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Plant Foods for Human Nutrition 55: 97–110, 2000.
© 2000 Kluwer Academic Publishers. Printed in the Netherlands.
Effect of soaking, cooking and germination on the
oligosaccharide content of selected Nigerian legume
seeds
H.A. OBOH, M. MUZQUIZ∗, C. BURBANO,C. CUADRADO,
M.M. PEDROSA, G. AYET and A.U. OSAGIE1
Area de Tecnología de Alimentos, SGIT-INIA, Apdo. 8111, 28080 Madrid, Spain;
1Department of Biochemistry, University of Benin, P.M.B. 1154, Benin City, Nigeria (∗author
for correspondence)
Received 6 April 1999; accepted in revised form 15 January 2000
Abstract. The identity and quantity of and effect of processing on raffinose oligosacchar-
ides in raw, mature seeds of lima beans (Phaseolus lunatus), pigeon peas (Cajanus cajan),
African yam beans (Sphenostylis sternocarpa) and jackbeans (Canavalia ensiformis)were
investigated. Sucrose, raffinose, stachyose and verbascose were identified by HPLC in all
thelegumeseeds.Thetotalα-galactoside contents of the seeds in decreasing order were
African yam beans 3.84 mg/100 mg; white lima beans 3.62 mg/100 mg; cream pigeon peas
3.51 mg/100 mg; red lima beans 3.37 mg/100 mg; jackbeans 2.83 mg/100 mg and brown
pigeon peas 2.34 mg/100 mg. The predominant oligosaccharide was verbascose in pigeon
peas and stachyose in the other three legumes. Cooking unsoaked seeds brought about a
greater reduction in the total α-galactoside content than soaking for nine hours. The removal of
oligosaccharides was higher in legumes cooked in alkaline solution than in water. Germination
quantitatively reduced raffinose, stachyose and verbascose while sucrose was increased in all
seeds except red lima beans and jackbeans.
Key words: Legumes, Oligosaccharides, Processed, Raffinose, Stachyose, Verbacose
Introduction
Grain legumes are a major source of cheap protein for humans in West Africa.
Animal protein is expensive, therefore, supplementing the diet with legume
seeds helps to alleviate protein deficiency in human nutrition [1].
Lima beans, pigeon peas, African yam beans and jackbeans are under-
utilized legumes in Nigeria [2]. The chemical compositions of these grain
legumes were evaluated and shown to contain high quantities of proteins,
amino acids and minerals [3]. Despite the rich composition of nutrients, these
legumes are not normally selected as food sources because of their hard seed
coats which lead to long cooking periods and the use of expensive, scarce
98
fuels. Furthermore, the antinutritional factors in legume seeds reduce protein
digestibility [4] and the nutritive value [5].
Raffinose oligosaccharides (e.g., stachyose, raffinose and verbascose), are
present in legumes [6]. They produce flatulence in man and animals due to
the absence of the enzyme α-galactosidase which is needed for hydrolysis of
the α-1,6 galactosidic linkage of these oligosaccharides in the lower intest-
ine. These sugars then undergo anaerobic fermentation by bacteria producing
carbon dioxide, hydrogen and small amounts of methane gas that cause flat-
ulence which is characterized by abdominal rumblings, cramps, diarrhea and
nausea [7].
Plant breeding could be one approach to the reduction of flatulence; but
Ryan & Farmer [8] have suggested that oligosaccharides may play a role
in seed viability. Eliminating oligosaccharides from the plant itself could,
therefore, adversely affect the growth and yield of the legumes. In Nigeria,
legume seeds are processed and consumed in a variety of forms. The most
common domestic methods include soaking, cooking, cooking in alkali solu-
tion and dehulling. The effects of soaking, cooking and dehulling on the
oligosaccharide content of cowpeas have been reported [9]. The effects of
domestic processing on the oligosaccharide content of faba beans, lentils,
common beans and cowpeas have also been investigated [10]. Little inform-
ation is available, however, on oligosaccharide contents in legumes such as
lima beans and African yam beans. The reduction of flatulence is necessary
for the utilization of these legumes as more acceptable sources of inexpensive
protein.
