Standardisation of the grating surface of cassava graters for gari
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Date
2015-07-13
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Abstract
Cassava is the third largest source of food carbohydrates in Africa after rice and maize. It is
drought tolerant and gives reasonable yields where other crops do not grow well, thus, acting
as a famine reserve. Nonetheless, cassava undergoes post harvest physiological deterioration
(PPD) after three days of harvest. Therefore, there is the need to process it within three days
after harvesting. Grating of cassava is one of the popular means of processing. Cassava is
grated and processed into gari; a popular meal in West Africa, especially in Ghana and
Nigeria. Modifications have been made on graters to improve and increase its efficiency.
However, it is observed that, there is no standard in the making of the grating surface (teeth)
of these graters. Manufacturers of these graters sometimes produce the teeth in a dense
random form. Materials for making these food processing surfaces are usually mild steel
which rust with time although stainless steel is sometimes seen. The grating of cassava for
gari does not always give the desired size of mash. Replacement of teeth is somewhat
cumbersome as there is no laid down procedure for making the grating surface; thus, the need
to standardize the grating surface of the cassava grater. In this project, a survey was done to
know the existing patterns of cassava grating surfaces in three regions of Ghana; Western,
Central and the Ashanti regions. From the knowledge gathered from surveys and review of
literature, three grating surfaces were designed and fabricated. They were tested on an
already existing grater design. Results after the mash was made all the way into gari by a
particular processor (to ensure some level of consistency) were compared to three already
existing teeth, two of which were saw toothed and the other punched using a mechanical
shaker. In the process of standardizing the grating surface of the cassava grater, important
factors such as tooth size, inter tooth spacing, tooth angle and material type were considered.
The recommended tooth diameter was ±0.04mm from 3.01mm while the inter tooth spacing
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was ±0.08mm from 8.05mm. The brick form of arrangement of teeth is also preferred to
ensure effective contact between the cassava and the grating surface.
Description
A thesis submitted to the Department of Agricultural
Engineering
Kwame Nkrumah University of Science and Technology
in
partial fulfillment of the requirements for
the award of
Master of Science (Food and Post Harvest Engineering)
College of Engineering, 2015