Saffron as the world's most expensive spice is very sensitive and loses its active compounds in exposure to environmental conditions. In this work, microencapsulation of saffron extract by various biopolymers was studied as an effective way to preserve its active compounds. Emulsions with a constant ratio of saffron extract/wall material of 1:20 and two levels of total solids (TS of 30 and 40%), were prepared using a homogenizer, and then spray dried. Powders were characterized in terms of powder yield, encapsulation efficiency, and retention of saffron active components, microstructure, and moisture content. Retention of picrocrocin, safranal and crocin after spray drying was analyzed by measuring absorbance at 257, 330 and 440 nm, respectively. It was observed that a mixture with 40% TS consisting of maltodextrin, gum Arabic and gelatin in the weight ratio of 0.94:0.05:0.01 retained the highest amount of picrocrocin, safranal and crocin, by retention values of 90.06, 80.37, and 91.03%, respectively. Both encapsulation efficiency and powder yield were positively influenced by total solids content, which could be related to the emulsion viscosity and droplet size. To conclude, a mixture of maltodextrin, gum Arabic and gelatin was efficient for saffron extract encapsulation by spray drying.

1. Retention of saffron bioactive components by spray drying
encapsulation using maltodextrin, gum Arabic and gelatin as wall
materials
Hamid Rajabi a
, Mohammad Ghorbani a
, Seid Mahdi Jafari a, *
,
Alireza Sadeghi Mahoonak a
, Ghadir Rajabzadeh b
a
Department of Food Materials and Process Design Engineering, University of Agricultural Sciences and Natural Resources, Gorgan, Iran
b
Research Institute of Food Science and Technology, Mashhad, Iran
a r t i c l e i n f o
Article history:
Received 22 February 2015
Received in revised form
25 May 2015
Accepted 27 May 2015
Available online 5 June 2015
Keywords:
Saffron
Encapsulation
Spray drying
Active components
Biopolymers
a b s t r a c t
Saffron as the world's most expensive spice is very sensitive and loses its active compounds in exposure
to environmental conditions. In this work, microencapsulation of saffron extract by various biopolymers
was studied as an effective way to preserve its active compounds. Emulsions with a constant ratio of
saffron extract/wall material of 1:20 and two levels of total solids (TS of 30 and 40%), were prepared
using a homogenizer, and then spray dried. Powders were characterized in terms of powder yield,
encapsulation efficiency, and retention of saffron active components, microstructure, and moisture
content. Retention of picrocrocin, safranal and crocin after spray drying was analyzed by measuring
absorbance at 257, 330 and 440 nm, respectively. It was observed that a mixture with 40% TS consisting
of maltodextrin, gum Arabic and gelatin in the weight ratio of 0.94:0.05:0.01 retained the highest
amount of picrocrocin, safranal and crocin, by retention values of 90.06, 80.37, and 91.03%, respectively.
Both encapsulation efficiency and powder yield were positively influenced by total solids content, which
could be related to the emulsion viscosity and droplet size. To conclude, a mixture of maltodextrin, gum
Arabic and gelatin was efficient for saffron extract encapsulation by spray drying.
© 2015 Elsevier Ltd. All rights reserved.
1. Introduction
Saffron from about 3000 years ago has been cultivated and used
because of its unique features (Deo, 2003). Saffron, the dried and
colored-red stigma of Crocus sativus L., belongs to the Iridaceae
family, and is produced largely in Asia (particularly Iran)
(Fernandez Pandalai, 2004; Kafi, Koocheki, Rashed, Nassiri,
2006; Khazaei, Jafari, Ghorbani, Kakhki, 2014; Xuabin, 1992).
Today, saffron has found many uses ranging from fragrances to dyes
and medicines (Melnyk, Wang, Marcone, 2010). In recent years,
despite of its high price, the use of saffron is steadily increasing, due
to changes of consumer preference towards natural products hav-
ing functional properties (Knewstaubb Henry, 1988).
Three main active compounds identified in saffron are crocin,
picrocrocin and safranal (Carmona, Zalacain, Sanchez, Novella,
Alonso, 2006; Nassiri-Asl Hosseinzadeh, 2014; Tarantilis,
Polissiou, Manfait, 1994) which lose their nature when exposed
to light, heat and oxygen. Crocin and picrocrocin undergo to
oxidation and hydrolysis reactions; meanwhile safranal, which
causes the fragrance in saffron, is volatile at ambient temperatures.
Therefore, encapsulation of saffron extract could result in a powder
with a longer shelf life.
Encapsulation is defined as a protective method for active
compounds which are sensitive to environmental conditions
(Ahmed, Akter, Lee, Eun, 2010; Borgogna, Bellich, Zorzin, Lapasin,
Cesaro, 2010; Jafari, Assadpoor, He, Bhandari, 2008; Medina-
Torres et al., 2013; Saenz, Tapia, Chavez, Robert, 2009). On the
other hand, during encapsulation, active compounds are packaged
within a matrix or membrane (Akhavan, Jafari, Ghorbani,
Assadpoor, 2014). Encapsulation of herbal products could
improve process capability, easy maintenance and low cost de-
livery, protect against environmental conditions and improve final
product qualities (Deladino, Anbinder, Navarro, Martino, 2008;
Shu, Yu, Zhao, Liu, 2006).