The present investigation was aimed at identifiying and quantifiying the
oligosaccharide content after soaking in water, cooking of unsoaked and
soaked seeds, cooking of unsoaked seeds in 0.1% alkaline solution and ger-
mination of lima beans, pigeon peas, African yam beans and jackbeans and to
describe a method suitable for reducing flatus-producing factors in legumes.
Materials and methods
Red lima beans (Phaseolus lunatus), white lima beans (Phaseolus lunatus),
brown pigeon peas (Cajanus cajan), cream pigeon peas (Cajanus cajan),
black African yam beans (Sphenostylis sternocarpa) and jackbeans (Canava-
lia ensiformis) were bought from the market in the Uromi and Igueben areas,
Edo State, Nigeria. All bean samples were cleaned by hand, dried in an air
oven (Gallenkamp, UK) at 70 ◦C for five hours and milled to pass through
a 100-mesh sieve (Cyclotec 1093, Tecator AB, Sweden). All flour samples
were stored in air-tight plastic containers at –10 ◦C until analyzed.
99
Preparation of processed samples
Cooking (W/C): One hundred grams (100 g) of bean seeds were added to
distilled water (1:5 w/v) at 100 ◦C and cooked in a glass beaker on an electric
hot plate (Ikatherm HCT, Ika, Staufen, Germany) for 3 h.
Cooking in 0.1% alkaline solution (W/C/K): ‘Kanwa’ rock salt was pur-
chased from New Benin market, Benin City, Nigeria. The rock salt was ground
into fine powder in an analytical grinder (A10, Ika, Staufen, Germany) and
dried at 70 ◦C for 16 h in an oven (Gallenkamp, UK). The dried powder was
cooled in a desiccator for 24 h and stored in a stoppered glass bottle at 24 ◦C.
One hundred grams of bean seeds were added to boiling 0.1% Kanwa solution
(1:5 w/v) and cooked in a glass beaker on an electric hot plate (Ikatherm HCT,
Ika, Staufen, Germany) for 2.5 h. The pH of the Kanwa solution was 11.0.
Soaking and cooking (S12h/C): One hundred grams (100 g) of bean seeds
were soaked in a glass beaker for twelve hours in distilled water (1:5 w/v) at
24 ◦C. The soak water was discarded and the bean seeds were cooked in a
glass beaker on an electric hot plate (Ikatherm HCT, Ika, Staufen, Germany)
in fresh distilled water at 100 ◦C for 2.5 h. In all cooking processes, the level
of cooking water was kept constant by the addition of boiling distilled water
or 0.1% alkaline solution. The cooked seeds were drained and dried at 70 ◦C
in an oven (Gallenkamp, UK) for 16 h. The dried seeds were cooled in a
dessicator, milled to pass trough a 100-mesh sieve (Cyclotec 1093, Tecator
AB, Sweden). Bean flours were stored in an air-tight container at –10 ◦C
until analyzed (1 month aproximately).
Germination (S9h/G0-S9/G96): One hundred grams (100 g) of bean seeds
were surface sterilized for 30 min in a 1% sodium hypochlorite solution. The
bean seeds were rinsed five times with distilled water (1:3 w/v) and soaked
for 9 h in a glass beaker in tap water (1:3 w/v). The presoaked seeds were
allowed to sprout on sterile germinating trays lined with filter paper which
was kept moist by layers of damp cotton wool. Germination was carried out
at 25 ◦C with 8 h of daylight per day. Samples were collected at 0 h (control),
12 h, 24 h, 48 h, 72 h and 96 h. The germinating seeds were dried and milled
into flour, as indicated above for cooked samples.
Extraction and evaluation of α-galactosides from bean flour
Oligosaccharides were extracted and analyzed as described by Muzquiz et al.
