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Indian gooseberry or aonla is a very rich source of ascorbic acid. Its ascorbic acid lost during the process of drying. Therefore effect of 4 different drying methods investigated on ascorbic acid and other quality factors under storage. Drying methods viz., sun drying, oven drying, microwave drying and fluidized bed drying, significantly affect the quality and ascorbic acid content of dried aonla powder. Among 4 drying methods, fluidized bed drying found best. At the start of experiment dried powder with fluidized bed drying had highest ascorbic acid content (272.74 mg / 100 g), total sugars (39.41 g / 100g), reducing sugar (33.69 g / 100g), and lowest content of tannin (8.8 g / 100g), browning index (0.02 OD at 440 nm) and acidity (9.94 g / 100g). The quality parameters deteriorated under storage irrespective of the drying method and ascorbic acid steadily lost during 90 days of storage. However, powder making with fluidized bed drying was acceptable even after 90 days of storage and contains 205.5 mg / 100g ascorbic acid. It is recommended that aonla can be dried with fluidized bed drying at a temperature of 65oC with air velocity of 90 m/min.
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727
PAREEK & KAUSHIK: EFFECT OF DRYING METHODS ON QUALITY OF INDIAN GOOSEBERRY
Journal of Scientific & Industrial Research
Vol. 71, November 2012, pp. 727-732
*Author for correspondence
E-mail: sunil_ciah@yahoo.co.in
Effect of drying methods on quality of Indian gooseberry
(Emblica officinalis Gaertn.) powder during storage
Sunil Pareek* and R A Kaushik
Department of Horticulture, Rajasthan College of Agriculture, Maharana Pratap University
of Agriculture and Technology, Udaipur, Rajasthan, India 313 001
Received 17 April 2012; revised 03 August 2012; accepted; 01 October 2012
Indian gooseberry or aonla is a very rich source of ascorbic acid. Its ascorbic acid lost during the process of drying. Therefore
effect of 4 different drying methods investigated on ascorbic acid and other quality factors under storage. Drying methods viz., sun
drying, oven drying, microwave drying and fluidized bed drying, significantly affect the quality and ascorbic acid content of dried
aonla powder. Among 4 drying methods, fluidized bed drying found best. At the start of experiment dried powder with fluidized
bed drying had highest ascorbic acid content (272.74 mg / 100 g), total sugars (39.41 g / 100g), reducing sugar (33.69 g / 100g), and
lowest content of tannin (8.8 g / 100g), browning index (0.02 OD at 440 nm) and acidity (9.94 g / 100g). The quality parameters
deteriorated under storage irrespective of the drying method and ascorbic acid steadily lost during 90 days of storage. However,
powder making with fluidized bed drying was acceptable even after 90 days of storage and contains 205.5 mg / 100g ascorbic acid.
It is recommended that aonla can be dried with fluidized bed drying at a temperature of 65
o
C with air velocity of 90 m/min.
Keywords: Aonla, Indian gooseberry, Ascorbic acid, Drying methods, Nutritional composition, Storage.
Introduction
Aonla or Indian gooseberry (Emblica officinalis
Gaertn.) is one of the most important traditional and
underutilized fruits of Indian origin, having immense
potential for cultivation on marginal or waste lands. It
belongs to the family Euphorbiaceae and sub-family
Phyllanthoidae. The fruit is highly nutritive and richest
source of vitamin C among fruits after Barbados cherry
1
.
The edible fruit tissues of aonla contain about 3 times
more protein and 160 times more vitamin C as compared
to apple
2
. The fruit contains leucoanthocyanin or
polyphenols which retard the oxidation of vitamin C and
presence of astringency. Hanif et al.
3
noted marked
antioxidant effect of gallic acid present in aonla fruits.
Tannins containing gallic acid, elagic acid, and glucose
retard the oxidation of vitamin C and renders its value as
antiscorbutic in the fresh as well as in dried conditions.
Aonla is also a source of carbohydrates, carotene,
thiamine, riboflavin, and minerals like iron, calcium and
phosphorus
4
.
The fresh aonla fruits are not popular as a table fruit
due to their high astringency and its storability after
harvesting is also limited
5
. The other methods of extending
shelf life are by cold storage, sun drying, and hot air
drying or by processing to preserve, pickle, juice, syrup,
squash and dehydrated powder
6
. Among these processes
dehydration offers many advantages. Several drying
methods are commercially available and the selection of
the optimal method is determined by quality requirements,
raw material characteristics, and economic factors.
