Effect of Full and Partial Substitution of Sesame Seeds with Bambara Groundnuts and Peanuts on the Quality of Sudanese Traditional Food (Khemiss-tweria)
In this study, de-hulled Bambara groundnuts and peanuts flours were used for full and partial substitution of sesame seeds in production of khemiss-tweria. The proximate analysis of de-hulled Bambara groundnuts flour, peanuts, sesame seeds and pearl millet flour were conducted. The chemical analysis of control and developed khemiss-tweria indicated that the contents of moisture and ash ranged between 4.00±0.03 to 4.28±0.04% and 2.50±0.01 and 4.86±0.04%, respectively, while the contents of protein, fat, crude fiber and carbohydrate ranged from (15.06±0.02 to 24.19±0.03%) (6.69±0.03 to 10.88±0.02%) (2.12±0.03 to 2.50±0.01%) and (62.27±0.02 to 68.40±0.01%), respectively. On the other hand, the in vitro protein digestibility ranged from (75.52±0.02 to 93.16±0.04%). The most significant effect of de-hulled Bambara groundnuts flour and peanuts addition, in production of khemiss-tweria was the improvement of protein quality. Khemiss-tweria made from millets bread and peanuts had the highest in vitro protein digestibility. The sensory analysis of the different types of khemiss-tweria revealed that there was a significant differences in colour while there were no significant differences between the various types of khemiss-tweria products. However, peanuts gave higher scores to the khemiss-tweria whereby peanuts fully replaced sesame seeds than the products made from other blends.
Received: January 22, 2012;
Accepted: March 24, 2012;
Published: May 11, 2012
Khemiss-tweria is a food product virtually confined to the region of Darfur.
The usefulness and attractiveness of this food should have been enough incentive
to justify its widespread production in the country. The fact that this did
not happen may be taken as an indication that the product may have been only
recently invented or perhaps introduced from other African countries (Dirar,
1993). This food is important for travelers, farmers and gum Arabic workers
in western Sudan. The starting material of the khemiss-tweria is whole millet
grains, half of which is malted, sun dried and reduced to fine flour and the
other half is turned into flour and then fermented. The fermented dough is cooked
into kissra-hamra and then kneaded with the millet malt flour when it has cooled
to room temperature (Dirar, 1993). Half an hour is given
for amylolysis to precede to the correct degree before water is added to further
thin the batter and the container incubated overnight for fermentation.
|| Kissra-assala and khemiss-tweria production (Dirar,
The next morning the batter is baked into kissra sheets and then dried in the
sun and crumbled. For preparation of khemiss-tweria, the dry crumbled kissra-assala
is mixed with roasted sesame in ratio of 6:1, respectively and a little sugar
and a dash of salt are added to taste. The mixture is pounded in a mortar to
give a coarse meal comprising khemiss-tweria as presented in Fig.
1 (Dirar, 1993).
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). In much of Africa, Bambara groundnut
is the third most important legume after groundnut (Arachis hypogaea)
and cowpea (Vigna unguiculata) (FAO, 2001; Mkandawire,
2007). The crop has a number of production advantages in that it can yield
on poor soils with little rainfall as well as produce substantial yields under
better conditions. It is nutritionally superior to other legumes and is the
preferred food crop of many local people (FAO, 2001;
Mkandawire, 2007). Bambara groundnut is a rich source
of protein (16-25%) and its seeds are valued both for their nutritional and
economic importance. The seeds command a high market price, with demand far
outweighing supply in many areas. However, despite these important attributes,
the agro-ecological and genetic potential of Bambara groundnut have not yet
been fully realized nor its full economic significance determined (FAO,
2001; Mkandawire, 2007). The crop is still cultivated
from local landraces rather than varieties bred specifically for particular
agro-ecological conditions or production systems (FAO, 2001;
Mkandawire, 2007). In western Sudan, Bambara groundnut
is not a part of the main dish in the table of the local people; its consumed
as a salt-boiled snack food (Yagoub and Abdalla, 2007).
This study aimed to improve the nutritive value of khemiss-tweria using de-hulled
Bambara groundnuts seeds flour and peanuts instead of sesame seeds.
