AJST, Vol. 2, No. 2: December, 2001 71
African Journal of Science and Technology (AJST)
Science and Engineering Series Vol. 2, No. 2, pp. 71-80
INFLUENCE OF FERMENTATION AND COWPEA STEAMING ON SOME
QUALITY CHARACTERISTICS OF MAIZE-COWPEA BLENDS
S. Sefa-Dedeh,Y. Kluvitse and E.O. Afoakwa*
Department of Nutrition & Food Science, University of Ghana
P. O. Box LG 134, Legon-Accra, Ghana. (*author for correspondence)
* E-mail: e_afoakwa@xmail.com Tel/Fax: 233-21-500389
ABSTRACT: Fermentation and cowpea steaming can be used to improve the protein quality and
quantity of fermented maize dough. In the production of maize-cowpea blends, it is important that the
quality characteristics are evaluated to determine their functionality in the products. A 5x4x2x2
factorial experiment with cowpea level, fermentation time, cowpea steaming time and fermentation
method as the variable was performed. The cowpeas were dehulled, steamed, dried at 65EC for 24
hours and milled into flours. Maize was soaked in water (18 hours), drained and milled into flour.
The maize-cowpea blends were made into a 50% moisture dough, fermented for the specified periods,
dried at 65EC and milled into flour. Samples were evaluated for pH, titratable acidity, water absorption
and sugars. The pH and titratable acidity of the samples were affected by fermentation time, steaming
time, and the levels of cowpeas in the blend. Cowpeas was the main source of glucose/galactose.
Fermentation caused a reduction in stacchyose and glucose/galactose. The mixing of cowpea flour
with fermented maize dough prior to drying (single component fermentation) gave similar effects on
sugar concentrations as detected in the co-fermented samples (multi-component fermentation).
Fermentation and steamed cowpea fortification can be used to produce high protein fermented
cereal foods with reduced anti-nutritional factors.
Key words : Fermentation, steamed cowpeas, cowpea fortification, chemical composition, functional
properties, weaning foods.
INTRODUCTION
Fermentation is widely applied in the processing of cereals
for the preparation of a wide variety of dishes in developing
countries (Obiri-Danso,1994). In Ghana, over 90% of cereal
based traditional foods are prepared from fermented maize
dough. The soaking of the grains in excess water allows
the selection of desirable micro-organisms, such as lactic
acid bacteria, yeasts, and moulds (Sefa-Dedeh et al., 1999;
Sefa-Dedeh & Cornelius, 2000). The activity of these microorganisms
reduces pH and increases the titratable acidity
of the substrate. A number of fatty acids are also produced
(Akinrele,1970; Plahar & Leung, 1982). Mensah et al. (1990)
studying the properties of fermented maize dough
observed significant inhibition of pathogenic bacteria.
Cooking the dough into porridge reduced the antimicrobial
effect but there was still significant inhibition of
pathogens. The antimicrobial property could be an
important strategy for the reduction of the high levels of
faecal bacteria in cereal foods in the developing countries
Most African traditional gruels are made from cereals and
the result is gruels that have low nutritional value as they
are not adequate sources of micro- and macro-nutrients
(Brown,1991). During cooking, the starch binds water,
requiring considerable amounts of water to bring the
consistency of the porridge to a level suitable for child
feeding. This lowers the energy and nutrient density of the
porridge considerably. This high volume/high viscosity
characteristic referred to as dietary bulk makes it difficult
for infants fed on these gruels to satisfy their nutrient
requirement, which is considered as a major problem of
malnutrition in areas where cereal staples are the main foods
(Ljungqvist et al., 1981). Recently, more attention has been
directed towards the fulfilment of protein energy
requirements because of the widespread occurrence of
protein energy malnutrition (PEM) and linear growth
retardation in developing countries. The techniques
commonly employed in traditional weaning food
developments, include the formulation of high quality
protein mixes (foods) using cereals and legumes such as
cowpeas and soybeans.