[11]. The sample (0.5 g) was homogenized in aqueous ethanol (80%, 5 ml)
for1minat24◦
C using an Ultraturrax homogenizer (T25, Ika, Staufen, Ger-
many). The mixture was centrifuged (Econospin, Sorvall Instrument, USA)
100
for 5 min at 500 g. The supernatant was decanted and the procedure repeated
twice. The combined supernatants were evaporated to dryness in a rotary
evaporator (Rotavapor R-3000, Büchi, Switzerland) connected with a vacuum
controller (Vacobox B-171, Büchi, Switzerland) at 35 ◦C and redissolved
in 1 ml double deionized water. The extracts were passed through Dowex
50 WX8 (200–400 mesh, Serva, Germany) and QMA minicolumns (Waters,
USA) with a Supelco vacuum system (Bellefonte, PA, USA). Water (3 ×
1 ml portions) was added to flush the columns and the combined extracts and
washings were collected and injected (20 µl) into the HPLC system.
Samples were analyzed using a Beckman System Gold Instrument (USA)
composed of a pump (Programmable Solvent M 126), a refractive index de-
tector (M 156), an Analog Interface (M 406), an injection valve (Altex) and
the System Gold Software for integration. A Spherisorb-5-NH2column (250
x 4.6 mm i.d., Waters, USA) was employed with acetonitrile/water (65:35,
v/v) at 1 ml/min as the mobile phase. Individual sugars were quantified by
comparison with external standards of pure sucrose, raffinose and stachyose
(Sigma, St. Louis, MO, USA); verbascose was supplied and purified by Prof
K Gulewicz. Calibration curves were constructed for all four sugars and a
linear response was evident for the range of 0–5 mg/ml with a correlation
coefficient of 0.99. Two extractions were made for each flour sample and one
injection for each extract.
Statistical analysis. The data were analyzed for variance using a BMDP–
7D ANOVA program (WJ Dixon, BMDP Statistical Software Release, 1988).
The mean values were compared using Duncan’s multiple range test. Signi-
ficance was accepted at p60.05 level.
Results and discussion
The total galactoside contents and the different types of raffinose oligosac-
charides present in the raw bean seeds are shown in Table 1. HPLC revealed
the presence of sucrose, raffinose, stachyose and verbascose.
Stachyose was found to be the predominant sugar in lima beans, jack-
beans and African yam beans while verbascose was the predominant oli-
gosaccharide in pigeon peas. Similar results were reported by Revilleza et al.
[12] in lima beans and jackbeans. The results revealed significant (p<0.05)
differences between species and varieties of the raw bean seeds. The low-
est oligosaccharides content was found in brown pigeon peas and jackbeans
(2.35 mg/100 mg and 2.83 mg/100 mg, respectively). Brown pigeon peas
and cream pigeon peas had an oligosaccharides content that was significantly
(p<0.05) different, while red and white lima beans were not significant
101
Table 1. Composition of α-galactosides of raw of lima beans, pigeon peas, African yam beans and jackbeans
(mg/100 mg)1
Sample Sucrose Raffinose Stachyose Verbascose Total
galactosides
Lima beans
(Red) 0.806 ±0.021 0.297 ±0.016 2.829 ±0.077 0.246 ±0.063 3.372 ±0.002 a
Lima beans
(White) 0.770 ±0.018 0.277 ±0.016 3.157 ±0.112 0.194 ±0.011 3.628 ±0.085 a,b
Pigeon Peas
(Brown) 1.186 ±0.149 0.423 ±0.057 0.857 ±0.065 1.067 ±0.110 2.346 ±0.232
Pigeon peas
(Cream) 1.666 ±0.012 0.620 ±0.003 1.562 ±0.070 3.517 ±0.079 a,b
African
Yam beans 1.090 ±0.003 0.664 ±0.002 2.863 ±0.036 0.317 ±0.027 3.844 ±0.011 b
Jackbeans 1.443 ±0.260 0.284 ±0.012 2.298 ±0.038 0.248 ±0.016 2.830 ±0.034
1Values are means ±standard error of two determinations. Means followed by the same superscripts are not
signicantly different at 5% level by Duncan’s multiple range test.
102
(p> 0.05) different. These results agree with those reported by Burbano et
al. [13] who established that oligosaccharide content was influenced by both
variety and environment.