Because of its heat sensitivity, the aonla is very
difficult to dry while maintaining its nutritional quality.
Very little information on drying processing of aonla is
available in the literature. Among various drying methods
available, open sun drying and solar drying have been
exploited to some extent and has the limitation of high
solar radiations
7
. Murthy & Joshi
8
and Pragati et al.
9
studied on fluidized bed drying of aonla. The detailed
scientific study is essential to develop a complete package
of appropriate technology for the production of
dehydrated aonla flakes of high quality. This will enable
the growers to get good remuneration as well as the
consumers to get nutrition product round the year.
728 J SCI IND RES VOL 71 NOVEMBER 2012
Fluidization involves the passing of fluid upwards
through a bed of particles and expanding it. The minimum
fluidization velocity will be reached when the pressure
drop over the column is equal to the weight of the bed
divided by its cross sectional area. Physical processes,
which use fluidized beds, include drying, mixing,
granulation, coating, heating, and cooling. All these
processes take the advantage of excellent mixing
capabilities of the fluid bed. Good solids mixing gives
rise to good heat transfer, temperature uniformity, and
ease of process control. Fluidized beds are currently used
for drying materials such as fruits, vegetables, and other
food items
10,11
.
The present primary study is aimed toward this
direction with aonla, cultivar ‘Chakaiya’, being used for
the experimentation. The methods used were direct solar
drying, oven drying, microwave drying and fluidized bed
drying. The data on the quality parameters for different
drying methods are recorded.
Materials and Methods
Location of the Experiment
The experiment was carried out in the Post Harvest
Technology Laboratory of Department of Horticulture,
Rajasthan College of Agriculture, Maharana Pratap
University of Agriculture and Technology, Udaipur,
Rajasthan. The fluidized bed drying treatment was applied
in the College of Technology and Agricultural
Engineering, MPUAT, Udaipur.
Fruits
The mature aonla fruits cv. ‘Chakaiya’ of uniform
and similar size were obtained from a private orchard of
Nathdwara District in a single lot. These were washed
under tap water to remove adhering dust and reduce the
surface microflora.
Treatment Application
The selected material was sliced to 5 mm thickness.
About 200 g of the sliced sample was taken for drying.
The fruit slices were dried using different methods viz.,
direct solar drying, oven drying, microwave drying and
fluidized bed drying until the moisture level was below
15%. The sliced sample was evenly spread on to an
aluminum tray and kept under sunlight for drying. Another
sample was then spread on to the perforated tray of the
oven, which was set to the required temperature of 65
o
C.
Yet another sample was taken in the microwave oven
and dried at a temperature of 65
o
C. The fourth sample
was taken in the perforated mesh container of the
fluidized bed dryer. The initial weight of the container
with slices of aonla was noted. An electronic top pan
weighing balance, having capacity of 5 kg with an
accuracy of 0.01 g was used for the purpose of weighing.
The air velocity was adjusted using the anemometer and
the air flow adjusting valve. The thermostate was set so
that the desired temperature was achieved. The aonla
slices were dried at a temperature of 65
o
C with air
velocity of 90 m/ min. Then the loaded container was
placed inside the plenum chamber of the fluidized bed
dryer. The drying was continued until the moisture
content of the slices reached about 15%. The dried fruit
pieces in each of the drying method were ground in a
mortar and pestle and then in a Cyclotech grinder. The
dehydrated aonla powder were sealed in air tight
polyethylene sealing machine and stored for 90 days.
Observations
The aonla powder was used for the estimation of
various nutrients i.e., total sugars
12
, reducing sugars
13
,
ascorbic acid
14
, titrable acidity
14
, total tannins
14
, and
browning
15
.
Statistical Analysis
The experiments were designed complete randomly
in factorial. The data obtained were subjected to
statistical analysis for analysis of variance using standard
methods. Values were considered at 95% confidence
level (p< 0.05) and all experiments were performed in
triplicate
16
.
Results and Discussion
Total Sugars
The data revealed that the total sugars content
(Table 1) was affected by all the drying treatments. It
was found that the total sugars content of fluidized bed
dried aonla was significantly higher (39.41 g/100 g) than
other treatments. The total sugar content in direct solar
dried aonla was 22.18 g / 100 g, which was significantly
lower than the oven dried aonla (25.59 g /100 g). The
total sugar content of microwave dried aonla was found
to be significantly higher (27.46 g /100 g) than both oven
dried and sun dried aonla but lower than the fluidized
bed dried aonla (39.4 g /100 g) before storage.
