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Organisation: Institut des Forets, Department Fruits ett Agrumes (IDEFOR, DFA)
Author: Achille N'Da Adopo
Edited by AGSI/FAO: Danilo Mejia (Technical), Beverly Lewis (Language&Style), Carolin Bothe (HTML transfer)

CHAPTER XIII PLANTAIN CASE STUDY: POST-HARVEST OPERATIONS


2.2 Harvesting

2.3 Transport

2.7 Packaging

2.8 Storage


2. Post-Production Operations

Banana plantain belongs to climacteric fruits characterised by temporary increase of respiration (Cheftel, 1976). This sudden increase of respiration is called climacteric phase or crisis, which precedes or coincides with observed changes during ripening of plantain:

- Progressive fading of the green colour of the skin;

- Brutal decrease of the hardness of the pulp;

- Occurrence of aromatic flavour.

During its development on the tree, the hardness of the pulp of banana reaches a maximum point that is approximately 2/3 of the growth cycle of the fruit. Then hardness decreases continuously until harvest (Deullin, 1966).

Hardness measurements of the pulp of the plantain on French sombre and Orishele cultivars during their development indicate a permanent decrease of the pulp breaking strength from 65 to 70 days after dropping of female flowers. This stage corresponds to hardness pics for a growing and development cycle of the cluster of about 100 days (corresponding to the maximum yield) (Sery, 1985).

The change of the colour of the skin from green to yellow, the softening of the fruit and characteristic odours, constitute the most practical and fastest physical characteristics signalling the ripening of the plantain.

The decrease of the hardness of fingers (the pulp breaking strength), practically nil at the climacteric stage, has a very important consequence for the fruit as it is subjected to brutal handling in the traditional sector. After harvest, the finger, even if it is still very green, softens continuously and becomes less and less breakable compared to the freshly picked. This phenomenon considerably reduces the number of fingers broken or removed normally encountered during loading and unloading operations.

The period of green life or pre-climacteric phase is closely linked to the harvest stage. The time between harvest and ripening decreases as harvesting is delayed.

In the commercialisation sector, clusters are often harvested when they have nearly reached the ultimate stage of development. In these conditions (air temperature from 24 to 35_C, hygrometry from 70 to 90 percent), ripening occurs in 5 to 7 days. This corresponds very often in the traditional sector to the length of time between harvest and delivery to the most distant urban markets (400 to 700 km).

Traditional cropping provides the most important share of production (at least 80 percent of commercialised clusters). In this production system, the offer is not regular. One can consider as very good the selling on a weekly basis of 10 to 20 clusters by a producer after his self-consumption needs. The gathering by intermediaries can last from 2 to 4 days. The cluster, which has reached the consumption market then, has a potential of green life duration that is quite limited.

If intermediaries can choose the plantain in the stages of filling they want, they cannot control the accelerated loss of freshness in a system where goods are not carefully handled, are piled-up and finally exposed to direct sunshine directly on the floor or the tarmac (See Figure 15).

Figure 15: POOR STORAGE CONDITIONS
Poor storage conditions meaning quick decreasing of initial commercial value of clusters

Cluster protection is easier at the producer level: waiting for the arrival of buyers, the plantain can be placed under the shade of banana trees and covered with their large leaves. This type of product storage under good conditions without any cost, has the advantage of banana leaves cut at the same time as the cluster are laid down to avoid scratching crops against the floor during harvest (See Figure 16). This process also allows the farmer to slow down ripening of the cluster for a few days, pending the arrival of the buyer. Intermediaries are more at ease to bargain for reduced prices when damage is obvious or when there are important signs of loss of freshness of the product.

Figure 16a-d: HARVESTING HARVESTING HARVESTING HARVESTING
Harvesting for sale by the producer

When the buyer abides by his collection calendar, plantain is removed from the producer at green stage. The ripening will occur only at the level of the intermediary, during transport or on the stalls in the consumption market.

If one thinks that after harvest, ripe clusters are more likely to bring about post-harvest losses than green clusters, one should recognise that in the current traditional system, methods to reduce possible losses are relatively more efficient at the level of producers than at the level of intermediaries. Post-harvest manipulations with intermediaries are the same in all the producing countries and this brings about the same effects on plantains, that is ripening and a quick loss of commercial value (Mihailov, 1986; Kuperminc, 1985; N'da Adopo, 1993).