MATERIALS AND METHODS
Materials: The seeds of Bambara groundnuts, peanuts, sesame and pearl millet grains were collected from the farm located at Um-Gouna village, Southern Darfur State, Sudan, during the harvesting period of the year 2008. The seeds were carefully cleaned and freed from foreign materials.
Preparation of de-hulled Bambara groundnuts flour: Bambara groundnuts seeds were soaked, manually decorticated, sun dried and milled into fine flour (Rekord A. Gbr, Jehmlich GmbH, Nossen, Germany) then the flour was passed through 60 mesh screen, bottled and kept at 5°C for all further studies.
Kissra-assala preparation: A traditional method described by Dirar
(1993) was followed whereby kissra-assala was backed from 8 kg of pearl
millet grains half of it were malted, sun dried and reduced to fine flour and
the other half were turned into flour (1:2 w/v) water was added and then fermented.
The fermented dough was cooked into aceda (stiff porridge) called kissra-hamra.
The kissra-hamra, was then knead with the millet malt flour when it was cooled
to room temperature. About half an hour was given for amylolysis to proceed
to the correct degree before water (1:2 w/v) was added to further thin the batter
and the container incubated overnight for fermentation. The next morning the
batter was baked into sheets of kissra-kass, the kissra sheets were sun dried
and crumbled and finally pounded by mortar and pestle to coarse crystals of
Preparation of traditional and developed khemiss-tweria: The formulation of khemiss-tweria was carried out by mixing the coarse kissra-assala and roasted sesame seeds for the control sample in ratio of 6:1, kissra-assala and roasted peanuts in ratio of 6:1, kissra-assala, roasted sesame seeds and de-hulled Bambara groundnuts flour in ratio of 6:0.5:0.5 and kissra-assala, roasted peanuts and de-hulled Bambara groundnuts flour in ratios of 6:0.5:0.5 and designated as Kh1, Kh2, Kh3 and Kh4, respectively. Amount of 50 g sugar and 15 g salt were added to 1000 g of each of the above mixtures. Then the mixtures were well mixed to comprise the various types of khemiss-tweria. The produced samples were bottled and kept at room temperature for all further studies.
Sensory evaluation: A panel of fifteen members composed of darfurain
adults male and female were used to judge the quality of the different types
of khemiss-tweria. 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 khemiss-tweria 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).
Chemical analysis: Proximate analysis of de-hulled Bambara groundnuts,
peanuts, sesame seeds, pearl millet and the different types of khemiss-tweria
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). Total carbohydrate
content was calculated by subtracting the previous components from 100.
In vitro protein digestibility: In vitro protein digestibility
of de-hulled Bambara groundnuts and the different types of khemiss-tweria were
carried out according to the three-enzyme method as 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) was used in the determination.
Sample preparation: Twenty grams from Kh2 (6:1 (kissra:peanuts))
khemiss-tweria were defatted using hexane according to Coomes
et al. (1965). The residual solvent was dried off from the defatted
sample by heating in oven at 105°C for 30 min as described by Sulieman
et al. (2008). The moisture content of the defatted sample was carried
out according to AOAC (2005).
Toxin extraction: Ten grams from defatted Kh2 sample were
placed into a 250 mL conical flask then thoroughly mixed in 10 mL distilled
water using a glass rod. Hundred milliliters chloroform were then added and
the flasks were stoppered with a rubber plug coated with aluminum foil to protect
the rubber from the corrosive action of the chloroform. The flasks were shaken
for 30 min on a Griffin shaker to ensure good extraction. The contents of each
flask were shaken and filtered using Whatman No. 1 filter paper (24 cm). The
chloroform was then evaporated to dryness in a water bath (70°C). The dried
extracted sample was washed in 200 mL chloroform. Twenty five microliter of
the solution were spotted by a micro syringe on the prepared coated plates.
Twenty five milliliters of the standard samples (AFB1) were also
placed, an air dryer was used. The plates were developed on a solvent system
of toluene, acetic acid and formic acid at 6: 3: 1. AFB1 was visualized
under long wave UV light (366 nm); the mixture of AFB1 standard spot
and samples spots were combined to determine the concentration of AFB1.