Even after 90 days of storage, the trend in total sugar
content as a result of different drying methods remained
the same. Total sugar content was decreased with
increase in storage period in all the drying methods. The
729
PAREEK & KAUSHIK: EFFECT OF DRYING METHODS ON QUALITY OF INDIAN GOOSEBERRY
total sugar content of aonla was maximum just after
drying whereas it was minimum at the end of storage in
all the methods. The rate of decrease was decreased
with the advancement of storage period. A steady decline
in total sugar content in direct solar dried Banarasi aonla
at 90 days of storage
17
have also been reported. A similar
trend in Desi and Banarasi cultivars of aonla has been
found
18
. The decrease in total sugars might be due to the
non-specific hydrolysis of macromolecules,
interconversion of sugars and aggregation of monomers
during storage
19
.
Reducing Sugars
The reducing sugars content (Table 1) was found to
be highest in fluidized bed dried aonla (33.69 %), followed
by microwave dried aonla (21.19 %) and oven dried aonla
(19.56 %). The minimum reducing sugars was found in
direct solar dried aonla (15.44%) at the start of
experiment. A comparison of mean values of reducing
sugars showed that the reducing content was significantly
higher in fluidized bed dried aonla. On mean value basis,
the oven dried aonla was superior to microwave dried
aonla, whereas, solar dried aonla showed lowest values
of reducing sugars. However, higher reducing sugar
content in osmo-air dried aonla followed by indirect solar
dried aonla has been reported
9
.
During storage, with the advancement of storage
period reducing sugar content decreased significantly in
all the drying methods. At the end of storage period the
lowest per cent reduction was recorded in fluidized bed
drying (20.18%) followed by solar drying (39.18%), oven
drying (42.59%) and microwave drying (58.28%) over
the start of experiment. This might be due to the
dehydration reactions causing sugars to become
unsaturated and highly reactive, the hexose reducing
sugars are partially converted to 2-furaldehyde and 5-
hydroxymethyle-2-furaldehyde
20
, which remain
undetected in a reducing sugar test. A decrease in
reducing sugars during storage in dried aonla has been
reported
18
.
Titrable acidity
The lowest titrable acidity (Table 1) was found in
fluidized bed dried aonla (5.94%), whereas it was highest
in microwave drying (6.26%) and intermediate in solar
(6.02%) and oven dried (6.11%) aonla. The titrable
Table 1 - Total sugars, reducing sugars, ascorbicacid, tannins and titrable acidity of dried aonla fruit during storage (dry weight basis)
Storage Drying methods
period Direct solar Oven drying Microwave Fluidized bed
(days) drying drying drying
Total sugars (g/100 g)
0 22.18 + 0.141 25.59 + 0.048 27.46 + 0.038 39.41 + 0.512
30 21.94 + 0.136 24.89 + 0.031 26.75 + 0.0489 37.08 + 0.0560
60 21.53 + 0.408 24.67 + 0.086 26.52 + 0.127 36.65 + 0.311
90 21.40 + 0.362 24.25 + 0.095 26.18 + 0.148 36.27 + 0.308
Reducing sugar (g/100 g)
0 15.44 + 0.076 19.56 + 0.041 21.19 + 0.235 33.69 + 0.286
30 14.33 + 0.0562 18.58 + 0.042 18.03 + 0.065 29.88 + 0.072
60 12.81 + 0.071 14.80 + 0.148 13.48 + 0.128 28.09 + 0.146
90 9.39 + 0.032 11.23 + 0.053 8.84 + 0.046 26.89 + 0.051
Total tannin content (mg/100 g)
0 15.45 + 0.162 15.05 + 0.158 14.73 + 0.115 8.80 + 0.055
30 10.82 + 0.587 10.16 + 0.331 10.11 + 0.776 4.67 + 0.544
60 7.86 + 0.041 6.98 + 0.415 6.63 + 0.172 3.08 + 0.435
90 7.59 + 0.199 5.32 + 0.255 5.47 + 0.112 2.15 + 0.231
Titrable acidity (g/100 g)
0 6.02 + 0.091 6.11 + 0.040 6.26 + 0.006 5.94 + 0.005
30 6.29 + 0.088 6.38 + 0.135 6.51 + 0.028 5.98 + 0.007
60 6.48 + 0.022 6.57 + 0.008 6.74 + 0.148 6.06 + 0.005
90 6.54 + 0.006 6.62 + 0.031 6.82 + 0.004 6.13 + 0.011
Values are mean + SE of three independent determinants. CD for storage periods x methods for total sugars, reducing sugars, total tannins
and acidity are 0.07345, 0.7635, 1.2461 and 0.2731, respectively
730 J SCI IND RES VOL 71 NOVEMBER 2012
acidity showed steady increase in storage duration in all
the four methods of drying. However, it was lowest in
fluidized bed dried aonla (6.13%). The increase in acidity
might have been due to formation of acids due to
interconversion of sugars and other chemical reactions
21
which accelerated at high ambient temperature. Also,
de-esterification of pectin molecules occurs during
storage resulting in the loss of jelly grade which leads to
a gradual decrease in methoxyl content and increase in
titrable acidity
22
. However, a decrease in acidity level in
dehydrated aonla during storage has also been reported
18
.
