Ugba, the Fermented African Oilbean Seeds; its Production, Chemical Composition, Preservation, Safety and Health Benefits
Ugba is the Ibo name of the fermented African Oilbean seeds (Pentaclethra macrophylla, Benth). It is a traditional food condiment generally produced by natural (local) fermentation in homes as a small family business. It is an important and cheap source of protein for people whose staple foods are deficient in proteins. It is also eaten as a delicacy and used as flavouring for soup. This write up aims to review all published studies on ugba in the direction of the various methods used in the production, the chemical composition of the seeds, the microorganisms involved and the biochemical changes that occur during fermentation and optimization of the fermentation. The nutritional and food values, toxicological properties, health promoting potentials, microbiological safety as well as the storage and preservation have also been highlighted.
February 13, 2010; Accepted: May 04, 2010;
Published: June 23, 2010
Ugba is the Igbo name for the fermented African OIlbean seeds (Pentaclethra
macrophylla, Benth). It is called Ukana by the Efiks in Southern Nigeria.
It is consumed by an estimated 15 million people in Eastern Nigeria, majority
of whom are Igbos (Odunfa and Oyeyiola, 1985). It is
a traditional food generally prepared in homes as a small family business. The
method of production varies from one producer to another resulting in a non-uniform
product (Njoku and Okemadu, 1989). The beans that have
been fermented for more than three days are taken as a delicacy. Well fermented
beans are added to soup as flavouring (Odunfa and Oyeyiola,
1985). It is widely consumed in eastern states of Nigeria with tapioca,
stock fish and garden eggs and leaves. It can also be eaten with bitter kola
(Garcinia kola) or kola nuts (Cola acuminate and C. nitida)
and when prepared with gardenegg leaves is used to eat yam and cocoyam (Okafor
et al., 1991; Mbajunwa et al., 1998).
It is an important and cheap source of protein for people whose staple foods
are deficient in proteins (Obeta, 1983). The quantity
of ugba produced annually is not known, since the seeds are collected by individuals
and sold in the market to ugba producers.
Nature of the plant and the seeds: Oilbean seeds for ugba production
are obtained from a perennial legume tree, Pentaclethra macrophylla,
Bentham, commonly called the oilbean tree. The trees are often planted
along the sides of roads as shade trees and around communities as cash crops.
The fruit is a black, hard and woody pod measuring about 35-36 cm long and 5-10
cm broad. When mature it splits open explosively to release about eight flat,
glossy brown seeds measuring about 5-7 cm in diameter and weighing between 15-20
g (Keay et al., 1964; Odunfa,
Chemical composition of seeds: The oilbean seeds contain 4-17% carbohydrate,
44-47% oil which has been found to be rich in oleic acid (Nwokedi,
1975; Odoemelam, 2005) and linoleic acid (Onwuliri
et al., 2004). Onwuliri et al. (2004)
also found out that the saturated fatty acid, lignoceric acid, occurred in high
amounts constituting about 10% of the total fatty acid concentration. Some workers
said that the oil content could be as low as 38% (Kar and
Okechukwu, 1978). They also reported that the oil contains about 75% saturated
fatty acids and 25% unsaturated fatty acids. Table 1 (Achinewhu,
1983) shows the fatty acid content of the seeds. Both saturated and unsaturated
fatty acids are found in the seeds. For the saturated fatty acids, lignoceric
acid appears to be present in the largest amount constituting about 12% while
palmitic acid is the least with 3.4%. Behemic acid is also present with 5.2%.
The major unsaturated fatty acid in the seeds is linoleic acid constituting
42.8%. Oleic acid is also present in appreciable amounts (29.0%). Linolenic
and gadoleic acids are present in very small amounts (3.2 and 0.28%, respectively).
|| Fatty acid composition of African oilbean seeds*a
|*As percentage of total oil. aAchinewhu
The presence of appreciable amounts of behenic and lignoceric acids is not
desirable for edible oils (Odunfa, 1986a).
However, Odoemelam (2005) believes that the high degree
of unsaturation makes it suitable for cooking purposes and for use as a drying
oil for cosmetics, paints and varnishes.
Also they have been found to contain 36.2-43.89% crude protein which contains
the 20 essential amino acids. However, the sulphur containing amino acid content
is much lower than those found in other plant proteins (Mbadiwe,
1978; Mba et al., 1974; Odoemelam,
2005). The high content of other essential amino acids makes the seeds a
potential source of protein (Achinewhu, 1982). Table
2 shows the amino acid profile of the seeds. Glutamic acid appears to be
the largest amino acid contained in the seeds. This may be responsible for its
use as a flavouring for soups in south eastern Nigeria. Aspartic acid, lysine
and phenylalanine are also present in appreciable amounts in the seeds.
