Nano-encapsulation of saffron extract through double-layered multiple emulsions of pectin and whey protein concentrate

Journal of Food Engineering 165 (2015) 149–155

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Nano-encapsulation of saffron extract through double-layered multiple emulsions of pectin and whey protein concentrate Afshin Faridi Esfanjani, Seid Mahdi Jafari ⇑, Elham Assadpoor, Adeleh Mohammadi Department of Food Materials and Process Design Engineering, Faculty of Food Science and Technology, University of Agricultural Sciences and Natural Resources, Gorgan, Iran Pishro Food Technology Research Group, Gorgan, Iran

a r t i c l e

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Article history: Received 4 February 2015 Received in revised form 12 June 2015 Accepted 17 June 2015 Available online 18 June 2015 Keywords: Nano-particles Double layer Multiple emulsions Saffron

a b s t r a c t In this study, nano-particles of saffron extract (<100 nm) were encapsulated by spray drying. For this objective, the primary saffron water extract-in-oil (W/O) micro-emulsion containing 10% (w/w) saffron extract was re-emulsified in order to prepare W/O/W multiple emulsions, with a dispersed mass fraction of 0.25, and stabilized using protein (whey protein concentrate (WPC))/polysaccharide (pectin). Also, the encapsulation efficiency of crocin, picrocrocin and saffranal as core materials and surface characteristics of spray dried powders were investigated. Our results revealed that W/O/W multiple emulsions stabilized by sequential adsorption of WPC/pectin was the most efficient technique resulting in the better encapsulated efficiency for crocin, picrocrocin and saffranal, low yellow color (b⁄) surface and, smooth surface in final powders, mainly due to fabrication of stable wall materials obtained by sequential adsorption of WPC and pectin. Ó 2015 Elsevier Ltd. All rights reserved.

1. Introduction Saffron has been used in a wide variety of industries, including food, pharmaceutical and, cosmetics due to its natural colorant, antioxidant and therapeutic properties. Crocin, picrocrocin, and saffranal are the major compounds of saffron responsible for its color, aroma, and flavor, respectively (Basker and Negbi, 1983; Sampathu et al., 1984; Zeng et al., 2003). These compounds are rather unstable and influenced by the final processing temperature, storage temperature, pH, light, oxygen, enzymes, proteins and metallic ions (Patras et al., 2010). Microencapsulation is a technique for coating of bioactive materials (like crocin, picrocrocin, and saffranal) in the form of micro- and nano-particles and, providing protection or controlling the release of the entrapped ingredients. There are different methods for encapsulation in the food industry and spray drying is a common and affordable way to do this (Gouin, 2004; Jafari et al., 2008a; Bhandari, 2004). Improving the encapsulation efficiency during spray drying, which is preventing volatile losses and extending the shelf-life of the products by minimizing the amount of unencapsulated ⇑ Corresponding author at: Department of Food Materials and Process Design Engineering, Faculty of Food Science and Technology, University of Agricultural Sciences and Natural Resources, Gorgan, Iran. E-mail address: [email protected] (S.M. Jafari). http://dx.doi.org/10.1016/j.jfoodeng.2015.06.022 0260-8774/Ó 2015 Elsevier Ltd. All rights reserved.

material at the surface of powder particles, is the major emphasis for microencapsulation of food flavors and oils (Jafari et al., 2008b). Infeed model food systems (water, carrier, and flavor) play a key role in optimising the encapsulation efficiency. These systems can be prepared by different models including maltodextrins, protein or polysaccharide based systems, and emulsion systems. The W/O/W multiple emulsion stabilized by biopolymers is a major food system for creating spherical spray dried powder particles in which hydrophilic ingredients are encapsulated in the inner aqueous phase (Rodríduez-Huezo et al., 2004; Mlalila et al., 2014). The choice of resistant wall materials can affect the encapsulation efficiency of entrapped compounds within W/O/W multiple emulsions. Therefore, applying double-layer techniques (oil droplets coated by double-layered interfacial membranes) for producing W/O/W multiple emulsions, can efficiently coat oil particles during emulsification and result in improved stability to environmental stresses of encapsulated ingredients (Bouyer et al., 2012; Giroux et al., 2013). Rodríduez-Huezo et al. (2004) revealed powders obtained by spray-drying of double-layer W/O/W multiple emulsions showed the best morphology, highest microencapsulation efficiency, and highest total carotenoids retention and a high biopolymer blend (gum Arabic, mesquite gum and maltodextrin) to primary emulsion ratio also produced a high microencapsulation efficiency. Rajabi et al. (2015) working on saffron extract microencapsulation observed that a mixture with 40% TS consisting of