Ascorbic Acid
Just after applying drying methods, the highest
ascorbic acid was found in fluidized bed dried aonla
(272.74 mg/100 g), followed by microwave dried (198.40
mg/100 g), oven dried (181.15 mg/100 g) and solar dried
aonla (170.11 mg/100 g). All the four drying methods
used in the study affect ascorbic acid content significantly
on all the four storage periods (Fig. 1). The ascorbic
acid content of aonla fruit dried by fuidized bed drying
has also been reported to be significantly higher than hot
air tray drying and sun drying
17
.
Ascorbic acid content of dehydrated aonla decreased
further when stored for 90 days. On 90 days of storage,
highest per cent reduction was observed in fluidized bed
drying (24.64%), followed by microwave drying (18.94%),
oven drying (15.50%) and least in sun drying (12.95%)
over the start of experiment (Fig. 1). The reduction in
ascorbic acid content might be due to oxidation during
storage at high ambient temperature. A similar trend in
the reduction of ascorbic acid in direct solar dried
‘Banarasi’ aonla
17
, osmo-air, oven, direct solar and
indirect solar dried ‘Chakaiya’ aonla
9
, and in solar tunnel
dried and sun dried ‘Banarasi730’ aonla
23
have been
reported.
Tannins
Highest tannin content (Table 1) was recorded in
solar dried aonla (15.45%) followed by oven dried
(15.05%), microwave dried (14.73%) and lowest in
fluidized bed dried aonla (8.80%). The decrease in tannin
content in fluidized bed dried aonla might have due to
more controlled conditions of temperature and air velocity
and also with the fluidized nature of drying particles.
The total tannin content of dried aonla just after drying
was highest and decreased significantly during storage.
This decrease in total tannins in dried aonla might have
been due to the action of the enzyme polyphenoleoxidase
which might have converted tannins into other products
24
.
Browning
Colour of dried aonla is an important quality
parameter. Browning index of dried aonla was determined
as optical density values. The data regarding change in
browning (Fig. 2) during dehydration and storage showed
that the extent of browning was affected significantly
under different treatments. Fluidized bed dried aonla had
minimal browning (OD 0.020) whereas maximum optical
density value was recorded in solar dried aonla (0.075).
The browning in oven dried aonla was significantly lower
than that in microwave dried aonla. Optical density of
powder during storage (dry weight basis)
0
50
100
150
200
250
300
350
Direct solar
drying
Oven drying Microwave
drying
Fluidized bed
drying
Drying methods
Ascorbic acid mg/100g
0 day
30 day
60 day
90 day
Fig. 1Ascorbic acid (mg/100g) content in dried aonla fruit power during storage (dry weight basis)
731
PAREEK & KAUSHIK: EFFECT OF DRYING METHODS ON QUALITY OF INDIAN GOOSEBERRY
direct solar dried ber has been found to be higher than
optical density of indirectly solar dried ber
25
. The loss of
white colour in sun dried fruits was possibly due to the
photo-oxidation of carotenoids after long exposure to light
and oxygen.
Optical density values of dried aonla were
progressively increased with the increase in storage
period from 0 days to 90 days. The increase in browning
might be due to a wide range of residual peroxidases,
polyphenoloxidases and lipoxigenases even after
blanching, as in green peas
26
.
