Effect of Bambara Groundnut Flour (Vigna subterranea (L.) Verdc.) Supplementation on Chemical, Physical, Nutritional and Sensory Evaluation of Wheat Bread
Mohammed A.Y. Abdualrahman,
Ali O. Ali,
Elamin A. Elkhalifa
Abdelmoneim E. Sulieman
Bambara groundnut (Vigna subterrenea (L) Verdc) is a major source of vegetable protein in sub-Saharan Africa. And the aim of this study was to enhance the nutritional value of wheat bread through the addition of bambara groundnut flour to wheat four. For this, bambara groundnut seeds were soaked in tap water, manually decorticated, sun dried and milled into fine flour. Proximate analysis of flours of de-hulled bambara groundnut and wheat were conducted. Flour of de-hulled bambara groundnut was used for bread supplementation in ratios of 5, 10 and 15%. Rheological properties of the control flour and wheat flour supplemented with 10% of de-hulled bambara groundnut flour were conducted. The total area and dough development time increased. However, water absorption, stability and extensibility respectively decreased, from 71.3; 8.5; 190 in the control flour to 71.0; 5.5; 180 in the 10% supplemented flour. The increases in the resistance to extension and proportional number from 260 to 280 and 1.37 to 1.56, respectively resulted in stiff dough. The most important effect of wheat bread supplementation was the improvement of protein quantity from 13.74±0.02% for the control bread to 15.49±0.02, 17.00±0.05 and 18.98±0.02% for the 5, 10 and 15% blending ratios, respectively. The in-vitro protein digestibility progressively increased from 84.33±0.03 in the control bread to 85.42±0.04, 86.57±0.04 and 87.64±0.03 in breads containing 5, 10 and 15% bambara groundnut flour. The sensory attributes of different types of bread showed that, a significant difference was observed in texture, colour and overall acceptability. However, the panelists gave higher score for 10% de-hulled bambara groundnut flour bread than bread made from other blends. The loaf weights, loaf volume and specific volume increased. However, while the loaf weight increased with addition of 15% de-hulled bambara groundnut flour, both of loaf volume and specific volume decreased. Nutritional value of wheat bread can be enhanced by the addition of de-hulled bambara groundnut flour at a level of up to 10%.
to cite this article:
Mohammed A.Y. Abdualrahman, Ali O. Ali, Elamin A. Elkhalifa and Abdelmoneim E. Sulieman, 2012. Effect of Bambara Groundnut Flour (Vigna subterranea (L.) Verdc.) Supplementation on Chemical, Physical, Nutritional and Sensory Evaluation of Wheat Bread. Pakistan Journal of Biological Sciences, 15: 845-849.
Received: October 03, 2012;
Accepted: January 16, 2013;
Published: February 12, 2013
The shortage of food protein in the world, especially in developing countries,
dictated the search for new sources of protein is very important to substitute
or to supplement the existing protein sources. Many foods commonly designated
as proteins, are accurately called protein-rich foods. The legumes have been
given great attention to utilize them in various types of food having advantages
of wide distribution through out the developing countries, in addition to the
high protein content (Guthrie, 1971).
Bambara groundnut (Vigna subterranea (L.) Verdc.) is an indigenous grain
legume grown mainly by subsistence women farmers in drier parts of sub-saharan
Africa (FAO, 2001; Mkandawire, 2007).