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maltodextrin, gum Arabic and gelatin in the weight ratio of 0.94:0.05:0.01 retained the highest amount of picrocrocin, saffranal and crocin, by retention values of 90.06%, 80.37%, and 91.03%, respectively. Serfert et al. (2013) investigated the oxidative stability of encapsulated fish oil by spray drying and showed O/W interface produced with Beta-lactoglobulin and low methoxylated pectin gave the best protection of the oil. Recently, Raei et al. (2015) found that higher alginate concentration resulted in higher lactoferrin encapsulation efficiency and nanocapsuls prepared with thermal treatment had a higher efficiency (almost 100%) along with smaller particle sizes (mostly < 100 nm). As far as we know, there is no available scientific literature about nano-encapsulation of saffron extract via W/O/W multiple emulsions and spray drying. Consequently, the objective of this study was to evaluate different types of model food systems (including maltodextrin, whey protein based systems, and double layer or single layer W/O/W multiple emulsion systems) and propose a new technique for producing spray dried powders containing saffron extract in order to have a higher encapsulation efficiency. 2. Materials and methods Saffron was provided from Torbat heydariyeh farms, Khorasan-e-razavi, Iran. Sunflower oil and sodium azide was purchased from FRICO (Sirjan, Iran) and Sigma–Aldrich (St. Louis, USA), respectively. Maltodextrin was obtained from Qinhuangdao starch Co. (DE 16-20, China) and citrus pectin with a degree of methyl esterification of 71.1% and Galacturonic acid >65% was purchased from MP biomedical (Netherland). Whey protein concentrate (80% protein) and sorbitan monooleate (Span 80) was obtained from Sapoto cheese (USA) and Merck (Germany), respectively. All other general chemicals used in this study were of analytical grade. 2.1. Saffron extracts preparation and analysis For extraction of saffron compounds, the procedure of Kumpati et al. (2003) was adopted by some modifications. 10 g of saffron powder was mixed with 150 ml water in a dark colored bottle and, placed in an incubator with shaker for 24 h. A rotor–stator homogenizer (10,000 rpm for 10 min, Heidolph Silentcrusher, Germany) was used for maximum extraction of saffron bioactive compounds. After homogenization, the extract was filtered under vacuum, and kept in the freezer at 18 °C until doing the tests. ISO/TS 3632 procedure (2003) was used for the measurement of saffron components. According to ISO, picrocrocin, saffranal and crocins are expressed as direct reading of the absorbance of 1% aqueous solution of dried saffron at 257, 330 and 440, respectively. After the extraction was over, the solution was passed through a Whatman filter paper No. 42. Then, 2.5 ml of the filtrate was transferred to a 50-ml volumetric flask and made to the mark with distilled water. The final concentration of the powdered saffron in water was 0.005% (w/v). Results are obtained by direct reading of the absorbance, D, at three wavelengths by using the T80+UV/VIS spectrophotometer (PG-Instruments-LTD, USA) equipped with a 1-cm path quartz cell, as follows: E% 1cm ð440 nmÞ : absorbance at 440 nm ðmaximum absorbance of crocinsÞ; E% 1cm ð330 nmÞ : absorbance at 330 nm ðmaximum absorbance of safranalÞ; E% 1cm ð257 nmÞ : absorbance at 257 nm ðmaximum absorbance of picrocrocinÞ : E% 1cm ¼ ðD  10;000Þ=ðm  ð100  HÞÞ ð1Þ