The toxin extraction was carried out as described by Abdel-Hameed
(2000) and Sulieman et al. (2003, 2008).
Estimation of aflatoxin concentration: The visible fluorescence of the
sample was compared with AFB1 standard spots on the same chromatoplates.
If the spots of the smallest volume of sample were too intense to match with
the standards, the sample would be diluted and re-chromatographed. The concentration
of AFB1 in μg kg-1 was calculated according to Coomes
et al. (1965) as follows:
||Volume, in μL, of aflatoxin (μL) B1 standard
of equivalent intensity
||Concentration of aflatoxin B1 standard (μg mL-1)
||Volume, of solvent (μL) required to dilute the final extract
||Weight, of original sample (g) contained in final extract
||Volume, of sample (μL) required to give florescence intensity comparable
to that of S μL of the B1 standard
RESULTS AND DISCUSSION
Proximate analysis of de-hulled Bambara groundnuts flour, peanuts, sesame seeds and pearl millet flour showed that the contents of moisture and protein are higher than that of peanuts, sesame seeds and pearl millet flour as shown in Table 1.
The moisture, crude protein, ash, fat, crude fiber and total carbohydrate contents
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. However, 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 peanuts moisture content is (6.0±0.06%). The data is close agreement
to the value of (5.8%) that determined by Atasie et al.
(2009) and (5.7%) that reported by Boutros (1986).
The protein content (27.93±0.03%) falls within the range of (20-50%)
that reported by Nwokolo and Smartt (1996) and higher
than (26.7%) reported by Boutros (1986). Ash content (2.66±0.04%)
is lower than (3.8%) reported by Atasie et al. (2009)
and higher than (2.3%) that found by Boutros (1986). The
fat content (47.34±0.01%) is higher than (47.0%) that determined by Atasie
et al. (2009) and lower than (49.2%) that found by Boutros
(1986). The fiber content is (2.12±0.07%). The data is lower than
(3.70%) as found by Atasie et al. (2009). The
carbohydrate content (19.95±0.08%) is much higher than (1.81%) that reported
by Atasie et al. (2009) and (14.6%) that found
by Boutros (1986).The in vitro protein digestibility
(91.61±0.02%) is lower than (93.06±0.042%) reported by Elsheikh
and Mohamedzein (1998).
The moisture content of sesame seeds (3.5±0.05%) is lower than (5.8
and 4.59%) that reported by Joshi (1961) and Gopalan
et al. (1982), respectively. The protein content is (25.44±0.02%).
The value is higher than (19.30%) that reported by Joshi (1961)
and (18.30%) that found by Gopalan et al. (1982).
The ash content (4.48±0.05%) is lower than (5.2 and 5.7%) found by Gopalan
et al. (1982) and Joshi (1961), respectively.
The fat content is higher (50.15±0.02%). The fat content is lower than
(51.09%) reported by Joshi (1961) and higher than (43.3%)
determined by Gopalan et al. (1982). The carbohydrate
content is (15.58±0.01%). The data obtained is lower than (21.20%) found
by Joshi (1961) and (25%) that determined by Gopalan
et al. (1982).
The moisture content of pearl millet flour (7.38±0.04%) is lower than
the range of (10.09-10.95%) reported by Modu et al.
(2005) and (8.0%) that found by Boutros (1986).
||Chemical composition and in vitro protein digestibility
of de-hulled Bambara groundnuts, peanuts, sesame seeds and pearl millet
|DBGF: De-hulled Bambara ground nut flour, ND: Not determined
The protein content (11.74±0.06%) is within the range of (11.34-12.97%)
found by Modu et al. (2005) and higher than (9.7%)
reported by Boutros (1986). The ash content is (2.16±0.03%).
The data is higher than the range of (1.20-1.52%) determined by Modu
et al. (2005) and (1.7%) found by Boutros (1986).
The fat content (5.41±0.02%) is higher than the range of (3.67-4.51%)
determined by Modu et al. (2005) and lower than
(5.8%) found by Boutros (1986). The fiber content is (2.30±0.03%).
