7–433

Powder Technology 274 (2015)

Contents lists available ScienceDirec

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Powder Technology
j o u r n a l h o m e p a g ew: w w . e l s e v i e r . c o m / l o c a t e / p o cw t e

Effect of inlet temperature on physicochemical properties of spray-dried

jamun fruit juice powder

Swaminathan Santhalakshmy, Sowriappan John Don Bosco ⁎, Sneha Francis, Mallela Sabeena
Keywords: increased the moisture content of the powder, and led to the formation of larger particles. Powder samples showed water
Syzygium cumini activity values below 0.3, which is good for powder stability. The colour of the jamun juice powder was mainly affected by
Spray drying inlet temperature, leading to the formation of powders that were significantly brighter and less purple as the inlet temperature
Maltodextrin increased. Glass transition temperature ranged from 55.85 to 71.78 °C. Powders produced at lower inlet temperatures showed
Inlet temperature smoother particle surfaces, whereas higher inlet temperature showed spherical particles with some shrinkage as analyzed by
Jamun fruit juice powder scanning electron microscope.
© 2015 Elsevier B.V. All rights reserved.
Department of Food Science and Technology, Pondicherry University, Puducherry, India

article info abstract

Article history: The aim of the present investigation is to study the effect of inlet temperatures on the physicochemical properties of spray-
Received 6 June 2014 dried jamun juice powder. The inlet temperatures varied from 140 to 160 °C, whereas other parameters like outlet temperature
Received in revised form 2 January 2015 (80 °C), maltodextrin concentration (25%) and feed flow rate (10 mL/min) were kept constant. Moisture content, water
Accepted 5 January 2015 activity, bulk density, solubility, hygroscopicity, colour, powder morphology, particle size and glass transition temperatures
Available online 12 January 2015 were analyzed for the powder samples. Higher inlet temperature

1. Introduction sjdbosco@yahoo.com (S.J. Don Bosco).

Jamun (Syzygium cumini) commonly known as Indian

http://dx.doi.org/10.1016/j.powtec.2015.01.016 0032-5910/©
blackberry, is an underutilized fruit from the Indian 2015 Elsevier B.V. All rights reserved.
subcontinent and it belongs to the Myrtaceae family. The outside environment and to protect against oxidation [4]. The
jamun fruits are available abundantly during the summer most commonly used microencapsulating agents are
season for a short period. Jamun fruit attracted the attention of maltodextrin, gum arabic or a combination of both. The addition
researchers and food processors as a potential source of food of carrier agents into the feed solution influences the properties
ingredients. The fruits are deep purple or bluish in colour with and stability of powder. The addition of high molecular weight
pinkish pulp and are widely consumed as a fruit and also used additives to the product before atomizing is a widely used
for the treatment of various diseases as an astringent, alternative that increases glass transition temperature [5]. Tonon
antiscorbutic, diuretic, antidiabetic, and in chronic diarrhea et al. [6] reported the significant effect of inlet air temperature on
and enlargement of the spleen [1,2]. Its fruit is a rich source of
the physicochemical properties of the spray-dried powder. The
anthocyanins whose content is equivalent to that of blueberries
quality of reconstituted spray-dried powder is good because the
and black currants and higher than that of blackberries, all
product temperature is rarely elevated above 100 °C [7]. Spray-
widely acclaimed anthocyanin-rich edible fruits. The fruits are
dried jamun juice powders can be added to food systems for a
edible and are reported to contain vitamin C, gallic acid,
variety of functional benefits. Ideally, spray-dried jamun juice
tannins and anthocyanins including delphinidin, cyanidin,
powder should reconstitute instantly or serve as an anthocyanin-
petunidin, malvidin-glucoside and other components, whichare
rich additive. There are numerous reports on antioxidant activity
responsible for the deep purple colour [3]. These beneficial
of jamun fruit and their stabilities. However, there is limited
effects are mostly due to the presence of bioactive compounds,
information of how encapsulating agents and drying conditions
such as pigments and phenolic compounds.
may influence the physicochemical properties of jamun fruit
Spray drying is not only a useful method of changing
powder.
liquids into solids for increasing shelf-life and stability of the
The present study investigates the effect of inlet temperature
product but reduced volume also helps in easy handling. Spray
drying is one of the common methods for encapsulating on spray drying of jamun juice and evaluates the physical
sensitive ingredients by using carrier agents that will act as a properties of the powder produced. The influence of temperature
coating material or ‘wall’ to isolate them from the on the microstructure of the powder is analyzed. 2. Materials and
methods
⁎ Corresponding author at: Department of Food Science and Technology, Pondicherry
University, R.V. Nagar, Kalapet, Puducherry 605 014, India. E-mail address:
38 S. Santhalakshmy et al. / Powder Technology 274 (2015) 37–43
2.1. Sample preparation samples (10 mL) was titrated against 0.1 N NaOH (standardized
using standard oxalic acid) using phenolphthalein indicator. The
Fresh jamun (S. cumini) fruit was purchased from a local end point was noted (the colour changed from colourless to pale
market in Puducherry, India. It was immediately processed pink). Total acidity was calculated in terms of citric acid using
without further storage. Jamun fruit was washed, deseeded and the formula:
extracted by using a fruit juicer (Philips HL1631/J; Amsterdam,
Netherlands) and the juice was filtered using 3 layers of cheese Acidityð Þ¼%
cloth. The carrier agent— maltodextrin (MD) (Himedia, Mumbai)
Titre value Normality of NaOHWeight of the sample Equivalent weight of citric acid 10
with 20 DE (1:4 w\v)—was added to the juice at different
concentrations of 15, 20, 25 and 30%. Then, the juice and carrier 1000

