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Dehydration for Better Quality Value Added Product of Bitter Gourd (Momordica charantia L.)

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An experiment was carried out to evaluate the dehydration and rehydration characteristics of bitter gourd (Momordica charantia L.) fruits. The slices of bitter gourd were blanched in boiling water and steam for 1, 2 and 3 minutes respectively. The slices were then dried at 65°C, 60°C and 55°C in a cabinet dryer up to constant moisture content.After final dehydration, rehydration for 10minutes, 20minutes, 30minutes, 50minutes, 70minutes and 90 minutes were undertaken respectively. There were seven treatments, replicated thrice and experiment was laid out in completely randomized design. The moisture content declined rapidly in bitter gourd rings dried at 65°C.The rehydration ratio recorded was 6.42, coefficient of rehydration was 13.91 and percent water in rehydrated sample was 88.14% respectively in water blanched samples. Hence, it is concluded that, among the three drying temperatures and two blanching methods, better dehydration and rehydration characters were reported in samples dried at 60°C and blanched in water for 2 minutes.
*Corresponding Author: Donal Bhattacharjee, Department Of Post harvest technology of Horticulture crops, Faculty of
horticulture, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur,Nadia,West Bengal, India 39
Indian J. Pharm. Biol. Res. 2016; 4(4):39-45
Research article
Dehydration for Better Quality Value Added Product of Bitter Gourd (Momordica charantia L.)
Donal Bhattacharjee*, Satyabrata Das , R.S. Dhua
Department of Post Harvest Technology of Horticultural Crops, Faculty of Horticulture, Bidhan Chandra Krishi Viswavidyalaya,
Mohanpur- 741 252, Nadia, West Bengal, India
ARTICLE INFO:
Article history:
Received: 14 October 2016
Received in revised form:
30 October 2016
Accepted: 15 November 2016
Available online: 31 December 2016
Keywords:
Bitter gourd,
Blanching,
Dehydration,
Rehydration,
Vapour,
Water
ABSTRACT
An experiment was carried out to evaluate the dehydration and rehydration characteristics of
bitter gourd (Momordica charantia L.) fruits. The slices of bitter gourd were blanched in
boiling water and steam for 1, 2 and 3 minutes respectively. The slices were then dried at
65°C, 60°C and 55°C in a cabinet dryer up to constant moisture content.After final
dehydration, rehydration for 10minutes, 20minutes, 30minutes, 50minutes, 70minutes and 90
minutes were undertaken respectively. There were seven treatments, replicated thrice and
experiment was laid out in completely randomized design. The moisture content declined
rapidly in bitter gourd rings dried at 65°C.The rehydration ratio recorded was 6.42, coefficient
of rehydration was 13.91 and percent water in rehydrated sample was 88.14% respectively in
water blanched samples. Hence, it is concluded that, among the three drying temperatures and
two blanching methods, better dehydration and rehydration characters were reported in
samples dried at 60°C and blanched in water for 2 minutes.
Introduction
Bitter gourd (Momordica charantia L.) is a member of the
Cucurbitaceae family and known as Karela commonly in
India. The important bitter gourd growing states are
Maharashtra, Gujarat, Rajasthan, Punjab, Tamil Nadu, Kerala,
Karnataka, Andhra Pradesh, West Bengal, Orissa, Assam
Uttar Pradesh and Bihar. The immature fruits are used in a
wide variety of culinary preparations. It can be fried, deep-
fried, boiled, pickled, juiced and dehydrated [1]. The fruits are
antidotal, antipyretic tonic, appetizing, stomachic, antibilious
and laxative. It has an action similar to insulin, thus helping in
glucose metabolism. It purifies blood, activates spleen and
liver and is highly beneficial in diabetes [2]. The fruit has
great potential as a food source in both developing and
industrialized countries. It is rich in iron, phosphorus and
ascorbic acid which can supplement the requirement of
nutritious food which is a prerequisite for a healthy life, not
only for basic human survival, but also for safeguarding strong
digestive, immune, cognitive, and other health functions.
Thus, it can ensure food security which exists when all people,
at all times, have physical, social and economic access to
sufficient, safe and nutritious food which meets their dietary
needs and food preferences for an active and healthy life.The
preservation of vegetables can avert huge wastage as well as
make them available in the lean season at remunerative prices.