The crop has advantages over more favored species in terms of nutritional value
and tolerance to adverse environmental conditions (FAO, 2001;
Mkandawire, 2007). Bambara groundnut is an annual crop,
which resembles groundnut (Arachis hypogaea) in both cultivation and
habitat. It is one of the five most important protein sources for many Africans
(Chittaranjan, 2007). Adu-Dapaah and
Sangwan, (2004), reported that the seed is regarded as a completely balanced
food because it is rich in iron 4.9-48 mg/100 g, compared to a range of 2.0-10.0
mg/100 g for most food legumes, protein 18.0-24.0% with high lysine and methionine
contents, ash 3.0-5.0%, fat 5.0-7.0%, fiber 5.0-12.0%, potassium 1144-1935 mg/100
g, sodium 2.9-12.0 mg/100 g, calcium 95.8-99 mg/ 100 g, carbohydrate 51-70%,
oil 6-12% and energy 367-414 kcal/100 mg. Bambara groundnut is a tropical food
legume in Sudan and other tropical areas (Yagoub and Abdalla,
2007). Due to the high price of meat and fish, much importance is now placed
on grain legumes as a source of proteins in all the developing countries. Legumes
are rich not only in proteins, but in other nutrients such as starch (Yagoub
and Abdalla, 2007). In Sudan, bambara groundnuts is grown in rainfed areas
of Darfur, Kordofan and Gadarif and its consumed as a salt-boiled snack
food beside maze and cowpea. The aim of this study is to enhance the nutritional
value of wheat beard through the addition of bambara groundnut flour to wheat
MATERIALS AND METHODS
Source of materials: Bambara groundnut seeds were collected from Um-Gouna
village (Southern Darfur State, Sudan) during harvesting period of the year
2008. The seeds were carefully cleaned and freed from foreign materials. Wheat
flour (72% extraction) was obtained from Sayga Company, Khartoum, Sudan.
Preparation of de-hulled bambara groundnuts flour: The cleaned bambara
groundnuts seeds were soaked for 18 h, manually decorticated, sun dried and
milled into fine flour (Rekord A. Gbr, Jehmlich GmbH, Nossen, Germany) then
the flour was passed through 60 mm mesh sieve (British standard). The flour
was kept in an airtight container at room temperature (32°C) pending further
Preparation of control and wheat flour supplemented bread: The bread
dough formula as shown in Table 1 was: wheat flour (100%),
compressed yeast (1%), salt (1.5%), sugar (4%), oil (2%), commercial bread improver
(Top bake 400) and de-hulled bambara groundnuts flour at (0, 5, 10 and 15%)
levels. Percentages are based on flour weight. The bread making performances
of flours (control and blends) were determined using the modified method as
described by Badi et al. (1978). The dough was
made in specified mixer from (wheat and de-hulled bambara groundnut) flours
for 5 min at medium speed. The dough was rested for 15 min and then scaled,
molded up into round balls and allowed to rest for another 15 min, then molded,
up into pans and placed in the fermentation cabinet for final proof (1 h), then
baked. After baking, the loaf weight was immediately determined using sensitive
balance. Loaf volume was determined using rapeseeds displacement volumeter method
according to Pyler (1973). However, the method was modified
by using pearl millets seeds instead of the rapeseeds. Specific volumes were
calculated by dividing the loaf volume by its weight.
Chemical analysis: Proximate analysis of flours of de-hulled bambara
groundnuts seeds and wheat grains and breads supplemented with different ratios
of de-hulled bambara groundnuts flour were conducted for the contents of moisture,
ash and crude fat according to the (AOAC, 2005) Crude
protein was carried out according to the AOAC (1990).
Crude fiber was determined by acid/alkali digestion method according to the
AOCS (1985). The total carbohydrate content was calculated
by subtracting the previous components from 100.
In-vitro protein digestibility: The in-vitro protein digestibility
of different types of bread was measured according to the three-enzyme method
which was described by Hsu et al. (1977) and (Satterlee
et al., 1979) in which a multi-enzyme solution of (1.6 mg trypsin,
3.1 mg chymotrypsin and 1.3 mg peptidase per milliliter) were used in the test.
|| Physicochemical characterization of mixture used in the manufacture
of wheat bread
Rheological properties: The dough rheological properties for the control
wheat flour and flour containing 10% of de-hulled bambara groundnut flour were
carried out using Farinograph and Extensograph according to (AACC,
2000) method. The water absorption, dough development time, stability, mixing
tolerance index and weakening were determined using Farinograph (Model Type
No: 81010, Duisburg, Germany). The total area, extensibility, elasticity and
proportional number were determined using Extensograph (Brabender, Duisburg
Nr. 185511, type 601203).