Preparation of ugba: Methods for ugba preparation vary from one community
to the other. In this method described by Obeta (1983),
the seeds are boiled in water for 16-18 h to remove the tough testa. The cotyledons
are then sliced, boiled again for 30 min and left overnight in water at room
temperature. The sliced cotyledons are then washed in water and packaged in
leaves of banana.
Another method described by Odunfa and Oyeyiola (1985)
and Odunfa (1986a) shows that the seeds are boiled in
water over an open fire for 4-5 h or even up to 12 h. The cotyledons are then
removed from the seed coats and washed. The cotyledons are again boiled overnight
over a low flame, allowed to cool, drained and washed several times to remove
bitter components in the cotyledons and soaked for a period of 6 h. The cotyledons
are then cut into long thin slices which are mixed with salt, put in a clean
pot, covered and fermented for up to 5 days at room temperature. Usually after
2-3 days of fermentation the sliced cotyledons are wrapped in banana leaves
and tied tightly.
Njoku and Okemadu (1989) also described another production
method. The seeds are boiled for 5-8 h, after which the hard shells are removed.
The cotyledons are cooled, washed and sliced into 4-5x0.1-0.2 cm slices. These
are washed again and boiled for another 1-2 h, cooled and soaked in water for
about 10-12 h. They are washed and allowed to drain for ½-1 h. in a basket
lined with banana leaves (Musa sapientum linn). They are then wrapped
about 40-50 g of slices using another leaf (Mallotus oppositifolius)
and incubated for 72 h at room temperature.
Another method has been described by Sokari and Wachukwu
(1997). These workers said toasting the bean seeds in hot (100°C) sand
and holding for a further 30 min at 100°C significantly improved dehulling.
They also said that slicing to 1 mm, boiling for 30 min and soaking for 2 h
removed the bitter taste associated with the seeds. They claimed that the technique
reduced the general production time by 2 days and the quality of ugba produced
from this process was the same as that produced from the rather more cumbersome
and time-consuming traditional technique.
The differences in the various processing methods are responsible for the variations in the products from one community to the other. The wrapped ugba at different stages of fermentation are sold to consumers and they are often told the length of fermentation at the time of purchase.
Microorganisms involved in the fermentation: Several workers have investigated the microorganisms involved in the fermentation (Table 3).
Only bacteria are involved in the fermentation (Obeta,
1983; Odunfa and Oyeyiola, 1985; Ejiofor
et al., 1987; Ogueke and Aririatu, 2004).
The main fermenting microorganisms have been identified to be proteolytic Bacillus
sp. (Obeta, 1983) which include B. subtilis (most
predominant), B. licheniformis, B. megaterium, B. macerans
and B. circulans.
||Succession of the major microorganisms encountered in fermentation
of sliced oilbean seeds (per gram)e
Their numbers increased tremendously from 103 at the start of fermentation
to 108 at the end of the fermentation (72 h). Other bacteria identified
in the fermenting slices include coagulase negative Staphylococcus sp.,
Micococcus sp. (their numbers decreased after 72 h of fermentation),
Leuconostoc mesenteroides; Lactobacillus plantarum, Streptococcus
lactis, Proteus sp., Enterobacter sp. and E. coli.
Some workers isolated the yeasts Candida tropicalis and Geotrichum
candidum during fermentation (Ejiofor et al.,
Since protein hydrolysis is the major biochemical change in ugba fermentation
(Oyeyiola, 1981), it can be assumed that the Bacillus
sp. are the main fermenting organisms. They were found to persist until the
end of the fermentation and their numbers increased throughout the period of
fermentation while the numbers of others decreased after 24 h of fermentation
(Obeta, 1983). Also Bacillus sp. are important
sources of proteases (Fogarty and Griffin, 1973). The
other bacteria only managed to grow on the little carbohydrate present in the
seeds, majority of which may have been lost due to leaching during the preparatory
stages (Ruiz-Teran and Owens, 1999). The disappearance
of these bacteria could also be due to the activities of B. subtilis,
the predominant bacterium in the fermentation, which is known to produce the
antibiotic bacitracin. The antibiotic may have inhibited the growth of these
bacteria and the disappearance of Micrococcus sp. especially at 96 h
of fermentation is believed to be due to this (Ogueke and
Aririatu, 2004). Micrococcus sp. are very sensitive to bacitracin
(British Pharmacopoeia Commission, 1993).