Among the different methods of preservation, dehydration is
one of the best methods of preservation of fresh vegetables.
When moisture is removed, they can be preserved over a long
period with minimal microbial attack [3, 4]. Dehydration can
reduce the bulk weight of vegetables, protect from browning
and can be stored for long. In the process of dehydration, the
moisture is removed by the application of artificial heat under
controlled conditions of temperature, humidity and air flow.
Blanching as a pretreatment to drying protects their colour,
texture, and nutrients and inactivates harmful enzymes.The
heat from blanching helps slow or stop the enzyme activity
that can cause undesirable changes to reduce quality, which
preservation methods such as drying cannot stop. Studies have
shown that pre-treating vegetables by blanching in boiling
water or steam intensifies the destruction of potentially
harmful microorganisms on the surface of the vegetable
CODEN (USA): IJPB07 ISSN: 2320-9267
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Bhattacharjee et al Indian J. Pharm. Biol. Res., 2016; 4(4):39-45
Research Article 40
during drying, including Escherichia coli O157:117,
Salmonella species and Listeria monocytogenes. Blanching
also relaxes tissues of produce thus reduces the drying time
asthe cells in produce loose their wall integrity when blanched
and thus bound water is lost faster during drying than when
unblanched[5,6].There is a good prospect of dried bitter gourd
for production of value added products. Through processing
the market value of dehydrated product may be increased and
production can be maximized. Thus, farmers would be
benefited and encouraged to expand production. With keeping
the above views in consideration, the investigation was
conducted to study the dehydration and rehydration
characteristics of bitter gourd.
Materials and Methods
The experiment was carried out in the laboratory conditions of
the Department of Post Harvest Technology of Horticultural
Crops, Bidhan Chandra Krishi Viswavidyalaya, West Bengal,
India. Fresh fruits of bitter gourd cv. Meghna-2 were used for
the present experiment.Firm, mature, uniform in colour and
appearance fruits without any blemishes of medium size were
selected for dehydration. The fruits were chopped from stem
to blossom end using a stainless steel knife into uniform
thickness of 0.6 cm. To obtain more uniform flesh, 2.0 cm of
flesh at the stem end and blossom end were discarded. The cut
pieces of bitter gourd were blanched in boiling water.Vapour
blanching was done by using an autoclave at 121°C for 1, 2
and 3 minutes respectively. Blanched pieces were then dipped
in a quick cooling solution of potassium metabisulphite 0.25%
for 1 minute. After blanching the sample was uniformly
spread on wire mesh to form a thin layer. This final sample
contained 500 g of sliced bitter gourd. Bitter gourd slices were
then dried at 65°C, 60°C and 55°C in a cabinet dryer up to
constant moisture content. The dried samples were sealed
properly in polyethylene bags. After final dehydration,
rehydration with warm water (60-70°C) for 10, 20, 30, 50, 70
and 90 minutes were undertaken. The product was drained till
dripping of water stops. There were seven treatments viz., T1-
Control, T2- Water blanching for 1 minute, T3- Water
blanching for 2 minutes, T4- Water blanching for 3 minutes,
T5- Vapour blanching for 1 minute, T6- Vapour blanching for
2 minutes, T7- Vapour blanching for 3 minutes. The analysis
of data obtained in experiments was analyzed by Completely
Randomized Design to test statistical significance at p≤0.05,
with three replications, by adopting the standard statistical
procedures [7]. The means between treatments were compared
by Duncan’s multiple range tests (DMRT)[8]. The moisture
content of the dried samples were recorded during the entire
period of drying followed by rehydration ratio, coefficient of
rehydration and percent of water in rehydrated material.
Moisture content
The moisture content of dried slices was determined by drying until the weight of the dried sample become stable [9]. The moisture
content of the dehydrated fruit was expressed as:
Moisture content of dehydrated sample = 
 x 100 (%)
Rehydration ratio
The rehydration ratio was expressed as a ratio of water absorbed by the dried sample to the weight of the dried sample[10].
Rehydration ratio = 

where,
Wr = drained weight of the rehydrated sample
Wd = weight of the sample used for rehydration
Coefficient of rehydration
The coefficient of rehydration of the rehydrated samples was calculated by using the following formula [11].