Sensory evaluation: A panel of fifteen members composed of adult male
and female was used to judge the quality of the different types of bread supplemented
with various ratios of de-hulled bambara groundnuts flour compared to the control
bread. The panelists were asked to evaluate each sample for appearance, texture,
colour, flavour and overall acceptability using a 9 point hedonic scale from
1 to 9 as follows: 1: Extremely bad, 2: Very bad, 3: Bad, 4: Fairly bad, 5:
Satisfactory, 6: Fairly good, 7: Good, 8: Very good, 9: Excellent as described
by Iwe (2002). The order of presentation of the various
samples was randomized and given codes before being tested by the panelists.
Statistical analysis: Data of organoleptic evaluation of the different
types of wheat bread were subjected to the analysis of variance procedure and
the means were separated at 0.05 levels according to the method described by
Snedecor and Cochran (1980).
RESULTS AND DISCUSSION
The proximate analysis of flours of de-hulled bambara groundnuts and wheat
indicated that, the contents of moisture, crude protein, ash and fat of de-hulled
bambara groundnuts flour are higher than that of wheat flour; while the contents
of crude fiber and carbohydrate are lower as presented in Table
The contents of moisture, crude protein, ash, fat, crude fiber and carbohydrate
of de-hulled bambara groundnuts flour are (7.5±0.04, 32.16±0.04,
3.24±0.01, 6.49±0.02, 1.08±0.03 and 57.03±0.04%),
respectively. Generally, the end products that are made from low ash content
samples were brighter and more uniform in colour than those made from high ash
content (Eltayeb, 2005). The in-vitro protein
digestibility of de-hulled bambara groundnuts flour is (81.95±0.05%).
The wheat flour contents of moisture, ash and fat are (6.78±0.02, 1.67±0.03
and 2.58±0.02%), respectively. The data are lower than (8.40, 1.90 and
2.60%), respectively reported by Kent (1983). The crude
protein content of wheat flour is (12.58±0.03%). The data is lower than
(13.0 and 13.30%) found by Kent (1983) and Kamaljit
et al. (2011), respectively. Ahmed (1995)
reported moisture content of Sudanese wheat cultivars ranged from 6.33 to 8.6%.
The crude fiber and carbohydrate contents are (2.73±0.02 and 80.44±0.07%),
respectively. The data are higher than (2.70 and 71.40%) reported by Kent
As shown in Table 3, wheat-de-hulled bambara groundnuts flour
blends decreased the amount of water required for optimum development of dough
bread and the stability, respectively from 71.3; 8.5 in the control flour to
71%; 5.5 in the supplemented flour. Park et al. (1997)
reported that, fortifying bread with added fiber and antioxidant increased the
water absorption from 68 to 93%. However, development time, mixing tolerance
index and weakening are respectively increased from 4.5; 30; 60 in the control
flour to 5.0, 60; 80 in the supplemented flour. The increase of dough development
time may be attributed to nature of bambara groundnuts flour. It is, however,
evident that the addition has a diluting effect on wheat gluten and hence a
negative effect on gluten strength as reflected by the high mixing tolerance
index and weakening.
As shown in Table 4, the total area increased from 85 in
the control flour to 126 in the supplemented flour.
