Proximate Composition and Nutritional Evaluation of Underutilized Legume Psophocarpus tetragonolobus (L.) DC. Grown in Manipur, Northeast India
Psophocarpus tetragonolobus (L.) DC. (Winged bean), a lesser known nutritious leguminous plant is grown luxuriantly in Manipur State, North-east India. Almost all the plant parts; leaves, flowers, immature pods, matured seeds and tubers are edible. Winged bean plant parts viz., seeds (tender, matured and fully matured seed), pods case (tender, matured and fully matured pod case) and tubers were chemically analysed on dry weight basis. The concentration of crude protein, fat, and fibre, total sugar, reducing and non-reducing sugars, starch, total amino acid and minerals (Ca, K, Mg, Fe, Zn, Mn, Cu and Co) were analysed. The results indicated that the highest crude fat (1.7%) was present in mature seed and crude protein was present in fully mature seed (50.7%). The maximum amounts of total sugar (488.90 mg g-1), non-reducing sugar (415.95 mg g-1) and starch (420.60 mg g-1) were recorded in tuber. The plant was also found to have significant quantity of minerals. As regard to the mineral content, mature pod case showed the maximum amount of K (8.9 mg g-1), Ca (8.06 mg g-1) and Mg (5.72 mg g-1). Thus, among the stages taken for analysis, mature pod case contains the maximum amount of macro- and micro-elements. So P. tetragonolobus has got a great future prospect, if properly exploited may serve as a supplementary source of protein and minerals, as a subsidiary food material in Manipur.
May 04, 2012; Accepted: May 19, 2012;
Published: June 29, 2012
In the quest for newer plant sources to combat protein-calorie malnutrition
in developing countries, the winged bean (Psophocarpus tetragonolobus)
with its versatile attributes has received special attention. The entire plant,
from flowers and leaves to tuberous roots and seeds, is fit for human consumption.
The nutritional advantages of winged bean lie in its seeds which possess protein
and oil contents equivalent to that of soybeans. It is now being grown in more
than 70 countries where it has met with varied success depending upon the prevailing
climate and edaphic conditions (Misra et al., 1987).
The winged bean has aroused great interest in recent years as a protein source.
NAS of the United States of America (NAS, 1981) reported
that winged bean is a promising source of protein and oil. Banerjee
(1985) reported the nutritional potential of the winged bean. Misra
et al. (1987) reported the assay of some nutritional and antinutritional
factors in different cultivars of winged bean seeds of different regions. Kantha
et al. (1986) studied the nutrient, antinutrient contents and solubility
profiles of nitrogen, phytic acid and selected minerals in winged bean flour
grown in Sri Lanka. Mnembuka and Eggum (1995) compared
the nutritive value of winged bean and other legumes grown in Tanzania. Amoo
et al. (2006) evaluated the chemical value of winged beans, Pitanga
cherries and orchid fruit. Khomdram et al. (2011)
also gave the dietary values of eight selected herbs of Lamiaceae which are
commonly utilized by Manipur, having high content of potassium, nitrogen, magnesium
and calcium on dry weight basis. Several studies have indicated the high nutritive
value of winged bean seeds.
Winged bean is locally known as Tengnou-manbi in Manipur and constitutes as
a favourite supplementary delicacy. The purpose of utilization of this legume
is oriented only by traditional boundaries i.e., curries like Iromba and Singju
(salads) and people regard them with less importance. Manipur state which extends
between 23°59'N-25°47'N and between 92°59'E-94°46'E with total
geographical area of 23,327 km2, lies in the North-eastern part of
India and falls under Indo-Myanmar hotspot regions of the world (Myers
et al., 2000). Exploitation of underutilized legumes is an important
approach to combat the protein-malnutrition in developing countries. The present
research programme aimed in providing basic information on the proximate and
mineral composition of underexploited and underutilized winged bean of Manipur.
MATERIALS AND METHODS
Winged bean seeds collected locally were grown experimentally in field. The
seeds were sown in May, 2008. The first flowering was observed in September,
2008. Sampling of the plants were conducted at three stages where they could
be best utilised i.e., (i) Tender Pod Case (TPC) stage (8 days after flowering),
(ii) Matured Pod Case (MPC) stage (14 days after flowering) and (iii) Fully
Matured Pod Case (FMPC) stage (25 days after flowering), the seeds were categorized
into three stages (i) Tender Seed (TS), (ii) Matured Seed (MS), (iii) Fully
Matured Seed (FMS) and (iv) Tuber (after one year of growth). All these pods,
seeds and tuber at different stages of development were taken and analyzed separately
||Plant parts of Psophocarpus tetragonolobus (L.) DC,
(a) Climbing habit, (b) Flower, (c) Pods, (d) Dissected pod showing seeds
arrangement, (e) Tuberous root and (f) Different stages of pods
Plant samples were air dried at 24±1°C and ground with a Remi grinder
and sieved (1 mm). The powder samples were stored in desiccators at room temperature
at 24±1°C until analysis. The following determinations were performed
on the flour samples of the plant.
