light green (index 1).
Angles in the fingers are rounded.
Leaves turn yellow.
HARVESTING DATES
Variety Weeks from Flower Emergence Days from “False Hand” Appearance
Latundan
9 – 11
Harvest not earlier than 70 hanging days
Lakatan
12 – 14
Harvest not earlier than 80 hanging days
Saba/Cardaba
20 – 24
Harvest not earlier than 118 hanging days
Postharvest Handling and Packaging
Immediately after harvest, fruits are cooled to the storage temperature. This stage, called precooling, should be rapid. Fruit can be cooled using cold air (room cooling, forced air cooling), cold water (hydro-cooling), direct contact with ice, or evaporation of water from the fruit (evaporative cooling, vacuum cooling). Plantain and banana are usually cooled with cold air, to prevent temperatures becoming too low, which can cause chilling injury.
High humidity reduces water loss, and increases storage life. However, high humidity also encourages fungal growth. A relative humidity of 90% provides the best compromise for storing plantain and banana. Humidity can be raised in a container or room by spraying water in a fine mist. Humidity is reduced by venting. Humidity can be controlled with the help of a humidistat. Traditional methods for increasing the storage humidity include spraying fruit intermittently with water, storing fruit on wet sacking, and storing fruit in boxes filled with moist coir or sawdust. Although effective, these methods can cause excessive wetting, which leads to fruit splitting and reduces market quality. Air circulation is an effective method used to reduce temperature in storage rooms. However, ventilation also increases water loss from fruit, by removing the saturated layer of air that surrounds the fruit. If ventilation is used to reduce temperature, water loss can be reduced by:
covering fruit with tarpaulins
packing fruit into bags, boxes, or cartons
wrapping fruit in polyethylene bags or heat shrink plastic films
At the packing house, the bananas are then separated into hands. The hands are washed in a solution (2% alum, 20% chlorine) to sterilize them, and to prevent latex from cut fruit staining the peel, and then treated with fungicide.
The hands are then packed into fiberboard boxes. The boxes may be lined with polythene, or the hands may be sealed in polythene bags (refer to photos below). The boxes are stowed at a specific stack height and configuration in refrigerated stores or transport containers. At the destination countries, the unripe bananas are distributed to ripening depots, where the ripening process is initiated with ethylene gas. Bananas are then distributed to retail outlets/markets. The storage life of bananas, using these techniques, is 4-8 weeks.
Physiological Changes
Commercial banana are harvested when they have become plump, but are still green. Once the bananas are picked, hormones in the fruit convert certain amino acids into ethylene gas. Ethylene gas, in turn, stimulates the production of several enzymes that change the color, texture and flavor of the banana.
Enzymes sweeten and soften the banana, and change the color of the peel. The enzyme that makes bananas sweet is called amylase. Amylase breaks down the starch in the banana fruit. When the starch is broken into its smaller sugar components, called glucose, the banana tastes sweet. The enzyme that softens the banana is called pectinase. Pectinase breaks down the cell walls in the banana fruit so that it becomes less firm. The peel of the banana also becomes softer as it ripens. Other enzymes break down chlorophyll molecules in the banana. The green pigment of chlorophyll is destroyed and replaced by yellow, red or blue pigments. Depending on the type of banana, the result is either the golden yellow color (dessert banana), or shades of red or purple for other banana varieties. Once the banana peel has been softened, it bruises much more easily. Bruising causes yet another enzyme called polyphenoloxidase to speed up oxidation, which turns a banana peel brown. Eventually the entire peel will turn almost black. Even when a fresh banana is bruised, a brown spot will often develop. The flesh of the banana will also turn brown if the bruising is deep enough. Bananas fresh from the market are often not fully ripe. Green bananas are tougher and therefore easier to ship.