Since the bean seeds were boiled for hours before fermentation the microorganisms
involved in the fermentation could not have originated from the beans. The bacteria
involved in the fermentation probably were introduced through the air, water,
utensils, leaves used in wrapping or by handling during the preparatory stages
(Obeta, 1983; Odunfa and Oyeyiola,
1985). Example Staphylococcus sp. are more commonly associated with
the skin and hence are easily disseminated through handling. Also addition of
salt would selectively favour the growth of Staphylococcus and Micrococcus
sp. which are known to be salt tolerant (Adam and Moss, 1999).
Changes that occur during fermentation: Various biochemical changes
occur during the fermentation. Obeta (1983) found that
pH increased from 6.5 at 0 h to 9.0 at 48 h and declined to 7.1 at 72 h. The
rise in pH has been attributed to the abundant production of ammonia during
the fermentation due to protein hydrolysis and deaminase activity. The increase
in pH would encourage the growth of Bacillus sp. which have been found
to grow well at pH 7.0 to 8.0 (Odunfa and Oyeyiola, 1985).
The drop in pH to 7.1 at 72 h could be attributed to the fact that B. subtilis
and B. licheniformis use ammonia as nitrogen source (Odunfa,
1986b). However, Odunfa and Oyeyiola (1985),
Njoku and Okemadu (1989) and Ogueke and Aririatu (2004)
found that pH rose throughout the fermentation from 5.0-5.7 at 0 h to 7.9-8.7
after 3-5 days of fermentation.
The temperature of fermentation was observed to increase from about 30.8 to
34.5-38.5°C within the first 24-36 h of fermentation and decreased gradually
afterwards to 30-32.5°C at the end of fermentation (Odunfa
and Oyeyiola, 1985; Njoku and Okemadu, 1989). Thus
ugba fermentation is exothermic. This initial increase in temperature has been
attributed to the intense metabolic activities of the microorganisms (period
of maximum microbial activity) and represents the most active and important
period of the fermentation. This is because enzyme studies (Njoku
and Okemadu, 1989) have revealed that the α-amylase, proteolytic and
lipolytic enzyme activities attained their maximum levels at 24-36 h of fermentation.
Thus it could be the enzymes already produced rather than the presence of the
microorganisms that continued the fermentation later.
Moisture content was also found to increase throughout the period of fermentation
(52-56.90% to 71.20-73%) (Odunfa and Oyeyiola, 1985;
Njoku and Okemadu, 1989; Ogueke
and Aririatu, 2004). The increase in moisture is believed to be due to the
hydrolytic activities of the microorganisms. However, the high moisture level
has been suggested to predispose the product to rapid spoilage (Odunfa
and Oyeyiola, 1985; Ogueke and Aririatu, 2004).
Njoku and Okemadu (1989) detected α-amylase, proteolytic
and lipolytic enzymes from the start of ugba fermentation. These enzymes attained
their maximum levels at 24-36 h. They suggested that this could be assumed to
be the period of maximum microbial activity. The initial enzyme activity detected
could be due to the activity of the natural microflora of the oilbean which
developed particularly during the soaking of the cooked beans. Njoku
and Okemadu (1989) therefore suggested that it could well be that fermentation
began much earlier during the soaking of the sliced beans. Some workers (Enujiugha
et al., 2002, 2004) have demonstrated that
the raw seeds contain both α-amylase and lipase. They observed that the
specific activity of the purified α-amylase from the raw and fermented
seeds were 0.037 mL-1 min-1 and 0.88 mL-1 min-1,
respectively. They also claimed that these enzymes complement the bacterial
enzymes during fermentation. However, since the seeds were boiled for several
hours before fermentation they could not have contributed to the fermentation
as the boiling must have inactivated them. The proteinase enzyme is considered
the most important enzyme in ugba fermentation. Njoku and
Okemadu (1989) detected a sevenfold increase in the level of amino nitrogen
while Enujiugha (2003) also observed a steady increase
in the level of amino nitrogen from 1.23 to 13.68 mg Ng-1 DM after
72 h of fermentation. Only a two fold increase in reducing sugar was found,
while the activity of lipase was minimal compared to the other two enzymes (Njoku
and Okemadu, 1989). This agrees with the report of Achinewhu
(1986) that fermentation has no appreciable effect on the fatty acid content
of P. macrophylla. The minimal activity of the lipase could be attributed
to the effect of NaCl that is usually added during fermentation. Enujiugha
et al. (2004) in their study of the lipase activity in dormant seeds
of African oilbean seeds observed that the activity of lipase isolated from
the seeds were inhibited up to 36% by NaCl. However, they found that presence
of Ca2+ increased the activity of the enzyme by 64%.
