An Overview of Food Preservation Methods in Practice in Africa

Countries in sub-Saharan Africa are most affected by chronic food insecurity, confirmed by statistics which show that 35% of the population in this region is malnourished. Out of the 174 countries listed in the Human Development Index by the UNDP, (1,2) the lowest 22 are African. Preservation of food has a beneficial role in food security; as such preserved foods have longer shelf lives. In the tropical regions high temperatures and humidity induces accelerated deterioration of fresh foods. This accelerated deterioration is responsible for post harvest loses that are estimated to be as high as 30% for some crops. Preservation of food could significantly reduce the post harvest loses, consequently reducing the food insecurity. The Tanzanian official website (3) on food security, describes ‘Food insecurity’ as follows: The aggregate national food availability in Tanzania is not of plenty, but that of a critical balance between production and needs’.

People are judged to be "food secure" when they have regular access to sufficient foods for a healthy and productive life. The process to attain food security must be sustainable with maintenance of infra- structure and the environment.

In the advanced nations food preservation methods like canning; freezing, freeze-drying, chemical additives, sterilization, irradiation, fumigation, genetic modifications and packaging systems have found wide use in commercial and consumer acceptability but not without controversies on matters of health and the environment. Despite the drawbacks, developed nations have attained a high level of food security. Preservation methods such as salting have declined in the developed world in preference to newer methods that are machinery based, technologically advanced and sometimes energy intensive.

In the tropics however, preserving food based on low energy consumption, simpler machinery and storage at ambient temperatures, appears to be alternatives that are more economical. Methods such as drying, salting, smoking or in combinations like smoking with drying or salting with smoking and drying and the use of herbs and spices including fermentation are in common practice in the poorer regions of the world notably sub-Saharan Africa.

Critical appraisal of the preservation methods in practice:

The suns heat in the tropics is a renewable and sustainable energy source that can be used in drying and to drive fermentation processes. Wood fuel can be regenerated and renewed as biomass, for use in drying and smoking, while salt, an abundant naturally occurring chemical, can be used for salting. It is therefore possible to assume that drying; smoking, salting and fermentation processes currently in practice in Africa are affordable and sustainable. The tiny proportion or absence of tropical foods in world markets does not reflect the energy potential available, suggesting that something is wrong and steps should be taken to address the problem.

Drying:

Sun drying is used by many farmers world wide to render stability to crops for storage. Traditional African drying methods include spreading the material on flat stones, linen, canvas, wire-mesh, or leaves and even on the soil. Products dried in this traditional method are subject to spoilage from unsuspected or abrupt rains, windborne dirt, vermin, vermin excrement, insects, insect parts, and worms including dirt from the activities of the workers. Toxins can also develop in such uncontrolled drying set-ups leading to degradation of quality beyond edibility. This way of preserving food by drying on open systems is unhygienic with detrimental bearing on consumer acceptance and competition in commerce.

To improve the current practices, small modifications are needed that utilizes the sun heat energy effectively and more efficiently by applying the current scientific knowledge. Solar drying in an enclosed system, offers an indirect or direct drying of food crops with added advantages of hygiene, quality control and predictability. The use of simple enclosures that allow heat generation such as the flat plate collectors or other designs of solar heat collectors (4, 5, 6 & 7) provide many advantages in the quality of dried products. In an increasing hungry world, solar drying offers a cheap and hygienic way of preserving food. (8). Drying food products is an energy intensive process, that may be expensive when fossil fuels are used but relatively cheap when the free suns heat is exploited. The cost element in the sources of energy used could also influence product cost and may have an advantage on product competitiveness.

An enclosed system design, may help to reduce or eliminate contaminants. There is also the advantage of the possibilities of using direct or diffuse sunlight by covering the enclosure, influencing the appearance and quality of dried products. Maintaining the appearance of dried green leafy vegetables and spices like mint can be achieved by controlling the degree of light during sun drying. Controlling the quality of dried leafy vegetables or herbs could improve consumer acceptance paving the way to commercial exploitation. A closed system also offers enhanced speed of drying and higher temperatures that will produce quality-dried products, free from toxins developing on storage. Using the application of science, with strategic planning and administration, through teaching, guidance and proper management, the current methods of drying foods in Africa could be improved. The improvements could increase the state of food security.

Salting and Smoking:

The preservation of food by salting or smoking face the same challenges similar to those discussed in drying such as of poor hygiene, non-uniformity of process and quality control. Some preservation processes of curing fish like cod and hake by burying in a pit in the ground is neither desirable nor necessary from scientific or hygiene standpoint and may hinder acceptability. Meat and fish for family consumption can be dried over a wood fireplace with smoking taking place at the same time. Many foods can be preserved by smoke.Beef, pork, fish, hearts, tongue, liver, cheese, nuts, chicken, hard boiled eggs, berries, even oranges are some examples of foods that improved in storage after being smoked.

To improve the current practices, all practitioners could be given guidance in the art and science of salting, smoking and drying. Improvements in process control with a higher level of hygiene and an adequate product packaging are a necessary pathway towards a desired goal of food security and commerce.

Fermentation:

This process occurs naturally, requiring minimal energy input. In Africa this process is exploited crudely to make countless variety of alcoholic beverages. Many such beverages have neither found wide consumer acceptance nor marketability due to lack of quality control, hygiene, product aesthetics and poor packaging. The process of fermentation has been used for food fortification and detoxification (9,10). Cassava root a major food product in sub-Saharan Africa, contains in the poisonous sap chemicals termed, cyanogenic glucosides that are removed (detoxified) using the process of fermentation. The various methods described (11) for detoxification of cassava need improvements in order to achieve quality and reproducibility.

Progress in this field can be made by studying to find our why in Africa, a natural process like fermentation with such potential is not fully exploited.

Conclusion:

Traditional food preservation in Africa is practised in many communities mainly at household level, but lacks process uniformity, product quality control and packaging. These factors are an obstacle to consumer acceptability and the lack of marketability. Despite the drawbacks observed in food preservation, there is some success in quality products like banana chips, cassava flour, and crisps, dried beef, and beverages from tropical fruits that have shown potential for wider commercial distribution.

References:

1- UNCED accessed via www.undp.org The United Nations Conference on Environment and Development), held in Rio de Janeiro in 1992

2-UNDP accessed via www.undp.org United Nations Development Program

3-Food Security website accessed via www.tanzania.go.gov The official Tanzania Government Website

4-Merrigan JA Sunlight to electricity 2nd Edition (Photovoltaic Technology and business prospects. MIT Press Cambridge, Massachusetts, London 1982

5-Mcveigh JC Sun Power 2nd Edition An introduction to the applications of Solar energy Pergamon Press Elmsford New York USA 1983

6-MeinelAB and Meinel MP Applied Solar energy-An introduction. Addison Wesley Publishing co 1976

7-Norton TW Solar energy experiments for high School and college studies. Rodale press 1977

8-Richard Williams J Solar energy- Technology and applications Ann Arbor Science, Michigan 1974

9-Kimaryo VM, Massawe GA, Olasupo NA, Holzapfel WH The use of a starter culture in the fermentation of cassava for the production of "kivunde", a traditional Tanzanian food product Int J Food Microbiol 2000 Jun 56:179-90

10- Ekundayo, JA (Contributor) An Appraisal of Advances in Biotechnology in Central Africa (pages 243-271) in the book Fungal Biotechnology Edited by Smith, JE Berry, DR. Kristiansen, B. Academic Press (1980)

11-Mroso PV Food preservation at home, a strategy in food security Benedictine Publications Ndanda 2002 Tanzania.