Rapid ripening of the product during commercialisation may be attributed to several factors:

1- Harvest stage and harvest techniques;

2- Packaging mode and type of transport;

3- Storage and conservation modes.

Generally, the cluster that is in the commercial process will follow one of these two patterns:

- Ripening before loss of freshness;

- Ripening after loss of freshness.

(See Table 12).

Table 12: Aspect of the clusters found on markets of different traditional channels in Cameroon, Côte d'Ivoire and Ghana, according to levels of filling of fingers and commercialisation duration from harvest

 

Early or medium stage of harvest

Advanced stage of harvest

Distribution deadline 1 to 3 days

* green cluster* fresh or withered

* green or ripe cluster* fresh

Distribution deadline 4 to 6 days

* green cluster* withered

* well ripened cluster

Distribution deadline 7 to 9 days

* green or ripe cluster* withered

* well ripened or rotting cluster* withered

The cluster which has reached maturity and which is ready for harvest presents certain external characteristics:

- Rounded and very little angular finger lines (the earlier the harvest, the more angular the lines);

- Increase of green pigmentation of apex of fruits;

- Drying of finger tips;

- Drying of floral pieces;

- Presence of cracked fingers or ripe fingers (generally at the level of the first hands).

At this stage, the plant presents only 4 to 6 living leaves maximum against 8 or more at the beginning and middle of the growth and development of the cluster.

The degree of filling for harvest varies according to eating habits, cooking and destination of clusters. Harvest for immediate domestic consumption in Côte d'Ivoire, could produce ripe fingers whereas for sale the cluster will be full and green. The Horn and false Horn plantains are often more rounded than those of French type at harvest.

At the cutting stage (75 to 95 days) of medium size cultivars (Corne 4 and French sombre comprising 5 to 8 hands), many big clusters comprising at least 10 hands (for example cultivar Essong in Cameroon) often present angular fingers, due to the reduced number of leaves which are alive and capable of ensuring an important photosynthetic activity for quick filling of so many fingers (Osafo, 1986).

Tables 13 and 14 present data at harvest obtained from Orishele and French sombre cultivars. Hardness of the pulp is measured at the level of median transversal cut of fingers using a crossbow penetrometer of Cosse type (6 mm diameter nozzle).

Table 13: Pulp hardness in kg/cm²

Harvest stage (days after loss of flowers)

65 à 71

75 à 80

85 à 95

Orishele

2 - 1,8

1,8 - 1,6

1,5 - 1,2

French Sombre

4,6 - 4,3

4,3 - 4

4,1 - 3,2

Table 14: Pulp/skin weight ratio

Harvest stage (days after loss of flowers )

65 à 71

75 à 80

85 à 95

Orishele

1,3 - 1,5

1,5 - 1,65

1,6 - 1,7

French Sombre

1,15 - 1,3

1,3 - 1,5

1,5 - 1,7

2.2 Harvesting

Harvest is done for self-consumption (1 to 3 clusters per week), for sale to possible buyers alongside the road or village track (about 10 clusters maximum) or on request of intermediaries. The number of clusters in the later case depends on demand and supply of the producer compared to the clusters, which have reached physiological maturity.

Harvest is performed to avoid or reduce damages (See Figure 16). A technique often used in Latin America and Africa is to do use a big knife commonly utilised for fieldwork called a machete. An oblique wound of 6 to 8 cm is made in the wrong trunk at approximately 0,8 to 1,5 m under the level of the last hands in the axis of the cluster.

The depth of the wound in the wrong trunk should be reduced inversely by the size of the cluster. One can slightly shake the plant by kicking at the level of the wound with the back of the machete. Placing a fork under the stave can also monitor the fall of the cluster. The cluster will be held in the middle by its rachis before being separated from the tree.

When this technique is mastered, the product does not suffer from any shock. The operation requires a maximum of 30 seconds. There are practically no losses in the field due to post-harvest practices.

Harvest for self-consumption, in the field or behind the hut is incidentally done by both sexes. Harvest of larger quantities of clusters (about 10) for sale are generally undertaken by men (the husband, a planting agent, etc.).

The length on which the stave is cut often depends on the destination of the product:

1) Show the freshness of the cluster. It will then be possible later on to cut it one or many times according to the length of sale, in order to present a fresher section to the clients and convince them that the cluster has been harvested that day or for a few hours only;

2) Identify the owner of the cluster, the producer or intermediary puts marks or writes initials on it).