agent were mixed together until complete dissolution. About 2 kg

of jamun fruit was used for each experiment. The pH, total
soluble solids and moisture content of the jamun juice was 2.3.5. Turbidity
determined by the method described by Ranganna [8]. The turbidity of jamun juice and reconstituted powder
samples was measured by a UV spectrophotometer (UV-1800,
2.2. Spray drying process Shimadzu, Japan) at 900 nm using distilled water as a blank [12].

Experiments were performed using a pilot plant spray dryer at 2.3.6. Bulk and tapped density
a drying rate of 0.6 kg of water h−1 under various combinations of A known quantity of spray-dried jamun juice powder was
operating parameters. The spray-drying assembly used in the loaded into a 10 mL graduated cylinder and the volume
present study consists of a two-fluid nozzle to atomize liquid feed occupied was recorded and then used to calculate the bulk
into fine droplets, and a drying chamber where the atomized density (ρB) (weight per volume) The tapped density (ρT) was
liquid comes in contact with the hot air. This is followed by two calculated by tapping the cylinder for 5 min (32 taps per
cyclone separators. The first cyclone separator collects coarser minute) using a densitometer (M/s Shah Brothers, Mumbai,
particles and the second traps the fine and ultrafine particles. The India) with displacement amplitude of 6.5 cm. The final
chamber diameter is 32 cm and the height volume was then read and used to calculate the tapped density
of the chamber is 55 cm. The diameter of two-fluid nozzle is 1.4 [13].
mm. The feed flow rate was controlled through the speed of the
peristaltic pump. The spray dryer can be operated at an inlet 2.3.7. Particle density
temperature ranging from 130 to 170 °C and outlet temperature The particle density (ρP) was measured using the method
(OT) ranging from 75 to 95 °C. For each spray-drying suggested by Jinapong et al. [14]. Briefly, 1 g of dried powder
experiment, 100 mL of feed was pumped over a wider period of sample was transferred into a 10 mL measuring cylinder with a
time which varied depending on the feed flow rate. In this work, glass stopper. A total of 5 mL of petroleum ether was then
the feed flow rate was fixed as 10 mL/min. Pressure ranged from added to this sample and shaken for some time so that all the
0.8 to 1.2 kg/cm2. The temperature of the feed mixture was 25 °C. particles were suspended. Finally, the wall of the cylinder was
Dried powder samples were collected in the glass bottle at the rinsed with 1 mL of petroleum ether and the total volume of
base of the cyclone and stored in airtight containers in a the petroleum ether and suspended particles were read. The
desiccator containing silica gel until further analysis. The samples powder density was calculated as follows:
were labeled as A, B, C, D and E for IT 140, 145, 150, 155 and
160 °C, respectively.

