Effects of spray-drying parameters on physicochemical properties of powdered fruits

INTRODUCTION
Dehydration of food allows extending its shelf life
by reducing the chemical and microbial activities [1].
Drying reduces the moisture content of powder, which
guarantees a long and safe storage [2]. High-water
content makes fruit juices highly perishable products
with high transportation costs. In this regard, powdered
fruit juices are an attractive option for the food business:
they are stable, space-effective, and easy to transport [3].
Atomization, droplet-hot air interaction, and moisture
evaporation are the three essential processes of spraydrying
[4].
Fruits usually undergo such procedures as open
sun-drying, hot air drying, solar drying, microwavedrying,
freeze-drying, and spray-drying. However,
these methods have some disadvantages. For example,
hot air drying is time-consuming, and freeze-drying is
rather expensive [5, 6]. Spray-drying is a highly suitable
process for heat-sensitive products producing powders
with good quality [7–9]. Spray-dried powders have good
dispersion characteristics and are easy to incorporate
into food products [10]. Some resent studies introduced
spray-dried powders from cempedak jackfruit and kuini
mango [11–13].
Spray-drying is an effective means of making
inhalable powders [3]. The list of physicochemical
parameters that affect powders during spray-drying
includes such process factors as viscosity, particle
size, liquid feed flow rate, temperature and pressure
of the drying air, the kind of atomizer, etc. As a result,
optimizing the drying process is critical for obtaining
goods with improved sensory and nutritional properties,
as well as for increasing process yield. Studies that
feature surface characteristics of powder particles can
provide better knowledge of the production process and
optimize the powder composition [4].
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Effective spray-drying requires a careful selection
of operating conditions. For particles ≤ 2 μm, spraydrying
has a poor cyclone collection efficiency. A
common spray-dryer has an average output of 20–50%,
but a new high-performance cyclone developed by the
Swiss company BÜCHI increased it to ≥ 70%. Another
significant problem with spray-drying is the lack of
control over the mean droplet size. As a result, droplets
come in a wide range of sizes, and pneumatic nozzles
can cause clogging. Ultrasonic nozzles produce more
consistent droplets and more uniform size distribution of
the powder [7, 8].
Some difficulties, such as stickiness, hygroscopicity,
and solubility, can be overcome by introducing the
carrier agents before atomization. Biopolymers
and gums are the most popular carrier agents.
These compounds are typically associated with
microencapsulation. They can minimize powder hygroscopicity,
protect delicate food components from
unfavorable ambient circumstances, reduce food
component volatility and reactivity, and improve the
appearance of the finished product [10].
Fruit storage provides their off-season supply.
However, some fruits tend to rot during storage and lose
their nutritional content. The benefits of a dried extract
over traditional liquid forms include cheaper storage
costs, increased concentration, and active component
stability. Spray-drying can produce powders with
precise quality criteria in a continuous process [14]. It
is a one-stage technology that turns liquid meals or
suspensions into powder form. Spray-drying is also used
in pharmacy for tablet coating. Spray-drying has three
primary steps: (1) atomizing the liquid feed, (2) creating
and drying the droplets, and (3) droplet motion.
Problem statement. Spray-dried fruit juice powders
have high sugar solids content and usually assume
amorphous state [14]. Some recent studies describe
the advances in the spray-drying of sugar-rich foods,
including fruit juices, pulp, and honey with or without
carriers [15]. Products with low molecular weight
sugars, e.g. fructose, sucrose, and glucose, have a very
low glass transition temperature. Sucrose, glucose,
and fructose have the glass transition temperature of
62, 32, and –5°C, respectively. They reduce the glass
transition temperature of sugar-rich foods, which are
prone to caking during storage [16]. The hygroscopic
and thermoplastic nature of dried materials, such as
fruit juice powders, are known to cause adhesion to
dryer walls, reduce the drying yield, increase stickiness,
and decrease solubility [17]. These sugars are very
hygroscopic, which increases their stickiness and
tendency to agglomeration [18].
Organic lactic, malic, tartaric, and citric acids also
make spray-drying difficult. When tartaric, citric, and
malic acids were applied at concentrations of ≥ 10% dry
matter, they reduced the powder recovery. As a result,
spray-drying of fruits with high acid content required
more maltodextrin [19]. Spray-drying below +20°C of
glass transition temperature helped avoid stickiness
but was not economically feasible [20]. Spray-dried
blood fruit powder was found to have high solubility
and good retention of resveratrol content [21]. This work
features the effect of different spray-drying parameters,
e.g. temperature, flow rate, flow rate, and carrier
concentration, on food powders.
STUDY OBJECTS AND METHODS
The study was carried out at UCSI University in
Malaysia’s Faculty of Applied Sciences, Department
of Food Science and Nutrition. It featured scientific
and methodological literature, publications in scientific
journals, conference papers, patents, regulatory
papers, and Internet resources. The data were grouped,
categorized, compared, and consolidated. Because
1995 was the year that the topic of spray-drying was
first highlighted, the review includes high-quality peerreviewed
English-language papers published between
1995 and 2021. Most publications were Scopus indexed.