Banana fruit are highly susceptible to chilling injury during low temperature storage. The skins of fruit stored at 3 and 8 °C gradually darkened as storage duration increased. This chilling effect was reflected in increasing membrane permeability as shown by increased relative electrolyte leakage from skin tissue. In contrast, banana fruit stored for 8 days at 13 °C showed no chilling injury symptoms.Exposure of banana fruit to the ethylene binding inhibitor 1-methylcyclopropene (1 l l-1 1-MCP) prevented ripening. However, this treatment also enhanced the chilling injury accelerated the occurrence of chilling injury-associated increased membrane permeability. 14C-ethylene release assay showed that ethylene binding by banana fruit stored at low temperature decreased with reduced storage temperature and/or prolonged storage time. Fruit exposed to 1-MCP for 12 h and then stored at 3 or 8 °C exhibited lower ethylene binding than those stored at 13 °C. Thus, chilling injury of banana fruit stored at low temperature is associated with a decrease in ethylene binding. The ability of tissue to respond to ethylene is evidently reduced, thereby resulting in failure to ripen (Yueming Jiang et al., 2004).
During shipping, the environment of the bananas is carefully controlled so that ripening is slowed. The temperature is kept low, and the concentration of ethylene is controlled so that enzyme activity is minimized.
Postharvest Treatment
Storage Atmosphere: Respiration can be reduced, and hence storage life increased, by modifying atmospheric composition within the storage area. However, this method can be costly, and therefore is less used.
Normal atmospheric composition is approximately 21% oxygen, 78% nitrogen, and 0.03% carbon dioxide. By reducing the proportion of oxygen and raising the carbon dioxide, the rate of respiration is reduced, and plantain and banana ripening is delayed. For example, bananas stored in 5% carbon dioxide and 3% oxygen at 20 °C have been stored for more than 6 months.
Control of atmospheric composition requires a sealed environment. Sealed storage rooms, where levels of atmospheric gases can be monitored and adjusted, are expensive. A cheaper alternative is a plastic tent. Plastic tents are used in Malaysia and the Philippines to extend the storage life of Pisang Mas (Golden banana).
A simple and cheaper method is to seal fruit in polythene (polyethylene) bags. Plantains sealed in polythene bags remain green for a longer period than fruits stored in perforated polythene bags, paper bags, or wet coir. As the fruits respire, the atmosphere within the bag decreases in oxygen and increases in carbon dioxide. Respiration is then inhibited because of the reduced oxygen.
Plantain and banana may be sealed individually, or several fruits may be bagged together. When several plantains or bananas are stored together in a bag, the first fruit that ripens produces ethylene, and this causes other fruit to ripen. Therefore, only bag together fruit of the same maturity. Although polythene bags can extend storage life, there are a number of problems associated with their use.
In one study, storing bananas in polythene bags at 20 °C delayed ripening by up to 6 days. Also, weight loss was reduced and there was less mechanical damage. High humidity develops in polythene bags. This reduces water loss from fruit, and also has a lubricating effect, which protects fruit from physical damage.
High humidity within bags can result in development of crown rots, caused by Gleosporium musarum. These rots are controlled with fungicides such as benomyl and TBZ.
‘Green soft’ or ‘boiling’ may also occur in fruit stored in polythene bags. The peel remains green, but the pulp becomes soft and develops an off-flavor and odor. This disorder results from storing fruit in high levels of ethylene and carbon dioxide, with low oxygen. ‘Green soft’ can be avoided by including an ethylene absorber in the bag (see below), or using semipermeable polythene.
Polythene bags are now widely used in Australia to extend storage life of fruit. Studies in Sudan and Ghana confirmed the advantage of using polythene bags to extend storage life, but the technology has not been adopted in these countries. Reasons may be lack of information or unavailability of materials. However, it is more likely that polythene bags were not suited to the current system of handling, or that the extra investment in materials and time was not rewarded by higher profit at the market. To avoid high costs, cheap and easily available materials, such as moist jute bags, can also be used.
Effect of Ethylene: Since ethylene helps initiate and stimulate ripening, and mature fruit gives off this gas in small amounts, ripening can be hastened by covering the bunch with a plastic bag.