ρP ¼
2.3. Powder analysis
Total volume of petroleum ether and suspended particles mLWeight of the
powder gð Þ ð Þ− 6
2.3.1. Product yield
The product yield of samples after spray drying were
calculated according to the following formula [9].
2.3.8. Porosity and flowability
Obtained spray dried powder gð Þ The porosity (ε) of the powdered sample was calculated
using particle density (ρP) and tapped density (ρT). The
Product yieldð Þ ¼% ð Þþ ð
flowability of powder was expressed as Carr index (CI) (Table
Þ 100
1) in terms of tapped density (ρT) and bulk density (ρB) as
Jamun juice g carrier agent g
described by Jinapong et al. [14]

2.3.2. Moisture content ε ¼ ρP−ρT

The moisture content of the powders was analyzed using the
AOAC 100
[10]. ρP

2.3.3. Water activity (aw)

The water activity of the powders was measured using an ¼ ρ −ρ 100
T B

electronic dew point water activity meter (Aqualab Series 4TE, ρT

Decagon Devices, Inc., Pullman, Washington, USA).

2.3.4. Total acidity

The total acidity of the fresh jamun juice and reconstituted
powders was determined by titration method [11]. Each of the
 S. Santhalakshmy et al. / Powder Technology 274 (2015) 37–43 39
2.3.9. Cohesiveness (Hausner ratio) Where a = amount of powder (g) being used, b = moisture
The cohesiveness of the powders was evaluated in terms of content in the powder, and % TS = dry matter in percentage in
Hausner ratio (HR) (Table 2), calculated from the bulk density the reconstituted powder after it has been passed through the
(ρB) and tapped density (ρT) [14]. sieve.