The conference papers were chosen based on their
citation quantity and keywords. The review did not
include books and non-academic resources.
RESULTS AND DISCUSSION
Basic principles of spray-drying. Spray-drying
involves five major stages [22, 23]:
1) Concentration. The feed is concentrated before
being pumped into the spray-dryer;
2) Atomization. The fluid products are dispersed into
fine droplets and pumped into the drying chamber via an
atomizer;
3) Droplet-air contact. The atomized feed comes in
contact with the hot gas. Water evaporates, leaving a
dry product. The contact time between spray-droplets
and the hot air is very short, which provides an efficient
drying process of heat sensitive materials without
thermal decomposition;
4) Droplet drying. It occurs in two sub-stages. The
first sub-stage happens at a relatively constant rate.
During this sub-stage, the surface of the droplets is
quickly moisturized by the water trapped inside the
droplets. The second sub-stage happens when the
surface of the droplets runs out of moisture. This substage
yields a dried product;
5) Separation. The dried powder passes through the
cyclone and is then collected in the collection vessel.
The air is exhausted from the top of the cyclone and
passes through the bag filter.
Main properties of spray-dried powders. Primary
powder properties include hygroscopicity, moisture
content, solubility, particle density, particle size
distribution, appearance, color bulk density, particle
morphology, and surface composition [24]. In addition
to moisture content, some important characteristics of
spray-dried powders also include particle porosity, size,
and rehydration [20]. As a result, scientific publications
concentrate mostly on the effect of feed qualities and
drying conditions on the physical properties of powder,
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although the results are sometimes confusing [25]. The
spray-dried powders are analyzed in a few common tests
( Table 1).
The powder yield depends on the kind of fruit
and the carrier agent. For example, orange juice
powder has a big range of yield, from 25 to
85% [49]. However, acai juice powder yield was
reported as 48.49% [26]. The moisture content is
one of the main characteristics of powder which
affects mainly solubility and bulk density [24].
Moisture content of spray-dried tomato powder was
reported as 3.11–9.30%, whereas watermelon juice
powder obtained by the same method had 1.47–2.48%
moisture content [50, 51].
Fruit juice powder has a high hygroscopic feed and
thermoplastic nature. As a result, it sticks to the dryer
walls, which is one of the major problems in spraydrying
[52]. The other reason might be its low melting
point temperature, high water solubility, and low glass
transition temperature [53]. Stickiness normally occurs
if particles are not dry enough when they come in
contact with one another or with the drying wall and
thus stick to the drying chamber [19]. Stickiness causes
operational issues and lowers the yield [16, 14].
Reported hygroscopicity of 12.48–15.79 for acai
powder, while Rodrigues-Hernandez et al. stated
36.32–48.93 for cactus pear juice powder [26, 54].
According to Fitzpatrick et al., particle size and particle
distribution eventually have significant impact on the
powder flowability, handling, and processing [43, 55].
Solubility is another important property of powders
[49, 50]. It can be affected by compressed air
flow rates, carrier agents, and low feed rates [24]. The
water solubility index increased when maltodextrin
reached 96% [56]. According to Mahendran, 30%
of maltodextrin produced a guava powder with 95%
solubility, whereas 60% of maltodextrin added to guava
juice decreased the solubility to 86% [38]. Bulk density
is an important powder property as it determines the
size of containers, which eventually affect the handling
and transportation costs.
Consumers prefer it when the powder is reconstituted
well and can be instantly dissolved in water [20, 57].
Mango powder showed a good reconstitution property:
it completely dissolved in warm water at 40°C with no
suspended particles in the solution [52]. Reconstituted
pineapple powder was found to have a lower lightness
but a higher redness and yellowness, probably, as a
result of the non-enzymatic browning reaction that
occurred during spray-drying [58].
Youssefi et al. measured the color change in the
pear cactus juice powder and its reconstituted solution.
The slight changes in the color (ΔE) ranged from 6.7 to
9.8 [17]. L* was affected neither by the drying
conditions nor by the color change, only by the
maltodextrin concentration. The L* values of the
reconstituted samples (13.00–16.00) were similar to
those of the untreated juice (13.02), which meant that the
spray-drying process did not darken the finished product.
Factors affecting the properties of spray-dried
powder. Table 2 shows the production of different
fruit powders obtained by spray-drying. Spray-drying
parameters are important and must be controlled as
they affect the quality and quantity of powder. Some
parameters of spray-drying include inlet and outlet
temperature, air flow rate, feed flow rate, atomizer,
carrier agents, and concentration. Different parameters
affect such powder properties as bulk density, solubility,
hygroscopicity, particle size, flowability, and glass
transition temperature [50].
Inlet air temperature and outlet temperature.
Table 2 demonstrates the effects of inlet air temperature
on the physicochemical properties of spray-dried
fruit powders. Such powder properties as moisture
content, bulk density, particle size, hygroscopicity, and
morphology are all affected by the initial settings of
inlet air temperature [61]. Inlet air temperature proved
a more important factor than maltodextrin content,
judging by bulk density, caking, and water solubility
index [62].