Reducing ethylene levels delays ripening. Using chemical ethylene absorbents or oxidizers, to reduce ethylene inside polythene bags, is a feasible method for extending storage life. Ethylene can be absorbed by activated carbon, or oxidized by potassium permanganate, ozone, ultraviolet light, or the use of catalysts.
The simplest ethylene absorber consists of an inert carrier, such as vermiculite or rice hulm and ash, impregnated with potassium permanganate. Potassium permanganate absorbs free ethylene. Recently, Japanese researchers have made plastic bags coated with zeolites, which absorb both oxygen and ethylene. Zeolite use is at an early stage, but may eventually result in an appropriate technology for extending storage life of plantain and banana.
Chemical coating of fruit: Researchers have investigated some chemical and physical treatments of fruit, as a cheaper way of extending storage life (Olorunda A.O & Aworh OC. 1984). The main methods investigated so far are
chemical coating of fruits
treatment with gibberellic acid
radiation
There is commercial interest in the use of chemical fruit coatings, such as Prolong and Semperfresh, to delay ripening. These formulations are based on sucrose esters and carboxymethyl cellulose, and they are water dispersable. They provide a microfilm coating on the fruit surface. This film has no effect on water movement, but it may restrict the rate of gas movement through the skin of the fruit, slowing down respiration.Studies have shown that Prolong and Semperfresh delay the ripening of plantains by 8-10 days at 30 °C and low humidity. Hence, chemical coatings have potential use where temperature and humidity cannot be controlled.However, fruit coating has not been accepted in the banana trade, mainly because of high costs. Also, the subsequent ripening of the coated fruit is unpredictable, and uneven.
Treatment with gibberellic acid: Dipping of fruit into gibberellic acid was shown to delay ripening of bananas at high humidity, but not at low humidity. This method has not been adopted commercially.
Radiation: Studies in the USA and India have reported that storage life can be extended by irradiating bananas after harvest. Doses of 200-400 Gy increased storage life by 4-8 days at 24-28 °C. However, some types of plantain might be damaged by these doses. Also, the technology is not widely available, and is expensive; and despite acceptance by the USA Food Council, radiation is still unacceptable to consumers in many countries because of negative associations.
Types of Packaging
Several available packaging materials:
woven large bamboo or rattan baskets lined with dried banana leaves or newsprints
wooden crates of 30 kg capacity
12 kg capacity cartons.
1. Local Market:
The fruits are packed in bamboo baskets, wooden crates and corrugated cartons. These containers are lined with newspapers, banana leaves or polyethylene sheets. The linings are used to prevent the fruits from injuries during further handling.
As much as possible bamboo baskets are avoided, for they can easily be deformed. The baskets are also unstable and can easily roll off during transport. The sharp edges of the baskets may also puncture the fruit. The collapsible wooden crates with veneer slots functions better.
2. Export Market:
Export bananas are picked green, and then usually ripened in ripening rooms when they arrive in their country of destination. These are special rooms made air-tight and filled with C2H4 gas to induce ripening. Bananas can be ordered by the retailer “ungassed”, however, and may show up at the supermarket still fully green. While these bananas will ripen more slowly, the flavour will be notably richer, and the banana peel can be allowed to reach a yellow/brown speckled phase, and yet retain a firm flesh inside. Thus, shelf life is somewhat extended. The flavour and texture of bananas are affected by the temperature at which they ripen. Bananas are refrigerated to between 13.6 and 15 °C during transportation. At lower temperatures, the ripening of bananas permanently stalls, and the bananas will eventually turn grey.
Bananas being exported are packed in cartoon boxes with fiber boards at the bottom. These boxes are lined with thin polyethylene films. Holes, 2.5 cm in diameter on the sides of the boxes are provided for ventilation.
For Middle East shipments, vacuum packing is used. Air is sucked from 0.05 mm thick plastic bag before it is sealed and the box stapled. The approximate weight of the package is 13 kg.