Coefficient of rehydration = 




 
Percent water in rehydrated sample
The drained weight of the rehydrated sample being known, the per cent water content in the rehydrated material is given by [11].
% water in rehydrated sample = 

 x 100
Bhattacharjee et al Indian J. Pharm. Biol. Res., 2016; 4(4):39-45
Research Article 41
Results
Moisture content: The data presented graphically in Figure-1,
2 and 3 revealed that the moisture content decreases
continuously with enhancement of time. The moisture
expulsion was found to be faster initially, up to 12 hours.
Among various blanching treatments, the appearance of the
slices was good in T3 (water blanching for 2 minutes)
compared to control. The average duration of drying was
about 24 hours. The moisture content of bitter gourd slices
when dried at 60°C, were brought down to 8.67 % (T2- water
blanching for 1 minute and T3- water blanching for 2 minutes).
The moisture exclusion was found to be faster initially, up to
16 hours. Among water and vapour blanching treatments, the
appearance of the slices were at par with each other. The
whole process of dehydration took approximately 28 hours for
the moisture to become constant. On drying at 55°C, the
moisture content of bitter gourd slices were reduced to 7.11 %
in T3 (water blanching for 2 minutes). The green colour of the
bitter gourd slices became brownish due to degradation of
chlorophyll pigments and the texture turns out to be very
crispy in all the treatments including control. Among water
and vapour blanching treatments, the appearance of the slices
were at par with each other. The whole process of dehydration
took approximately 28 hours for the moisture to become
constant. Among the three drying temperatures, dehydration
was faster when dried at 65°C compared to other two drying
temperatures.
Rehydration ratio: The data illustrated that time, temperature
and blanching methods effect have a reasonable impact on the
rehydration ratio of the samples dried at 65°C, 60°C and 55°C
respectively. The soaking in hot water showed that a
maximum rehydration ratio (6.35) in water blanched (T3-
Water blanching for 2 minutes) bitter gourd slices dried at
65°C. The curves as graphically presented in Figure-4, 5 and 6
demonstrated the highest rehydration ratio 6.42 (T3- Water
blanching for 2 minutes) dried at 60°C after 90 minutes of
soaking. Similarly, the rehydration ratio of the bitter gourd
slices when dried at 55°C was recorded maximum (5.85) in T3
(Water blanching for 2 minutes). Among the three drying
temperatures and two blanching methods, the highest
rehydration ratio was reported in water blanched (Water
blanching for 2 minutes) samples and lowest in control dried
at 60°C soaked in hot water for 90 minutes.
0
20
40
60
80
100
1 4 8 12 16 20 24
Moisture content (%)
Time (hours)
Figure-1 Influence of blanching methods on
moisture content of bitter gourd fruits dried
at 65°C
T1
T2
T3
T4
T5
T6
T7
0
20
40
60
80
100
1 4 8 12 16 20 24 28
Moisture content (%)
Time (hours)
Figure-2 Influence of blanching methods on
moisture content of bitter gourd fruits dried
at 60°C
T1
T2
T3
T4
T5
T6
T7
0
20
40
60
80
100
1 4 8 12 16 20 24 28
Moisture content (%)
Time (hours)
Figure-3 Influence of blanching methods on
moisture content of bitter gourd fruits dried
at 55°C
T1
T2
T3
T4
T5
T6
T7
Bhattacharjee et al Indian J. Pharm. Biol. Res., 2016; 4(4):39-45
Research Article 42
Coefficient of rehydration: The coefficient of rehydration of
bitter gourd slices dried at 65°C, 60°C and 55°C respectively
are presented in Table-1. The coefficient of rehydration for the
dehydrated bitter gourd slices when dried at 65°C was highest
within the first 35 minutes during which majority of moisture
absorption took place. Additional increases were recorded up
to 90 minutes of soaking. The curves exhibit the characteristic
moisture absorption patterns where initial high rate of water
absorption is followed by slower absorption in later stages.
The highest coefficient of rehydration (2.86) was found in T3
(Water blanching for 2 minutes) and the lowest in control.
Similarly, the coefficient of rehydration when dried at 60°C
for bitter gourd slices was recorded highest within the first 35
minutes. Supplementary increases were documented up to 90
minutes of soaking. The highest coefficient of rehydration
(13.91) was established in T3 (Water blanching for 2 minutes)
and the lowest in control (2.76) after 90 minutes of soaking.
