Post-harvest operations refer to those activities undertaken to transport, process, trans- form, preserve or store harvested agricultural products in order to enhance their economic value by increasing their nutritional value and availability over time and space and there- fore, their price or market value. The relevant activities include such unit operations as threshing, cleaning, sizing, shelling, peeling, grating, cutting, slicing, chipping, grind- ing, milling, comminuting, cooking, drying, pasteurizing, fermentating, handling and transporting. Although some authorities treat threshing together with harvesting (of ce- reals especially), at the level of operation of small-holder farmers it is considered more appropriate to treat threshing as a post-harvest operation because the two activities are quite separate.
Tools and machines retain the definitions given in the introduction. Therefore, we are concerned here with tools used, and machines powered by human beings to perform the indicated post-harvest unit operations. Naturally, small-holder or peasant farmers form the majority of those who use the human-powered tools and machines, especially the tools for post-harvest operations. Some post-harvest unit operations for certain crops, such as peeling of cassava or extraction of melon (egusi) seeds from the pod, can be performed using only hand tools because viable machines for them, human-powered or otherwise, simply do not exist. In such cases, there is really no choice but to live with the inherent tedium and low efficiency.
But because of the nature of the majority of post-harvest operations involved, small-to- medium-scale commercial farmers, and even non-farmers, also use the human-powered tools and especially, machines, to some advantage. Nevertheless, the fact of the situation is that, given the natural limitations of human-powered machines (tedium, low power, low capacity, and low efficiency), most human-powered machines for post-harvest unit operations have motorized counterparts, powered by electric motors or internal combus- tion engines. Of course, motorized machines are preferred by small-scale commercial farmers, or by non-farmers who use them mostly to serve peasant farmers, who naturally prefer the custom services to the tedium of manual operation.
Nevertheless, there are literally hundreds of food products processed by peasant farm- ers using hand tools and human-powered machines not found in the literature. Many of them are specific to certain localities outside of which they may not be known even in the same country. As already stated, manual processing of these products is time- consuming and tedious; the conditions prevalent at this level of operation generally are unsanitary and inherently unhygienic, with little attention paid to quality control, making the wholesomeness and quality of the products, perforce, variable and uncertain.
Some Common Tools for Crop Processing by Peasant Farmers Knives
Many post-harvest unit operations for processing of agricultural products by peas- ant farmers are performed with the group of tools classified as knives. For example, cutting, peeling, slicing, chipping and many size-reduction operations are carried out
Figure 1.6. World of Knives and Cutters for Traditional Crop Processing.
using knives, which come in numerous sizes and shapes, as shown in Fig. 1.6. Knives are as indispensable and ubiquitous in post-harvest crop processing operations by peas- ant farmers as hoes and machetes are in their field operations for primary agricultural production.
Mortar and Pestle Systems
Next to knives, mortars and pestles are the next most commonly used tools in peasant crop processing operations. They are used for threshing, grinding, milling, size reduction and all unit operations that can be performed by pounding or rubbing. A mortar is a strong vessel, usually of wood in this context, in which materials are pounded or rubbed with a pestle. The popularity of the mortar-and-pestle system derives from the fact that the peasant farmers are able to produce the tools for themselves. Mortars are produced from trunks and pestles from appropriately sized branches of hard or high-density wood of trees such as the iroko, oil-bean trees, etc. Naturally, mortars and pestles vary a great deal in size, shape and weight, depending on the intended applications, as illustrated in Fig. 1.7. A mortar may be large enough to admit six to eight persons, standing, with long pestles to pound its contents together/simultaneously, to macerate parboiled palm fruits in peasant palm-oil processing operations, or, in the preparation of yam foo-foo or fufu
Figure 1.7. Mortar and Pestle Systems.
(Sierra Leone), for communal work-team feeding. Or the mortar/pestle system may be just large enough to grind a few grains of pepper for a small pot of soup for a bachelor.
Miscellaneous Processing Tools
There are, of course, many processing unit operations by peasant farmers that cannot be carried out with knives or mortar/pestle systems but require unique tools such as:
shellers for maize, groundnuts or such prodded crops; graters for cassava and other roots and tubers; sifters for meals and flours; and winnowers for grain. Some of these tools are illustrated in Fig. 1.8 without further comments, since they generally are very simple in form and construction.
Some Common Human-Powered Processing Machines Manual Machines That Can Replace the Knife
For a limited number of unit operations for which the peasant farmer uses a knife, there exist some human-powered machines or equipment. Such machines that can replace the knife in traditional or peasant processing operations include roller root cutters, cassava graters, vegetable cutters/slicers, etc. Some of the machines are illustrated in Fig. 1.9. On the whole, such machines do not make a significant impact on the post-harvest processing operations of peasant farmers.
Manual Machines That Replace the Mortar/Pestle System
It is perhaps correct to state that for most mortar/pestle systems in peasant or traditional operations, there are viable human-powered machines as alternatives. The machines are
Figure 1.8. Some Miscellaneous Manual Processing Tools and Machines. A - Different types of hand tools for shelling corn; B - Gari frying machine with manual operation arrangement; C - Manual
Bitter-leaf processing machine.
Figure 1.9. Some Manual Processing Machines That Can Replace the Knife.
A - Roller root cutter; B - Disk vegetable cutter/slicer; C - Pedal-assisted manual cassava grate.
either hand- or foot-operated, and commonly include grinders, mills, hullers, decorti- cators, shellers, crushers, presses and winnowers/separators, as illustrated in Fig. 1.10.
Their impact on peasant farmers’ operations is quite significant, especially in terms of the custom services that small-scale non-farmer operators of these machines provide, as mentioned earlier.