where D is the specific absorbance; m is the mass of the saffron sample, in grams; H is the moisture and volatile content of the sample, expressed as a mass fraction (Sarfarazi et al., 2015).     % Crocin content E% 1cm 257 , picrocrocin content E1cm 257 and,   saffranal content E% 1cm 257 in saffron extract were 240.83, 150.6, and, 81.53, respectively. 2.2. Biopolymer solution preparation Hydrated solution of the outer aqueous phase of W/O/W multiple emulsions were prepared by dissolving pectin and maltodextrin powders in buffer solution (phosphate buffer, pH = 6) while stirring at 50 °C for 30 min and kept overnight to warrant a full saturation of the polymer molecules. In the case of Whey protein concentrate (WPC), the WPC powders were dispersed in buffer solution (phosphate buffer, pH = 6). The pH of WPC solutions was adjusted back to pH 6.0 using 1 M HCl if required and kept refrigerated for 24 h for complete hydration; Then the solutions were heat-treated at 70 °C for 20 min, and cooled down quickly. The total concentration of dissolved solids was composed of 27 wt% maltodextrin and 8.2 wt% of emulsifying ingredients (including 8% WPC and 0.2% Pectin). 0.004% of sodium azide was included in the solutions as an antimicrobial substance. 2.3. Preparation of infeed aqueous materials Two model food systems (including matrix of maltodextrin, whey protein based systems and double layer or single layer W/O/W multiple emulsion systems) were prepared for nano-encapsulation of saffron extract: (a) Maltodextrin and WPC was produced by mixed 8% WPC, and 27% maltodextrin and dissolving in distilled water at ambient temperature (25 ± 1 °C) to obtain 35% total solids concentration. The solution was kept in refrigerator for complete hydration in 24 h. Then, saffron extract and solution of maltodextrin/WPC as wall materials were mixed in a weight ratio (w/w) of 1:3.5 (extract: wall material). The pH of mixtures adjusted on 6.0 with phosphate buffer, and then mixed with a magnetic stirrer (120 rpm, 10 min). (b) W/O/W multiple emulsion systems were prepared in two different ways; a single layer multiple emulsion stabilized by whey protein (WPC) alone and, a double layer multiple emulsion stabilized by complex of whey protein (WPC) and pectin (simultaneous and sequential adsorption) according to Mohammadi et al. (2016). Briefly, first, W/O micro-emulsions were produced by drop-wise addition of 10% saffron extract into the mixture of 60% sunflower oil and 30% Span 80 while stirring (300 rpm). After each addition, the system was given enough time to become transparent and isotropic. The coarse W/O/W multiple emulsions were prepared by gradually adding W/O micro-emulsions into the outer aqueous phase while blending by a homogenizer (12,000 rpm for 5 min at 10 °C, Heidolph Silentcrusher, Germany) and then these coarse emulsions were further emulsified using mentioned homogenizer (15,000 rpm for 8 min at 10 °C). W/O/W multiple emulsions stabilized by sequential (layer by layer) adsorbed WPC and pectin were produced in two stages. First, the primary W/O micro-emulsion was gradually added into aqueous solution of WPC and maltodextrin while blending by homogenizer (12,000 rpm for 5 min at 10 °C, Heidolph Silentcrusher, Germany), and then this emulsion was gradually added into aqueous solution of pectin while homogenization