72 AJST, Vol. 2, No. 2: December, 2001
S. Sefa-Dedeh
The application of cowpea-fortification to fermented cereal
porridges have been reported to increase the nutritive
value. As well, the total nutrient density increases by more
than two-folds as a result of reduction in viscosity (Marero
et al., 1980; Afoakwa,1996; Sefa-Dedeh et al, 2000). Cowpea
steaming has been developed to control the infestation of
cowpea seeds during storage. It involves the exposure of
cowpea seeds to steam followed by drying to acceptable
storage moisture contents. Sefa-Dedeh and Demuyarko
(1994) investigated the effects of steaming and storage on
some physico-chemical properties of cowpea seeds and
flour. They reported that whilst the steaming resulted in an
increase in water absorption capacity of the flour samples,
the steamed seeds showed reduced water absorption
capacities. They also observed characteristic differences
in the viscoamylograph data following steaming, which is
an indication of the ease of cooking of the samples. Further
studies on some chemical and functional properties of
steamed cowpea fortification to weaning foods will provide
insight into the compatibility of steamed cowpea as a food
ingredient and the success with which steamed cowpeas
can be incorporated into various weaning foods.
This study was aimed at investigating the influence of
fermentation and steamed cowpea fortification on some
chemical and functional properties of fermented maizecowpea
blends.
MATERIAL AND METHODS
Materials
Maize (Zea mays) and cowpea (Vigna unguiculata) were
used in the experiments. An improved variety of maize
(Abeleehi) was purchased from Ejura Farms, Accra. Dent
corn and Blackeye peas obtained from the Centre for Food
Safety and Quality Enhancement (CFSQE), University of
Georgia, Atlanta and used for the study. All the samples
were stored at a cold room (4°C) during the study period.
Sample preparation
Whole cowpeas were soaked in water for 4 minutes to
loosen the seed coats. The seeds were drained and dehulled
using a disc attrition mill (Agrico Model 2A, New Delhi).
The hulls were separated by floatation in water. One portion
was dried in an oven temperature of 65°C for a period of
20-24 hours and the remaining portion steamed for 4
minutes. Subsequently, the steamed seeds were oven dried
at 65°C and milled into flour using a disc attrition mill
(Agrico Model 2A, New Delhi). Whole maize grains were
soaked in water (1:3, w/v) at 28°C for 18 hours. The steep
water was drained and the grain milled using a disc attrition
mill (Agrico Model 2A, New Delhi). Several formulations
were prepared by the addition of weighed portions of
dehulled and steamed cowpea flour to maize meal before
fermentation. The resulting meal was kneaded into a 50%
moisture dough, allowed to ferment at room temperature
for a period of 0 - 72 hours. Other blends were formulated
by the addition of cowpea flours to the maize dough after
fermentation. The preparations were dried in an oven at
65°C and milled into flour.
Experimental Design :
A 5 x 4 x 2 x 2 factorial experimental design was used and
the principal factors were:
i. Cowpea level : 0, 5, 10, 15 and 20 % ;
ii. Fermentation time : 0, 24, 48 and 72 hours;
iii. Steam treatment : 0 and 4 minutes,
iv. Fermentation method : Single and multiple component.
Samples were evaluated for pH, titratable acidity, water
absorption, and mono-, di- and oligosaccharides.
Methods
pH and titratable acidity
Ten grams of dried flour was mixed with 100ml distilled
water. The mixture was allowed to stand for 15 minutes,
shaken at 5 minutes intervals and centrifuged at 3000 rpm
for 15 minutes using a Denley centrifuge (Model BS4402/
D, Denley, England). The supernatant was decanted and
its pH was determined using a pH meter (Model HM-30S,
Tokyo, Japan). Ten (10)ml aliquots (triplicate) were titrated
against 0.1M NaOH using 1% phenolphthalein as indicator.
Acidity was calculated as grams lactic acid/100g sample.
Water absorption capacity
Five grams of sample was weighed into a centrifuge tube
and 30ml of distilled water at temperatures of 25 and 70°C
added independently for the analysis at 25 and 70°C
respectively. The mixture was stirred and allowed to stand
for 30 minutes and centrifuged using a Denley centrifuge
(Model BS4402/D, Denley, England), at 3000 rpm for 15
minutes. The supernatant was decanted and the increase
in weight noted by weighing. The water absorption
capacity was expressed as a percentage of the initial sample
weight. The determination was done for duplicate samples.