Among several encapsulation techniques, spray drying is the
effective and most common one in the food industry (Jafari et al.,
* Corresponding author. Pishro Food Technology Research Group. Tel./fax: þ98 17
32426 432.
E-mail address: smjafari@gau.ac.ir (S.M. Jafari).
Contents lists available at ScienceDirect
Food Hydrocolloids
journal homepage: www.elsevier.com/locate/foodhyd
http://dx.doi.org/10.1016/j.foodhyd.2015.05.033
0268-005X/© 2015 Elsevier Ltd. All rights reserved.
Food Hydrocolloids 51 (2015) 327e337

2. 2008; Pang, Yusoff, Gimbun, 2014; Re, 1998; Reineccius, 2001,
2004; Shahidi Han, 1993), and one of the oldest encapsulation
methods. The method consists of liquid atomization into small
droplets, a drying step carried out using a warmed gas and
collection of the solid particles (Beck-Broichsitter, Schmehl, Seeger,
Gessler, 2011). Selection of appropriate wall materials is one of
the main steps in microencapsulation process (Pang et al., 2014).
Common microencapsulation agents such as gum Arabic (GA) and
maltodextrin (MD) are often used for herbal or plant-related
products (Bhusari, Muzaffar, Kumar, 2014; Fazaeli, Emam-
Djomeh, Ashtari, Omid, 2012; Janiszewska, 2014; S¸ ahin-
Nadeem, Dinçer, Torun, Topuz, €Ozdemir, 2013; Silva, Vieira,
Hubinger, 2014; Turchiuli, Munguia, Sanchez, Ferre, Dumoulin,
2014). For instance, Khazaei et al. (2014) employed two bio-
polymers, namely MD and GA to microencapsulate the anthocya-
nins of saffron petals. Furthermore, Castro-Mu~noz, Barragan-
Huerta, and Ya~nez-Fernandez (2014) investigated the spray dry-
ing microencapsulation of clarified juice extracted from purple
cactus pear using gelatin (GE) and MD.
There is no information available on microencapsulation of
saffron extract by spray drying. Most of the works in literature deal
with microencapsulation of colorants (Barbosa, Borsarelli,
Mercadante, 2005; Rocha, Favaro-Trindade, Grosso, 2012; Shu
et al., 2006), flavors (Baranauskien_e, Venskutonis, Dewettinck,
Verhe, 2006; Bayram, Bayram, Tekin, 2005; Liu, Zhou, Zeng,
Ouyang, 2004; Reineccius, 1988; Reineccius, Ward, Whorton,
Andon, 1995) or essential oils (Kanakdande, Bhosale, Singhal,
2007; Rosenberg, Kopelman, Talmon, 1990; Soottitantawat
et al., 2004, 2005; Soottitantawat, Yoshii, Furuta, Ohkawara,
Linko, 2003) alone, but saffron stigma has all three type of these
ingredients and therefore, microencapsulation of its extract, is a
complex process. Crocin is a water-soluble glycosidic carotenoid
responsible for color, picrocrocin causes a bitter-taste and safranal
is the main volatile oil present in saffron (Caballero-Ortega, Pereda-
Miranda, Abdullaev, 2007).
The objective of this work was to study the microencapsulation
of saffron extract by spray drying with binary and ternary blends of
MD, GA, and GE as wall materials. The microcapsules were evalu-
ated for the retention of saffron active components, moisture
content and encapsulation efficiency. Scanning electron micro-
scopy was also used to observe the microstructural characteristics
of encapsulated powders.
2. Materials and methods
2.1. Saffron powder preparation
Saffron was picked before sunlight from a farm around Torbat-E-
Heydariyeh (Iran). Stigmas were separated from the other part of
flowers. In order to determine the optimal drying method, three
methods were pre-investigated considering drying at room tem-
perature (25 C ± 1), dehydration with electrical oven (60 C ± 1),
and microwave drying (1000 W). Our results showed (data not
given) that the highest content of saffron active components (SAC)
was obtained when saffron treated at higher temperatures and
lower times. Among the mentioned methods, drying with micro-
wave at 1000 W resulted in the least SAC degradation during the
process. Dried stigmas were crashed and sieved (0.421 mm
meshes). Prior to use, the saffron powder was kept in an air-tight
plastic bag within a desiccator at room temperature to prevent
moisture absorption.
GA was provided by SD Fine Chemical Co. Limited, Mumbai
(India). MD with a dextrose equivalent (DE) of 16.5e19 was pur-
chased from Aldrich (USA). GE (Bovine, Art., 4078) and Ethanol
were supplied by Merck (Germany).