ρT 2.3.13. Water solubility index and water absorption index

HR ¼ Water solubility index (WSI) and water absorption index
ρB (WAI) were determined using the method described by Gomez
[17]. A total of 2.5 g of dry powders were added to 30 mL of
water at 30 °C in a
2.3.10. Wettability 50 mL centrifuge tube, stirred intermittently for 30 min and
The wettability was evaluated according to the method then centrifuged for 10 min at 5100 rpm. The supernatant was
described by Vissotto et al. [15], considering the time required carefully poured off into a petri dish and oven-dried overnight.
for 1 g of powder deposited on the liquid surface to become The amount of solid in the dried supernatant as a percentage of
completely submersed in 400 mL of distilled water at 25 °C. the total dry solids in the original 2.5 g sample gave an
indication of the WSI. Wet solid remaining after centrifugation
2.3.11. Solubility was dried in an oven overnight. WAI was calculated as the
The solubility of the powder was determined by Eastman weight of dry solid divided by the amount of dry sample.
and Moore's [16] method with some modifications. A total of 1
g of powder sample was mixed into 100 mL of distilled water 2.3.14. Colour
in a blender at high velocity (1550 rpm for 5 min). The The colour of the spray-dried jamun juice powder was
moisture content of the powder was about 3.2%; as a result, 1 measured by using Colorflex (Hunter Associates Laboratory
g of powder was added to 100 mL of distilled Inc., Reston, VA, USA). The CIE L* (light\dark), a* (red\
green) and b*(yellow\blue) values were obtained. Colour
Table 1 intensity in terms of chroma (C*) was calculated by the
Classification of powder flowability formula, C* = (a*2 + b*2)1/2, whereas hue angle (H°) was
based on Carr index (CI). calculated by the formula H° = tan−1 (b*/a*). The hue angle
CI (%) Flowability
values of 0°, 90°, 180° and 270° denote pure red, pure yellow,
b15 Very good pure green and pure blue colours, respectively. Hue angle
15–20 Good describes the colour perception and chroma describes the
20–35 Fair saturation of colour [18].
35–45 Bad
N45 Very bad 2.3.15. Hygroscopicity
Table 2 Hygroscopicity was evaluated based on the method
Classification of powder cohesiveness based
on Hausner ratio (HR).
described by Cai and Corke [19] with modifications. A total of
HR Cohesiveness 1 g of the sample was placed in a container at 25 °C with a
saturated NaCl solution (75.29% relative humidity). Samples
b1.2 Low
were weighed after one week, and hygroscopicity was
1.2–1.4 Intermediate
expressed as grams of adsorbed moisture per 100 grams of dry
N1.4 High
matter.
water. This solution was transferred to some experimental
tubes and centrifuged at 3000 rpm for 5 min and allowed to
2.3.16. Particle size distribution
settle completely for 30 min. An aliquot of 25 mL of the
The particle size of all the powder samples was measured by
supernatant was transferred to preweighed petri dishes and
using a particle size analyzer (Malvern Instruments, Malvern,
immediately oven-dried at 105 °C for 5 h. The solubility (%)
UK). Reconstituted powder was placed into the particle size
was calculated as the weight difference.
analyzer and the data acquisition was recorded automatically
[20]. The mean particle size of the powder was recorded and was
2.3.12. Dispersibility
reported in nanometers (nm).
Dispersibility measurements were performed according to
the procedure described by Jinapong et al. [14]. A total of 10
mL distilled water at 25 °C was poured into a 50 mL beaker. 1 2.3.17. Glass transition temperature
g powder was added into the beaker. The stopwatch was The glass transition temperature (T g) of the powders was
started and the sample was stirred vigorously for 15 s making determined using a differential scanning calorimeter (Q600 SDT
25 complete movements back and forth across the whole and Q20 DSC; TA Instruments). Approximately 5 mg of the
diameter of the beaker. The reconstituted powder was poured powder samples were placed into aluminum pans and equilibrated
through a sieve (212 μm). The sieved powder was transferred with magnesium chloride–saturated solution (relative humidity,
to a weighed and dried aluminum pan and dried for 4 h in a hot 32.8%) in desiccators at 25 °C until equilibrium was reached
air oven at 105 °C. The dispersibility of the powder was (about one week). Samples were then hermetically sealed with
calculated as follows: lids and weighed. The equipment was calibrated with indium
(Tmelting = 156.6 °C) and dry nitrogen was used as the purge gas
(70 mL/min). Samples were heated at 10 °C/min from 10 to 150
ð Þ ¼ ð10 þ aÞ% TS °C and then cooled to 25 °C at 10 °C/min. An empty pan was
Dispersibility % used as a reference. The midpoint values for glass transition
a ð100−bÞ=100 temperature of the samples were calculated using the software
Thermal Advantage, version 1.1A (TA Instruments).
40 S. Santhalakshmy et al. / Powder Technology 274 (2015) 37–43
2.3.18. Scanning electron microscopy 4.18% (Table 4), which is sufficient to make food powder
The particle morphology of powders was analyzed by microbiologically safe. The moisture content of the powders
scanning electron microscopy (Hitachi, Model: S-3400 N, Tokyo, increased with an increase in the inlet temperatures, which may
Japan). The samples were separately mounted on aluminum stubs be the due to crust formation on the drop surface. During spray
using double scotch tape and sputter-coated with a thin layer of drying, the drying of a drop takes place in two stages. In the first
gold. Finally, each coated sample was transferred to the stage, most of the drying occurs as a result of free moisture
microscope where it was observed at an acceleration potential of vaporization from the surface of the droplet. In the second stage,
2.5 kV. drying rate is lowered as a result of crust formation at the drop
surface and the concentration of unbound water to the inner part
of the droplet [22]. Especially for sugar-rich products,
2.3.19. Statistical analysis
evaporation is controlled by moisture diffusion in the crust
The experiments were carried out in triplicate and the data
[23].
was analyzed statistically using SPSS software SPSS 20.0 (SPSS
Inc., Chicago, USA) and the means were separated using
3.2.1.2. Water activity. Water activity is the availability of free
Duncan's multiple range test (p ≤ 0.05). All the data are presented
water in a food system responsible for any biochemical or
as the mean with the standard deviation.
microbiological reactions. High water activity indicates more free
water available for biochemical or microbiological reactions and,
3. Results and discussion hence, shorter shelf life [24]. All the powder samples showed
water activity values below 0.3 (Table 4), which is good for
3.1. Jamun juice composition powder stability. The average water activity of powders ranged
from 0.18 to 0.25; thus, they can be considered biochemically or
Table 3 shows the physicochemical properties of jamun fruit microbiologically quite stable. Similar water activity values were
juice. It can be seen that the jamun fruit juice has a low pH (3.1), obtained by Quek et al. [24] and Tonon et al. [25] while studying
which inhibits microbial growth. Total soluble solids were with watermelon and acai powders, respectively.