Optimization of ugba fermentation: Several workers have conducted studies
on ways of optimizing the production of Ugba. Most of the studies have been
on the modification of some parameters that affect the fermentation such as
temperature and Relative Humidity (RH), the use of starter cultures and immobilized
cells in the fermentation process. Isu and Njoku (1998)
the influence of temperature, relative humidity and microenvironment on the
natural fermentation of Ugba. Their results suggested that fermentation may
have been faster at 80% relative humidity. They suggested that the traditional
method of wrapping with leaves of Mallotus oppositifolium presumably
produced warmth and a humid environment while limiting the accessibility of
air to the fermenting substrate. Thus the 80% RH created a more humid environment
than the atmospheric RH of 74.5% which was more favourable for the fermentation
process. They also found that a temperature of 35°C was most suitable for
the fermentation generating a peak amino-nitrogen content of 19.6 mg N/100 g
dry matter within 48 h. Thus reducing fermentation time by 24 h. as against
the 72-96 h. in the traditional fermentation process.
The use of immobilized cells of Bacillus sp. in the fermentation process
has also been carried out by some workers. Isu and Ofuya
(2000) studied the use of pure cultures of Bacillus subtilis attached
to cowpea and maize granules in the fermentation process. These workers monitored
changes in pH, amino-nitrogen and protease activity which they said were the
fermentation indicators. They found out that in comparison with the natural
fermentation changes in these indicators were more pronounced in the fermentation
carried out with the immobilized cells (Table 4). For example
the protease activity increased from 4.5 to 27.65 mg N/min for the immobilized
cells as against 10.5 mg N/min produced by the natural fermentation.
The use of the immobilized cells resulted in the reduction of the fermentation time to 48 h. as compared to 96 h. for the natural fermentation process. The authors attributed the increased activity observed with the immobilized cells to the increase in cell density per unit reactor and enhanced cell wall permeability and metabolism. Their sensory evaluation studies also showed that the products from immobilized cell fermentation were well accepted. The cultures were also stable and viable for 6 months on the granules of cowpea.
The use of starter cultures of B. subtilis and the spores in association
with cowpea granules were studied by Isu and Abu (2000).
They observed that the viability of the cells in association remained stable
at 94.5% for 6 months at 30°C and up to 10 months at 4°C while the viability
of the spores in association remained at 96% for up to 10 months at both 4 and
30°C. They also observed that the indicators of fermentation were more pronounced
than in the natural fermentation and fermentation was completed within 48 h.
The use of such cultures for fermentations can be applied to the indigenous
technologies of the developing countries. This type of starter culture will
enhance process standardization and uniform product quality (Isu
and Ofuya, 2000). It will also eliminate the chances of contamination by
potential food poisoning and other disease causing and spoilage microorganisms.
|| Effect of different starter cultures on ugba fermentation
|aIncrease within 48 h; bIncrease within
72 h; cIncrease within 96 h
Nutritional value of ugba: Table 5 shows the mineral
and vitamin content of the seeds. The vitamin content of the seeds is low while
they are poor sources of calcium and phosphorus (Duke, 1981).
Odoemelam (2005) has also shown that the seeds contain
sodium (236.2 ppm) and potassium (181.3 ppm). The contents of niacin and riboflavin
have been found to decrease during fermentation. Mineral content also decreased
during fermentation while no phosphorus could be found in ugba (Duke,
However, since ugba is usually eaten with fish or added as a condiment to soup
containing animal proteins, much of the needed calcium and protein may be obtained
from these sources (Odunfa, 1986a).