2.2. Preparation of saffron extract
Saffron extract was prepared by extraction of dried powdered
stigmas in water: 50 %v/v ethanol for 2 h. The proportion of solvent
to saffron powder was kept at weight ratio of 100:1. The extract was
filtrated (Whatman filter paper No. 42) and then concentrated in a
rotary evaporator (BUCHI Rotaevaporator R114, Germany) for about
30 min until 90% of the solvent was removed and stored at 4e5 C
prior to the next stage. Picrocrocin, safranal and crocin content of
saffron extract was determined using a UVeVis spectrophotometer
(DR5000, Hach-Lange, Germany) by measuring the absorbance at
257, 330 and 440 nm, respectively, as described by Orfanou and
Tsimidou (1996).
2.3. Preparation of feed composition
Different amounts of MD, GA and GE were used as carriers so
that the resulted emulsion total solids were equal to either 30 or
40% (w/w). Compositions of MD, GA and GE mixtures at different
design points are listed in Table 1. Each formulation was prepared
by blending and rehydrating the carriers in distilled water (40 C)
by magnetic stirrer (IKA®
C-MAG HS 7) at 350 rpm for 2 h. After
dissolution, the mixture was placed overnight in the refrigerator
(5 ± 1 C) to obtain full hydration. The next day, concentrated
saffron extract was added to the feed at proportion of 1:20
(saffron extract:carrier, mass/mass) and homogenized by a
rotorestator homogenizer (Ultra-Turrax IKA®
T25) at 13,600 rpm
for 2 min.
2.4. Measurement of viscosity
A rotational programmable viscometer (DV III Ultra, Brookfield
Engineering Laboratories, USA) at 25 C using the SC4-18 and SC4-
31 spindles was used for viscosity measurement. The temperature
of emulsions was brought to equilibrium and maintained constant
throughout experiments by means of a thermostat tank. The
measurements recorded at shear rate of 50 sÀ1
were considered as
emulsion viscosity.
2.5. Measurement of surface tension
Surface tension was determined by the Du Nouy ring method
(Kruss K100 Tensiometer, Germany) at 25 C. Deionized water was
used to calibrate the tension meter for surface tension
measurements.
2.6. Microencapsulation by spray drying
Spray drying process was performed in a BUCHI mini spray
dryer (B-191, Switzerland). The emulsions were fed into the drying
chamber through a peristaltic pump. The inlet and outlet air tem-
perature were maintained at 180 ± 5 C and 90 ± 5 C, respectively.
The air flow, rate of feeding and atomization pressure were 600 l/h,
5 ml/min and 20 psi, respectively, for both total solids content. The
powders obtained were stored to exclude light and were kept
at À20 C until analyzed.
2.7. Powder yield determination
Powder yield was measured through determination of recov-
ered product given by the ratio between the total recovered
product mass and the mass of extract initially fed into the spray
dryer, and it was expressed by the following equation (Leon-
Martínez, Mendez-Lagunas, Rodríguez-Ramírez, 2010):
H. Rajabi et al. / Food Hydrocolloids 51 (2015) 327e337328

3. y ¼
ðW2 À W1Þ À XwbðW2 À W1Þ
MV TS
 100 (1)
where y is the powder yield (%), Xwb is the moisture content in wet
basis (wb), MV is the volume of extract feed (L), Ts is the content of
total solids (g dry matter/L), while W1 and W2 are the weight (g) of
the powder receptacle before and after spray drying, respectively.
2.8. Encapsulation efficiency (EE)
In order to determine encapsulation efficiency of saffron com-
ponents, 100 mg of each powder (containing 5 mg of initially added
saffron) was dissolved in 100 ml distilled water. On the other hand,
saffron extract with concentration equivalent to 100 mg encapsu-
lated powder was prepared by dissolving 5 mg of saffron powder in
100 ml distillated water followed by filtration. The absorbance of
these solutions was measured at 275, 330 and 440 nm. EE of each
component was calculated through the following equations
(Sarfarazi, Jafari, Rajabzadeh, 2015):
EE ¼
A1%
1cmM$P
A1%
1cmS$P
 100 (2)
A1%
1cmðlmaxÞ ¼ A Â 10; 000=mð100 À HÞ (3)
where EE is the encapsulation efficiency, A1%
1cmðlmaxÞ is the absor-
bance at the respective wavelength (maximum absorbance of the
corresponding compound), A is the specific absorbance, m is the
sample weight (g), H is the moisture and volatile matter content,
A1%
1cmM$P is the absorbance at the respective wavelength in
microencapsulated powder, and A1%
1cmS$P is the absorbance at the
respective wavelength in saffron extract.
2.9. Moisture content
Powders' moisture content (MC, % w.b.) was determined by
drying in a vacuum oven at 70 C until constant weight. Samples
were allowed to cool to room temperature in desiccators containing
silica gel (Jayasundera, Adhikari, Adhikari, Aldred, 2011).
2.10. Scanning electron microscopy (SEM)
Microencapsulated saffron powders were observed under a
scanning electron microscope (S-360, Cambridge, England). Pow-
ders were attached to specimen stubs using a 2-sided adhesive tape
and left in desiccators containing phosphorous pentoxide for 48 h.