The value is higher than (2.0%) that reported by Boutros (1986).
The carbohydrates content (78.39±0.02%) is higher than the range of (70.15-72.52%)
that found by Modu et al. (2005) and lower than
(72.8%) that reported by Boutros (1986).
The proximate analysis and in vitro protein digestibility of the various types of khemiss-tweria are presented in Table 2.
There is slight variation in moisture contents of various types of khemiss-tweria
(4.25±0.02, 4.15±0.03 and 4.28±0.04%). The data are higher
than (4.0±0.03%) of control sample and lower than (8.32±0.14%)
reported by Ali et al. (2010). However, the low
moisture contents in the various types of khemiss-tweria, it is indication of
better quality and the long shelf life of the products. The protein contents
are increased (15.89±0.01, 23.55±0.03 and 24.19±0.03%).
The protein contents are higher than (15.06±0.02%) of control sample
and (10.87±0.21%) as reported by Ali et al.
(2010). However, there are concomitant increase in protein contents with
the additional increases of peanuts and de-hulled Bambara groundnut flour. The
estimated ash contents are decreased (4.08±0.02, 3.90±0.02 and
2.50±0.01%). The data are lower than (4.86±0.04%) of control sample
and exceeded the value of (2.20±0.26%) that reported by Ali
et al. (2010). The fat contents are decreased (9.44±0.01,
7.68±0.04 and 6.69±0.03%). The data are lower than (10.88±0.02%)
of control sample and higher than (7.94±0.2%) reported by Ali
et al. (2010). The crude fiber contents (2.19±0.01, 2.30±0.01
and 2.12±0.03%) are lower than (2.50±0.01%) of control sample
and (2.64±0.4%) that reported by Ali et al.
(2010). The carbohydrate contents are decreased; however, in case of (Kh2)
sample the carbohydrate content is increased. The in vitro protein digestibility
are decreased (80.60±0.03 and 75.52±0.02%); however, in case of
(Kh2) the in vitro protein digestibility is increased (93.16±0.04).
The contents of in vitro protein digestibility are comparable to the
findings of Ali et al. (2010) who reported a
value of (79.96-82.49%) for khemiss-tweria supplemented with seinat flour and
the finding of Suleiman et al. (2003) who reported value of (83.6-84.2%)
for cookies fortified with 10-30% of cow pea flour.
The Kh2 sample was not detected with aflatoxin (AFB1).
However, the data is agreement with that of (Sulieman et
al., 2008), who reported that roasting reduces the (AFB1)
levels in contaminated peanuts.
|| Chemical composition and in vitro protein digestibly
of different types of khemiss-tweria
|Kh1: 6:1 (kissra:sesame seeds) control sample,
Kh2: 6:1 (kissra:peanuts), Kh3: 6: 0.5:0.5 (kissra:sesame
seeds:de-hulled Bambara groundnuts flour), Kh4: 6: 0.5:0.5 (kissra:peanuts:de-hulled
Bambara groundnuts flour)
|| The mean scores for sensory attributes of different types
|Means based on 9 points scale (9 = excellent, 1 = extremely
bad), a,bMeans within the same columns having the
same letters are not significantly different according to the Duncan's multiple
range tests, Kh1: 6:1 (kissra:sesame seeds) control sample, Kh2:
6:1 (kissra:peanuts), Kh3: 6: 0.5:0.5 (kissra: sesame seeds:de-hulled
Bambara groundnuts flour), Kh4: 6: 0.5:0.5 (kissra:peanuts:de-hulled
Bambara groundnuts flour)
The mean score for sensory attribute of the different types of khemiss-tweria are presented in Table 3. The data indicated that there are no significant differences as regard to appearance, texture, flavour and overall acceptability. However, the panelist gave higher score for overall acceptance to the Kh2 (peanuts substituted) sample.
It could be concluded that, the nutritional quality of developed khemiss-tweria
is improved as a result of de-hulled Bambara groundnut flour supplementation
and peanuts and sesame seeds substitution.
We express our gratitude to the laboratories staff members of Food Technology Departments, Nyala Technical College and University of Gezira for their continuous assistance during the period of this study.
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