Inlet air temperature can range from as low as
80°C for red beet to as high as 205°C in for pear cactus
[54, 63]. However, the normal range for spray-drying
is 110–160°C [50, 64]. Nevertheless, Phisut reported that
the inlet air temperature of 150–220°C is commonly
used for food spray-drying [61]. Some recent studies
of spray-drying of guava, pineapple, and bael powder
revealed the inlet air temperature of 148, 160, and 166°C,
respectively [65–67].
Quek et al. found that the moisture content of
spray-dried powder decreased as inlet air temperature
and outlet temperature grew higher [51]. The outlet
temperature should be the same to maintain the
product quality. For every 2–3°C increase in the inlet
air temperature, the outlet air temperature is usually
increased by 1°C. According to [49, 51, 68], a higher
inlet air temperature reduced the residual moisture
content. When the inlet air temperature was increased,
the moisture content fell down because the heat transfer
happened at a faster rate between the product and the
drying air [61].
The inlet air temperature can also affect the
hygroscopicity of powder [61]. Similarly, powders
produced at higher inlet air temperatures were more
hygroscopic [24, 26]. Higher inlet air temperatures
lowered the moisture content in the powder, causing the
powder to absorb moisture from the environment [61].
Inlet air temperature can also affect bulk density. In
particular, increasing the inlet air temperature caused
the bulk density to drop [49]. For instance, the bulk
density of acai juice powder decreased as the inlet air
temperature increased [26].
When temperature increased during spray-drying,
case-hardening appeared at the outer layer of atomized
powder [61]. Particle size was reported to increase
together with temperature. Higher drying temperatures
resulted in faster drying rates, triggering an early
structural formation and preventing the particles
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Table 1 Spray-dryer conditions in fruit powder production
Powder Initial
sample
Total
solids
Inlet
temperature,
°C
Outlet
temperature,
°C
Aspirator rate/air
velocity
Feed rate Atomization
rate/
compressor
pressure
Analysis References
Acai Pulp – 138–202 82–114 73 m3/h, 0.06 MPa 5–25 g/min – Process yield,
moisture content,
hygroscopicity,
anthocyanin
retention, outlet
temperature
[26]
Amla Juice – 120–200 81–119 75 m3/h 13–15 mL/min 0.12 mPa Moisture content,
hygroscopicity,
bulk density,
water solubility
index, surface
morphology,
DPPH, total
phenolic content
[27]
Andes
berry
Juice 9°B 12 70 10 m3/h 485 mL/h 4 bar Particle
morphology,
size, thermal
analysis, volatile
compounds,
anthocyanin
activity
[28]
Bayberry
Juice 11°B 150 80 100% (35 m3/h) – 439 L/h Product recovery,
moisture content,
water activity,
glass transition
temperature,
surface
composition
[29]
Ber Juice – 170–210 – 40–80 m3/h 1 L/h
9–21%
– Color, bulk density,
hygroscopicity,
packed density,
outlet temperature
[30]
Black
currant
Extract Final
35°B
150, 160,
180, 205
70, 70,
85, 100
– – – Total polyphenol,
antioxidant
activity
[31]
Black
mulberry
Juice – 110–150 – 800 L/h 150 mL/h 4.65 bar Yield, moisture
content, bulk
density, solubility,
surface
morphology,
glass transition
temperature,
particle size
[32]
Blackberry
Pulp – 140–180 99–115 35 m3/h 0.49 kg/h 0.36 m3 air
flow
Moisture content,
hygroscopicity,
anthocyanin
content,
color, surface
morphology,
particle size
[33]
Blueberry
Extract 30%
total
solids
160 70 – – 23 000 rpm Particle size, true
density, waterbinding
capacity,
anthocyanin
content
[34]
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Continuation of Table 1
Powder Initial
sample
Total
solids
Inlet
temperature,
°C
Outlet
temperature,
°C
Aspirator
rate/air
velocity
Feed rate Atomization
rate/
compressor
pressure
Analysis References
Cantaloupe
Juice – 170–190 75–77 – – – Moisture content,
water activity,
vitamin C,
β-carotene content,
dissolution, surface
morphology
[35]
Elderberry
Juice 10–13°B 70–120 – – 180 & 300 mL/hr – Total phenolic
content, color
[36]
Gac Aril – 120–200 83–125 56 m3/h 12–14 mL/min 0.06 mPa Moisture content,
water activity, bulk
density, antioxidant
activity, color total
carotenoid, water
solubility index
[37]
Guava Concentrate
10.5°B 160 80 – – 40 000 rpm Moisture content,
pH, titratable
acidity, total sugars,
vitamin C, total
soluble solids
[38]
Slurry – 170–185 80–85 4 kg/m2 18–20 rpm – Moisture content,
solubility,
dispersibility,
vitamin C
[39]
Indian
gooseberry
Juice 19% 120/160 80 – 1.2 mL/min 2.4×102 kPa Moisture content,
water activity,
vitamin C,
dissolution
[40]
Lime Juice 9.5 140–170 – – 1.75 g/min 5 bar Powder recovery,
bulk density,
surface morphology
color
[41]
Orange Juice 56–57% 160 65 – – – Color, moisture
content, titratable
acidity, water
activity, particle
size, bulk density,
glass transition
temperature
[42]
Pitaya Juice 50% 145–175 – – 400 L/h 4.5 bar Moisture content,
water activity,
color, true density,
bulk density, tap
density, Carr Index,
Hausner ratio,
glass transition
temperature,
particle size,
surface morphology,
betacyanin content
[43]
Pomegranate
Juice 20–44°B 110–140 – 0.53 m3/min 7 mL/min – Moisture content,
hygroscopicity,
anthocyanin
content, color,
solubility, bulk
density, yield, total
phenolic content,
antioxidant activity
[44]
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from shrinking during drying [69]. A higher inlet air
temperature produced powder with larger particles and
greater swelling [70]. A lower inlet air temperature
resulted in shrunk and smaller particles.