Effects of processing on legume oligosaccharides
The effects of processing on the sugars and total α-galactoside contents of the
legumes are shown in Tables 2–7. Cooking in water (W/C) resulted in a loss
of total α-galactosides ranging from 21% in brown pigeon peas (Table 4) to
a 67% in white limas (Table 3) compared to the corresponding raw samples.
Cooking in 0.1% alkaline solution produced a significantly (p<0.05) higher
reduction of total α-galactosides, in relation to the content of raw seeds, in all
seeds except white lima beans. Both processes involved cooking; therefore,
these reductions may have been due to heat induced hydrolysis of the oli-
gosaccharides to simple disaccharides and monosaccharides [14]. The current
findings are in agreement with those reported for cowpeas [15]. The greatest
losses in total oligosaccharide content of alkaline-cooked samples compared
to water-cooked samples may have been due to the fact that the alkaline
medium aids leaching and solubility of sugars during cooking.
The combined effects of soaking and cooking (S12h/C) led to increased
sugar losses in most of the legumes studied, which is in agreement with data
reported by Uzogara et al. [16]. The total α-galactosides content of soaked
and cooked seeds was significantly (p<0.05) lower than water-cooked seeds
of brown pigeon peas (Table 4), cream pigeon peas (Table 5) African yam
beans (Table 6) and jackbeans (Table 7). In contrast, Rao and Belavady [17]
reported an increase ranging from 30% to 100% in oligosaccharide content
after cooking. The difference could be explained by the fact that the cooking
water was not discarded in the study by Rao & Belavady [17] whereas in the
current study and that of Iyer et al. [18], the soak and cooking waters were
eliminated as is commonly practiced.
Soaking for nine hours (S9h/G0) reduced the total α-galactoside contents
of the seeds to different extents. Losses of 2% in jackbeans (Table 7) and 58%
in cream peas (Table 5) were observed when compared with raw seeds. These
losses were significant (p<0.05) for all seeds except red lima (Table 2) and
jackbeans (Table 7). This could be a result of the relative hardness of the seed
coat which limits the uptake of water and may prevent the leaching of the α-
galactosides into the soak water. Significant reductions in the α-galactoside
contents of soaked common beans, including cowpeas, lentils and faba beans,
were reported by Abdel-Gawad [10]; the extent of the losses was enhanced
as the soaking time increased.
Tables 2–7 data also show the changes in total and individual α-galac-
tosides due to germination. Stachyose declined progressively until 96 h of
103
Table 2. The composition of α-galactosides (mg/100 mg)1of raw, processed and germinated red lima beans
(Phaseolus lunatus)
Treatments Sucrose Raffinose Stachyose Verbascose Total
galactosides
Raw 0.806 ±0.021 0.297 ±0.016 2.829 ±0.077 0.246 ±0.063 3.372 ±0.002 g
W/C 0.232 ±0.011 0.123 ±0.013 1.614 ±0.005 0.100 ±0.010 1.837 ±0.008 c,d,e
W/C/K 0.274 ±0.021 0.087 ±0.010 1.043 ±0.054 n.d.21.130 ±0.064 a,b
S12h/C 0.392 ±0.024 0.182 ±0.017 1.447 ±0.027 0.106 ±0.006 1.735 ±0.050 c,d
Germination
S9h/G0 0.818 ±0.042 0.305 ±0.013 2.830 ±0.027 0.124 ±0.009 3.259 ±0.049 g
S9h/G12 0.467 ±0.007 0.166 ±0.011 1.950 ±0.060 0.116 ±0.005 2.232 ±0.076 e,f
S9h/G24 0.403 ±0.012 0.143 ±0.003 1.658 ±0.065 0.120 ±0.009 1.921 ±0.072 d,e
S9h/G48 0.400 ±0.005 0.136 ±0.002 1.680 ±0.008 0.113 ±0.000 1.929 ±0.009 d,e
S9h/G72 0.344 ±0.005 0.124 ±0.001 1.334 ±0.023 n.d. 1.458 ±0.024 b,c
S9h/G96 0.231 ±0.003 0.103 ±0.006 0.830 ±0.039 0.137 ±0.009 1.070 ±0.024 a,b
1Values are mean ±standard deviation of duplicate determinations.