2.3 Transport

In the traditional channel, the plantain is generally transported in clusters from the field to the farm and from one intermediary to the other. The cuttings into hands, bunches or fingers occurs at the last stage of commercialisation with the detailers.

The type of transportation varies according to the number of clusters to be carried, the distance to run and local removing methods:

- Carried by people (1 to 3 clusters);

- Trolley pushed or pulled by people (15 to 25 clusters);

- Bicycle or motorcycle (1 to 7 clusters);

- On the roof of travellers' transport van (50 to 60 clusters);

- Truck (400 to 700 clusters);

- By railway (more than a thousand clusters).

Clusters are thrown into the vehicle, piled-up one on top of the other, without any care. The major concern is to convey maximum of the product while occupying all the available space. One overloads the vehicle in order to make one trip only. These careless operations bring about twisting of peducules, breaking and dropping of many fingers (Figure 5c, 17 and 18). The practice in general in Africa (Mihailov, 1986).

Figure 17: VIEW OF A LORRY
View of a lorry (7 tons) full of bunches at arrival at the urban market. Approximately 500 bunches are piled into the vehicle.

Figure 18: PILE OF BROCKEN AND REMOVED FINGERS
Pile of brocken and removed fingers during handling and transport, collected below the lorry. According to the lot of bunches in the left, these fingers are equivalent to 50 bunches.

Figure 18a-c: TRANSPORT TRANSPORT TRANSPORT
Transport in the past (Simmonds, 1959)

Most commonly, the carrier is not the owner of the clusters; he is only charged with the responsibility to transport goods to destination. To load or unload 7 to 8 tons (450 to 650 clusters) requires at each destination, 3 to 4 specialised goods handlers apart from the carrier. These goods handlers are real auxiliaries of the channel. These goods handlers wait on the premises where the collected plantains are gathered at he level of producers and on the markets of destination of the clusters. The work is done in sequence:

- A loader «a specialist>> is charged with arranging the clusters in the truck following a process that he masters. One makes sure to arrange the clusters tightly, sometimes breaking them or twisting the fingers;

- Another «specialist» loader (the identifier) in urban market arranges on the fruits in lots, referring to the initials marked by intermediaries on the staves;

- The last goods handlers transmits to the first ones the clusters in one direction or the other, according to loading and unloading situation.

Five to 6 seconds are necessary to throw a cluster into a truck and place it tightly that makes approximately 1 hour for all the collected goods. The identification of clusters and their classification on arrival in town requires as much time. It takes a total of 2 hours to load and unload 500 clusters. The cost of loading or unloading of a cluster including its identification and sorting was 10 F CFA per cluster in the Southwest district of Cameroon (N'da Adopo, 1992). The transport of the cluster per truck (7 to 8 tons) of this district up to Douala cost 180 F CFA. Compared to the costs in abundant periods, 500 F CFA/cluster at the producer level, 915 and 1000 F CFA respectively for wholesaler and detail sale, revenues and charges are shown in Table 15.

Table 15: Gains estimates (F CFA) of the various actors according to the type of circuit: Road Tombel (Zone II) to Douala in high production season (December 1990 to February 1991). Reference: 500 clusters, medium weight _15 kg/cluster.

Type of circuit

Producer himself

Retailer (supplying from the producer)

Wholesaler (supplying from the producer)

Retailer (supplying from the wholesaler in town)

Buying cost from the producer

 

250.000

250.600

 

Individual transport Douala-Ngoussi-Douala

5.000

5.000

5.000

 

Collection:- loader

5.000

5.000

5.000

 

Collection - other handlers

5.000

5.000

5.000

 

Transportation of clusters

90.000

90.000

90.000

 

Unloading- off loaders-

5.000

5.000

5.000

 

Unloading identifier

5.000-

5.000

5.000

-

Charges

110.000

115.000

115.000

-

Gross return

-

-

365.000

-

Selling price (wholesale) (Douala)

457.500

-

458.330

458.330 (buying in bulk from wholesaler in town)

Net return (wholesale) (Douala)

347.500 less production cost

-

93.330 (186 F/bunch)

 

Return (retailer)

-

365.000

-

-

Retail selling price

500.000

500.000

-

500.000

Net return in retail in clusters in Douala

390.000 less production cost

135.000 ( 270 F/cluster )

-

42.000 ( 84 F/cluster )

Source: (N'Da Adopo, 1992)

Although product losses during transportation are scarce, this stage is the most delicate and risky of distribution. The harvested plantain can be lost totally or in part in the following situations:

- Lack of respect for the appointment or collection deadline of the harvest by the intermediary;

- Mechanical failure or accident of the vehicle during transportation, immobilising goods for several days.