The moisture content in the powder was reported to
improve solubility: the solubility of spray-dried raisin
extracts and tomato concentrates increased together
with the moisture content [18, 24, 50, 51]. The solubility
of spray-dried roselle and tomato powder decreased as
the drying temperature fell [24, 71]. A larger spray-dryer
affected the beetroot powder color changes, namely
increased the a* value and decreased the b* value [72].
Quek et al. focused on the color of spray-dried
watermelon powder [51]. When the inlet air temperature
increased, the b* value increased. However, the
a* values increased at 145–165°C and started to decrease
at 175°C. The lightness of the powders decreased when
the temperature grew higher. At a higher inlet air
Continuation of Table 1
Powder Initial
sample
Total
solids
Inlet
temperature,
°C
Outlet
temperature,
°C
Aspirator
rate/air
velocity
Feed rate Atomization
rate/compressor
pressure
Analysis References
Red beet Concentrate
20%
total
solids
150, 165,
180, 195,
210
87–115 56 m3/h 390–560 g/h – Moisture
content,
hygroscopicity,
drying ratio,
drying rate,
productivity,
bulk density,
color, Tg,
betayanin
content
[45]
Red
pitaya
peel
Puree – 155–175 75–85 900 m3/min – 15 000 rpm Color,
hygroscopicity,
moisture
content,
solubility,
water activity,
betacyanin
retention
[46]
Satureja
Montana
L.
Extract – 135–140 60–70 – – 20 000–21 000 rpm Yield, moisture
content,
bulk density,
hygroscopicity,
water solubility
index, total
phenolic
content, total
flavonoid,
sensory
evaluation
[47]
Sea
buckthorn
Juice – 148.79–
191.21
65–9 2.1 kg/cm3 30 rpm 50 Hg Moisture
content,
dispersibility,
vitamin C,
overall color
change
[48]
The table is based on the findings of this study
temperature, the color of the powders turned darker. Red
color decreased when the inlet air temperature rose [51].
The stability of heat sensitive pigment depended on
the inlet air temperature. The lycopene content in
watermelon juice powder decreased at a higher inlet
air temperature, which was in agreement with another
publication on tomato pulp [50]. The reduction of
lycopene content was likely due to thermal degradation
and oxidation. On the other hand, Tonon et al. also
reported that the inlet air temperature affected the
anthocyanin content in acai juice powder [68]. A higher
inlet air temperature also decreased the amount of
pigments in powder [61].
Atomization rate and air flow rate. Tables 3 and 4
illustrate the effects of atomization rate and air flow
rate, respectively. As for atomization rate, spray-drying
uses different ranges of speed. Atomization rate had
a positive effect on sirih powder yield [73]. Amla and
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Table 2 Effects of inlet air temperature on physicochemical properties of spray-dried fruit powders
Powder Inlet air
temperature,
°C
Yield/
recovery,
%
Moisture
content
Water
activity
Hygroscopicity
Density
Porosity
Particle
size
Caking Solubility
Color Pigment
Antioxidant
activity
Vitamin
C
References
Acai 138–202 +ve –ve – +ve – – +ve – – – –ve – – [26]
Acerola
pomace
170–200 – –ve – –ve – – – –ve +ve – – – – [59]
Amla 100–200 – –ve – –ve –ve – – – NS L*+ve – –ve – [27]
Ber 170–210 – – – +ve –ve – – – – – – – – [30]
Black
mulberry
110–150 +ve –ve – – –ve – – – +ve – – – – [32]
Blackberry
140–180 – –ve – –ve – – NS – – L*+ve –ve – – [33]
Cantaloupe
170–190 – –ve – – – – – – – L*–ve
a*+ve
b* NS
– – – [35]
Gac 120–200 – –ve –ve – –ve – – – – L* NS
TC
NS
–ve –ve – [37]
Guava 170–185 – –ve – – – – – – +ve – – – +ve [39]
Jujube 140–160 – NS – +ve – – – – – L*–ve
TC +ve
– – +ve [60]
Lime 140–170 +ve NS – +ve – – – – – – – – – [41]
Orange
juice
110–170 – –ve – NS – NS – – – – – – – [49]
Pitaya 145–175 – –ve – – – – – – – LNS NS – – [43]
Pomegranate
110–150 NS –ve – NS +ve – – – +ve TC
+ve
a*–ve
–ve +ve – [44]
Red
pittaya
peel
155–175 – –ve –ve –ve – – – – +ve L* +ve
a*–ve
–ve – – [46]
Watermelon
145–175 – –ve NS – –ve – –ve CI NS
HR NS
+ve L*–ve
a* NS
b*+ve
–ve – – [51]
+ve – positive effect; –ve – negative effect; NS – no significant effect; – – not reported
orange powder with greater moisture content resulted
from an increase in atomization rate [27, 49]. However,
Tee et al. stated that raising the atomization rate by
80–100% produced sirih powder with low moisture
content and low hygroscopicity [73].