Samples were coated with a thin layer of gold under vacuum and
were examined at an accelerating voltage of 8.80 kV.
2.11. Statistical analysis
Extreme vertices design with augmented axial points in mixture
designs was used to obtain various proportions of MD, GA and GE
for saffron extract microencapsulation by spray drying. The entire
triangular region consisting of 26 design points was covered for
experiments. MINITAB Release 16 (Minitab Inc., PA, USA) software
was used for data analysis. All experiments were done in triplicate
and average values were reported.
3. Results and discussion
3.1. Effect of TS on the retention of saffron bioactive components
during encapsulation
The average values of encapsulation efficiency for SAC are
shown in Fig.1. With respect to the total solids content, this variable
had a positive effect on the encapsulation efficiency, i.e., higher
solids content resulted in higher encapsulation efficiencies. It is
shown that the most important factor determining the retention of
volatiles and encapsulation efficiency of food oils during spray
drying is the dissolved solids content in the feed (Jafari, He,
Bhandari, 2007a, 2007b). Our results revealed that encapsulation
efficiency of three major components of saffron increased by higher
TS. This result can be attributed to the emulsion droplet size, which
decreases when total solids content is increased (Jafari et al., 2008).
Many studies have shown that lower emulsion droplet size leads to
higher encapsulation efficiency of oils and flavors (Jafari et al.,
Table 1
Proportions of maltodextrin (MD), gum Arabic (GA) and gelatin (GE) as per mixture design.
GE (g) GA (g) MD (g) Amount (g) Formulation GE (g) GA (g) MD (g) Amount (g) Formulation
1.5 2 36.5 40 14 1.5 6 22.5 30 1
1.125 4.5 24.375 30 15 0.75 0 29.25 30 2
0.5 6 33.5 40 16 0 4 36 40 3
0.75 6 23.25 30 17 0.5 2 37.5 40 4
1.5 0 28.5 30 18 0 6 24 30 5
0 0 40 40 19 1.125 1.5 27.375 30 6
2 4 34 40 20 1 0 39 40 7
0 0 30 30 21 1.5 3 25.5 30 8
1 8 31 40 22 1.5 6 32.5 40 9
2 0 38 40 23 0 8 32 40 10
0.75 3 26.25 30 24 2 8 30 40 11
0.375 4.5 25.125 30 25 1 4 35 40 12
0 3 27 30 26 0.375 1.5 28.125 30 13
Fig. 1. The average value of encapsulation efficiency for saffron main components in
microencapsulated powders with different TS (30 and 40%).
H. Rajabi et al. / Food Hydrocolloids 51 (2015) 327e337 329

4. 2008; Liu et al., 2001; Soottitantawat et al., 2005). Tonon, Grosso,
and Hubinger (2011), studying the microencapsulation of flaxseed
oil using gum Arabic as wall material, also verified that the
encapsulation efficiency directly was influenced by the total solids
content.
These results also can be related to the emulsion properties.
Emulsion viscosity is increased as a function of total solids con-
centration, thus, is required shorter time to form a crust and
reducing the circulation movements inside the droplets and
resulting in higher retention (Jafari et al., 2008). It was observed
that a mixture with 40% TS consisting MD, GA and GE in the weight
ratio of 0.94:0.05:0.01 retained the highest amounts of picrocrocin,
safranal and crocin, by retention values of 90.06, 80.37 and 91.03%,
respectively. Liu et al. (2001) found that addition of GE at 1% (w/w)
in combination with GA as the emulsifier noticeably increased the
encapsulation efficiency of ethyl butyrate, due to faster formation
of crust on the surface of droplets.
One reason for decreased SAC retention at 30% TS may be bubble
inflation-bursting phenomenon. Reducing the soluble solids con-
tent in the feed results in an increase in the amount of water
available to evaporate which leads to a decrease in solution vis-
cosity followed by a softer surface to allow the particle to expand;
this phenomenon becomes more prevalent at lower TS (30%). Liu,
Furuta, Yoshii, and Linko (2000) found that the plausible break-
down of flavor emulsions on inflation of the droplets, and sur-
passing the droplet temperature higher than its boiling point
causes a rapid decrease in flavor retention during microencapsu-
lation by spray drying. Also, Pang et al. (2014) reported similar
results in spray drying of Orthosiphon stamineus extracts.
3.1.1. Picrocrocin retention
Encapsulation efficiency of picrocrocin varied from 54.57 to
90.06%. As shown in Fig. 1, picrocrocin retention was significantly
affected by the total solids content. A lot of researches have been
performed on the influence of different carriers alone or in com-
binations on the encapsulation efficiency of flavors (Madene,
Jacquot, Scher, Desobry, 2006). Optimum operating conditions
and emulsion properties could minimize the loss of flavor in-
gredients. Also, wall material properties have a significant effect on
the stability of oxygen-sensitive flavors (Reineccius, 1988). Bayram
et al. (2005) studied spray drying of sumac flavor and found that
encapsulation efficiency increased with increase in soluble solids
content.