10.6°Brix. Colour parameters are an important feature reflecting
the sensory quality of the juices. The juice has a dark purple 3.2.1.3. Total acidity and turbidity. The total acidity and turbidity
colour as indicated by the values L⁎, a⁎ and b⁎ (Table 3). of spraydried powder samples are depicted in Table 4. Total
acidity was found to
Table 3
Physicochemical properties of jamun juice. Table 4
Analysis Values⁎ Powder yield and physicochemical properties of spray-dried jamun juice powder.
be higher in the powder sample produced with the lower
Moisture content (%) 91.4 ± 0.2
temperature and with an increase in inlet temperature the
Water activity (aw, 25 °C) 0.99 ± 0.0
acidity decreased. Powder sample A (140 °C) showed the
Acidity (% citric acid) 1.04 ± 0.03
highest acidity (0.65%) whereas sample E (160 °C) showed the
pH (25 °C) 3.1 ± 0.0
lowest (0.32%) acidity value. Turbidity values showed
Total soluble solids (°Brix) 10.6 ± 0.17
significant differences (p b 0.005) between the samples
Turbidity (Abs, 900 nm) 0.79 ± 0.00
Total sugars (g/100 g) 5.35 ± 0.11
produced at different temperatures. The highest turbidity value
Colour variables
(2.00) was shown by sample A followed by samples B, C, and
L⁎ value 0.75 ± 0.03 D, whereas the lowest value was shown by sample E (1.00).
a⁎ value 2.89 ± 0.08
b⁎ value 0.32 ± 0.03 3.2.1.4. Bulk, tapped and particle density. The effect of inlet
Chroma 2.90 ± 0.09 temperature on bulk density is depicted in Table 4. Jamun juice
Hue angle 6.37 ± 0.46 powder produced at different inlet temperatures showed
⁎ Mean ± standard deviation of triplicate analysis. nonsignificant difference in bulk density. The highest bulk
3.2. Spray drying process density was shown by sample D (0.29 g/mL) at an inlet
temperature of 155 °C, whereas the lowest bulk density was
The jamun juice was spray-dried using maltodextrin of 20 DE shown by sample C (0.24 g/mL) at an inlet temperature of 150
as carrier agent and the results are presented in Table 4. The inlet °C. Ferrari et al. [26] observed higher bulk density values for
temperature of the spray dryer was optimized while other spray-dried blackberry powder when a blend of maltodextrin
parameters such as outlet temperature 80 °C, feed concentration and gum arabic was employed as a carrier agent. The heavier
14°Brix, pressure 1.0 kg/cm2, and feed flow rate 10 mL/min were the material, the more easily it is accommodated into the
kept constant for further process. The optimum results were spaces between the particles, occupying less space and
obtained at inlet temperatures varying from 140 to 160 °C. The resulting in higher bulk density values. Chegini and Ghobadian
inlet temperature was optimized based upon the yield of the fruit [27] reported that spraydried powders with higher moisture
juice powder. The yield of the powder increased with an increase contents tend to have a higher bulking weight because of the
in temperature. The maximum yield (8.25%) of spraydried fruit presence of water, which is considerably denser than the dry
powder was obtained at 150 °C. solid. This behavior can be associated with the results
observed in our study because jamun juice powders produced
3.2.1. Powder analysis with maltodextrin showed higher moisture content and higher
bulk density. With respect to tapped density, powder samples
3.2.1.1. Moisture. Moisture content is an important property of showed significant difference (p ≤ 0.05) between A, B and D
powder, which is related to the drying efficiency. Moisture and C and E. The highest tapped density was shown by sample
content of a microencapsulated product plays an important role in B (0.48 g/mL) at an inlet temperature of 145 °C, whereas the
determining its flowability, stickiness and storage stability due to lowest tapped density was shown by sample E (0.38 g/mL) at
its effect on glass transition and crystallization behavior [21]. an inlet temperature of 160 °C. The lower the bulk density, the
Moisture content of jamun juice powders varied from 3.22 to more occluded air within the powders and, therefore, a greater
 S. Santhalakshmy et al. / Powder Technology 274 (2015) 37–43 41
possibility for product oxidation and reduced storage stability. an inlet temperature of 160 °C (Sample E) showed the lowest
Lower bulk density also implies greater volume for packaging wettability value (82.67 s), whereas the highest value (116 s)
[28]. With lower moisture contents, jamun juice powder was was shown by sample A (140 °C). Table 4 shows that an
found to be more compact. This occurs mainly with higher increase in the inlet temperature decreased the wettability time.
inlet temperature, lower feed rates and higher atomization Wettability is inversely related to the particle size because
pressure. larger particles show more spaces between them, being more
easily penetrated by water. On the other hand, smaller particles
3.2.1.5. Porosity. The porosity values showed nonsignificant are less porous, making it more difficult for the liquid to
differences (p b 0.05) among the powder samples, ranging penetrate into the food matrix, which results in poor
from 90.77 to 92.60% (Table 4). The higher values of porosity reconstitution properties [33].
indicate the presence of a larger number of spaces between the The dispersibility of spray-dried jamun juice powder
particles, containing oxygen available for degradations showed significant difference (p b 0.05) between samples.
reactions. Tonon et al. [20] reported that spray-dried acai Jamun juice powders produced with an inlet temperature of
powder produced with tapioca starch presented lower porosity 140 °C (sample A) showed the lowest dispersibility values
values (91.88), whereas sample E (160 °C) showed the highest value
(95.70). From our results, it is clear that with an increase in the
(68%) in comparison to the samples encapsulated with inlet temperature, dispersibility increased. A similar trend that
maltodextrin or gum arabic (75%). was reported by Reddy et al. [34] for spray-dried goat milk
powder.
3.2.1.6. Flowability (Carr index) and cohesiveness (Hausner
ratio). Table 4 shows the effect of inlet temperature on 3.2.1.8. Solubility. The effect of different inlet temperatures on
flowability of spray-dried powder samples. Flowability is an solubility is shown in Table 4. At the highest temperature (160
important property for dried particles and was expressed as the °C), sample E showed the highest solubility (99.67%),
Carr index (CI). The higher value of the Carr index indicates whereas at the lowest temperature (140 °C), sample A showed
poor flowability. The spray-dried jamun juice powder had the lowest solubility (87.67%). The results indicated that the
similar flow characteristics and were considered as very solubility of powders increased with increasing inlet
cohesive powders by their Hausner ratio (HR) given in Table temperatures. The same trend was reported by
4, and as classified in Table 2. This is in accordance with their Phoungchandang and Sertwasana [35] for spray-dried ginger
high Carr index (CI) (Table 4), which indicated that their juice, and by Izidoro et al. [36] for spray-dried green banana
flowability was poor (Table 1). However, adequately free- starch. As the carrier agent used in
flowing powders were produced at higher temperatures (N140
°C), with a maltodextrin/jamun juice ratio of 1:4. Table 5