Conclusion
Fluidized bed drying at a temperature of 65
o
C and
wind velocity of 90 m/min found the best drying method
of aonla slices. The browning index was minimum in this
method and hence was found superior. The nutrient
retention in fluidized bed drying with special reference
to ascorbic acid was found highest. The tannin content
was also lowest in this method of drying. Hence, fluidized
bed drying can be recommended for drying of aonla slices.
Acknowledgements
Authors are thankful to National Agricultural
Innovation Project, Indian Council of Agricultural
Research, New Delhi, India for providing financial support
to conduct the research. We are also thankful to
Dr. G.P. Sharma for providing the fluidized bed drying
facility.
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... Aonla or Indian gooseberry (Emblica officinalis G) is one of the most important traditional and under-utilized fruits of Indian sub-continent origin, having immense potential for cultivation on marginal and waste lands (Pareek and Kaushik, 2012). Total area and production under aonla cultivation in India is 110 thousand hectares and 1282 thousand tonnes, respectively (Anonymous, 2014). ...
... Aonla is not consumed as fresh in its raw due to its highly acidic and astringent taste. It is, therefore, processed into various value added products, viz., preserve (Damame et al., 2002), candy (Nayak et al., 2012), juice (Jain and Khurdiya, 2005), pickle (Premi et al., 1999), supari (Singh et al., 2012), slices , powder (Pareek and Kaushik, 2012) etc. ...
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Aim: Methodology: Results: Interpretation: The present study aimed to investigate the impact of Emblica officinalis juice as an antibrowning agent on Solanum anguivi L. juice where enzymatic browning reaction occurs naturally. The fresh fruits of S. anguivi (S) and E. officinalis (E) were weighted at five different proportions such as S1-100g:E0-0g; S0-0g:E1-100g; S1-25g:E3-75g; S1-50g:E1-50g and S3-75g:E1-25g. Each combination was ground using a domestic mixer to extract the juice without adding water and analyzed for its characteristics such as color value, browning index, and acceptance level through a sensory evaluation which was recorded at two different intervals (0 and 90 min). Overall color analysis (DE*) indicates that E. officinalis juice significantly reduced the enzymatic browning reaction by its concentration and postponed the brown color development in all three combinations of extracted fruit juices during the storage period. Although, the browning index was high in all the combinations of juices at 0 and 90 mins, except S1-25g:E3-75g, since it had a higher concentration of E. officinalis. The sensory evaluation opted that S1-25g:E3-75g was accepted by all panel members. The FTIR spectral peak revealed the presence of various functional compounds such as carbohydrates, phenol, iron, alkanes, primary amines, esters, aromatics, phosphorous compounds, aliphatic amines, ketones, bromo and halo compounds. The present study demonstrated that the enrichment of S.anguivi juice with E. officinalis concentration had prevented the browning that often occurred due to enzyme catalyst where the reaction of conversion of o-quinones in the presence of oxygen, and o-quinones polymerise into undesirable brown color compound. The developed juice could be used in the formulation of nutraceutical-based ready-to-serve (RTS) beverages that might be the solution for preventing several diseases.
... Moisture content of the oyster mushroom samples was determined based on the method as given in details by Pareek and Kaushik (2012). Colour of oyster mushroom samples was determined by Hunter Lab colorimeter. ...
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Manuscript type: Mushrooms are characterized as the fruiting bodies of fungi and are fruitful source of high-quality protein and vitamins with low calories. Among the three most cultivated species, the oyster mushroom stands with limited shelf life (2-3 days at refrigerated conditions). Elevated quotients of browning reaction and restricted shelf life obliges the preservation of species as a matter of concern. A suitable pre-treatment along with the drying method is very important to retain the bioactive compounds of oyster mushroom. Pre-treatment optimization prior to oyster mushroom drying was carried out in two steps which involved individual and combined effects of blanching (70 to 90 o C) and chemical treatments. Thereafter, it was dried in a recently developed multi-mode novel drying unit under hot air and vacuum drying (50-70 o C) conditions. Pre-treatment with citric acid and blanching at 80 o C for 2 min resulted in the lowest residual activity of polyphenol oxidase. Retention of phenolics, flavonoids, ascorbic acid and antioxidant compounds were higher in the samples dried using vacuum drying. Increase in temperature from 50 to 70 o C significantly decreased the bioactive compounds and colour of vacuum dried samples. In samples dried using hot air-drying, the higher retention of bioactive compounds and colour was obtained at 60 o C as compared to 70 o C and 50 o C. Page model was found to be the best fitted model among the different models studied. Analysis inferred the usefulness of optimised pre-treatment and vacuum drying technique at low temperature for drying of oyster mushrooms.