Microencapsulation of other flavor compounds has also been
studied (Balassa, Fanger, Wurzburg, 1971; Brenner, 1983; Schultz,
Dimick, Makower, 1956; Szente Szejtli, 1986; Taylor, 1983;
Zilberboim, Kopelman, Talmon, 1986). It should be noted that
increase in the emulsion viscosity could act effectively in protecting
flavoring ingredients against thermal degradation and other
destructive agents during drying stage by increasing the surface to
volume ratio due to decrease in the size of atomized droplets. Also,
increasing the soluble solids content could increase the encapsu-
lation efficiency of flavoring compounds at the early stage of drying
(Bayram et al., 2005).
3.1.2. Safranal retention
Safranal is a volatile compound and unstable in ambient tem-
peratures. The microencapsulation procedure protects ingredients
which are volatile or sensitive to heat, light, or oxidation (Jafari
et al., 2008). Encapsulation efficiency of safranal varied from
44.57 to 80.37%. As mentioned above for picrocrocin retention and
shown in Fig. 1, safranal retention was significantly affected by the
total solids content. A similar result was reported by Rosenberg and
Sheu (1996) in microencapsulation of ethyl butyrate and ethyl
caprylate using whey protein as wall material. They found that
retention of these volatiles was significantly affected by wall solids
concentration, i.e. retention increased at higher TS from 10 to 30%.
Reineccius (1988) illustrated that after emulsion atomization in the
desiccation chamber, volatile compounds tend to evaporate with
water molecules which causes to volatile loss in early stage of
drying, thus, facilitating crust formation around the atomized
droplets which prevents the evaporation of volatile compounds,
and increasing the efficiency.
The effect of wall material content in the emulsion on the
encapsulation efficiency of volatile during spray drying was also
investigated by others (King, 1988; Menting, Hoogstad, Thijssen,
1970; Reineccius, 1988; Rosenberg Sheu, 1996) and all of them
obtain similar results with ours.
3.1.3. Crocin retention
Sometimes, the color changes of extracts is one result of
destructive reactions (Cortes-Rojas, Souza, Oliveira, 2014). Crocin
retention ranged from 41.86 to 91.03 % and was significantly
influenced by the total solids content (Fig. 1). We found that
microencapsulated powder obtained with a 40% total solids content
and high-ratio of MD had significantly higher color strength than
others. The lowest value of crocin retention was related to
MD:GA:GE in a ratio of 24:4:2 for 30% TS. Other researchers have
obtained similar results in microencapsulation of color ingredients
by spray drying such as Rodríduez-Huezo et al. (2004) in caroten-
oids encapsulation using GA, gellan gum and MD, Shu et al. (2006)
in lycopene microencapsulation using GE and sucrose by spray
drying, and Chen and Tang (1998) in carrot pulp encapsulation
using spray-dryer, with sucrose and GE as wall materials.
3.2. Effect of TS on the powder yield
Powder yield varied from 60.48 to 87.03% and was significantly
influenced by the total solids content (Fig. 2). In contrast to results
obtained for SAC retention, powder yield in some cases was
showing a trend vice versa, i.e., decreased with increasing in the
total solids content of the emulsions. Although the average powder
yield for emulsions prepared with 40% TS was higher than other
ones, but the maximum yield was obtained with 30% TS. In the case
of different wall materials, yield was maximized for MD:GA:GE in
the ratio of 77.5:20:2.5 (30% TS).
Different factors could affect the powder yield of spray dried
herbal extracts such as operating conditions of spray dryer (Ersus
Yurdagel, 2007; Frascareli, Silva, Tonon, Hubinger, 2012; Jangam
Thorat, 2010; Souza Oliveira, 2006; Toneli, Park, Negreiros,
Murr, 2010), carrier type and its ratio in the emulsions (Barbosa
et al., 2005; Bayram et al., 2005; Couto et al., 2011; Fernandes,
Fig. 2. The average powder yield of microencapsulated saffron at two levels of TS.
H. Rajabi et al. / Food Hydrocolloids 51 (2015) 327e337330

5. Candido, Oliveira, 2012; Krishnan, Bhosale, Singhal, 2005;
Krishnan, Kshirsagar, Singhal, 2005), and wall:core ratio
(Frascareli et al., 2012; Hogan, McNamee, O'Riordan, O'Sullivan,
2001).
3.3. Effect of TS on powder moisture content
The moisture content (MC) of the powders was measured to be
in the range of 2.705e5.33%. The powders produced by spray
drying method have a very low MC, in the range between 2.9 ± 0.02
to 4.66 ± 0.21% (w/w) (Couto et al., 2013). From the standpoint of
medicinal usage of saffron, according to the literature (convention,
2007), acceptable MC for spray dried pharmaceutical powders, is
lower than 5% (w/w). Therefore, it could be concluded that all of our
products had suitable levels of residual moisture content.
Total solids content affected the powder moisture content
(Fig. 3). By increasing TS from 30 to 40%, MC decreased from 5.33 to
2.705% revealing solids content had a positive effect on powder MC.