AJST, Vol. 2, No. 2: December, 2001
Influence of Fermentation and Cowpea Steaming on some
Quality Characteristics of Maize-cowpea Blends
73
Determination of mono-, di- and oligosaccharides
Sugars were extracted from maize/cowpea blends using a
mixture of chloroform : methanol (1:1, w/v) and water as in
Havel, Tweeten, Seib, Wetzel and Liang (1977). Extract was
concentrated under vacuum, made to 5 Ml with de-ionized
water. The extract was filtered with 0.22m PTFE filters and
stored in 5 mL ampoules at a cold room temperature of 0°C.
Ten microlitres (10 μm) samples were analyzed by High
Performance Liquid Chromatography (HPLC) using a
Hitachi system equipped with a Hewlett Packard Integrator
and Shimadzu Refractive Index Detector. Separation was
done on a 220 x 4.6 mm amino propyl column (amino-spheri-
5, Brownlee Labs, Santa Clara) eluted with a 70:30 v/v mixture
of acetonitrile : water which contained 0.01% tetraethylene
pentamine (TEPA) as recommended by Aitzemuller (1978).
Quantification was against authentic external standards
of the sugars detected and a lactose internal standard.
Statistical analysis
The data obtained from the chemical and functional
determinations were statistically analyzed using
Statgraphics (Graphics Software System, STCC, Inc. U.S.A).
Comparisons between sample treatments and the indices
were done using analysis of variance (ANOVA) with a
probability p < 0.05.
RESULTS AND DISCUSSION
pH and acidity
The solid-state fermentation of maize dough had a drastic
effect on pH. Within the first 24 hours of fermentation, the
pH decreased from 6.3-4.0 (Fig. 1). After 72hrs of
fermentation, the pH of the dough was 3.87. Fortification
with up to 10% of unsteamed cowpea yielded fermented
dough with comparable pH as the unfortified maize dough.
Samples containing 15-20% unsteamed cowpea however
showed a relatively high pH (Fig. 1A).
The proteins in the cowpea may have contributed to the
high pH. Steaming of cowpea prior to addition to maize
appeared to promote fermentation (Fig.1B). These samples
had relatively lower pH than their unsteamed samples.
Fortification up to 20% steamed cowpea provided samples
with comparable pH as the 100% maize samples. The data
suggests that maize can be fortified with up to 20% level
and fermented to produce a dough with low pH. Analysis
of variance on the data showed that only fermentation
time had a significant effect (p<0.05 ) on dough pH.
Duncan’s multiple comparison tests indicated that the
unfermented maize samples were distinctly different from
the fermented maize samples. The samples fermented for
24 hours were significantly different from those fermented
for 72 hours. The 48 hour-fermented samples however
0 24 48 72
3
4
5
6
7
Ferme nta tion time (Hours )
pH
5
10
15
20
0
0 24 48 72
3
4
5
6
7
Fermentation time (Hours)
pH
5s
10s
15s
20s
0
Figure 1. Effect of steam treatment and cowpea concentration on the pH of unsteamed (A) and steamed (B) cowpeafortification
at concentrations of 0 - 20% of fermented maize-cowpea blends
74 AJST, Vol. 2, No. 2: December, 2001
S. Sefa-Dedeh
compared favourable with the other two samples (Table 1).
Table 1. F-ratios of process variables of the functional
properties
Fermentation time 65.175* 187.35* 14.783*
Cowpea level 0.2815 1.917 6.786*
Steam treatment 0.343 0.387 0.009
* Significant F-ratios at p<0.05
Process variable pH Acidity Water absorption
The major carboxylic acids produced during the
fermentation of maize dough have been identified as lactic,
butyric, acetic and propionic acids (Plahar & Leung, 1982).
The acidity of maize dough increased with fermentation.
The addition of unsteamed cowpea lowered the acidity of
the maize dough (Fig. 2A).
Steaming the cowpea prior to the addition to maize led to
increases in acid production during fermentation for upto
48 hours. However, acidity decreased slightly during the
final 24 hours of the fermentation period monitored
(between 48 and 72 hours). Analysis of variance on the
data showed that fermentation time had a significant
(p#0.05) effect on acidity. In addition the acidity level
associated with each fermentation time was dependent on
whether the cowpea has been steamed (Table 1) the ability
of the cowpea-fortified maize dough system to ferment
and produce acids comparable to the traditional maize
dough system is beneficial. Mensah et al. (1990) reported
that the antimicrobial properties of fermented maize dough
due to the acids produced during fermentation. This was
reported to reduce incidence of diarrhoea in infants
consuming fermented maize porridge. The cowpea-fortified
maize dough will have two important attributes, such as
antimicrobial properties and high protein content. This will
make it useful in the formulation of weaning foods.