Estimation of proximate composition: The moisture content was determined
by drying in an oven at 80°C for 24 h and is expressed on a percentage basis.
Crude fat content was determined using Soxhlet apparatus method. Crude protein
content in plant sample was estimated by the Kjeldahl method (Gupta,
2006). Crude fibre was determined by acid and alkaline digestion method
following the procedures of Chopra and Kanwar (1980).
Estimation of carbohydrates, amino acids and proteins: Different methods
were followed for estimation of total soluble sugar, reducing sugars, non-reducing
sugars and starch. Total soluble sugar was estimated following the method of
Dubois et al. (1951). Reducing sugars was estimated
by dinitrosalicylic method following the procedures described by Sadasivam
and Manikam (1992). Estimation of non reducing sugars was estimated following
Malhotra and Sarkar (1979). Starch was analysed by following
method of Anthrone reagent described by Thimmaiah (2006).
The total free amino acid was estimated by following method of Moore
and Stein (1948). The total soluble protein content was estimated by the
method of Lowry et al. (1951).
Estimation of minerals: Wet digestion method of Capar
et al. (1978) was followed for the analysis of different minerals.
K was estimated in a systronics-105 flame photometer. Sulphur and Phosphorus
were estimated in a UV-VIS double beam Spectrophotometer following the procedures
described by Murthy (2006) and Gupta
(2006). Ca, Mg, Mn, Zn, Fe, Cu and Co was analyzed by using Perkin Elmer
atomic absorption spectrophotometer, Analyst AA-200.
Statistical analysis: The data obtained were statistically analyzed with one-way ANOVA. Comparison of means was performed using Tukeys HSD test (SPSS.16). Significance differences between means were determined at p<0.05. The data were reported as means and ±Standard Deviation (SD).
RESULTS AND DISCUSSION
The proximate composition and biochemical constituents of the winged bean parts
at different three stages are given in Table 1. It was observed
that the crude fat ranged from 0.47% in FMS and FMPC to 1.7% in MS. Higher value
of crude protein (50.7%) was found in FMS while minimum value of crude protein
(17%) was noticed in tuber which was higher than values reported by Banerjee
(1985), Tadera et al. (1984) and Amoo
et al. (2006). The crude protein present in seed is close proximity
with the value reported by Cerny et al. (1971).
The crude fat content was highest in case of MS (1.7%) and minimum in FMS and
FMPC (0.47%). At maturity the pod start drying up and thus decrease in fat content.
All the samples showed variation in crude fibre contents ranging from 2.76 to
24.58% (Table 1). In the present study the crude fibre content
of the seed samples (5.55 to 12.65%) are in close proximity with those of winged
bean seed (6.12 to 8.73%) reported by Misra et al.
(1987). The value of crude fibre is also comparable to the value reported
by Cerny et al. (1971). Gajameragedera
and Ravindran (1989) reported that crude fibre of seed ranged from 6.1 to
8.8%. As the maturity proceeds, the crude fibre content increases from TS to
FMS (5.55 to 12.65%) and also increased from 19.01 to 24.58% (TPC-FMPC) in pod
case (Table 1).
||Proximate and biochemical constituents in different plant
parts of Psophocarpus tetragonolobus
|-: Not done, values are Means in the same row followed by
the same superscripts are not significantly different at the 5% level of
In the present investigation, the amount of crude protein and crude fat increased
significantly because of the maturity. The higher amount of crude protein was
recorded in case of MPC (44.6%) and in MS (47.2%) (Table 1).
The low crude fibre content of MPC (21.86%) and MS (8.57%) amongst the plant
stages makes the mature pod palatability. The total sugar was found to be highest
in tuber (488 mg g-1) and minimum in case of TPC (62.6 mg g-1).
Starch content in tuber (420.6 mg g-1) is similar to that of potato
reported by Tadera et al. (1984). Among all the
seeds, the fully mature seed of winged bean was the highest (396.10 mg g-1)
value of starch. As the maturity approaches, the total amino acid increases
from 33.5 to 64.6 mg g-1. The FMS contains maximum amount of total
soluble protein (152.70 mg g-1) content and minimum values found
in FMPC (41.30 mg g-1) (Table 1).The maximum and
minimum reducing sugar content ranged from 115 mg g-1 in FMS to 73.0
mg g-1 in tuber. The values of non-reducing sugar varied from 5.50
mg g-1 in TPC to 415.95 mg g-1 in tuber.