The increase in total solids concentration results in higher viscosity
and less water available for evaporation, leading to lower moisture
content. However, for solids concentrations above 30%, the increase
in emulsion viscosity may reduce water diffusion, resulting in
powders with higher MC. Similarly, Fernandes et al. (2008),
investigation spray drying microencapsulation of Lippia sidoides
essential oil, found that increase in the TS from 30% to 60% led to a
decrease in MC from 5% to 4%.
3.4. Effect of wall material proportions on the retention of saffron
bioactive components during encapsulation
As shown in Figs. 4e6, change in the wall material proportions
resulted in SAC retention variations. This trend could be explained
through emulsion properties i.e. viscosity and surface tension
which are crucial parameters to evaluate the behavior of solutions
during spray drying considering the morphology of spray-dried
powders and the incident of particle ballooning (Hecht King,
2000). Increasing emulsion viscosity up to a point that is relevant
to optimum level could increase encapsulation efficiency. An in-
crease in the viscosity of the initial emulsion should help retention
because of reduction of internal circulations within droplets and
rapid semi-permeable membrane formation (Jafari et al., 2008).
Also, lower surface tensions considered as an index to claim the
emulsion is stable; better emulsion stability, higher efficiency
(Rosenberg Sheu, 1996).
In the case of all three bioactive components, at 30% TS, increase
and decrease of MD and GA proportions from reference blend had
Fig. 3. The average moisture content of microencapsulated saffron powders at two
levels of TS.
Fig. 4. Cox response trace plots of picrocrocin retention; A) 30% TS and B) 40% TS, Contour plot of picrocrocin retention; C) 30% TS and D) 40% TS.
H. Rajabi et al. / Food Hydrocolloids 51 (2015) 327e337 331

6. Fig. 5. Cox response trace plots of safranal retention; A) 30% TS and B) 40% TS, Contour plot of safranal retention; C) 30% TS and D) 40% TS.
Fig. 6. Cox response trace plots of crocin retention; A) 30% TS and B) 40% TS, Contour plot of crocin retention; C) 30% TS and D) 40% TS.
H. Rajabi et al. / Food Hydrocolloids 51 (2015) 327e337332

7. an inverse impact on the SAC retention. The use of MD up to an
optimum level depending on the core type, total solid content and
emulsion properties could improve efficiency. Pang et al. (2014)
reported this amount was 5.33% for encapsulation of O. stamineus
extracts by spray drying. Optimum MD level in our research at 30%
TS based on the lowest surface tension (data not shown) and
highest SAC retention was 87.5% (w/w). In the case of GA,
decreasing its proportion followed by increasing the MD amount in
the mixture caused a decrease in SAC retention due to decrease in
the emulsion viscosity and increase in the surface tension. Higher
GE proportions from reference blend up to 1% (w/w) due to increase
in viscosity caused an increase in SAC retention and vice versa.
Some researchers have increased the viscosity of the emulsion
without significantly changing its solids content through addition
of thickeners ( 1% w/w of wall materials concentration) like so-
dium alginate or gelatin and found similar results with ours (Liu
et al., 2001; Rosenberg et al., 1990).
Retention of each bioactive component at 40% TS was similar to
each other. In this way, SAC retention was increased by increasing
the GA proportion due to improvement in emulsion stability i.e.
increase in viscosity and decrease in surface tension. Hogan et al.
(2001) showed that microencapsulation efficiency of soy oil with
milk proteins and carbohydrate blends was positively correlated
with emulsion stability during the process. Increase of GE propor-
tion from reference blend due to excessive rise in viscosity and
related problems such as impossibility or difficulty of droplet at-
omization and larger exposure during atomization (Jafari et al.,
2008) could cause a decrease in the retention.
3.4.1. Picrocrocin retention
It can be observed in Fig. 4A that retention of picrocrocin at 30%
TS decreased as the amount of MD and GA varied from reference
blend (GE ¼ 2.5%, GA ¼ 10% and MD ¼ 87.5%). In the case of GE
effect on retention, its levels had an inverse effect on response
(retention of picrocrocin) than other two wall materials and the
retention was increased as the amount of GE increased from
reference blend. Cox trace plots showed that changes in GA and MD
levels had similar effects.
For retention of picrocrocin at 40% TS, a different trend was
observed (Fig. 4B). Picrocrocin retention decreased and increased as
the level of MD varied from reference blend. Also increase in GA
from references blend had a similar effect on retention; it remained
constant with GA decrease from references blend. However, as seen
in Fig. 1A, GE had a different trend than GA and MD. Picrocrocin
retention was decreased as the amount of GE varied from reference
blend. Cox trace plots showed that in both TS, GE level had the
greatest impact on retention of picrocrocin than MD and GA.