2.7 Packaging

Plantains are not placed in particular packaging in the traditional channel inside the country of production or between neighbouring countries in Africa. This happens for export to more remote markets, from Africa to Europe, and from South America to North America (Lescot, 1993). Packaging and all other operations try to follow the methods of the international commercial distribution of bananas.

More caution is taken for products destined for export:

- 2 people to harvest a cluster (one to cut, the other one to receive on a back with a foam carpet);

- Take the harvested product to the spot where it is going to be cut near the field or packaging warehouse, hang it on a gantry;

- Cut into hands or fingers with adapted tools («banacut» to remove hands, special knife, etc.);

- Wash and possibly soak in a fungicide;

- Package into cartons for transportation.

An analysis of packaging coast has been carried out, in hypothesis that 500 clusters (according to Table 15) are cut up and packed in cartons, in a field or on a farm and conveyed for sale in Douala (N'da Adopo, 1992):

- The shaft represents approximately 9 percent of the weight of the bunch. So the net weight of a bunch being able to pack is 13.65 kg, net weight of the 500 clusters is 6,825 kg (hands and fingers);

- The usual packages (cartons used to export bananas) are full at optimum with 19.0 kg of plantains; 6,825 kg require # 359 cartons;

- Handling and packaging;

. Cutting up.

The time required for this task is 1 minute per cluster per person. Therefore 500 clusters require 8.33 hours. It is necessary to recruit 9 handlers to complete cutting in 1 hour. Eight other packers are required to wash and clean the fruits before packaging.

To package requires 2 minutes per carton per person, or 3 hours per person for 359 carton It is advisable to recruit 3 persons. There is a requirement for 28 persons (8 for harvesting and 20 for cutting up and packaging) to finish these operations in 1 hour. The pay for agricultural labour is 110 F CFA /hour /person in the area of this study (Zone III, Figure 13), or 3 080 F CFA in total.

Loading the 359 cartons in the lorry requires 3 handlers, which 20 F CFA in total per carton (See Table 15), or 7 180 F CFA.

Total theoretical charge minimum is 10 260 F CFA (loading would require only 10 000 F CFA in the traditional circuit).

How many cartons are in the lorry?

- The dimensions (in meter) of the trailer of usual lorry (7 tons) are 5 (L) X 2.18 (W) X 0.26 (H) # 19 m3

- The dimensions of banana carton are 0.45 (L) X 0.35 (W) X 0.26 (H) = 0.04 m3.

A lorry can so contain 19/0.04 = 475 cartons. One needs 116 other cartons (and 162 clusters) to complete the

Loading, that is to say 662 clusters in total: for the same coast, it is cheaper to transport 662 corresponding to 475 cartons than 500 clusters.

But this method requires buying cartons. The coast of a carton is # 600 F CFA, that is to say an initial input of

285 000 F CFA. One carton can be used only for 4 to 5 trips in loading and unloading. In addition to these charges, it needs also workers to collect the cartons and keep them in the market places during marketing!

2.8 Storage

The producers harvest for self-consumption or an imminent sale. Contrary to the case of rice or maize, one doesn't stock so perishable product on the farm: There are no storage coasts at the farm level (See Table 16).

Harvesting takes place little by little according to the self-consumption needs. When these needs are satisfied and there are no buyers, the clusters are not harvested and plantain can ripen on the trees. The salesman provides his stand with clusters little by little according to the market. The objective is not to stock because the plantains will loss their freshness and their value.

Because the demand for well-ripened plantain is high, many sellers cover the fruits to accelerate ripening. They also use chemical products, which generate ethylene to obtain the same result (See Figure 23).

Figure 19: PLANTAINS COVERED
In urban markets plantains are usually covered by salers to accelerate ripening. See the little girl behind watching the stall.

Table 16: Handling Costs (NGN/t of plantain)

 

Producer

Wholesaler

Retailer

Transportation

16

43

39

Storage

0

91

15

Handling

16

134

54

Transportation cost as % of handling

100

32

72

Storage cost as % of handling

0

68

28

Source: Njoku J.E. and Nweke F.I., 1985

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