Sugars and Oligosaccharides
Cowpea
Xylose, fructose, glucose, galactose, sucrose, maltose,
raffinose and stachyose were determined in different
concentrations in whole cowpea (Table 2). Dehulling led
to an increase in the concentration of all sugars except for
maltose, glucose and galactose. This suggest that maltose,
glucose/galactose are concentrated in almost all the sugars
with the exception of sucrose, glucose and galactose. The
“-galactosides are known to constitute the major portion
of sugars in legumes seeds (Fleming, 1980). Stacchyose
was observed to be the major oligosaccharide, followed
by raffinose in the cowpea samples as reported by other
workers (Akpapunam & Markakis, 1979; Abdel-Gawad,
0 24 48 72
0
0.4
0.8
1.2
1.6
2
Fe rme nta tion time (Hours )
Acidity (%)
5
10
15
20
m
0 24 48 72
0
0.4
0.8
1.2
1.6
2
Fermentation time (Hours )
Acidity (%)
5s
10s
15s
20s
m
Figure 2. Effect of steam treatment and cowpea concentration on acid production of unsteamed (A) and steamed (B)
cowpea-fortification at concentrations of 0 - 20% of fermented maize-cowpea blends
AJST, Vol. 2, No. 2: December, 2001
Influence of Fermentation and Cowpea Steaming on some
Quality Characteristics of Maize-cowpea Blends
75
1992; Sosulski et al., 1982). The levels of stacchyose and
raffinose increased with dehulling. This observation was
contrary to initial studies reported by Akinyele and
Akinlosotu (1991) who detected a decrease in
oligosaccharide levels after dehulling cowpea seeds. The
longer pre-soaking period of 4 hours allowed in their
experiment might have facilitated leaching or initiated the
process of fermentation in the seed resulting in increased
“-galactosidase activity on the oligosaccharides.
Table 2. Levels of mono-, di- and oligosaccharides determined
in cowpea (Vignia unguiculata) samples (mg/100g dry matter)
Cowpea
sample
Xylose Fructose
Glucose +
Galactose
Sucrose Maltose Raffinose Stachyose
Whole 0.38 0.012 0.337 1.652 0.118 0.552 2.545
Dehulled 0.612 0.436 0 1.828 0.051 0.63 3.661
Dehulled &
Steamed
0.332 0.068 0.028 2.034 0.039 0.234 3.34
Maize
Maize was observed to have high concentrations of
glucose and galactose. Other sugars detected in the maize
were maltose, xylose and fructose (Table 3). The effect of
fermentation on the concentration of the sugars varied.
During the first 24 hours of fermentation, the concentration
of fructose, glucose and galactose decreased. Xylose and
maltose however showed a slight increase in concentration.
Further fermentation for 24 hours showed an increase in
all the sugars except xylose. Fermentation for 72 hours
showed a drastic reduction in the concentration of glucose/
galactose and maltose (Table 3). The levels of maltose,
glucose and galactose appeared to increase during the
first 48 hours of fermentation and drop drastically after 72
hours. Sucrose, raffinose and stacchyose were not
detected in the maize samples.