Parameters A B C D E

Powder yield (%) 6.35 6.62 8.25 7.98 7.16

Moisture (%) 3.22 ± 0.09c 3.31 ± 0.09c 3.94 ± 0.07b 4.14 ± 0.09a 4.18 ± 0.09a
aw (25 °C) 0.25 ± 0.00a 0.24 ± 0.02b 0.23 ± 0.01bc 0.22 ± 0.01c 0.18 ± 0.00c
TSS (°Brix) 30.63 ± 0.25b 30.80 ± 0.00ab 30.97 ± 0.06a 30.97 ± 0.06a 31.00 ± 0.00a
pH (25 °C) 3.30 ± 0.01a 3.28 ± 0.01b 3.23 ± 0.00c 3.23 ± 0.02c 3.23 ± 0.00c
Acidity (g/100 ml) 0.65 ± 0.01a 0.56 ± 0.01b 0.45 ± 0.01c 0.44 ± 0.01c 0.32 ± 0.00d
Turbidity (Abs, 900 nm) 2.00 ± 0.11a 1.66 ± 0.04b 1.19 ± 0.11c 1.01 ± 0.04d 1.00 ± 0.13d
Bulk density (g/ml) 0.26 ± 0.03a 0.28 ± 0.03a 0.24 ± 0.02a 0.29 ± 0.04a 0.25 ± 0.01a
Tapped density (g/ml) 0.45 ± 0.03a 0.48 ± 0.03a 0.39 ± 0.03b 0.45 ± 0.03a 0.38 ± 0.02b
Particle density (g/ml) 5.17 ± 0.12a 5.17 ± 0.15a 5.23 ± 0.15a 5.20 ± 0.10a 5.20 ± 0.10a
Porosity (%) 91.30 ± 0.59b 90.77 ± 0.34b 92.53 ± 0.51a 91.24 ± 0.57b 92.60 ± 0.25a
Flowability (%) 41.58 ± 4.51a 41.39 ± 3.75a 37.36 ± 4.29a 36.31 ± 9.74a 36.10 ± 2.98a
Cohesiveness 1.72 ± 0.14a 1.71 ± 0.11a 1.60 ± 0.11a 1.60 ± 0.25a 1.57 ± 0.08a
Solubility (%) 87.67 ± 0.58b 96.00 ± 6.93a 98.67 ± 2.31a 99.00 ± 1.00a 99.67 ± 0.58a
Wettability (s) 116.00 ± 2a 102.00 ± 2.65b 86.67 ± 1.15c 83.00 ± 1.73d 82.67 ± 1.15d
Dispersibility (%) 91.88 ± 1.46c 93.22 ± 1.32bc 93.54 ± 0.59abc 94.24 ± 1.06ab 95.70 ± 1.12a
Water solubility index 42.78 ± 2.68b 44.76 ± 1.29b 46.13 ± 2.40b 49.64 ± 0.62a 51.09 ± 1.41a
Water absorption index 44.66 ± 0.64a 44.16 ± 2.10ab 43.95 ± 1.00ab 41.99 ± 0.53b 35.96 ± 0.71c
Values are means ± standard deviation of triplicate analysis. Means with different letters in the same row indicate significant differences at p ≤ 0.05.