Retention contour plot (Fig. 4C) for 30% TS showed that area for
maximum retention (100% of initially added amount) was close to
the points, where GE was present at maximum. In practice, use of
this amount of GE due to increase in the emulsion viscosity fol-
lowed by problems in spraying, was not possible. At the point that
MD:GA:GE was at the ratio of 25.5:3:1.5, retention was at accessible
maximum level, namely 60% of initially added amount. In the case
of 40% TS (Fig. 4D), we found that the area of maximum retention
(80% of initially added amount) was at points, where GE was kept
under 0.5% of TS. Retention levels dropped to 70% of initially added
amount at a point with the highest amount of MD and without GA.
3.4.2. Safranal retention
Cox trace plot (Fig. 5A) showed that the behavior of both MD and
GE on retention of safranal at 30% TS was approximately similar and
showed a trend similar to the picrocrocin. In contrast, the GA level
had a different effect on response than the other two components
and retention of safranal was slightly decreased as the amount of
GA increased and remained constant with decreased from refer-
ence blend.
As shown in Fig. 5B, retention trend of safranal at 40% TS was
different from others. Safranal retention decreased and increased as
the level of MD and GA decreased and increased from reference
blend. But as seen in Fig 3B, GE had a different influence compared
with GA and MD. Safranal retention was decreased as the amount of
GE varied from reference blend. Cox trace plots showed that in both
TS, GE level had the greatest impact on the retention of safranal
than MD and GA.
Contour plot (Fig. 5C) for retention levels of safranal at 30% TS
showed that the area of maximum retention was at points, where
GE was at maximum amounts that as mentioned above was un-
reachable. Retention levels decreased from 70 to 60% of initially
added amount with increase in MD level and decrease in GE level
without any GA. Retention level in all of the experimental points in
40% TS (Fig. 5D) varied in the range of 60e80% of initially added
amount that had an incremental trend with decrease in GE level.
3.4.3. Crocin retention
Cox trace plot (Fig. 6A) showed that retention of crocin at 30% TS
increased as the amount of GE increased from reference blend. An
interesting trend was observed when GA amount decreased from
reference blend that retention at first was increased and then
decreased. Crocin retention was decreased in four conditions: in-
crease and decrease of MD, increase of GA and decrease of GE from
references blend.
About crocin retention at 40% TS, as shown in Fig. 6B, we
observed a trend similar to safranal retention, although MD had
Fig. 7. Cox response trace plots of spray dried saffron powder yield; A) 30% TS and B) 40% TS.
H. Rajabi et al. / Food Hydrocolloids 51 (2015) 327e337 333

8. severe effects on crocin retention than picrocrocin. Also, it clearly
shows that GE level had the greatest impact on the retention of
crocin than MD and GA.
In the case of MD selection with different DE, in the pretest
experiments (data not shown), we found that MD with a high DE
(16.5e19) was better than low DE for SAC retention. In contrast to
our results, Wagner and Warthesen (1995), revealed that among
MD with different DE, the highest efficiency was obtained with
maltodextrin 4 DE for a- (89%) and b-carotene (87%). Desobry,
Netto, and Labuza (1999) also reported an efficiency of 62 and
78% for trans- b-carotene encapsulated, with MD 25 DE and MD 4
DE/glucose (82:18), respectively.
Contour plot of crocin retention (Fig. 6C) in all of the experi-
mental points was in the range of 50e60% of initially added amount
that represents the low efficiency of this wall materials at 30% TS.
On the opposite side at 40% TS (Fig. 6D), retention level at 13 points
in constraint region was at acceptable range from 70 to 90% of
initially added amount that may be due to achieving an optimum
viscosity as a result of increase in TS and also the use of GE.
3.5. Effect of wall materials proportion on the powder yield
As shown in Fig. 7, the effect of wall material proportion on
powder yield at 30 and 40% TS was completely disparate. In the 30%
Fig. 8. Cox response trace plots of powder moisture; A) 30% TS and B) 40% TS.
Fig. 9. Scanning electron micrographs of spray-dried saffron microcapsules at 30% TS. (A) MDeGA (90:10), (B) MDeGE (90:10), and (C) MDeGAeGE (85:1:5).
H. Rajabi et al. / Food Hydrocolloids 51 (2015) 327e337334

9. TS, powder yield was increased with higher GA and MD and lower
GE from reference blend. Also, powder yield was rapidly decreased
with higher GE and lower MD from reference blend. It could be said
that GA decreases from reference blend had not effect on powder
yield.
In the case of 40% TS, powder yield increased with variation of
MD and GE from reference blend. In contrast to MD and GE, powder
yield decreased with variation of GA from reference blend. In both
30 and 40% TS, GE level had the greatest influence on the powder
yield than MD and GA.
3.6. Effect of wall materials proportion on powder moisture content
It can be observed from Cox trace plot (Fig. 8A) that the MC of
microencapsulated powders decreased as the amount of MD and
GA decreased and GE increased from reference blend. As shown in
Fig. 8B, the effect of GA and GE on MC was similar to 30% TS. While
the MC of powders varied as the amount of MD decreased from
reference blend. Thus, the wall material type and ratio can influ-
ence the MC of microencapsulated powders. In contrast to our re-
sults, Dian, Sudin, and Yusoff (1996) reported that MC values for
microencapsulated palm oil by spray drying method were not
affected by the type of wall material.
