Expert consultation on planning ... in Africa - 5.4. African workshop for improvement and development of drying fruits in Ghana

- E. Gyabaah - Yeboah

INTRODUCTION

The demand for vegetables, fruits, tubers and spices and the importance of these crops in the diet of the average Ghanaian cannot be over emphasised. Their demand especially out of season has led to the exploitation of methods of preservation. One feature of the distribution of these highly perishable food crops in Ghana throughout the year is that it is highly skewed. Soon after the harvest the local markets become flooded with the commodities over and above the demand for consumption. Excess supply available at the time of harvest could be preserved and stored against the lean season. The lopsided fashion of preservation and storage of such perishable food items make their prices fluctuate considerably in the periods between two successive harvests of these crops. It is estimated that Ghana looses 15% - 30% of her cereal crop and 30% 40% of the starchy crops and vegetables annually because of lack of storage and preservation facilities. Reduction of these losses through appropriate preservation methods could increase the domestic shortfall in food supply by 20% - 30%.

The excess supply at time of harvest' which are left to rot' can be preserved against the periods of lean supply. The various methods of preservation of these crops are drying or dehydration (air' sun' fire) bottling and canning. Sun-drying is however, the oldest traditional method of food preservation in Ghana. The advantage of such preservation methods lies in the fact that since the items are treated in a natural condition' they are not very different in appearance and flavour from the fresh items when served. An added advantage of sun-drying is that a lot of the produce can be dried at a time.

SITUATION OF SUN-DRYING IN GHANA

Sun dried vegetables, spices and tubers feature prominently in the Ghanaian diet during the lean season. Since sundrying especially of vegetable is the most popular preservation method' it is undertaken in all the regions of the country. Ideally all vegetables intended for sun drying must be fully mature at harvest time. In most cases all defective items are discarded and vegetables' fruits and spices at different stages of maturity are never mixed. The crops are then washed' trimmed and cut into pieces according to the type of fruit or vegetable. In spices' the stalks and calyx are removed. Spices are subjected to blanching' that is hot water or steam treatment to improve the storage qualities and preserve the natural qualities. Traditionally tubers are not blanched before drying.

The traditional method of sun-drying in Ghana has no definite methods nor special equipment. Products for Bun-drying are spread on rooflope' on concrete constructions, along roadsides and in courtyards. There is a disadvantage of the products being subjected to contaminations from dust' flies' and even human beings.

MARKETED SUNDRIED VEGETABLES, FRUITS, TUBERS, SPICES

The moat important marketed sundrier vegetables, fruits, tubers and apices are tabulated below:

i. Vegetables:

Okro, (Hibiscus esculentus), tomatoes (Lycopersicum esculentum) shallots (Allium ascalonicum and on a smallscale leafy vegetables).

ii. Fruits

Plantain, (Muse) bananas (muse) palm fruits (Elaeis guineensis) groundnuts (Arachis hypogen)

iii. Tubers

Cassava (Mahihot esculenta) yam (Dioscorea Alata)

iv. Spices

Various types of pepper (Capsicum annum spp.) - hot pepper, black pepper.

PROBLEMS OF SUN-DRYING IN GHANA

One of the major problems of sun-drying in Ghana has been contamination. This has already been mentioned as a disadvantage but it can be a serious problem because in most cases the dried products are ground into powdery form to economise storage space. In this way items cannot be washed before use.
Another problem is that, if the products are not spread evenly or trimmed as uniform as possible, drying may not be even. This means some will dry faster that others while others may have higher moisture content and be of poor storage quality. In this case the poet-harvest losses which is being prevented is aggravated since in worse cases 50% of the produce can go bad.
A third problem is browning of some of those fruits and vegetables when exposed to air. This is especially so with plantain, banana and to a lesser extent cassava Along the coast where salt is abundant such products are immersed in salt solution to reduce browning.

IMPROVEMENT OF SUN-DRYING IN GHANA AND RELATED RESEARCH

The subject of improvement of traditional sun-drying methods for food preservation has engaged the attention of scientific work era especially at the Food Research Institute of the Council for Scientific and Industrial Research and the Ghana Atomic Energy Commission. Some of the improvements proposed are discussed below:

That there should be an exclusive drying yard which could be constructed with local materials. The drying yard should be equipped with a cutting and trimming table with a hardwood top. The shed will be reserved exclusively for grading' cutting' trimming and spreading on drying trays.
Where bamboo and other boards are available, raised platforms (similar to those used for cocoa) could be construct d to minimise contamination. Another sun drying unit which may be ideal is the sun-drying cabinet which consists of a rack with trays; each tray measuring 3 feet by 3 feet. Two of the trays can be held together by two hinges to allow them to be stretched out to form a 6 feet by 3 feet drying surface.
Improvement in packaging and storage are a prerequisite for better handling. Packaging should follow immediately after cooling the dried products. Large quantities could be packed in either high density polythene bags or in polythene lined juge bags. It has been observed that plastic bags and jute bags are also susceptible to insect and animal attacks. The packed products should be kept in a cool dry place to avoid deterioration. Alternatively, the dried products could be ground and packaged in tightly closed tins especially when the product is to be stored for a long period. This is especially true of garden eggs and the various species of spices.
Simple methods of sun-drying of specific vegetables, fruits, tubers and spices, clearly indicating the blanching temperature, duration of blanching to get the right moisture contort with the drying ratios have been devices as an improvement on the traditional sun-drying methods.
A specific example of such methods of sun-drying is the case of garden eggs. Hitherto, sun-drying of this particular vegetable was not popular. In recent years as a result of this simple but important research' sun-drying of vegetables has been popularised.

Method of sun drying of garden-eggs: Garden eggs tend to have worms in them as a result of over-maturity. This fact is evidenced by small holes in the vegetables. All those vegetables with such worms should be discarded. The rest should then be graded as to colour and size, and trimmed by removing the stalks and calyx, The garden eggs are then cut into four equal sizes and immersed in 10 tablespoonsful vinegar to a gallon water for 25 minutes. The cut pieces are blanched in water containing sodium carbonate (baking soda) at 90 C for three minutes, drained and then dried to a moisture content of 8% - 10%. The drying ratio is 10:1. The dehydrated garden eggs should then be ground into powder and stored in tightly covered tins.

Another suggestion is the use of preservatives to improve the colour and storage quality of the final dry products especially leafy vegetables. However this has not caught on well with producers since such chemicals are difficult to obtain.

ON-GOING PROJECTS

i. Food Preservation by Solar Drying

The major on-going project at finding alternative to traditional sun-drying in Ghana is solar drying. The Project is being undertaken by the Food Research Institute of the Council for Scientific and Industrial Research of Ghana.

ii. Food Preservation by Irradiation

Research into perishable food preservation by radiation is still in its infancy in Ghana. Most of the work done to date is at the exploratory stage. The Ghana Atomic Energy Commission is responsible for this type of Research.

Preliminary work has, however, demonstrated the potential of ionizing radiation in prolonging the shelf-life of onions, yams, fruits and vegetables.

OTHER AREAS OF RESEARCH

In the short term, research is being conducted to reduce the length of the drying time for all the vegetables and fruits through the development of new drying trays and improved blanching methods.

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