Average weights of the boxes vary depending on the importing country. For Japan, the required weight is about 12.5 kg per box. This contains 4-6 hands. Boxes exported to New Zealand and Hong Kong average 18 kg per box.
Storage and Transportation
Transport: Transport of bananas is usually done by trucks or jeeps. Even when transported only within their country of origin, ripe bananas suffer a high rate of damage and loss. Loaded bunches are closely packed and layered with green banana leaves to prevent shaking and bruises during transport. The vehicle should also be ventilated for inter-island shipments, bananas are loaded in 3 meter container vans with pallets. Cavendish are shipped from Davao to Manila in sealed polyethylene bags with ethylene (C2H4) scrubbers and packed in cartons. The ethylene scrubbers help in delaying the ripening of the fruits for more than one week. Fruits for export are kept in refrigerated ships maintained at 13° to 14°C. Bananas should not be placed in areas with extreme temperatures. The boxes should not be dropped, thrown, stacked in inverted position, rolled or tipped. If possible, horizontal dividers or separators should be constructed to prevent compression of commodities in the lower layers.
Storage: Packed fruits are either kept in cold storage or ripening rooms.
Optimum storage temperature for some banana cultivars
Cultivars
Optimum Temperature °C
Storage Period (days)
Saba/Cardaba
10
35
Latundan
14
21-28
Lakatan
13
28
Source: Banana Production by : Rene Rafael C. Espino, Ph. D., et al, 2001
Reference:
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“FAOSTAT: ProdSTAT: Crops”. Food and Agriculture Organization. 2005.
http://faostat.fao.org/site/567/DesktopDefault.aspx?PageID=567. Retrieved on 09-12-2006.
http://agroforestry.net/tti/Musa-banana-plantain.pdf
http://www.ctahr.hawaii.edu/nelsons/banana/
Kepler, A.K., and F.G. Rust. 2005. Bananas and Plantains of French Polynesia. Part I Traditional Non-Fe‘i Bananas: Descriptions, color photographs, status, and possible kinships with Hawai‘i’s ancestral bananas. Part II Color photographs of Western introduced Varieties. Part III Names & Synonyms of Extant and Recently Extirpated Varieties, Tahiti & the Marquesas Islands. Part IV Traditional Non-Fe‘i Banana Varieties, Society and Marquesas Islands: Known Historical Names, Meanings, and Locations dating back to the mid-19th Century. Part V Appendices. Unpublished.
Lassoudiere, A., 1974. La mosaïque dite a tirets du bananier Poyo en Cote d’ Ivoire. Fruits,. 29: 349-357. Page 4. Int. J. Virol, 3 (2): 96-99.
Lockhart, B.E. 1986. Occurence of canna yellow mottle virus in North America. Phytopathology 76: 995.
Nelson, S.C., R.C. Ploetz, and A.K. Kepler. 2006. Musa species (bananas and plantains), ver. 2.2. In: Elevitch, C.R. (ed.). Species Profiles for Pacific Island Agroforestry. Permanent Agriculture Resources (PAR), Hōlualoa, Hawai‘i. <http:// www.traditionaltree.org>
Olorunda AO, Aworh OC. 1984. Effects of Tal Prolong, a surface coating agent, on the shelf life and quality attributes of plantains. Journal of the Science of Food and Agriculture 35: 573-578.
Rene Rafael C. Espino, Ph. D., et al, 2000.Banana Production.“Tracing antiquity of banana cultivation in Papua New Guinea”. The Australia & Pacific Science Foundation.http://apscience.org.au/projects/PBF_02_3/pbf_02_3.htm. Retrieved on 2007-09-18
Yueming Jiang1, , Daryl C. Joyce3, Weibao Jiang4 and Wangjin Lu. 2004. Effects of Chilling Temperatures on Ethylene Binding by Banana Fruit Plant Growth Regulation 43: 109–115, 2004.Kluwer Academic Publishers. Printed in the Netherlands.