Analysis of the various types of mills/Traditional methods of grinding grain
The milling is one of the oldest cultural techniques of humanity. All civilizations that feed more or less exclusively from cereals were forced to develop technologies for grinding the grains of grain crops. In all traditional civilizations, grinding is the domain of women.
There are two different techniques:
- The grinding done by beating the grain (mortar and pestle)
- The grinding done by rubbing the grains between two stones (wheel mill)
The method of mortar and pestle is the most widely used in the West-African countryside. Before grinding, women usually soak the seeds, and then let them either sit overnight or for several hours in the sun, which allows the homogenization of the moisture inside the grains.
During the milling, the pounding mortar is interrupted by several sievings that allow to obtain a range of different products, from meal the the most fine flours. The advantage of this method is its versatility: The woman totally controls the operation, so that she can adapt according to the requirements and the available available.
The flour thus obtained contains between 22 and 26% water. Its rapid fermentation, appreciated in the culinary preparations, will not permit storage beyond one or two days. When the women change from this grinding by mortar and pestle to the dry grinding with the mill, they must learn to dry the grain after the shelling, and use less fermented flour, or ferment the flour by moistening it after milling it.
The pounding work is demanding and tiring. In Senegal, we calculated an average daily efficiency of 4 kg/h per woman (see Table 2), which is an order of magnitude. Knowing that a woman grinds approximately 4 to 6 kg of grain per day, this hard work will take her more than one hour of pounding per day. This quick calculation helps explains the success of the motorised mill. Even if women do not necessarily win a lot of time (given the transportation time, waiting, ...), they at least have a significant reduction in workdifficulty. They have to provide more intense physical effort to grind their daily grain.
| Maize | Millet | Sorghum | |
| Moisture contence | 24.5 | 25.8 | 23.2 |
| Weight (for a mositure contence of 10%) | 1805 g | 1820 g | 1785 g |
| Spend time grinding | 18.32 min | 14.43 min | 22.17 min |
| Spend time sieving | 12.67 min | 10.03 min | 14.90 min |
| Effiency | 3.5 kg/h | 4.5 kg/h | 2.9 kg/h |
| Fineness index[1] | 1.4 | 1.4 | 1.35 |
Table 2: Expenditure of time milling of sorghum, millet and maize, with mortar and pestle (Bamako, Mali) after Evaluation et choix de moulins, by Peter Löwe et Jean-Max Baumer, Rapport de mission pour APICA, mars 1986, 50 p.</ref> and Vanek, KV Small Scale Grain and Grinding Dehulling in Mali, FAO 1981.
The method of the wheel mill (original of Neolithic period) uses a flat stone slab and also a grinding stone. The wheel, operated by hand, is used to grind grains that are deposited on the slab. Two to three passes of the wheel is enough to get a coarse meal that falls gradually from the slab. It is a method that is still used in the rural areas of East Africa. The average yield of this method is 1.5 to 2 kg/h (after Evaluation et choix de moulins, by Peter Löwe et Jean-Max Baumer, Rapport de mission pour APICA, mars 1986, 50 p.).
References[edit | edit source]
- ↑ The standard for the manufacturing of American sieves has been used for determining the fineness index