Table 3. Levels of mono-, and disaccharides as determined
in maize (Zea mays) samples (mg/100g dry matter)
Fermentation
Time (Hours)
Xylose Fructose
Glucose +
Galactose
Maltose
0 0.705 1.093 9.636 0.21
2 4 0.788 0.678 9.566 0.277
4 8 0.481 0.69 10.213 0.438
7 2 0.473 0.597 1.056 0.14
Co-fermentation
Fermented maize and cowpea blends showed varied effects
of process variables on sugar and oligosaccharide
concentrations. In the system in which cowpea was cofermented
with maize (Figs. 3 & 4) the effects of process
A B
X y lo s e F r u c t o s e S u c r o s e M a lt o s e R a f f in o s e S t a c h y o s e
0
0 . 2
0 . 4
0 . 6
0 . 8
1
1 . 2
C o n c . m g /1 0 0 g s a m
0 h
2 4 h
4 8 h
7 2 h
X y lo s e F r u c t o s e S u c r o s e M a lt o s e R a f fin o s e S t a c h y o s e
0
0 . 2
0 . 4
0 . 6
0 . 8
1
1 . 2
C o n c . m g /1 0 0 g s a m
0 h
2 4 h
4 8 h
7 2 h
C D
X y l o s e F r u c t o s e S u c r o s e M a lt o s e R a f fi n o s e S ta c h y o s e
0
0 . 2
0 . 4
0 . 6
0 . 8
1
1 . 2
C o n c . m g / 1 0 0 g s a
0 h
2 4 h
4 8 h
7 2 h
X y lo s e F r u c t o s e S u c r o s e M a lt o s e R a f f i n o s e S t a c h o s e
0
0 . 2
0 . 4
0 . 6
0 . 8
1
1 . 2
C o n c . m g / 1 0 0 g s a
0 h
2 4 h
4 8 h
Figure 3. Effect of fermentation on the sugar levels in 5% (A), 10% (B), 15% (C) and 20% (D) unsteamed cowpea on cofermented
maize-cowpea blends
76 AJST, Vol. 2, No. 2: December, 2001
S. Sefa-Dedeh
A B
X y lo s e Fr u c t o s e S u c r o s e M a lt o s e R a f fin o s e S ta c h y o s e
0
0 . 2
0 . 4
0 . 6
0 . 8
1
1 . 2
1 . 4
C o n c . m g /1 0 0 g s a m
0 h r s
2 4 h r s
4 8 h r s
7 2 h r s
X y l o s e F r u c t o s e S u c r o s e M a lto s e R a ff in o s e S t a c h y o s e
0
0 . 2
0 . 4
0 . 6
0 . 8
1
1 . 2
1 . 4
C o n c . m g / 1 0 0 g s a
0 h r s
2 4 h r s
4 8 h r s
7 2 h r s
C D
X y lo s e F r u c t o s e S u c r o s e M a l t o s e R a ff in o s e S ta c h y o s e
0
0 . 2
0 . 4
0 . 6
0 . 8
1
1 . 2
1 . 4
C o n c . m g / 1 0 0 g s
0 h
2 4 h
4 8 h
7 2 h
X y lo s e F r u c to s e S u c ro s e M a l t o s e R a f fin o s e S ta c h o s e
0
0 . 2
0 . 4
0 . 6
0 . 8
1
1 . 2
1 . 4
C o n c . m g / 1 0 0 g s a
0 h
2 4 h
4 8 h
7 2 h
Figure 4. Effect of fermentation on the sugar levels in 5% (A), 10% (B), 15% (C) and 20% (D) steamed cowpea on cofermented
maize-cowpea blends
A B
5 1 0 1 5 2 0
0
2
4
6
8
1 0
1 2
1 4
C owpe a (% )
C o n c . m g/1 0 0 g s a mp le
0 h
2 4 h
4 8 h
7 2 h
5 1 0 1 5 2 0
0
2
4
6
8
1 0
1 2
1 4
C ow p e a (% )
C o n c . m g /1 0 0 g s a m ple
0 h
2 4 h
4 8 h
7 2 h
Figure 5. Effect of fermentation on glucose concentration in co- fermented maize-(A) unsteamed and (B) steamed cowpea
blends
AJST, Vol. 2, No. 2: December, 2001
Influence of Fermentation and Cowpea Steaming on some
Quality Characteristics of Maize-cowpea Blends
77
variables on xylose concentration was not conclusive.
Xylose was derived from both the maize and cowpeas.
The co-fermentation of maize with steamed cowpeas (10,
15 and 20%) appeared to increase the xylose concentration
(Figs. 4B, C & D) up to 48 h of fermentation after which a
decrease was observed. The system containing unsteamed
cowpeas however showed a consistent decrease in xylose
concentration with the 20% cowpea-fortified system (Fig.
3D). The sugars which are derived solely from cowpeas ;
sucrose, raffinose and stacchyose seemed to be affected
by fermentation. A general decrease with fermentation and
complete removal were observed. The sugars
predominantly from maize, being glucose/galactose (Fig.
5), maltose and fructose (Fig. 3 & 4) showed a general
reduction with fermentation. Steaming of cowpeas
appeared to assist this reduction.