Figure 2 and 3 show the mineral contents
in different parts of winged bean which is expressed on dry weight basis as
mg g-1. Singh et al. (2009) also supported
the view that, different legumes differ widely in their mineral composition.
In the present study, the K content (5.60 to 8.9 mg g-1) was the
most abundant mineral in all the parts of the stages. This was in agreement
with the observations of Amoo et al. (2006) and
Gajameragedera and Ravindran (1989). Mg content ranks
next to K in abundance in all the stages. Winged bean seeds, pod without seeds
and tuber contain significant amounts of minerals during all the developmental
stages. The K content of the samples used in this study are generally low compared
to K content of winged bean (8.00 to 10.55 mg g-1) as reported by
Gajameragedera and Ravindran (1989). However, appreciably
higher value of K (4.219 mg g-1) in winged bean had been reported
by Amoo et al. (2006). The values of sulphur content
in the samples are generally low with least value as 0.10 mg g-1
in tuber. The value of Ca content ranges from 2.79 mg g-1 (TS) to
8.06 mg g-1 (MPC). These values were within the ranged with that
of the values reported by Gajameragedera and Ravindran (1989).
||Macro-element contents in different parts of Psophocarpus
tetragonolobus on a dry weight basis
||Micro-element contents in different parts of Psophocarpus
tetragonolobus on a dry weight basis
There is significant difference in the P content of the seeds with highest
values found in tender seed (3.57 mg g-1) and lowest values in tuber
(0.17 mg g-1). These values are comparatively lower than those values
reported by Gajameragedera and Ravindran (1989). Mg
contents of 2.49 mg g-1 (FMS) to 5.72 mg g-1 (MPC) of
all the stages are higher than the ranged in winged bean (1.95 to 2.46 mg g-1)
reported by Gajameragedera and Ravindran (1989). The
Zn content 0.12 mg g-1 (FMS) to 0.32 mg g-1 (MPC) in the
seeds and pods are considerably lower than the values reported by Amoo
et al. (2006) for seeds of Psophocarpus tetragonolobus (364.76
mg kg-1), Eugenia uniflora (273.34 mg kg-1) and
orchid fruit Myristica (310.74 mg kg-1) but higher than those
contents reported by Gajameragedera and Ravindran (1989).
The pods and seeds are relatively low in Mn content (0.13-0.34 mg g-1).
The trace element reported by Gajameragedera and Ravindran
(1989) is comparatively low. The Fe contents are relatively low, ranging
from 1.33 mg g-1 in fully mature seed to 3.33 mg g-1 in
mature pod case. The values of Cu content in the samples are generally low with
the highest values as 0.56 mg g-1 in mature pod case and the least
value as 0.19 mg g-1 in tender pod case. And no marked differences
were observed with regard to the trace minerals. Among all the stages the mature
pod contain maximum amounts of K (8.9 mg g-1), Ca (8.06 mg g-1),
Mg (5.72 mg g-1) and the least concentration of K (5.60 mg g-1)
and Mg (2.49 mg g-1) was found in FMS where Ca (2.57 mg g-1)
content was found to be minimum in MS. The content of trace-elements are also
found maximum in MPC with the values of Fe (3.33 mg g-1), Zn (0.32
mg g-1), Mn (0.34 mg g-1), Cu (0.56 mg g-1)
and Co (0.04 mg g-1) and minimum in FMS with values of Fe (1.33 mg
g-1), Zn (0.12 mg g-1), Mn (0.13 mg g-1). At
the maturity mostly the content of elements showed slightly high and then decline
at fully matured stage. Phosphorus and sulphur are found to be decrease with
maturity in all the stages. Thus, among all the stages taken for analysis, mature
pod contains the maximum amount of macro-elements and micro-elements.
In the present study, the winged bean which is a common leguminous plant is
taken by the people of Manipur as vegetables. The plant is found to have significant
amount of protein, carbohydrates, amino acid and minerals and higher amount
of starch. Potassium is found to be maximum among the minerals. This legume
is available at cheaper rate than other preferred legume by the local people.
The analytical data suggests that the nutritive winged bean seed can be used
as a food source. The bean merits wider use in India and other parts of the
Tropics. As its nutritive value is remarkably similar to soybean in view of
its nutritional potential, concentrated effort are needed to popularise this
economical, protein rich legume as a vegetable for an economically backward
state like Manipur.
Authors are grateful to the Head, Centre for Advanced Study in Life Sciences Department, Manipur University and to the Head, Biochemistry Laboratory, College of Agriculture, Central Agriculture University for providing all facilities and encouragements during the research programme.
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