Reducing Postharvest Losses of Horticultural Commodities in Nigeria through Improved Packaging

Introduction

Nigeria produces a wide variety of familiar tropical fruits including citrus, mango, papaya, guava, pineapple, banana, watermelon and a variety of little-known indigenous African fruits such as the African star apple (Chrysophyllum albidum), hog plum (Spondias mombin), native pear (Dacryodes edulis) and African or wild mango (Irvingia gabonensis). The country is a leading producer of pepper (capsicums) and large amounts of tomatoes, plantain, onions, okra and other vegetables are grown in its diverse agro-ecological zones that range from humid in the south to sub-humid in the middle belt and semi-arid/arid in the north. Fresh fruits and vegetables are inherently more liable to deterioration under tropical conditions characterised by high ambient temperatures and humidities, and a high incidence of pests and diseases. Consequently, postharvest losses of fruits and vegetables are extremely high in Nigeria (30-50 %), exacerbated by poor marketing, distribution and storage facilities.

The typical marketing system for fruits and vegetables in Nigeria consists of three stages. In the first stage, smallholder farmers offer small surpluses to traders in the village markets or first assembly points. From here the traders move the accumulated produce along the market channel to secondary collection centers. The third stage involves the movement of the produce to central wholesale markets in urban centers. The produce is transported from the farm gate to the primary and secondary collection centers primarily as headloads or by means of farm animals, carts, bicycles, motorbikes and motor vehicles of all sorts and, from there, to urban central wholesale markets mainly in open, non-refrigerated trucks with capacities ranging from less than 10 t to up to 30 t (Fig. 1).

Smaller units are transported in ‘kombi’ buses and ‘pick-ups.’ The traditional marketing channels for foods in Nigeria evolved in response to the food production pattern characterised by a large number of peasant farmers with small, often less than 1 ha, non-contiguous holdings. Even though the existing marketing channels are grossly inefficient, in terms of the high postharvest losses, they deserve more credit than they are given, when viewed against the backdrop of the available market resources (both physical and financial), and the highly perishable nature of fruits and vegetables. Mechanical damage to produce as a result of impact bruising, compression and vibration during transportation, and poor transport conditions, including bad roads, account for a good part of the postharvest losses of fruits and vegetables in Nigeria. Substantial losses (up to 20%) occurred in fresh tomatoes, pepper and onions transported from the production areas in northern Nigeria (Kano, Kaduna and Sokoto States) to an urban wholesale market (‘Shasha’) in Ibadan in south-western Nigeria.

Traditional and Improvised Shipping Containers

In Nigeria, fruits and vegetables are commonly transported loose (in bulk) or packed in raffia baskets, jute bags, fiberboard cartons and other improvised containers made from metal, plastic and wood which, invariably, have been previously used for the packaging of imported or locally manufactured goods. The traditional basket of the ‘inverted cone’ design offers little protection to perishable produce (Fig. 2).

Figure 2: Tomatoes packed in raffia baskets at an urban market

Since they invariably have no handles, the produce is compressed each time they are lifted as the pressure is transmitted inwards. Their rough surfaces puncture the produce accelerating decay and physiological breakdown. Baskets are difficult to stack and are not conducive to efficient handling or suitable for modern systems of transportation. Sacks or bags made from jute or similar fabrics have the advantage of being cheap and their mechanical strength is not adversely affected by moisture. However, jute bags offer little protection to produce from mechanical damage and are not suitable for packaging fragile, highly respiring produce where substantial self-heating may occur (Figure 3).

Figure 3: A large truck with produce packed in jute bags

Wooden containers have the advantages of strength, rigidity and better stacking qualities relative to other shipping containers. In industrialised countries, there has been a shift from wooden containers to the lighter fiberboard cartons and molded plastic crates that have smooth surfaces which reduce surface injuries to produce compared to wooden containers.

Improved Shipping Containers

Solid and corrugated fiberboard cartons made from wood pulp or treated paper are widely used for packing fresh fruits and vegetables in industrialised countries. They have some unique technical and economic advantages including light weight, smooth surface and low labor requirement for fabrication. In addition, they can be easily over-printed with attractive designs and are highly suitable for mechanised handling. However, their mechanical strength is affected by climatic conditions and they are less satisfactory for use in the humid tropics, unless treated, at additional cost, with wax or similar material that imparts protection from moisture.

Molded plastic containers made from polypropylene, high density polyethylene or similar plastics have the unique advantage of being practically impermeable to moisture. They are lightweight and strong, have smooth surfaces that can be easily cleaned and sanitised. They are returnable and, when properly designed (the stack/nest types), have good stack stability. These properties confer distinct technical advantages to plastic containers over fiberboard cartons, as shipping containers for fresh fruits and vegetables, especially in the humid tropics. The use of returnable, molded plastic containers coupled with careful harvesting practices (Figure 4) and investment in market infrastructure and roads will substantially reduce postharvest losses of perishable fruits and vegetables in Nigeria.

Figure 4: Hand harvesting citrus into a molded plastic container

Dr O. Charles Aworh is a Professor and former Head of the Department of Food Technology, University of Ibadan, Ibadan, Nigeria; E-mail: ocawo51@yahoo.co.uk or charles.aworh@mail.ui.edu.ng