||Chemical composition and in-vitro protein digestibility
of flours of de-hulled bambara groundnuts and wheat (72% extraction)
|DBGF: De-hulled bambara groundnuts flour, nd: Not determined
||Effect of de-hulled bambara groundnuts flour addition on the
physical properties of wheat flour as measured by the farinograoph instrument
|DBGF: De-hulled bambara groundnuts flour, BU: Brabender unit
||Effect of de-hulled bambara groundnuts flour addition on physical
properties of wheat flour as measured by the extensograph instrument after
|DBGF: De-hulled bambara groundnuts flour, BU: Brabender unit
||Chemical composition and in-vitro protein digestibility
of control bread and bread supplemented with different ratios of de-hulled
bambara groundnuts flour
|DBGF: De-hulled bambara groundnuts flour
|| Sensory evaluation and physical characteristics of control
bread and bread supplemented with different ratios of de-hulled bambara
|Means based on 9 points scale (9 = excellent, 1 = extremely
bad), Means within the same column having the same letters are not significantly
different (p≥0.05) according to the Duncan's multiple range tests, DBGF:
De-hulled bambara groundnuts flour
However, addition of de-hulled bambara groundnuts flour caused a drop in extensibility
with increases of de-hulled bambara groundnuts flour levels in the blend from
190 in the control flour to 180 in the supplemented flour. Addition of 10% de-hulled
bambara groundnuts flour was the suitable blend for bread making relative to
other ratios. The increases in the resistance to extension and proportional
number from 260 to 280 and 1.37 to 1.56, respectively resulted in stiff dough.
The proximate analysis and in-vitro protein digestibility of different
types of bread are presented in Table 5. There is slightly
variation in moisture contents of supplemented breads (5.41±0.02, 5.45±0.01
and 5.50±0.04%). The moisture contents are higher than (5.37±0.02%)
of control bread and lower than (12.6%) reported by Mepba
et al. (2007). The increases in moisture contents are probably due
to the nature of bambara groundnuts seeds which increased the overall water
holding capacity. The estimated protein contents are increased (15.49±0.02,
17.00±0.05 and 18.98±0.02%). The data are higher than (13.74±0.02%)
of control bread and (10.2%) reported by Mepba et al.
(2007). The increases in protein contents revealed that, bambara groundnuts
flour is a completely balanced food because it is rich in iron and protein with
high lysine and methionine contents (Rowland, 1993).
The ash contents are increased (1.58±0.03, 1.70±0.04 and 1.78±0.01%).
The data are higher than (1.27±0.01%) of control bread and lower than
(2.90%) found by Mepba et al. (2007). The fat contents
(2.67±0.04, 2.76±0.02 and 2.94±0.04%) are increased. The
results are higher than (2.40±0.02%) of control bread and (1.7%) determined
by Mepba et al. (2007). The crude fiber contents
are decreased. The crude fiber contents are lower than (2.51±0.02%) of
control bread and higher than (0.09%) determined by Mepba
et al. (2007). The carbohydrate contents are decreased (72.39±0.03%,
70.70±0.01 and 68.49±0.01%). The data are lower than (74.71±0.02%)
of control bread and (71.7%) reported by Mepba et al.
(2007). The increases in replacement levels of de-hulled bambara groundnuts
flour led to increase the in-vitro protein digestibility of wheat bread
(84.33±0.03 to 87.64±0.03%).
The sensory attributes and physical characteristics of different types of breads
are presented in Table 6. The data indicated that, there are
significant differences as regard to colour, texture and overall acceptability.
However, the acceptability of supplemented beads decreased with the increasing
of de-hulled bambara groundnuts flour in the blend. It seems that up to 10%
of de-hulled bambara groundnuts flour did not affect the bread quality. The
loaf weights, loaf volume and specific volume are respectively increased from
220; 64.50; 3.41 in the control bread to 240; 65.40; 3.67 in the 10% supplemented
bread. However, they decreased with the addition of 15% de-hulled bambara groundnuts
flour. The data are agreement with that of (Kamaljit et
al., 2011), who reported that, specific volume was also found to be
decrease with increase in level of incorporation of oat fiber, due to dilution
of gluten protein.
In conclusion, this study succeeded to develop a new product of wheat bread
of high nutritive value through utilization of Darfurain neglected crop (bambara
groundnuts flour). The most significant effect of bread supplementation is the
improvement of protein quantity and in-vitro protein digestibility and
enhancement of nutritional quality.
We expressed our gratitude to the laboratory members of Department of Food
Science and Technology, University of Gezira, and Central Laboratory, Ministry
of Science and Technology, Khartoum, Sudan and the Department of Food Technology,
National Research Centre, Al Dokki, Cairo, Egypt for their help and continuous
assistance during the period of this study.
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