The major sugars found in the seeds are stachyose, galactose and fructose while
saponins constitute about 2.1% of the seeds (Achinewhu,
1983). These saponins when hydrolysed would yield glucose, arabinose, rhaminose,
oleanolic acid and hederagenin. The content of these carbohydrate decreased
significantly as fermentation time increased (Monago et
However, Enujiugha (2003) has shown that fermentation
for 72 h slightly increased the crude protein and ash contents of ugba. The
amino nitrogen increased steadily from 1.23 mg N g-1 DM prior to
fermentation to 13.68 mg N g-1 DM after 72 h of fermentation. He
also found that the principal fatty acid linoleic acid increased from 60.68
to 67.57% of the total fatty acids while oleic acid decreased from 26.95 to
22.59%. Palmitic acid and other saturated fatty acids in the seed oil were also
slightly affected by the fermentation. However, Onwuliri
et al. (2004) found that fatty acid concentrations did not change
appreciably with processing and fermentation. There was also accumulation of
formic acid, acetic, lactic and butyric acids and got to 0.20, 0.18, 0.35 and
0.41 mg g-1 respectively after 72 h of fermentation.
|| Mineral and vitamin content of unfermented and fermented
Isichei and Achinewhu (1988) studied the nutritive
value of African oil bean seeds. The seeds were high in energy with a slight
difference between the gross energy value of unfermented and fermented oil bean
seeds. They also stated that the results obtained from the estimated protein
energy ratio (pe%) and net dietary protein calorie percent (NDpCal%)
showed that the two processed forms of the seed have the potential to satisfy
human protein and energy requirements.
Feeding of rats with unfermented (UOB) and the fermented (FOB) seeds resulted
in weight loss (-0.82 g and -0.11 g, respectively) (Table 6).
However, the average daily intake by the rats was higher for the fermented (5.06
g) than the unfermented (4.72 g). The unfermented and fermented seeds produced
a negative protein efficiency ratio (PER) in rats. The protein digestibility
was also low. Although, the oil bean seeds are rich in protein (Achinewhu,
1982), they suffer source nutritional drawback as they could not promote
nor maintain growth of rats. The poor performance has been attributed to the
presence of toxic components in the seeds which impair protein utilization (Isichei
and Achinewhu (1988). Mbadiwe (1978) attributed
the poor nutritional quality to the presence of growth-depressing factors. Onwuliri
et al. (2004) have shown that the seeds contain some anti-nutritional
factors which included cyanide, phytate, tannin and oxalate. The raw seeds were
found to contain the highest concentrations of all the anti-nutritional factors
except oxalate with the highest concentration (937.5 mg/100 g) in the boiled
seeds. However, they observed a progressive reduction in the level of all the
anti-nutritional factors at the different stages of processing and fermentation.
The fully fermented ugba had a reduction of 73.49% for cyanide, 79.41% for tannin,
76.92% for oxalate and 45.98% for phytate. Akindahunsi (2004)
studied the effect of salting, soaking before cooking and fermentation on the
proximate, anti nutritional and mineral content of the bean seeds. They significantly
decreased protein content by 10.5, 9.9 and 8.0%, respectively. However, the
energy levels increased from 312.5 kcal mol-1 in raw seeds to 450.9,
440.5 and 405.9 kcal mol-1, respectively after treatments. The zinc
levels increased while Mg, Na and K levels decreased.
Toxicology of ugba: The unfermented oil bean seeds contain a number of anti nutritional and toxic factors.
|| Weight gain, feed intake, PER feed efficiency ratio and digestibility
of test samples fed to the rats for 28 days*f
|UOB: Unfermented oil bean. FOB: Fermented oil
bean. *Only means followed by different letters within columns differ significantly
(p<0.05). fIsichei and Achinewhu (1988)
Achinewhu (1983), showed the presence of saponins while
Duke (1981) reported the presence of a poisonous alkaloid,
paucine in the oilbean seeds. Mbadiwe (1979) reported
the presence of caffeoylputrescine, a growth depressant. However, hemagglutinnins
were not found in the oil bean seeds (Toms and Western, 1971).
The presence or absence of these toxic substances in the fermented beans has
not been investigated. It is, however, believed that these substances are eliminated
during the processing and fermentation of the seeds, especially during the soaking,
where they can leach out into the water used for soaking. Other anti-nutritional
factors in the beans have been shown to reduce progressively during processing
and fermentation (Onwuliri et al., 2004). Ruiz-Teran
and Owens (1999) have also shown that such substances are leached out during
soaking in soya bean tempeh production. However, Akindahunsi
(2004). observed that salting and soaking before cooking and fermentation
did not have any effect on the level of tannins while the level of phytate increased.
Thus these may be responsible for the poor performance of the bean seeds during
feeding studies in rats by Isichei and Achinewhu (1988).