The coefficient of rehydration when soaked in hot water of
bitter gourd dried at 55°C was noted highest during the initial
phase which gradually slowed down in later stages. The
maximum coefficient of rehydration (7.35) was found in T3
(water blanching for 2 minutes) and the lowest in control
(2.03). Among all the treatments, the highest coefficient of
rehydration was reported in water blanched (Water blanching
for 2 minutes) dried at 60°C.
Table 1: Influence of blanching methods on coefficient of rehydration of bitter gourd fruits at time interval dried at 65°C,
60°C and 55°C
Treatments
Coefficient of rehydration at 65°C
10 minutes
20 minutes
35 minutes
70 minutes
90 minutes
T1
1.25 a
1.45 a
1.63 a
1.65 a
1.73 a
T2
2.34 g
2.54 f
2.54 e
2.65 e
2.67 e
T3
2.25 f
2.45 e
2.55 e
2.73 f
2.86 f
T4
1.85 e
2.04 d
2.03 d
2.15 d
2.24 d
T5
1.56 c
1.81 c
1.98 c
2.04 c
2.04 c
T6
1.65 d
1.78 c
1.94 bc
1.97 b
1.97 b
T7
1.45 b
1.73 b
1.92 b
1.94 b
1.96 b
C.D. (0.05)
0.048
0.040
0.041
0.049
0.036
0
1
2
3
4
5
6
7
10 20 35 50 70 90
Rehydration ratio
Time (minutes)
Figure-4 Influence of blanching methods on
rehydration ratio of bitter gourd fruits dried
at 65°C
T1
T2
T3
T4
T5
T6
T7
0
1
2
3
4
5
6
7
10 20 35 50 70 90
Rehydration ratio
Time (minutes)
Figure-5 Influence of blanching methods on
rehydration ratio of bitter gourd fruits dried
at 60°C
T1
T2
T3
T4
T5
T6
T7
0
1
2
3
4
5
6
7
10 20 35 50 70 90
Rehydration ratio
Time (minutes)
Figure-6 Influence of blanching methods on
rehydration ratio of bitter gourd fruits dried
at 55°C
T1
T2
T3
T4
T5
T6
T7
Bhattacharjee et al Indian J. Pharm. Biol. Res., 2016; 4(4):39-45
Research Article 43
SEm ±
0.016
0.013
0.014
0.016
0.012
Treatments
Coefficient of rehydration at 60°C
10 minutes
20 minutes
35 minutes
70 minutes
90 minutes
T1
2.07 a
2.25 a
2.47 a
2.73 a
2.76 a
T2
8.46 f
9.04 f
9.56 f
10.37 f
10.53 f
T3
10.83 g
11.45 g
12.13 g
13.76 g
13.91 g
T4
7.26 e
7.73 e
8.43 e
9.29 e
9.46 e
T5
6.76 d
7.44 d
7.87 d
8.45 d
8.76 d
T6
4.88 c
5.25 c
5.58 c
6.06 c
6.15 c
T7
2.96 b
3.15 b
3.35 b
3.56 b
3.75 b
C.D. (0.05)
0.035
0.052
0.041
0.038
0.037
SEm ±
0.011
0.017
0.013
0.012
0.012
Treatments
Coefficient of rehydration at 55°C
10 minutes
20 minutes
35 minutes
70 minutes
90 minutes
T1
1.53 a
1.63 a
1.73 a
1.94 a
2.03 a
T2
4.14 f
4.46 f
4.75 f
5.05 f
5.06 f
T3
5.83 g
6.34 g
6.95 g
7.33 g
7.35 g
T4
3.34 e
3.53 e
3.93 e
4.04 e
4.13 e
T5
2.87 d
3.04 d
3.24 d
3.53 d
3.65 d
T6
2.32 c
2.43 c
2.64 c
2.93 c
2.94 c
T7
1.84 b
1.94 b
2.03 b
2.25 b
2.34 b
C.D. (0.05)
0.041
0.039
0.043
0.041
0.039
SEm ±
0.013
0.013
0.014
0.013
0.013
(Means in the column followed by the same alphabet do not differ significantly by DMRT at 5%)
(T1- Control, T2- Water blanching for 1 minute, T3- Water blanching for 2 minutes, T4- Water blanching for 3 minutes, T5- Vapour
blanching for 1 minute, T6- Vapour blanching for 2 minutes, T7- Vapour blanching for 3 minutes)
Percent water in rehydrated material: The drying procedure
had a statistically significant influence on the percent water in
rehydrated material in rehydration characteristic of the bitter
gourd dried at 65°C, 60°C and 55°C. In Table-2, it is indicated
that with the increase in soaking time the percent water
increases gradually in the rehydrated samples. The percent
water absorbed by the dried sample reached highest during the
35 minutes duration followed by gradual increase in the water
content. The bitter gourd slices dried at 65°C, recorded highest
water absorption (88.14%) in T3 (water blanching for 2
minutes) up to 90 minutes of soaking followed by control the
lowest (86.32%). The percent water in rehydrated bitter gourd
when dried at 60°C, recorded the highest moisture content
86.24% (T3- Water blanching for 2 minutes). The rehydration
of the dehydrated bitter gourd dried at55°C indicated that the
moisture content was 86.03 % after 90 minutes of soaking in
T3 (Water blanching for 3 minutes). Among the three drying
temperatures and two blanching methods, the maximum
reconstitution after rehydration of dried bitter gourd slices
were reported in samples dried at 65°C and blanched in water
for 2 minutes.
