Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
names such as yucca (Central America), mandioca (South America), cassava
(English-speaking countries of Africa), and manioc (Madagaskar and French-speaking
countries of Africa). Brazil, Thailand, Malaysia, Indonesia, and Nigeria are the
major producers of cassava starch. 30,31 For starch production, the rootstock and, in
particular, the big-size tuberous roots of this moderate, low-input semishrubbery
perennial are used. Agricultural efforts, however, led finally to production yields of
approximately 50 t ha −1 . The major constraint in utilization of roots is their storage.
After harvest, roots rapidly deteriorate as a result of enzymatic decay or microbial
infestation. To avoid decay and reduction in starch yield in cultivating areas, roots
are processed within 24 h of harvest. Another way of preservation is dehydration in
tropical counties by sun drying of roots chopped into small pieces or chips. Another
alternative of preserving the economic value of cassava is by pellet production, which
delivers uniform pieces of high density. Utilization of dehydrated root material for
starch production is limited by starch quality. Even with specifically employed
treatments, the starch extracted from chips or pellets does not reach the criteria of
starch made from fresh and unspoiled roots. 32
Cassava roots are rich in carbohydrates (30 to 35%), the main fraction of which
is starch. Typical for roots, 3 to 5% of the carbohydrate fraction consists of fibers.
About 80% of the fraction is made of starch. Calculated on this basis, the carbohydrates
consist of fibers and about 80% of starch. The overall starch content may
vary from 25 and 30% depending on variety. On the other hand, roots are poor in
proteins (1 to 2%) and low in lipids, vitamins, and minerals. A major constraint in
utilization is the content of cyanogenic glycosides, linamarin and lotaustralin, in
bitter-tasting varieties of Manihot utilissima. For human consumption, these toxic
compounds can be easily destroyed by simple measures such as drying, soaking,
boiling, and fermentation. 33
8.5.2 PROCESSES
A unique feature of starch production from cassava is that because of its simplicity,
starch can be produced on all potential levels, from small-size handicrafts at the
farm level to the industry. The scheme of the specific steps in starch manufacture
resembles that of starch production from potato tubers. The main difference is in a
peeling procedure performed immediately after washing, wherein the corky region
at root ends and the protective epidermis are removed.
As regards the technological level achieved (cottage and small and large industrial
scales) in cassava starch production, equipment and techniques differ mainly
in precision of rasping or disintegration of roots (manual scraping of roots in contrast
to perforated plates, perforated rotating drums, or saw tooth blades arranged longitudinally
around the circumference of drums and, finally, modern rasping devices)
as well as techniques used in dewatering. Further steps are connected with screening
or extraction of starch from ruptured cell wall material, purification, and drying to
a moisture content of less than 12% to prevent microbial growth, preparation of
dried starch, and packing. Production capacities for modern cassava starch plants
during the harvesting season are 200 to 300 tonnes per day. 33