As for the air flow rate, Fazeli et al. and Goula and
Adamopoulos applied air flow rate of 400–800 and
500–800 L/h, respectively, to produce black mulberry
and tomato powders [32, 74]. Fazeli et al. reported that
the powder yield increased with faster air flow rate,
producing a powder of lower moisture content and
higher solubility [32]. Greater air flow rates reduced
the moisture content and increased the density [32, 74].
However, as the air flow rate increased, the solubility
of black mulberry fell down while that of tomato
increased [32, 74].
Feed solid content and flow rate. Table 5
summarizes the effects of feed flow rate on the
physicochemical properties of spray-dried powdered
fruits. Most of the initial sample used for spray-drying
were in the form of juice [36, 51, 76]. Two types of value
were reported for Brix sample solids. Moßhammer et al.,
used pear cactus juice with 65% of total solids while
Roustapour et al. reported lime juice with 12% total
solids as spray-drying feed [75, 76]. The Brix value
also depended on the fruit. For instance, bayberry juice
spray-dried into powder had Brix of 7–17°, whereas for
pomegranate juice it was 20–44° [65].
Different rates of spray-drying feed have also
become subjects of scientific research. Elderberry
juice was spray-dried into powder at the feed rate of
180 and 300 mL/h [36]. However, Ferrari et al. spraydried
blackberry pulp at the feed rate of 0.49 kg/h [33].
Bazaria and Kumar utilized feed flow rate of
400 mL/h to obtain high-quality spray-dried powdered
beetroot [78]. Ribeiro et al. used different levels of
intake temperature (110, 140, and 170°C), feed flow (0.36,
0.60, and 0.84 L/h), maltodextrin quantity (14–26%),
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improve the recovery by decreasing the stickiness
which causes the product to stick together or to the
drying chamber [16]. An ideal spray-drying carrier has
a high solubility, bland taste, and good emulsifying and
drying properties. Its limited solution viscosity is at
35–45% solids content; it is nonhygroscopic, nonreactive,
and cheap [83]. Maltodextrin, alginate, Arabic gum,
modified starch, inulin, and their combinations served as
carriers for spray-drying of carotenoid-rich goldenberry
(Physalis peruviana L.) juice, while cellobiose was used
as control [84].
Table 6 demonstrates different carrier agents in fruit
powder production, the most common carrier agents
being maltodextrin and Arabic gum. Arabic gum had
a high glass transition temperature and proved efficient
in flavor retention [85]. Arabic gum is expensive
because its supply from Middle East and Africa is as
unpredictable as its quality. Maltodextrin is not only
neutral in color and taste but also relatively cheap, which
makes is the most common carriern commercial spraydrying
[7, 16]. Maltodextrin consists of β-D-glucose
units that are linked by glycosidic bonds (1→4), with
dextrose equivalency (DE) that indicates its reducing
and maltodextrin dextrose equivalent (DE) as
independent variables (5, 10 and 15 DE) [79].
Tonon et al. observed that high feed flow rates
resulted in a lower yield [26]. This correlation was
related to the slow heat and mass transfer. Higher feed
flow rates triggered wall deposit, which reduced the
yield [80]. Feed flow rate also had an adverse effect on
the powder moisture content [77]. High feed flow rate
shortened the time of contact between the feed and the
drying air, thus decreasing the effectiveness of the heat
transfer. An increment in feed flow rate also affected
the evaporating intensity, which lowered the inlet air
temperature and increased the water content in the
powder [81]. Chen et al. reported that higher feed flow
rate resulted in low-hygroscopicity jujube powder [60].
In addition, higher feed flow rates increased the particle
size [80]. Higher feed flow rates increased the solubility
of fermented carrot-and -watermelon juice powder [82].