Table 2: Influence of blanching methods on percent water in rehydrated material of bitter gourd fruits at time interval dried
at 65°C, 60°C and 55°C
Treatments
Percent water in rehydrated material (%) at 65°C
10 minutes
20 minutes
35 minutes
50 minutes
70 minutes
90 minutes
T1
82.77 b
84.35 a
84.67 a
85.14 a
85.56 a
86.32 a
T2
84.04 d
86.15 e
87.29 f
87.64 e
87.65 f
87.70 f
T3
84.33 e
86.56 g
87.75 g
87.83 f
88.03 g
88.14 g
T4
82.32 a
85.05 b
86.36 c
86.69 c
86.99 d
87.42 e
T5
85.36 f
86.25 f
86.44 d
86.73 c
87.04 e
87.15 d
T6
84.35 e
85.56 d
86.76 e
86.84 d
86.86 c
86.92 c
T7
83.77 c
85.35 c
85.45 b
85.99 b
86.24 b
86.76 b
C.D. (0.05)
0.021
0.052
0.029
0.051
0.038
0.042
SEm ±
0.007
0.017
0.009
0.017
0.012
0.014
Treatments
Percent water in rehydrated material (%) at 60°C
10 minutes
20 minutes
35 minutes
50 minutes
70 minutes
90 minutes
Bhattacharjee et al Indian J. Pharm. Biol. Res., 2016; 4(4):39-45
Research Article 44
T1
79.74 a
80.89 a
82.53 b
83.65 b
84.14 a
84.49 a
T2
82.15 f
83.26 f
84.25 e
84.85 d
85.25 d
85.95 e
T3
81.84 e
83.13 e
84.44 f
85.14 e
85.94 f
86.24 f
T4
82.35 g
83.46 g
84.54 g
85.24 f
85.80 e
85.93 e
T5
80.43 c
82.14 d
83.23 d
84.05 c
84.35 b
84.95 d
T6
80.33 b
81.35 b
82.44 a
83.32 a
84.55 c
84.65 c
T7
80.75 d
81.96 c
83.03 c
83.64 b
84.34 b
84.55 b
C.D. (0.05)
0.061
0.056
0.056
0.035
0.052
0.052
SEm ±
0.020
0.018
0.018
0.011
0.017
0.017
Treatments
Percent water in rehydrated material (%) at 55°C
10 minutes
20 minutes
35 minutes
50 minutes
70 minutes
90 minutes
T1
79.54 a
81.14 a
82.74 a
83.25 a
83.63 a
83.75 a
T2
81.92 f
82.94 f
84.06 g
85.03 g
85.61 f
85.88 f
T3
81.85 e
82.83 e
83.75 d
84.76 e
85.63 f
86.03 g
T4
81.26 c
82.51 d
83.81 e
84.83 f
85.18 e
85.36 e
T5
81.33 d
82.24 b
83.49 b
84.24 b
84.71 d
85.25 d
T6
81.26 c
82.32 c
83.97 f
84.45 d
84.62 c
84.94 c
T7
80.94 b
82.48 d
83.54 c
84.35 c
84.54 b
84.66 b
C.D. (0.05)
0.033
0.052
0.042
0.046
0.050
0.048
SEm ±
0.011
0.017
0.014
0.015
0.016
0.016
(Means in the column followed by the same alphabet do not differ significantly by DMRT at 5%)
(T1- Control, T2- Water blanching for 1 minute, T3- Water blanching for 2 minutes, T4- Water blanching for 3 minutes, T5- Vapour
blanching for 1 minute, T6- Vapour blanching for 2 minutes, T7- Vapour blanching for 3 minutes)
Discussion
Dehydration is the process of removing water from a product
under controlled conditions of air flow, temperature and
humidity which reduces the moisture in the food to such a low
level that inhibits the microbial growth leading to decay and
spoilage[12].During drying the temperature increased to
supply energy necessary to transfer water to vapour phase
accelerates the reaction between different constituents in the
product. The vegetable loses moisture thereby increasing the
concentration of nutrients in the remaining mass. As the
temperature of drying increased, removal of moisture from the
plant material occurs at a faster rate, thus reducing time taken
for drying. Since, drying takes place at faster rate at higher
temperature probably the loss of volatile compounds and dry
matter along with moisture will be reduced resulting in
slightly better yield compared to low temperature drying
which takes longer time [13].The drying time decrease with
increase in temperature[14, 15]. Among the two blanching