2n.d.: not detected.
W/C: cooking, W/C/K: cooking in 0.1% alkaline solution, S12/C: soaking and cooking, S9h/G0-S9h/G96:
germination. Means followed by the same superscripts are not significantly different at 5% level by Duncan’s
multiple range test.
104
Table 3. The composition of α-galactosides (mg/100 mg)1of raw, processed and germinated white lima
beans (Phaseolus lunatus)
Treatments Sucrose Raffinose Stachyose Verbascose Total
galactosides
Raw 0.770 ±0.018 0.277 ±0.016 3.157 ±0.112 0.194 ±0.011 3.628 ±0.085
W/C 0.294 ±0.004 0.162 ±0.007 1.013 ±0.014 n.d.21.176 ±0.007
W/C/K 0.526 ±0.012 0.173 ±0.003 1.383 ±0.007 0.100 ±0.001 1.656 ±0.009 c
S12h/C 0.340 ±0.011 0.179 ±0.000 1.078 ±0.004 0.085 ±0.007 1.342 ±0.010
Germination
S9h/G0 0.349 ±0.015 0.309 ±0.014 1.927 ±0.011 0.180 ±0.007 2.416 ±0.032
S9h/G12 1.090 ±0.022 0.239 ±0.003 1.155 ±0.006 0.137 ±0.037 1.531 ±0.027 c
S9h/G24 1.255 ±0.002 0.230 ±0.025 1.678 ±0.055 0.128 ±0.018 2.036 ±0.098
S9h/G48 2.120 ±0.239 0.077 ±0.006 0.570 ±0.031 n.d. 0.647 ±0.025 b
S9h/G72 2.952 ±0.037 0.056 ±0.000 0.514 ±0.013 n.d. 0.570 ±0.013 b
S9h/G96 3.107 ±0.047 n.d. 0.402 ±0.071 n.d. 0.402 ±0.071 a
1Values are mean ±standard deviation of duplicate determinations.
2n.d.: not detected.
W/C: cooking, W/C/K: cooking in 0.1% alkaline solution, S12/C: soaking and cooking, S9h/G0-S9h/G96:
germination. Means followed by the same superscripts are not significantly different at 5% level by
Duncan’s multiple range test.
105
Table 4. The composition of α-galactosides (mg/100 mg)1of raw, processed and germinated brown pigeon
peas (Cajanus cajan)
Treatments Sucrose Raffinose Stachyose Verbascose Total
galactosides
Raw 1.186 ±0.149 0.423 ±0.057 0.857 ±0.065 1.067 ±0.110 2.346 ±0.232
W/C 1.770 ±0.024 0.454 ±0.007 0.755 ±0.005 0.648 ±0.023 1.858 ±0.036 d
W/C/K 1.445 ±0.054 0.377 ±0.036 0.603 ±0.002 0.457 ±0.004 1.436 ±0.039 c
S12h/C 1.439 ±0.009 0.358 ±0.003 0.508 ±0.000 0.379 ±0.001 1.245 ±0.005 c
Germination
S9h/G0 1.155 ±0.046 0.268 ±0.008 0.670 ±0.008 0.821 ±0.010 1.759 ±0.007 d
S9h/G12 1.201 ±0.016 0.152 ±0.003 0.544 ±0.017 0.652 ±0.009 1.348 ±0.011 c
S9h/G24 2.254 ±0.036 n.d.20.436 ±0.016 0.178 ±0.004 0.614 ±0.020 b
S9h/G48 2.306 ±0.030 0.060 ±0.009 0.350 ±0.016 0.181 ±0.018 0.591 ±0.008 b
S9h/G72 3.079 ±0.153 n.d. 0.485 ±0.049 0.120 ±0.005 0.605 ±0.054 b
S9h/G96 1.913 ±0.110 n.d. 0.473 ±0.023 n.d. 0.473 ±0.023 a,b
1Values are mean ±standard deviation of duplicate determinations.
2n.d.: not detected.