... There are two drying methods used in the processing of food products namely natural and artificial (Argyropoulos et al., 2011;Babu et al., 2018;Purwaningsih, 2012). The application of using this drying method is influenced by several factors namely temperature, drying time and type of material to be dried (Pareek and Kaushik, 2012). The less nutrient content is lost, the more effective the drying method is carried out (Zhang et al., 2019). ...
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... mg/100g.This reduction of ascorbic acid content was similar to the findings of Saini and Davar [3] who proved that the ascorbic acid losses are dependent on cooking time and temperature due to the thermal sensitivity of the vitamin C. The estimated vitamin C content after blanching is and vitamin c than cabinet drying at 80 and 90 °C. This is mainly because of the volumetric heating and faster moisture removal rate of microwave radiations [4]. ...
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This study was undertaken to optimise the vitamin C content during processing of Indian gooseberry (candy). Indi-an gooseberries were blanched (70-90 o C for 5-15 min and pressurised condition), syruped and then dried (cabinet and microwave) for candy processing. Blanching temperature of 80 o C for a time period of 20 min was found to be sufficient for the preparation of Indian gooseberry candy and retention of 315.5±19.53 mg/100g vitamin C was observed after blanching. The hardness and the chewiness of the blanched product were found to be 4.28±0.14N and 2.20±0.16N for 80 o C 20 min samples. Cabinet drying of the blanched sample (80 o C 20 min) at 70 o C gave the maximum retention on the final candy (217.75±7.4 mg/100g), followed by microwave drying (178±11.21 mg/100g).
... The moisture diffusion rate with microwave heating is exponential after 40 s, which confirms the simultaneous heat and moisture diffusion as expected in Equation (35). The relevant paper from the literature for microwave drying concludes that the desirable drying of gooseberry by any means poses constraints of maximum temperature to be 65 C with maximum nutrient contents (Pareek and Kaushik 2012). Hence, the experimental setup validates the computational and simulation model that is essential for optimisation of drying dynamics of gooseberry. ...
The health benefits of Indian gooseberry have resulted in a tremendous growth in its consumption in the form of tasty candy and marmalade prepared by drying process. The candy production process is limited by high drying time and plant size requirements as most of the processing production plants are equipped with conventional drying methods. Hence, the paper presents computational model defining relation between electric field pattern with heating and moisture diffusion in the product simultaneously. The boundary value applies on Maxwell’s equation solution as defined by gooseberry electrical properties. The solution to heat and mass transfer equation offers thermodynamic properties and profiles of gooseberry by microwave heating. The optimised process of moisture diffusion to the surface of gooseberry, followed by conventional heating, dries the sample uniformly and speeds up the process. The established relation offers a valid model for defining time for microwave and conventional heating of fresh gooseberry that takes it as an input and dries gooseberry candy as an output, thereby reducing the time of drying from 17 hours to 0.5 hour. The electromagnetic and thermodynamic results are obtained using simulation and are followed by experimental verification.
... Ascorbic acid being thermolabile biomolecule tends to degrade with an increase in temperature and will be more when storage temperature is 4°C compared to that at 27°C. A similar trend was observed by Pareek and Kaushik (2012) in dried Amla stored for 90 days at ambient condition. Though higher retention was observed at refrigerated followed by the ambient condition, from an economic point of view, dried grated Amla can be stored at the ambient condition with maximum retention of ascorbic acid. ...
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Effect of four different cultivars and salt pretreatment on drying of Amla (Emblica officinalis) gratings were studied. Quality attributes namely, ascorbic acid, total phenolic content, antioxidant activity and colour were evaluated for dried (using Cabinet tray dryer at 55 ± 2 °C for 8 h) and stored (refrigerated, ambient and accelerated condition) samples of four cultivars (Krishna, Kanchan, NA-7 and Chakaiya). Salt pretreated dried samples showed better retention of nutrients and colour as compared to untreated. Retention of ascorbic acid, total phenolic content and antioxidant activity (IC50 value) in pretreated dried samples were in the range of 79.51–84.89%, 176.5–220.3 mg GAE/g db and 9.48 to 17.74 mg/µl, respectively. Colour retention was also found to be better in salt pretreated samples. Ambient storage condition resulted in higher retention of ascorbic acid and colour compared to accelerated condition. Taking into consideration, the nutritional value of the fresh Amla, ability to retain nutritional value and color during drying and storage, NA-7 cultivar Amla (pretreated with 1% salt, tray dried at 55 °C for 8 h) is the most suitable for preparation of Amla powder. The method developed in the present work is devoid of blanching step and found to be effective in retaining the nutrients during drying and storage and can be employed also for drying of similar fruits and vegetables.