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(15,000 rpm for 8 min at 10 °C). All multiple emulsions were composed of 25% primary emulsion and 75% outer aqueous phase. 2.4. Emulsions droplet size Average droplet size of W/O/W multiple emulsions was immediately evaluated using Zetasizer (Malvern Instruments, Worcestershire, UK). Dispersant RI and Material RI was 1.33 and 1.40, respectively. Experiments were carried out at 25 °C. The instrument reports the mean particle diameter (z-average) and the polydispersity index (PDI) ranging from 0 (monodispersed) to 1 (very broad distribution). 2.5. Spray drying The infeed emulsions were transformed to encapsulated powders in a pilot-plant spray drier (Model SL 20, Novin Industry Co., Tehran, Iran) equipped with a pressure air atomizing nozzle at 1.5 bar air pressure, inlet air temperature of 140 ± 5 °C, and outlet air temperature of 90 ± 5 °C. The dried powder was collected and stored in dark bottle, air tight containers at 4 °C until tests. 2.6. Encapsulation efficiency and surface content analysis A modified method based on Bagheri et al. (2014) was used to extract crocin, picrocrocin, and saffranal from encapsulated powders. For determining the amount of crocin, picrocrocin and saffranal encapsulated within particles, 0.5 g powder sample was dispersed with 40 mL distilled water in a flask, and this mixture was homogenized for 30 min; after which 40 mL of ethanol-hexane (4:3, v/v) was added and the solution was again homogenized for 10 min. Then, it was centrifuged for10 min at 4000 rpm (25 °C), and upper and bottom phases were collected separately. The absorption of crocin and picrocrocin in upper phase and, in the case of saffranal, (because 30–70% essential oils of saffron relates to this compound), the percent absorption in upper (aqueous phase) and bottom phase (oil phase) was measured based on Section 2.1. The encapsulation efficiency (%) of crocin, picrocrocin and saffranal in the encapsulated powders was calculated using the following formula:

EEð%Þ ¼ ðC e =C t Þ  100

ð2Þ

where Ce is the content of crocin, picrocrocin, and saffranal released from capsules, and Ct is the total crocin, picrocrocin, and saffranal content added into the particle formation solution. 2.7. Surface color analysis In order to investigate the surface color of powders as an indicator of surface component content (saffron extract), the procedure of Mahdavee Khazaei et al. (2014) was adopted by some modifications. The yellow (b⁄) index at the powder surface was measured because of yellow–orange color of saffron extract. For all samples, color was measured using image processing system. The system comprised of a digital camera (Canon A550, Kuala Lumpur, Malaysia), an image-capturing box and image analysis software (Image j 1.47v). 10 gram of the powders was transferred into a Petri dish and was placed at the bottom of the box; the digital camera was fixed 20 cm on the top of sample and images were taken. Subsequently, by using Image J software, powders color was analyzed. Afterwards, the images were converted from RGB to Lab system by ‘‘color space converter’’ plugin and b⁄ factor of the samples was measured.

