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Report 3 of 5:
Buttering
Up - Zimbabwe
Introduction
Peanuts originated in South America, probably in Brazil, and have been cultivated since ancient times by Native Americans. Peanuts, or groundnuts as they are alternatively referred to, have also been used in African stews for over five hundred years and the Chinese have crushed peanuts into creamy sauces for centuries.
Peanuts are nutritious and high in energy. The seeds contain between 40 to 50 percent oil and between 20 to 30 percent protein. They are an excellent source of B vitamins. Peanut oil is popular as a high quality salad and cooking oil and it is commonly used in margarine. Many types of peanuts exist. Large seeded varieties are used for roasting and confectionery, and small seeded types are used for peanut butter and oil. Once the peanuts have been harvested, the plants can be used as feed for livestock such as cattle.
Cultivating groundnuts
Groundnuts require sunshine and need a warm growing season of between 120 and 140 days, with moderate rainfall during this time. They grow best on well-drained sandy soils because dark soils tend to stain the shells.
Groundnut plants grow to about 75 centimetres in height (30 inches) and can spread up to 1.2 metres (4 feet). There are two main varieties of groundnut plants. Some types of plants develop a bunchy erect growth and this is the bush variety. Others, called runners, spread over the ground. Hybrids of the two varieties have been developed and are commercially available. The pods of the bush variety contain one or two kernels in a thin shell. The runner variety has one to three kernels in a thicker shelled pod.
Peanut butter in Zimbabwe
Peanuts are an important part of the Zimbabwean diet. They have been grown in Zimbabwe for generations and the high protein "butter" produced from them is nutritionally significant for both children and adults.
Peanut butter is considered a staple food in Zimbabwe, adding nourishment and flavour to a variety of foods. It is used as a basic, everyday ingredient in most dishes, as well as being used as the main cooking oil. For example, peanut butter is used instead of cooking oil in the preparation of green vegetables, such as rape leaves and cabbage. The pan is spread with the thin peanut butter and heated, the vegetables are added and stirred in. The groundnut oil prevents burning which is particularly important as some of the leaves can be coarse and need plenty of cooking.
Peanut butter is also added to children’s bota at breakfast. Bota is a porridge of white or yellow maize meal, sorghum or other small grains. Meat in Zimbabwe is cooked and served with sadza which is made more palatable by serving with a peanut butter sauce. Sadza is a maize meal porridge.
Generating income through peanut butter production
Peanut butter is traditionally processed by groups of women from crops that they have grown themselves, with the roasted nuts being ground to an exceptionally fine, smooth consistency and used at the rural household level, with any surplus being sold off in an effort to raise money. Peanut butter production is one way for women to generate income for themselves and their families through sales. It is also important in raising nutritional levels in rural households because peanut butter is a high energy foodstuff which features largely in a family’s diet.
Peanut butter processing
The groundnut plants are harvested annually by being pulled or dug up. The pods are removed by picking.
Shelling
The peanuts are first shelled and cleaned. The shelling process can be greatly speeded up by a simple machine which presses the groundnuts against a wire screen to break the shells and separate the nuts.
Roasting
The peanuts are then roasted at 425°F (218°C) for between 40 and 60 minutes either on trays in an oven, with the nuts being turned by hand from time to time or, in equipment similar to that used for roasting coffee. The small rotary roaster allows each nut to become uniformly roasted. In Zimbabwe, the roaster is based on half of a 200 litre metal drum which is rotated by hand over hot coals to roast the nuts evenly. Baffles in the drum keep the nuts turning and prevent them burning on one side.
Decoating
After roasting, the nuts will be well browned and their skins will be loose. Once the nuts have cooled, it is necessary for the women to remove the dry skins from the kernels by rubbing them between their hands or gently brushing the dry skin away. An inspection will allow the manual removal of discoloured and other rejected material.
Grinding
Traditionally, the nuts are ground into a paste by hand. The women pound the nuts in a large mortar and then the rough paste is ground between heavy stones until the consistency is fine. This is a very time consuming activity. Nowadays, the nuts are often ground in a mill that may be powered by hand or with a motor. The type of mill used will depend on the scale of production.
Salt may be added at this stage at about 2% by weight. A special anti-oxidant chemical may be added to prevent rancidity, which will develop after a few months. However, to start with the product will probably be sold and used very soon after manufacture which means that it will not require such a long shelf life. The peanut butter is then packed into sterilised jars.
The type of peanut butter produced by this process is of the ‘crunchy’ variety, and adjustments on the mill can produce varying textures. For a smooth paste, the milling process may have to be repeated to obtain the desired texture.
Preserving peanut butter
To avoid separation of the oil and the settling out of the solids within the peanut butter after few days of storing, the preservative called glyceslmonsterode (GMS) can be added to the butter at 2-3% by weight. It is suggested that all of the GMS is added to a small amount of the peanut butter and then this should be mixed into the main batch of the produce.
Oil extraction
Oil contains high amounts of energy and fat-soluble vitamins (A, D, E, and K) and essential fatty acids. The oil content of peanut kernels is between 40 and 50%.
Peanuts are prepared for the oil extraction process by being shelled and cleaned. Oil production requires some type of press with which to extract the oil from the groundnuts and filtering equipment.
For further information, please contact:
This document is an output from a project funded by the UK Department for International Development (DFID) for the benefit of developing countries. The views expressed are not necessarily those of the DFID.
Further reading available from ITDG Development Bookshop
Peter Fellows
Traditional Foods: Processing for Profit
Here, processing ideas and techniques which are traditionally passed from one generation to the next by word of mouth are recorded by technologists from many countries in Africa, Asia and Latin America who have experience of producing the foods on a small-scale. The processes are presented along with technical information and advice designed to help existing businesses upgrade their production processes or diversify their product range in order to reach new markets, as well as providing ideas and information for new businesses.
Traditional Foods will be of interest to small-scale processors, development workers involved in supporting small enterprise programmes, aid agencies, and students of food science and of other disciplines. It includes a section on Nut pastes and specifically peanut butter.
£25.00 ITP& CTA PB 1997 ISBN 1853392286
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