Blend after maize fermentation
This system showed an interesting trend. Sugars such as
sucrose, raffinose and stacchyose derived solely from
cowpeas showed great reduction in concentration with
fermentation time (Figs. 6 & 7). This reduction was more
pronounced in the 5, 10, and 15% cowpea-fortified
fermented maize system. Apart from xylose, all other sugars
being glucose/galactose (Fig. 8), fructose and maltose
showed a general reduction with process variables. The
data suggest that the fermented maize dough with its 50-
55% moisture is an important media for the reduction of
sugars and oligosaccharides derived from cowpeas. It is
proposed that the reactions involving the sugars and
oligosaccharides from cowpeas may have occurred from
the time of mixing with the fermented maize dough to the
early part of drying at 65° C.
The data from the two fermented maize-cowpea systems
was subjected to analysis of variance. Table 4 is a summary
of the significant F-values from the analysis. Xylose was
affected by any of the process variables. Fermentation
time had a significant effect (p<0.05) on fructose, glucose/
galactose, maltose, raffinose and stachyose concentrations
(Table 4). The level of cowpeas in the blend affected the
glucose/galactose and stachyose concentrations. Steam
treatment affected only the maltose concentration.
Significant interactions were found between fermentation
time and all other process variables.
Table 4. Table of significant F-ratios of mono-, di- and
oligosaccharides fermented weaning foods
Process
variable s
Fructose Glucose +
Galactose
Maltose Raffinose Stacchyose
Fermentation time 43.079 48.972 3.501 5.142 20.372
Fort ification level - 4.074 - - 10.453
Steam t reatment - - 5.400 - -
Water absorption capacity
Process treatments of raw material are known to affect their
hydration properties (Philips et al., 1988). Water absorption
capacity was measured at room temperature (26°C) to
determine the behaviour of the cereal-legume flours in cold
water. This is an important index which can give valuable
information on the behaviour of the blend during
processing. Addition of cowpea improved the water
absorption potential of fermented maize dough (Table 6).
This was probably due to the influence of added protein in
the blends. Proteins are mainly responsible for the bulk of
water uptake and to a lesser extent the starch and cellulose
at room temperature. Sefa-Dedeh and Osei (1994) made
similar observations on a cowpea fortified fermented maize
dough system.
Steam treatment of cowpeas was observed to increase its
water absorption capacity from 166.8349% - 221.9613%.
For the unfermented and 24-hour fermented maize-cowpea
blends, steam treatment of cowpea seemed to cause a
decrease in water absorption potential.
Fermentation
time (Hours)
Cowpea level (%) Water absorption
of co-fermented
blends
Water absorption
of fermented
blends
0 114.6731 114.6731
0
5 142.6048 136.6179
10 143.3218 140.0624
15 144.9571 140.5073
20 137.3242 146.1079
0 118.6975 118.6975
24
5 124.1301 132.2226
10 124.2137 139.5657
15 121.8473 146.8565
20 134.0411 133.8545
0 120.7402 120.7402
48
5 127.1835 133.3353
10 130.1206 145.6074
15 134.2309 128.7172
20 137.0246 143.9276
0 114.2845 114.2845
72
5 122.7185 143.0052
10 136.0395 131.9409
15 138.8273 132.8310
20 139.9509 144.3295
Table 5. Water absorption capacities of fermented maize-unsteamed cowpea
blends (% dry matter basis)
However, 48 hours and 72 hours of fermentation the steamed
cowpea fortified blends had higher water absorption
capacities. Sefa-Dedeh and Demuyarko (1994) reported that
78 AJST, Vol. 2, No. 2: December, 2001
S. Sefa-Dedeh
A B
X y lo s e F r u c t o s e S u c ro s e M a lt o s e R a f fin o s e S t a c h y o s e