W/C: cooking, W/C/K: cooking in 0.1% alkaline solution, S12/C: soaking and cooking, S9h/G0-S9h/G96:
germination. Means followed by the same superscripts are not significantly different at 5% level by Duncan’s
multiple range test.
106
Table 5. The composition of α-galactosides (mg/100 mg)1of raw, processed and germinated cream pigeon
peas (Cajanus cajan)
Treatments Sucrose Raffinose Stachyose Verbascose Total
galactosides
Raw 1.666 ±0.012 0.620 ±0.003 1.335 ±0.006 1.562 ±0.070 3.517 ±0.079
W/C 1.796 ±0.276 0.423 ±0.069 0.596 ±0.000 0.629 ±0.108 1.350 ±0.121 c
W/C/K n.d.2n.d. 0.367 ±0.044 0.135 ±0.000 0.434 ±0.023 a,b
S12h/C 0.876 ±0.019 0.039 ±0.003 0.390 ±0.014 0.417 ±0.011 0.846 ±0.027
Germination
S9h/G0 1.362 ±0.013 0.033 ±0.004 0.632 ±0.032 0.824 ±0.040 1.489 ±0.076 c
S9h/G12 1.773 ±0.099 0.034 ±0.006 0.684 ±0.039 0.742 ±0.059 1.460 ±0.092 c
S9h/G24 2.603 ±0.049 n.d. 0.159 ±0.006 0.224 ±0.012 0.383 ±0.018 a
S9h/G48 2.879 ±0.045 n.d. 0.150 ±0.002 0.172 ±0.002 0.321 ±0.004 a
S9h/G72 3.199 ±0.189 n.d. 0.371 ±0.002 n.d. 0.371 ±0.002 a
S9h/G96 2.176 ±0.085 n.d. 0.597 ±0.015 n.d. 0.597 ±0.015 b
1Values are mean ±standard deviation of duplicate determinations.
2n.d.: not detected.
W/C: cooking, W/C/K: cooking in 0.1% alkaline solution, S12/C: soaking and cooking, S9h/G0-9h/G96:
germination. Means followed by the same superscripts are not significantly different at 5% level by Duncan’s
multiple range test.
107
Table 6. The composition of α-galactosides (mg/100 mg)1of raw, processed and germinated African yam
beans (Sphenostylis stenocarpa)
Treatments Sucrose Raffinose Stachyose Verbascose Total
galactosides
Raw 1.090 ±0.003 0.664 ±0.002 2.863 ±0.036 0.317 ±0.027 3.844 ±0.011
W/C 1.124 ±0.105 0.669 ±0.076 1.746 ±0.104 0.142 ±0.038 2.558 ±0.218 e
W/C/K 0.705 ±0.021 0.183 ±0.025 0.757 ±0.033 0.081 ±0.025 1.021 ±0.033 b,c
S12h/C 0.603 ±0.008 0.102 ±0.011 0.560 ±0.041 n.d.20.663 ±0.030 a
Germination
S9h/G0 1.086 ±0.058 0.423 ±0.018 2.403 ±0.099 0.214 ±0.022 3.040 ±0.095 f
S9h/G12 1.170 ±0.062 0.403 ±0.038 1.962 ±0.062 0.223 ±0.000 2.588 ±0.100 e
S9h/G24 0.948 ±0.029 0.433 ±0.008 2.583 ±0.009 0.220 ±0.017 3.235 ±0.000 f
S9h/G48 1.191 ±0.015 0.341 ±0.009 1.708 ±0.012 0.190 ±0.015 2.238 ±0.037
S9h/G72 1.752 ±0.207 0.166 ±0.023 1.085 ±0.002 0.163 ±0.021 1.414 ±0.046 d
S9h/G96 1.394 ±0.144 0.145 ±0.004 0.801 ±0.027 0.138 ±0.002 1.085 ±0.029 c
1Values are mean ±standard deviation of duplicate determinations.
2n.d.: not detected.
W/C: cooking, W/C/K: cooking in 0.1% alkaline solution, S12/C: soaking and cooking, S9h/G0-S9h/G96:
germination. Means followed by the same superscripts are not significantly different at 5% level by Duncan’s
multiple range test.