3.7. SEM analysis
The SEM microphotographs of the encapsulated powders pro-
duced at the various conditions (30 and 40% TS) are shown in Figs. 9
and 10.
It could be found that saffron extract microcapsules showed a
nearly spherical shape. Particle size distribution varied from 0.54 to
20.47 mm and the mean particle diameter for 30% and 40% TS was
6.69 mm and 7.81 mm, respectively. The increase in total solids
content resulted in larger particle sizes. This can be explained by
the viscosity of the feed emulsion, which increased with solids
concentration (Jafari et al., 2008). Hogan et al. (2001) and Jinapong,
Suphantharika, and Jamnong (2008) reported that particles' mean
diameter was increased with the rise of total solids content. They
attributed this result to the increment of the feed emulsion
viscosity.
The high temperature in the drying chamber and the size of
atomized droplets which are very fine leads to a rapid withdrawal
of water from it, resulting in wrinkles and depressions in the
powder surfaces (Rosenberg, Kopelman, Talmon,1985), as shown
in our samples too.
It was observed (Figs. 9 and 10) that the type and concentration
of each wall material had a meaningful impact on the morphology
of particles. Pang et al. (2014) found similar results in spray drying
of O. stamineus extracts while, different results are reported by
Fernandes et al. (2008). They observed microparticles produced
from different solid contents (30, 40, 50 and 60%) or from different
MD:GA proportions (4:1, 3:2, 2:3 and 0:1) had no significant dif-
ferences in appearance. Also, Ameri and Maa (2006) illustrated that
the water withdrawal rate from droplet and the type and concen-
tration of wall material as well as wall:core ratio are the main
factors which determine the shape and morphology of spray dried
particles. Optimal process conditions must be in a way to maximize
the drying rate.
Fig. 10. Scanning electron micrographs of spray-dried saffron microcapsules at 40% TS. (A) MDeGA (90:10), (B) MDeGE (97.5:2.5), and (C) MDeGAeGE (94:5:1).
H. Rajabi et al. / Food Hydrocolloids 51 (2015) 327e337 335

10. Fig. 9B and C shows a fragmented microcapsule, where it is
possible to observe its wall, that may be due to decrease in total
solids and viscosity. This defect in the structure may be one of the
reasons for the decrease in SAC retention at 30% TS compared with
other samples. Rocha, Trindade, Netto, and Favaro-Trindade (2009)
and Favaro-Trindade, Santana, Monterrey-Quintero, Trindade, and
Netto (2010) found similar results in casein hydrolyzate encapsu-
lation using MD and using blends of GE and soybean protein isolate
as carriers, respectively. The amount of dented particles in the
powder produced without GA was minimum, while, the percent of
dented particles tended to increase linearly with the increase in GA
concentration. At lower TS (30%) and high amount of MD, the
particle seems to have smooth and spherical surface along with
partial fragmented appearances in contrast to the ones at higher TS
(40%) and high amount of GA, which show more shrinkage. In
agreement with this finding, Pang et al. (2014) reported that in-
crease in the MD concentration from 0.53% to 10.67% leads to
particles with a smoother surface. Many researchers have reported
that the use of GA as wall material lead to nearly spherical dented
particles, while particles obtained from MD have a broken and
incomplete structure (Fernandes et al., 2008; Kanakdande et al.,
2007; Krishnan, Bhosale, et al., 2005; Krishnan, Kshirsagar, et al.,
2005; Vaidya, Bhosale, Singhal, 2006).
The highest size distribution uniformity, maximum percent of
dented particles and the highest encapsulation efficiency were
observed in the formulation containing all three wall materials at
40% TS that may be due to achieving an optimum viscosity as a
result of increase in TS and also the use of GE (Fig. 10C). Further-
more, as shown in Fig. 10, the lack of wall fissures or porosity on the
particle surfaces at 40% TS indicates a complete coverage of the
gum over the SAC.
4. Conclusion
The present study describes the use of three types of wall ma-
terials i.e. maltodextrin, gum Arabic and gelatin for the microen-
capsulation of saffron extract using spray-drying technique. Total
solids content had a positive influence on the encapsulation effi-
ciency and the SAC retention. These results could be related to
emulsion properties, mainly viscosity. Higher solids concentration
leads to bigger particle sizes, lower moisture contents and higher
powder yields. As far as the blends were concerned, the stability of
SAC increased as the quantity of gelatin decreased in its blend with
maltodextrin and gum Arabic up to 1% (w/w). The microencapsu-
lation process was optimized at 40% total solids, consisting of
maltodextrin, gum Arabic and gelatin in the w/w ratio of
0.94:0.05:0.01. The knowledge obtained from this study could be
important to improve the stability of worthwhile active
compounds.
Acknowledgment
Iran National Science Foundation (grant number 90000994) and
the Research Institute of Food Science and Technology should be
acknowledged for their financial support.
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