Hausner ratio (HR) values of obtained powders ranged the study is maltodextrin, which is an amorphous and
from 1.57 to 1.72 (Table 4). The highest value of cohesiveness noncrystalline material, thus it may lead to higher solubility.
was shown by sample A (1.72), while the lowest was shown
by sample E (1.57). According to the classification given by 3.2.1.9. Colour. The colour parameters L*, a*, b*, chroma and
Geldart et al. [29], powders of HR below 1.25 were classified hue angle for the powders are given in Table 5. Maltodextrin
as lowly cohesive. The cohesiveness of powders determines powders are white, while jamun juice is dark purple.
their consistency and flow properties—the lower the Consequently, all powders produced had a bright purple colour.
cohesiveness, the better the flowability of powders [30]. The colour of each powder sample depends on the inlet
Samborska et al. [31], in studies on spray drying of honey temperature (140 to 160 °C) in the dryer and the moisture
solutions of maltodextrin at 180 °C, received powders with an content. Powder A, which is the darkest of all powders because of
average cohesiveness as the HR values ranged from 1.2 to 1.4. the lowest inlet temperature (140 °C), is characterized by the
lowest values for L*. Inlet temperature of 140 to 160 °C did not
3.2.1.7. Wettability and dispersibility. Wettability can be affect chromatic coordinate a*and b* for spray-dried jamun juice
defined as the ability of a powder bulk to be penetrated by a powders. The main differences in the colour of powders were
liquid because of capillary forces [32]. Powders produced with mainly due to variations in the inlet temperature. With an increase
42 S. Santhalakshmy et al. / Powder Technology 274 (2015) 37–43
in inlet temperature, the hue angle increased. This indicates that reported that the mean diameter of spray-dried acai powder varied
there is a corresponding decrease in the purple colour when the between 13 and 21 mm.
inlet temperature is increased. This may be due to the substantial
degradation of anthocyanins at higher temperatures. Similar 3.2.1.13. Glass transition temperature (T g). Table 5 shows the Tg
results have also been observed in carrot and watermelon juices values of spray-dried powder ranging from 55.85 to 71.78 °C.
[37]. With an increase in inlet temperature, glass transition
temperatures decreased. Similar results were reported by Akkaya
3.2.1.10. Water solubility index (WSI) and water absorption et al. [22] for spray drying of carob molasses. These T g values
index (WAI). WSI is the reconstitution property used to study the were in the same range as those reported for acai powders
effect of process parameters. The highest water solubility index obtained by spray drying using maltodextrin [25]. At glass
was shown by sample E (51.09) at an inlet temperature of 160 °C, transition temperature, an amorphous material undergoes a
whereas the lowest water solubility index was shown by sample change from a very viscous glassy to rubbery nature due to an
A (42.78) at an inlet temperature of 140 °C (Table 4). The highest increase in molecular mobility and a decrease in viscosity at glass
water absorption index was shown by sample A (44.66) at an transition temperature, which may result in structural changes
inlet temperature of 140 °C, whereas the lowest water solubility such as stickiness and collapse of the product [42,18]. The glass
index was shown by sample E (35.96) at an inlet temperature of transition temperature (Tg) of a spray-dried powder can be used as
160 °C. Our results clearly show that water solubility index an indicator of stability during long periods of storage [5]. It is
increased with an increase in the inlet temperature whereas the well known that a slight increase in moisture content of
water absorption index decreased with increased inlet encapsulated powders containing sugar results in a decrease in
temperatures. A similar trend was reported by Phoungchandang glass transition temperature of the product below room
and Sertwasana [35] for spray drying of ginger juice. The instant temperature and the product will become sticky; hence,
property of a powder is defined as the ability of a powder to microencapsulated spraydried products should be kept below the
dissolve in water. Hence, the ideal powder would wet quickly and glass transition temperature to obtain higher stability.
thoroughly, sink rather than float and disperse/dissolve without
lumps [32].