Type and concentration of carrier agents. Selecting
the best drying aids is one of the most important steps
in spray-drying of fruits and vegetables. Drying aids, or
wall materials, or carriers, are mostly used to increase
the glass transition temperature of the feed. They can
Table 3 Effects of atomization rate on physicochemical properties of spray-dried powders
Powder Atomization rate Yield/recovery, % Moisture content Hygroscopicity Density Particle
size
Solubility References
Amla 30–50 – +ve NS NS – NS [27]
Sirih 80–100% +ve –ve –ve – –ve – [73]
Orange 10 000–25 000 rpm – +ve – NS NS – [49]
+ve – positive effect; –ve – negative effect; NS – no significant effect; – – not reported
Table 4 Effects of air flow rate on physicochemical properties of spray-dried powders
Powder Air flow rate Yield/recovery, % Moisture content Density Solubility References
Black mulberry 400–800 L/h +ve –ve +ve –ve [32]
Lime 47.1–57.8 m3/h +ve NS NS – [41]
Tomato 500–800 L/h – –ve +ve +ve [74]
+ve – positive effect; –ve – negative effect; NS – no significant effect; – – not reported
Table 5 Effects of feed flow rate on physicochemical properties of spray-dried fruit powders
Powder Feed flow
rate
Yield/
recovery, %
Moisture
content
Water
activity
Hygroscopicity
Density Particle
size
Solubility
Color Pigment
content/
retention
References
Acai 5–25 g/min –ve +ve NS – – – – – [26]
Jujube 3–5 m3/h – +ve –ve – – – L*–ve
TC
+ve
– [60]
Orange 150–450 – –ve – NS NS – – – [49]
Watermelon
and
carrot
2–5 mL/min – +ve – – – +ve – –ve [77]
+ve – positive effect; –ve – negative effect; NS – no significant effect; – – not reported
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Pui L.P. et al. Foods and Raw Materials. 2022;10(2):235–251
Table 6 Applications of different carrier agents in spray-drying of fruit powders
Powder Initial
sample
Carrier agent Concentrations/
percentage
Analyses References
Acai Pulp Matodextrin (DE20) & Arabic
gum
6% Process yield, moisture content,
hygroscopicity, anthocyanin
retention, outlet temperature
[8]
Amla Juice Maltodextrin 3–9% (w/v) juice Moisture content, hygroscopicity,
bulk density, water solubility
index, surface morphology,
DPPH, total phenolic content
[38]
Bayberry Juice Maltodextrin (DE 12 & 19) 1:1 (fruit juice) Moisture content, color [64]
Maltodextrin DE 10 10–50% Product recovery, moisture
content, water activity, glass
transition temperature, surface
composition
[29]
Black
mulberry
Juice Maltodextrin DE 6, 9, 20 8–16% Yield, solubility, bulk density,
moisture content
[32]
Blackberry Pulp Maltodextrin (DE 20) 5–25% Moisture content, hygroscopicity,
anthocyanin content, color, surface
morphology, particle size
[33]
Blackcurrant Extract Maltodextrin (DE 11, 18 and 21) Total °B 35 Total polyphenol and antioxidant
activity
[31]
Blueberry Extract Maltodextrin (DE 18.5) Total solids 30%
(blueberry solids 20%)
Particle size, true density, water-
binding capacity, anthocyanin
content
[34]
Cantaloupe Juice Maltodextrin (DE 9–13) 10% Moisture content, water activity,
vitamin C, carotene content, dissolution,
surface morphology
[35]
Elderberry Juice Acacia gum &
maltodextrin (DE 4–7)
5:1–5:4; 1:1 (juice) Total phenolic content, color [36]
Gac Fruit aril Maltodextrin DE 12 10–30% Moisture content, water activity,
pH, color, water solubility
index, bulk density, carotenoid,
antioxidant
[37]
Gooseberry Juice Maltodextrin 19% TSS Moisture content, Water activity,
vitamin C, dissolution time
[40]
Guava Juice Maltodextrin 500 RM1249 7–12% Moisture content, solubility, dispersibility,
vitamin C
[39]
Jucara Pulp Arabic gum, Maltodextrin,
Gelatin
Arabic gum and
Maltodextrin (5–55%),
Gelatin (5–15%)
Anthocyanin content, moisture
content, water activity, hygroscopicity,
solubility, total color
change, bulk density
[88]
Lime Juice Maltodextrin (DE 5) 10–30% Moisture content [76]
Mango Juice Maltodextrin, arabic gum,
starch wax, crystalline cellulose
Surface morphology, stickiness,
solubility, powder diffraction
[14]
Orange Concentrate
Maltodextrin (DE 6-21) – Glass transition temperature,
residue formation
[74]
Juice Maltodextrin and liquid glucose – Particle size, wettability time,
insoluble solids, bulk density,
moisture content
[49]
Pineapple Juice Maltodextrin (DE10) 10–12.5% Moisture content, color, bulk
density, solubility
[7]
Pitaya Juice Maltodextrin 20 and 30% Moisture content, water activity,
color, true density, bulk density,
tap density, Carr’s Index, Hausner
ratio, glass transition temperature,
particle size, surface morphology,
betacyanin content
[43]
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Pui L.P. et al. Foods and Raw Materials. 2022;10(2):235–251
reported 22.62% maltodextrin concentration as optimal
for spray-drying of feijoa pulp, while Dantas et al. used
23% of malto-dextrin to produce powdered avocado
drink [93, 94]. The flowability, color, antioxidant
activity, and phenol content of barberry powder were
optimal at 13% (w/w) of maltodextrin [95].