108
Table 7. The composition of α-galactosides (mg/100 mg)1of raw, processed and germinated jackbeans
(Canvalia ensiformis)
Treatments Sucrose Raffinose Stachyose Verbascose Total
galactosides
Raw 1.443 ±0.260 0.284 ±0.012 2.298 ±0.038 0.248 ±0.016 2.830 ±0.034 d
W/C 1.068 ±0.009 0.070 ±0.007 1.073 ±0.017 0.152 ±0.001 1.295 ±0.025
W/C/K 0.838 ±0.038 0.059 ±0.012 0.965 ±0.012 0.107 ±0.006 1.131 ±0.018
S12h/C 0.523 ±0.050 0.030 ±0.000 0.638 ±0.002 0.082 ±0.025 0.750 ±0.023 b,c
Germination
S9h/G0 1.531 ±0.006 0.369 ±0.021 2.207 ±0.035 0.208 ±0.014 2.784 ±0.042 d
S9h/G12 0.748 ±0.003 0.152 ±0.005 1.158 ±0.043 0.131 ±0.005 1.441 ±0.043
S9h/G24 0.981 ±0.051 0.052 ±0.001 0.778 ±0.008 0.033 ±0.033 0.863 ±0.024 c
S9h/G48 0.999 ±0.028 0.030 ±0.005 0.617 ±0.087 n.d.20.647 ±0.091 b
S9h/G72 0.812 ±0.020 n.d. 0.516 ±0.004 n.d. 0.516 ±0.004 a
S9h/G96 0.385 ±0.001 n.d. 0.485 ±0.043 n.d. 0.485 ±0.043 a
1Values are mean ±standard deviation of duplicate determinations.
2n.d.: not detected.
W/C: cooking, W/C/K: cooking in 0.1% alkaline solution, S12/C: soaking and cooking, S9h/G0-S9h/G96:
germination. Means followed by the same superscripts are not significantly different at 5% level by Duncan’s
multiple range test.
109
germination in lima beans, African yam beans and jackbeans achieving re-
ductions higher than 70% relative to the raw seeds. In brown and cream
pigeon peas, verbascose was completely eliminated at 96 h of germination
while stachyose was reduced around a 50% (Tables 4 and 5). Raffinose and
verbascose exhibited a similar trend during the germination of red lima beans
(Table 2), white lima beans (Table 3), African yam beans (Table 6) and jack-
beans (Table 7), being completely eliminated at 96 hours in white lima beans
and jackbeans. Sucrose levels increased during germination of white lima
beans, brown pigeon peas, cream pigeon peas and African yam beans (Tables
3–6). Conversely, red lima beans and jackbean seeds (Tables 2 and 7, respect-
ively) had decreased sucrose levels as the period of germination increased as
has been reported for germinating soybeans and cottonseeds [19].
The changes in total α-galactoside content, due to germination, indicated
that there were significant (p<0.05) reductions in all the germinating seeds.
In general, the greatest losses of total α-galactosides were obtained at 96 h of
germination. Similar findings have been reported for related legumes such as
black gram and mung beans [20]. Oligosaccharides of the raffinose family
are degraded by α-galactosidase which selectively cleaves galactose from
raffinose, stachyose and verbascose leaving behind sucrose. Different legume
seeds have variable levels of α-galactosidase activity [7]. The fact that sucrose
decreased during germination of red lima beans and jackbeans indicated that
sucrose, in addition to α-galactosides, can be degraded to release energy for
the germinating embryo.
It may be concluded that all the local methods of processing substantially
reduced raffinose family oligosaccharides in the grain legumes studied. Ger-
mination and cooking in alkaline medium caused the greatest losses of total
α-galactosides.
Acknowledgments
The authors are grateful for support from the INIA (SC95-004-C5). One
of the authors (H.A.O.) was supported by a grant from AECI of the Span-
ish Ministry of Asuntos Exteriores. The authors wish to thank the INIA for
awarding postdoctoral grants to C.C. and M.M.P.
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