3.2.1.11. Hygroscopicity. Hygroscopicity was found to increase

from 17.00 to 25.33 g absorbed water/100 g with an increase in
inlet temperature of 140 to 160 °C. Spray-dried jamun powder
showed a significant difference (p b 0.05) at varying inlet
temperatures (Table 5). Hygroscopicity values increased with an
increase in moisture content such that lower powder moisture
contents indicated lower hygroscopicity. In spray drying cactus
pear juice, Rodrigues-Hernandez et al. [38] observed that the
powders produced at lower inlet temperatures were the least
hygroscopic. From Table 5, it is clear that the inlet temperature
considerably influenced the powder's hygroscopicity. The
samples produced at higher temperatures were more hygroscopic,
which can be related to the powder's moisture content.

3.2.1.12. Particle size distribution. The mean particle size (Table

5) for jamun powder samples produced at different inlet
temperatures ranged from 145.30 to 463.23 nm. Higher inlet
temperatures resulted in larger

Colour values, hygroscopicity, mean particle diameter and Tg of spray-dried jamun juice powder.
Parameters A B C D E
c c bc b
L* value 60.92 ± 0.44 60.95 ± 1.68 62.48 ± 0.65 63.14 ± 1.45 67.24 ± 0.94a
a* value 24.02 ± 0.07d 27.11 ± 0.08c 27.80 ± 0.10b 29.12 ± 0.20a 27.08 ± 0.34c
b* value −12.13 ± 0.10b −13.21 ± 0.05c −11.16 ± 0.07a −13.18 ± 0.14c −12.06 ± 0.10b
Chroma 20.72 ± 0.04e 23.67 ± 0.12d 25.46 ± 0.08b 25.96 ± 0.17a 24.24 ± 0.09c
Hue angle −26.80 ± 0.13d −25.97 ± 0.15c −21.83 ± 0.12a −24.35 ± 0.14b −24.01 ± 0.14b
Hygroscopicity (g absorbed water/100 g) 17.00 ± 1.00c 18.33 ± 1.15c 22.33 ± 1.52b 23.33 ± 0.57b 25.33 ± 0.57a
Particle size (nm) 145.30 ± 4.06e 263.33 ± 4.51d 289.67 ± 4.04c 310.53 ± 3.72b 463.23 ± 5.59a
Glass transition (Tg) (°C) 71.78 69.63 68.38 59.53 55.85
Values are means ± standard deviation of triplicate analysis. Means with different letters in the same row indicate significant differences at p ≤ 0.05.

particles, which can be related to increased swelling as the drying

temperature increased. When a particle is subjected to higher
drying rates, the evaporation of moisture is rapid and promotes
the formation of a hard crust that does not allow particle
shrinkage during spray drying. However, if the inlet temperature
is lower, the particle remains moist for a longer period of time
and shrinks, thus decreasing its size [39]. Tonon et al. [40]
reported similar behaviors in spray-dried acai powders. Obon et
al. [41] obtained an average particle size of 10–12 mmfor cactus
pear juice produced by spray drying, whereas Tonon et al. [40]
 S. Santhalakshmy et al. / Powder Technology 274 (2015) 37–43 43
Fig.
a b 1.

Typical micrographs of spray-dried jamun juice powder produced at different

inlet temperatures (a) 140 °C, (b) 145 °C, (c) 150 °C, (d) 155 °C and (e) 160 °C.
3.2.1.14. Scanning electron microscopy. The morphological
characteristics of spray-dried jamun juice powder at different
inlet temperatures are shown in Fig. 1. Powders produced at
higher temperature (155 and 160 °C; Fig. 1d and e) showed
spherical particles with some degree of shrinkage compared to
the powders produced at lower temperatures (140 and 145 °C;
Fig. 1a and b) showing smooth surfaces. In case of sample C,
smoother surfaces are seen, which may be due to the high inlet
temperature (150 °C; Fig. 1c). Bigger size particles at lower
inlet temperatures were obtained, whereas more regular and

c d
spherical particles were seen at higher inlet temperatures.
Similar behaviors were verified for cactus pear [43], acai [40]
and milk [39] products produced by spray drying. Kurozawa et
al. [44] reported that shrinkage of the spray-dried particles is
related to differences in the drying rate, which is lower

e
44 S. Santhalakshmy et al. / Powder Technology 274 (2015) 37–43
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