... Demiray and Tulek [24] contemplated the impact of air three different temperatures on hue difference kinetics of carrot samples was inspected. Pareek and Kaushik [25] investigated the effect of drying techniques (solar dryer, Oven, Fluidized bed and Microwave) on the nature of Indian gooseberry powder amid storage. Surveyed characteristics include: Ascorbic acid, tannins, Total sugars, titrable acridity and reducing sugars. ...
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Vegetables play an important and irreplaceable role in the human beings daily life and other living animals on the planet. Henceforth, wastage of vegetables should be kept away by developing techniques for conservation and preservation of vegetables to an extended period. In this article, a double slope solar dryer was designed and fabricated at the terrace of the science block, NIT Puducherry, Karaikal. The decrease in the wetness content of specimens in the double slope solar dryer was empirically inspected for Karaikal climatic conditions. The effect of double slope natural convective based solar dryer in drying of potato compared with open sun drying operation adjacent each other in similar condition. Experiments were carried out to determine the dryer surface temperatures, air temperature, and the percentages of the wet basis wetness content from 11.00 am to 6.00 pm for two days. In the investigation, it was clear that designed and fabricated double slope natural convective solar powered dryer removed the high wetness content about 52.29% and in open drying technique it removed wetness content of 42.99% from the potato slices on first day. On second day similar weighted samples were investigated wetness removed by solar dryer is 51% and 43.92% in open drying. So developed solar dryer removed high amount wetness content and quality of dried potato slices was high when compared to open sun dehydrating. Accordingly, the developed double slope natural convective based solar dryer can be effectively utilized to dry the vegetable samples.
... Again, none of these differences were significant (p [ 0.05). Similar analytical results on solar dried amla samples have been reported earlier by Pareek and Kaushik (2012). Kaur and Kapoor (2002) have reported that more than 70% of antioxidant activities in amla fruits were correlated positively with total phenolic contents. ...
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Amla fruits were dried in the open sun to study the effects of various pre-drying treatments on the nutritional quality, rehydration and sensory characteristics. The sliced amla sample retained a maximum of 64% of ascorbic acid. Rehydration moisture content, rehydration ratio and coefficient of restoration were also maximum at 69%, 2.9 and 0.59 respectively for sliced treatment.
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In the present work an attempt has been made to study the dehydration of aonla (Indian gooseberry) fruits. Aonla fruits, being highly perishable, cannot be kept for long periods. Aonla contains a very high amount of vitamin C, which is highly volatile and susceptible to heat. Sun drying required the longest period of drying (660 min), while the shortest time of drying is with fluidized bed drying at 80°C with 115 m/min air velocity (120 min). The results indicate that there is great loss of most of the ascorbic acid in the aonla slices. This suggests that the drying exposure caused the loss of volatile biochemical compounds. The retention of ascorbic acid in the samples dried in fluidized bed drying is greater compared to those dried under sun and hot air tray.
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Drying of diced carrot (∼90% wet basis) was carried out in a laboratory microwave fluidized-bed dryer (MFB) and in a standard fluidized-bed dryer (FB). It was found that the drying time in the MFB dryer is 2-5 times shorter than in the FB dryer. Drying efficiency (DE) is a function of moisture content, microwave power and temperature of drying agent. Higher values of DE are obtained for MFB dryer. For both drying systems the water removal was proceeding in two-stage falling rate period (except short initial term).
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The influence of process temperature, feed flow rate and spout, and annular gas velocity on the drying process of mango pulp in a spout fluidized bed dryer was evaluated using a full factorial design. The process was carried out with an intermittent paste flow rate since the high sugar concentration of the fruit led to bed collapse using continuous feeding. The drying performance was assessed by the efficiency of powder production, product moisture, feed, and process time. The final product quality was evaluated by color, vitamin C, and carotenoid content. High process temperatures provided a better drying performance and product quality.