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2.8. Scanning electron microscopy of encapsulated powders The nano-encapsulated powders were sprinkled onto a two-sided adhesive tape and then coated with a thin layer of gold. Morphological features of particles were then observed by a field emission scanning electron microscope (S-4160 Cold Field-Emission SEM, Hitachi, Tokyo, Japan) with an accelerated voltage of 320 kV and photographed at 6000. 2.9. FTIR analysis The structure analysis of the WPC–pectin samples was examined by Fourier transform infrared spectroscopy (FT-IR). The IR spectra of the samples were recorded by FT-IR spectrophotometer (Shimadzu, japan) using attenuated total reflection technique. The spectrum was scanned in transmission mode from 400 to 4500 cm wavenumber range. The dry samples were blended with KBr powder and pressed into a disk before spectrum acquisition. 2.10. Statistical analysis Four different treatments were designed and the experiments were all carried out in triplicate. The collected data were analyzed by one-way ANOVA; the means were compared by the Duncan’s multiple range tests at the 95% level through SPSS version 21 (IBM, USA). 3. Results and discussion 3.1. Size distribution of emulsions The droplet size distribution of primary W/O micro-emulsion is presented in Fig. 1A. It shows that there are small dispersed droplets with a size well below 1 micron (<100 nm). Also re-emulsification of primary W/O micro-emulsions with biopolymers (WPC/pectin) resulted in W/O/W multiple emulsions with an increased size of dispersed droplets coated by biopolymers (Fig. 1B). Our analysis of droplet size distribution of W/O/W multiple emulsions revealed that double layering increased (P < 0.05) the average droplet size (Fig. 1B). It was found that W/O/W multiple emulsion stabilized by WPC alone formed small droplets with an average size of 436.3 nm and the W/O/W emulsions prepared by simultaneous and sequential adsorption of WPC–pectin had much larger droplet size of 536.3 and 482.3 nm, respectively (Table. 1). It may be due to the application of two biopolymers (WPC and pectin) which increases the thickness of outer layer of W/O/W multiple emulsions and results in an increase in their size. In agreement to the results obtained in the present study, Mohammadi et al. (2016) reported that W/O/W multiple emulsions prepared with a complex of WPC and pectin had larger droplets than their counterparts stabilized with WPC alone. Also, we found that the peak of droplet size distribution in W/O emulsions (Fig. 1A) was higher than W/O/W multiple emulsions (Fig. 1B) because decrease in droplets size results in increasing the number of particles; in W/O/W multiple emulsions, addition of biopolymers increased the size of particles, so naturally the number of droplets decreases. 3.2. Encapsulation efficiency Our result (Table 1) showed the encapsulation efficiency (EE%) of crocin, picrocrocin and, saffranal in spray-dried powders produced from double-layered W/O/W emulsions of WPC/pectin (sequentially and simultaneously adsorbed) was higher (P < 0.05),

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Number %

40

30

multiple emulsions with those made with simultaneous adsorbed WPC/pectin, it was found that sequentially adsorbed samples had generally higher EE (Table 1). This may be related to the aggregates of outer layer in this formulation; as a result, WPC and pectin would establish more connections between the wall biopolymers, so we can expect an improved stability of emulsions against environmental stresses of encapsulated ingredients. In agreement, Ganzevles et al. (2008) showed that the sequentially adsorption of protein and polysaccharide was thicker and denser than simultaneous adsorbed layers.

A

20

10

0 10

50 100

1000

3.3. Surface characteristics of saffron encapsulated powders

10000

Size (nm)

Fig. 1. The size distribution of W/O nano-emulsion (A) and role of the double layer formation of biopolymers on the size distribution of W/O/W multiple emulsions (B).

3.3.1. Surface color Our results with surface color (b⁄) analysis revealed that powders containing saffron extract obtained from matrix of maltodextrin/WPC had the highest b⁄ value, while W/O/W multiple emulsions stabilized by sequential absorption of WPC/pectin resulted in powders with a low b⁄, as shown in Fig. 2. Therefore, infeed model food system had a significant influence (P < 0.05) on the surface color (b⁄) of encapsulated powders containing saffron extract. This could be explained by the instability of maltodextrin/WPC matrix during spray drying process because of inadequate protection of core materials (crocin, picrocrocin, and saffranal), which results in increasing amount of unencapsulated material on the surface of powder particles and because of yellow-orange color of saffron extract, the yellow (b⁄) index at the powder surface is increased. On the contrary, when applying double-layer W/O/W emulsions, the core materials are inside the inner droplets and protected by multilayers; so the yellow (b⁄) color index at the surface of powder particles is decreasing; revealing a lower unencapsulated content.

compared with single-layer W/O/W emulsions stabilized with WPC alone or matrix of WPC/maltodextrin as the infeed model food systems. This difference may have arisen from the variation in the infeed model food systems. As a matter of fact, the layer around oil droplets created by double-layer biopolymers is elastic and could aggregate more than single-layer ones which results in improved stability of W/O/W multiple emulsions against environmental stresses of encapsulated ingredients (lutz et al., 2009). Therefore, in encapsulated powders obtained from double -layered multiple emulsions, nano-particles of saffron extract (<100 nm) were possibly enclosed and embedded more efficiently within the WPC/pectin complex and also, the resulted emulsions were more stable during spray drying process which is one of the critical parameters to have the optimum efficiency. Similarly, Adachi et al. (2004) reported that W/O/W microcapsules could be successfully prepared by spray-drying of W/O/W multiple emulsions containing an edible polysaccharide as wall material in the outer aqueous phase at a high concentration. When comparing encapsulated powders consisting of sequentially (layer by layer) adsorbed WPC/pectin through W/O/W