0
0 . 2
0 . 4
0 . 6
0 . 8
1
1 . 2
C o n c . m g /1 0 0 g s
0 h
2 4 h
4 8 h
7 2 h
X y l o s e F r u c t o s e S u c r o s e M a lto s e R a ff in o s e S ta c h y o s e
0
0 . 2
0 . 4
0 . 6
0 . 8
1
1 . 2
C o n c . m g / 1 0 0 g s
2 4 h
4 8 h
C D
X y lo s e F r u c to s e S u c ro s e M a l t o s e R a ff in o s e S t a c h y o s e
0
0 .2
0 .4
0 .6
0 .8
1
1 .2
C o n c . m g / 1 0 0 g s a
0 h
2 4 h
4 8 h
7 2 h
X y lo s e F r u c t o s e S u c r o s e M a lt o s e R a f f i n o s e S t a c h o s e
0
0 . 2
0 . 4
0 . 6
0 . 8
1
1 . 2
C o n c . m g /1 0 0 g s a
0 h
2 4 h
4 8 h
7 2 h
Figure 6. Effect of fermentation on the sugar levels in5% (A), 10% (B), 15% (C) and 20% (D) unsteamed cowpea on
fermented maize- cowpea blends
A B
X y lo s e F r u c t o s e S u c r o s e M a lt o s e R a ff in o s e S ta c h y o s e
0
0 . 5
1
1 . 5
2
C o n c . m g / 1 0 0 g
0 h r s
2 4 h r s
4 8 h r s
7 2 h r s
X y lo s e F r u c t o s e S u c r o s e M a l t o s e R a ff in o s e S ta c h y o s e
0
0 . 5
1
1 . 5
2
C o n c . m g /1 0 0 g s
0 h r s
2 4 h r s
4 8 h r s
7 2 h r s
C D
X y lo s e F r u c t o s e S u c r o s e M a lt o s e R a f fin o s e S t a c h y o s e
0
0 . 5
1
1 . 5
2
C o n c . m g /1 0 0 g s a
0 h
2 4 h
4 8 h
7 2 h
X y lo s e F r u c t o s e S u c ro s e M a lt o s e R a f f in o s e S t a c h o s e
0
0 . 5
1
1 . 5
2
C o n c . m g / 1 0 0 g s a m
0 h
2 4 h
4 8 h
7 2 h
Figure 7. Effect of fermentation on the sugar levels in5% (A), 10% (B), 15% (C) and 20% (D) unsteamed cowpea on
fermented maize- cowpea blends
AJST, Vol. 2, No. 2: December, 2001
Influence of Fermentation and Cowpea Steaming on some
Quality Characteristics of Maize-cowpea Blends
79
steamed cowpea flour possessed better water absorption
than raw cowpea flour.
Fermentation
time (Hours)
Cowpea level (%)
Water absorption
of co-fermented
blends
Water absorption
of fermented
blends
0 114.6731 114.6731
0
5 121.1686 129.8615
10 121.7534 135.8566
15 121.8169 133.2053
20 135.1617 140.4852
0 118.6975 118.6975
24
5 115.4199 125.4236
10 130.6627 122.1084
15 113.3782 115.4199
20 136.0908 133.6514
0 120.7402 120.7402
48
5 136.2266 137.4582
10 142.3521 146.7009
15 147.8524 148.1080
20 144.1065 152.9293
0 114.2845 114.2845
72
5 148.5680 138.0563
10 129.3342 149.2652
15 148.3491 148.0684
20 134.0860 153.3773
Table 6. Water absorption capacities of fermented maize-steamed cowpea
blends (% dry matter basis)
The gelatinization of starch and the denaturation of protein
that is the result of the application of heat treatment to
cowpeas has been suggested to improve the water
imbibing capacity of cowpea and mung bean proteins
A B
5 1 0 1 5 2 0
0
2
4
6
8
1 0
1 2
1 4
C o w p e a (% )
C o n c . m g /1 0 0 g s a m p le
0 h
2 4 h
4 8 h
7 2 h
5 1 0 1 5 2 0
0
2
4
6
8
1 0
1 2
1 4
C o w p e a (% )
C o n c . m g /1 0 0 g s a m p le
0 h
2 4 h
4 8 h
7 2 h
Figure 8. Effe ct of fermentation on glucose concentration in fermented maize- (A)unsteamed and (B) steamed cowpea blends
(Abbey & Ibeh,1988; del Rosario & Flores, 1981). Analysis
of variance indicated that cowpea fortification level and
the water absorption capacity of the blends. The effects of
steaming the cowpeas prior to its incorporation into the
maize dough was not statistically significant (Table 1).
CONCLUSION
Fermentation and steam cowpea fortification can be used
to produce high protein weaning foods with reduced antinutritional
factors without significant changes in product
quality profiles of the fermented weaning foods.
ACKNOWLEDGEMENT
This study was funded through the Bean-Cowpea
Collaborative Research Support Program by the United
States Agency for International Development - Grant No.
DAN-1310-G-SS-6008-00.
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