Table 7 shows the effects of maltodextrin concentration
on the physicochemical properties of spray-dried
powder. Maltodextrin reduced the moisture content,
which might be explained by the increment in feed
solids and the low amount of free water [38, 50, 51, 96].
With the use of it, the yield was 18–35% but there was
more deposit on chamber wall [49]. Maltodextrin
increased the yield up to 18–35% but the deposit
on the chamber wall reached 65–82% [49]. Yet the
capacity [86]. Lee et al. studied the use of additives as
carriers in spray-drying, as well as the impact on such
physicochemical parameters as hygroscopicity, flavor
retention, and color indexing [87].
Maltodextrin has been used to spray-dry sticky
products, e.g. orange, tamarind, blackcurrant, raspberry,
and apricot juice, honey, mango pulp, raisin
juice, lime juice, watermelon pulp, and sweet potato
puree because it facilitates the drying process [25].
The percentage of carrier agents incorporated ranges
from 3% for watermelon juice powder to 40–64% for
pomegranate juice powder [44, 51]. The concentration of
maltodextrin was 15, 20, and 25%, respectively, in the
production of spray-dried cempedak, papaya, and terung
asam powder [90–92]. However, Henao-Ardila et al.
Continuation of Table 6
Powder Initial
sample
Carrier agent Concentrations/
percentage
Analyses References
Pitaya Juice Maltodextrin DE 10 8–22% w/w Color, hygroscopicity, moisture content,
water activity, solubility, betacyanin
content
[46]
Pomegranate Juice Maltodextrin, arabic
gum, starch wax
8 and 12% Yield, solubility, color, total anthocyanin,
antioxidant
[17]
Seabuckthorn
fruit
Juice Maltodextrin DE 20 20–49 g in 100 mL Moisture content, solubility, dispersibility,
vitamin C, overall color difference
[48]
Strawberry Juice Maltodextrin 10–30% Vitamin C loss, solubility,
anti-caking, sensory
[89]
Watermelon Juice Maltodextrin (DE 9-12) 3 and 5% Moisture content, water activity,
dissolution, color, carotene content, sugar
[51]
Table 7 Effects of maltodextrin concentration on physicochemical properties of spray-dried powder
Powder Maltodextrin
concentrations,
%
Yield/
recovery,
%
Moisture
content
Water
activity
Hygroscopicity
Density Particle
size
Caking Solubility
Color Pigment
content/
retention
Antioxidant
activity
Vitamin
C
References
Acai 10–30 – NS – +ve – +ve – – – – – – [26]
Amla 3–9 – –ve – –ve NS – – NS L*+ve – –ve – [27]
Black
mulberry
8–16 +ve –ve – – –ve – – +ve TC– – – – [32]
Blackberry
5–25 – –ve – –ve – – – –ve – – [33]
Guava 5.95–
13.03
– +ve –ve – – – – +ve – – – –ve [39]
Pineapple
– – – – –ve BD – – –ve NS – – – [7]
Pitaya 20 30 – –ve NS +ve – NS L*+ve –ve – – [43]
Pomegranate
44.1–59.1 +ve –ve – –ve +ve BD – – +ve TC+ve
a*RP
–ve
+ve – – [44]
Red
pittaya
8–22 – +ve +ve +ve – – – +ve L*–ve
a*–ve
–ve – – [46]
BD – bulk density; TC – total color changes, +ve – positive effect; –ve – negative effect; NS – no significant effect; – – not reported
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Pui L.P. et al. Foods and Raw Materials. 2022;10(2):235–251
Table 8 Applications of Response Surface Methodology (RSM) in spray-drying of fruits
Powder Starting
material
Independent
variables
Response variables Optimization
Design Software References
Acai Juice Inlet air temperature,
feed
flow rate, maltodextrin
concentration
Process yield, moisture
content, hygroscopicity,
anthocyanin retention, outlet
temperature
RSM Rotatable central
composite
design
Statistica
5.5
[26]
Acerola Juice Inlet air temperature,
Drying aid/acerola,
percent replace
of maltodextrin by
crystalline cellulose
Moisture content,
hygroscopicity,
water solublity,
flowability
RSM Central
composite
design (CCD)
Minitab
15
[59]
Blackberry
Pulp inlet air temperature,
maltodextrin
concentration
Moisture content,
anthocyanin retention,
hygroscopicity, particle size,
color parameters
RSM Central
composite
rotatable design
Statistica
8.0
[33]
Cashew
apple
Juice Drying aid/juice, percent
replace
of maltodextrin by
crystalline cellulose
Ascorbic acid retention,
hygroscopicity, flowability,
water solubility
RSM RSM with 11
runs
Minitab
15
[85]
Guava Slurry Inlet air temperature,
maltodextrin
concentration
solubility, moisture content,
dispersibility, vitamin C
RSM CCRD – [39]
Jujube Juice Inlet air temperature,
maltodextrin
concentration, feed flow
rate
Moisture content, vitamin C,
color, hygroscopicity
RSM Box Behnken – [60]
Orange Juice Inlet air temperature,
atomization rate, flow
rate
Particle size, wettability
time, insoluble solids, bulk
density, moisture content
Full
factorial
design
Complete
random
design
– [49]
Pineapple
Juice Atomization
rate, maltodextrin
concentration
Apparent and true density,
color, moisture content,
solubility
Complete
factorial
design
3 repetition at
center point
– [7]
Pomegranate
