Application of cassava in fermented products
Cassava Alcohol
Cassava is one of the
richest fermentable substances for the production of alcohol.
The fresh roots contain about 30 percent starch and 5 percent
sugars, and the dried roots contain about 80 percent fermentable
substances which are equivalent to rice as a source of alcohol.
Ethyl alcohol is produced from many carbohydrate
materials. In Malaysia and some other countries, many factories
are equipped to use cassava roots, starch or molasses (by-product
of the sugar industry), the type of product depending on the
costs of the raw materials. When cassava is used, the roots
are washed, crushed into a thin pulp and then screened. Saccharification
is carried out by adding sulfuric acid to the pulp in pressure
cookers until total sugars reach 15-17 percent of the contents.
The pH value is adjusted by using sodium carbonate, and then
yeast fermentation is allowed for three to four days at a
suitable temperature for the production of alcohol, carbon
dioxide and small amounts of other substances from sugar.
Alcohol is then separated by heat distillation. The yield
of conversion is about 70-110 liters of absolute alcohol per
ton of cassava roots depending on the variety and method of
manufacture. The crude alcohol of cassava is described as
average in quality. It has a disagreeable odor, but can be
improved if the first and last fractions in the distillation
process are discarded. It is usually utilized for industrial
purposes, as in cosmetics, solvents and pharmaceutical products.
If the production is required for human consumption, special
care should be taken in handling the roots to rid them of
hydro cyanic acid.
Dried Yeast
Microbial protein is attracting growing interest owing
to the enormous protein requirements of the world. Among the
micro-organisms which are considered possible food sources,
yeast has perhaps stirred the greatest interest. Candida and
saccharomyces yeasts have had a well-established place for
many years as feed, and the technology of production, the
composition and the nutritive value of yeast are well known.
Most of the production of yeast is based
on such low-cost raw materials as waste liquids, wood hydrolyzates
and molasses. Starch-rich plant materials from wastes or surplus
production are also utilized as substrata for yeast production.
Cassava starch and cassava roots are being used in Malaysia
and some other countries for the production of yeasts for
animal feed' the human diet and for bakery yeast. The starch
is hydrolyzed into simple sugars (predominantly glucose) by
means of mineral acid or by enzymes. Certain yeasts are then
propagated which assimilate the simple sugars and produce
microbial cellular substances. The dry, inactive yeast contains
about 7 percent moisture and the raw protein content can vary
between 40 and 50 percent depending on the raw material.
The yield of yeast production also depends
on the raw material. In some applications of cassava starch
conversion into substances obtained from yeasts, a 38-42 percent
yield of yeast product containing 50 percent raw protein has
been obtained.
It is possible to distinguish three sectors
of the starch-using industries, in each of which cassava occupies
a fundamentally different position:
(a) Where irreplaceable by other starches.
In the manufacture of remoistening gums
cassava has no competitors for the time being. Attention should
be called, however, to the continuous efforts to adapt other
starches to the special demands of these industries, both
by chemical means as well as by the selection of starch-bearing
plants. Mention should be made of the so-called waxy-maize
starch, which approaches cassava in many respects.
(b) Where other starches are preferable
despite the cost factor.
Some of the more desirable characteristics
of other starches may be the result of further processing,
as, for instance, in the corn (maize) starch industry. Examples
are the thin boiling, chlorinated and other special starches.
Cassava furnishes only a crude starch with a wide range of
quality and characteristics.
(c) Where interchangeable with other starches.
In this case, price and marketing conditions
are the only controlling factors. Because of severe competition
from other kinds of starch, in this field cassava has lost
much ground of late.
It can safely be concluded that a market
for cassava of all grades will be found for many years to
come; however, the possibility of an expansion of its use
will depend to a great extent on improved techniques in processing
as well as on more efficient methods of marketing the flour.
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