However, there has not been any reported case of health problems resulting from
the consumption of ugba over the years.
Although saponins have been reported to be toxic, they may be beneficial since
they have been found to lower plasma cholesterol. Monago
et al. (2004) have shown that ugba fermented for up to four days
decreased the level of plasma cholesterol in rats, the rate of decrease increasing
with the time (days) of fermentation. Thus consumption of the well fermented
product promotes health. Chidozie (2006) has shown that
administration of the fermented seeds as a food supplement have greatly reduced
the risk of cancer and some tobacco related diseases and cancer patients who
had regular fermented oil bean seeds as food supplement showed marked improvements
in regaining quality health.
Flavour components of ugba: Fermented African oilbean seeds have typical
aroma and flavour. These are due to the various volatile compounds produced
by the fermenting microorganisms in the course of their metabolism. Not much
work has been done in this direction. However, Kabuo et
al. (2007) studied the various flavour and aroma components present
in the beans fermented with pure cultures of microorganisms isolated from ugba.
The sample fermented with B. subtilis and B. licheniformis were
found to produce the best ugba with its typical aroma and flavour. The compounds
identified were ethyl state (3.60%), ethyl oleate (4.70%), ethyl linoleate (14.14%),
ethyl phenol (6.94%) and ethyl phenol (6.94%) and ethyl octanoate (2.69%). The
control (naturally fermented) contained ethyl benzoate (18.40%), ethyl carbonate
(5.557%), methyl pentanone (1.67%) and ethyl octanoate (4.72%).
Packaging of ugba: Attempts have been made by some workers to effectively
package the product and thus extend the shelf life of the product. Ogbulie
et al. (1998) made attempts to package the product in low and high
density polyethylene sachets and aluminium foil wraps as well as treatment with
chemical preservatives such as 2% sodium chloride. However, none of the methods
could extend the shelf life beyond 8 days. Mbata and Orji
(2008) in their study applied a process of pasteurization at a temperature
of 98-100°C for 30 min, which they said completely eliminated all the organisms
present including the organisms used for the fermentation. This was able to
extend the shelf life to 8 days. They also made attempts to package them in
returnable and sterilizable bottles/cups. The containers were sterilized before
use and the products pasteurized in the containers. These were able to keep
for six weeks. The colour, taste, aroma, softness and other physicochemical
properties of the product before and after keeping for six weeks compared favourably
well with the locally produced ugba.
Enujiugha and Akanbi (2008) used conventional batch
retort procedures. The sliced and fermented beans were canned in three different
media (brine, refined ground oil and tomato sauce). The product was able to
keep for 6 months at ambient temperature storage. Total viable counts after
6 months of storage were 9.3x103, 1.7x104, and 6.0x103
cfu g-1 in brine, refined groundnut oil and tomato sauce respectively
while the free fatty acids content (g oleic acid) were 3.12, 2.54 and 3.98 respectively.
The peroxide values obtained after storage were 11.63, 9.54 and 10.02 meq kg-1,
respectively while the acid values (mg NaOH g-1 oil) were 6.43, 5.10
and 7.92, respectively. Sensory evaluation of the canned products showed that
the groundnut-oil canned product was least acceptable in terms of aroma and
overall acceptability although all the products showed increased softening and
colour darkening with the prolonged storage.
Microbiological safety of ugba: Various microbiological studies conducted
on ugba (Obeta, 1983; Odunfa and
Oyeyiola, 1985; Ogueke and Aririatu, 2004) showed
that food pathogens such as Clostridum perfringens, C. botulinum,
Salmonella sp., Shigella sp. and Vibrio sp. have not been
isolated from ugba. However, such bacteria as E. coli and Staphylococcus
aureus have been isolated. These are bacteria capable of causing food infections/poisoning.
But since the preparation of the delicacy or addition as condiment to soup involves
heating, they will be eliminated during the process. Azubuine
and Isu (2006) studied the fungal contamination of the fermenting product.
They isolated Aspergillus flavus, A. niger, Penicillium chrysogenum
and Fusarium sp. This poses a serious health risk as these are moulds
that produce mycotoxins in foods. This calls for the observation of Good Manufacturing
Practice (GMP) during the production. However, application of starter cultures
and immobilized cells in the fermentation process will eliminate these possibilities
of contamination with unwanted organisms.
However, their numbers decreased with increase in the number of days of fermentation. Thus the environment was not suitable for their growth and toxin production, especially with the increasing pH of the fermenting slices into the alkaline region.
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