treatments, water blanching gave appreciable results than
vapour blanching. This might be due to a more even heat
penetration in water blanching than the steam blanching [16,
17]. Among the three drying temperatures and two blanching
methods, the rehydration ratio, coefficient of rehydration and
percent water in rehydrated material improved with decrease
in temperature and reconstituted product was more appreciable
in water blanching. The success of drying largely depends on
the reconstitution properties of the dried products. Higher
rehydration ratio indicates higher reconstitutability, which is a
measure of recovery [18]. Dehydration increases the
crystallization of polysaccharide gels by bridging reactive
polymers groups closer together. In fresh vegetables, the free
hydroxyl groups of polysaccharides have a secondary valence,
which is almost completely fulfilled by water. These hydroxyl
groups lose their non-covalently bound water due to
dehydration. The shrinkage of the plant cells enables the
adjacent polysaccharides molecules to be drawn together and
thus fulfill the hydroxyl group’s valence [19]. Drying results
in toughened skins making it difficult for the water to
penetrate into dried foods. Pretreatments for drying are usually
designed to improve rehydration properties. Blanching
pretreatment to drying causes loss in solids, enzyme
denaturation, air removal from tissues, hydrolysis and
solubilisation of structural polymers such as protopectin [20].
It will also cause starch granules to gelatinise, influencing the
water binding capacity of the rehydrated product, as the
gelatinised form would hold more water than the crystalline
raw starch. Moreover, it expands intracellular air which flows
through the intracellular lamella [21].
Conclusion
Bitter gourd is a highly nutrient packed fruit but during peak
seasons due to lack of adequate processing facilities farmers
are bound to sell their produce at low prices. So, the value
addition of bitter gourd fruits by dehydration can be of high
potential for both small farmers as well as for large scale
industries which is relatively inexpensive, quick and easy in
management. With respect to the results it can be concluded
that, among the three drying temperatures and two blanching
methods, higher dehydration and reconstitution characters
were reported in samples dried at 60°C and blanched in water
Bhattacharjee et al Indian J. Pharm. Biol. Res., 2016; 4(4):39-45
Research Article 45
for 2 minutes. The rehydrated product could very well be
utilized for substituting the fresh product in off-season.
Acknowledgement
The first author duly acknowledges the financial assistance
received from INSPIRE Fellowship Programme of the
Department of Science and Technology under Ministry of
Science and Technology, New Delhi for conducting the
present investigation.
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Cite this article as: Donal Bhattacharjee, Satyabrata Das , R.S. Dhua. Dehydration for Better Quality Value Added Product of
Bitter Gourd (Momordica charantia L.)Indian J. Pharm. Biol. Res.2016; 4(4):39-45
. Antibacterial and antifungal evaluation of some chalcogen bearing ligands, their transition and non-transition metal complexes.
Indian J. Pharm. Biol. Res.2015; 3(3):1-6.
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