Juice Inlet air temperature,
maltodextrin
concentration, feed/ mix
concentration
Moisture content,
hygroscopicity, anthocyanin
content, color, solubility,
bulk density, yield,
total phenolic content,
antioxidant activity
RSM CCD Design
expert
6.0
[44]
Red
pitaya
peel
Puree Inlet air temperature,
outlet temperature,
maltodextrin
concentration
Color, hygroscopicity,
moisture content, water
activity, solubility,
betacyanin content
RSM CCD – [46]
concentration of maltodextrin is important in controlling
the quality of the powder. For instance, a higher amount
of maltodextrin dextrose equivalent made it possible
to obtain low-hygroscopicity liquorice [97]. Leyva-
Porras et al. investigated the effect of spray-drying
settings on the microencapsulation of bioactive
components and the physicochemical qualities of
strawberry juice with maltodextrin as a transporting
agent [98].
Reduction in maltodextrin generally improved the
solubility [7]. Similar observation was reported by
Moreirra et al., who used a drying assistance ratio of
cashew apple juice dry weight (5:1) and cashew tree
gum substituting maltodextrin in 50% of spray-drying
of cashew apple juice generated with high solubility
(> 90%) [59]. The solubility of spray-dried mango
powder decreased as the cellulose concentration grew.
At 9% of cellulose, the solubility values of mango
powder were 72, 71, and 31% using maltodextrin, arabic
gum, and waxy starch, respectively [14]. Quek et al.
studied watermelon powder production and discovered
that adding maltodextrin in greater quantities than 10%
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Pui L.P. et al. Foods and Raw Materials. 2022;10(2):235–251
drying parameter on powder properties. These
parameters included inlet air temperature, atomization
rate, air flow rate, and feed flow rate. The article also
summarized the effects of different carrier agents
on the powder. Inlet temperature of spray-dryer and
carrier concentration were found to increase the
product yield and solubility, as well as to decrease the
moisture content, pigment, and antioxidant content.
However, inlet temperature proved to be the main
factor that affected the powder density. On the other
hand, atomization rate had little effect on powder
properties. Certain powder properties depended on
the type of fruit and the range of parameters applied.
The review showed that the impact of additives and
encapsulation on the physicochemical parameters of
fruit extract powder is critical. Changing the spraydryer
settings can solve the technical obstacles in
spray-drying of fruit extracts. In addition, spray drying
is a newer and cheaper method of turning fruit extracts
into powder.
CONTRIBUTION
Liew Phing Pui gathered data, donated data
and analysis tools, conducted the study, wrote the
manuscript, and submitted it. Abdul Kalam Saleena
Lejaniya was in charge of data collection and data
contribution, formatted the manuscript and proofread
the article.
CONFLICT OF INTEREST
The authors note that they have no known conflicting
financial or personal interests that might have impacted
the findings of this study.
led to color loss [51]. These results confirmed those
obtained by Farimin and Nordin, who studied roselleand-
pineapple powder [96]. Papadakis et al. reported
that the exact color of each powder depended on the
ratio of raisin juice solids:maltodextrin solids [18].
Optimization of spray-drying process. Response
surface methodology is applied to determine the
optimum condition of spray-drying because this
procedure is comprehensive, simple, and highly efficient
[82, 99]. The central composite design builds a
quadratic model for the response variable without a
complete three level factorial experiment. Only by
optimizing the spray-drying process, food producers can
obtain better powder properties and yield [26].
Table 8 summarizes the use of response surface
methodology as optimization for spray-drying of
fruit powder. The main independent variables are
inlet air temperature, maltodextrin concentration,
and feed or flow rate [20, 26, 100]. Moisture content
and water solubility are the most important
properties of food powder [19]. However, yield and
hygroscopicity proved to be the common response
variables [26, 59]. Consequently, optimization of the
amount of carrier is an important step in making a
commercial product [16]. Li et al. applied the Box-
Behken method to obtain the optimal condition
of 142.8°C, 23.7% core material, and 11.7% feed
solid in spray-drying of plum [101]. Pandey et al.
reported the inlet temperature of 166.64°C and 9.26%
maltodextrin concentration as optimal conditions for
fruit slurry spray-drying process [102].
CONCLUSION
This review covered the basic principles of spraydrying
while determining the effects of each spray-