3.3.2. Encapsulated powder morphology Fig. 3 reveals the SEM microphotographs of the powders. Observations with SEM confirmed the presence of surface dents and wrinkles in powders obtained by maltodextrin/WPC matrix (Fig. 3A) showing EE of 62.55% crocin, 56.51% picrocrocin and 51.57% saffranal. This structure can allow higher air permeability into powders, reducing the protection of the encapsulated ingredient. The powders produced with W/O/W multiple emulsions (Fig. 3B–D) presented a spherical shape. As well as, the powder containing complex of WPC/pectin as outer wall material of W/O/W multiple emulsions by simultaneous and sequential method had less surface dents and pores than WPC alone as wall material (Fig. 3). It could be concluded that powders obtained from double-layer W/O/W emulsions with smooth surfaces, no cracks, and no dents are much better since they will have higher encapsulation efficiency (EE above 93% crocin, picrocrocin and saffranal). In other words, incorporating WPC/pectin into outer aqueous phase of multiple emulsions had a profound influence on the structure and

Number %

20

wpc wpc-pectin-seq wpc-pectin-sim

B

15

10

5

0 10

50 100

1000

10000

Size (nm)

Table 1 The influence of different infeed model food systems on encapsulation efficiency of spray dried powders containing crocin, picrocrocin, and saffranal. Sample codeA MD/WPC matrix WPC-10 WPC–pectin–Seq-10 WPC–pectin–Sim-10

Emulsion size Z-verage (d.nm) – 436.3 ± 0.25c 536.3 ± 0.18a 482.3 ± 0.29b

EE% of picrocrocin d

56.51 ± 0.31 89.37 ± 0.26c 96.82 ± 0.23a 95.96 ± 0.15b

EE% of saffranal d

51.57 ± 0.29 84.53 ± 0.3c 95.94 ± 0.2a 93.02 ± 0.16b

EE% of crocin d

62.55 ± 0.45 89.5 ± 0.34c 96.66 ± 0.38a 95.96 ± 0.23b

Powder moisture (wt%) 2.7 ± 0.04a 2.6 ± 0.08b 2.3 ± 0.05d 2.4 ± 0.02c

The experiments were performed with three replications. Different letters within the same column indicate significant differences (p < 0.05). A Treatment abbreviations: MD (maltodextrin), WPC (whey protein concentrate), WPC–pectin-Seq (whey protein–pectin by sequential method), WPC–pectin -Sim (whey protein–pectin by simultaneous method), 10 is the amount of dispersed phase (saffron extract) in primary w/o micro-emulsion. EE: Encapsulation Efficiency.

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25

3.4. FTIR analysis

Surface color parameter b*

a 20

15

b c

10

d

5

0

153

MD/W matrix

w-10

w-p-Sim-10

w-p-Seq-10

Encapsulation method Fig. 2. Surface color parameter b⁄ of encapsulated powders obtained from different infeed emulsions.

surface morphology of encapsulated powders, resulting in particles with smooth surfaces, less indentations and, higher EE. These findings are in agreement with the results of Ahn et al. (2008) who found the microspheres with higher encapsulation efficiency (96.6%) had a smooth surface and free from pores and cracks.

The appearance of amide groups in charged complex results from the interaction of carboxyl groups presented in pectin with amino groups presented in the protein. Therefore, FT-IR analysis was carried out to confirm the formation of amide in the complex charged complex of WPC and pectin in the saffron extract-loaded encapsulated powders prepared from maltodextrin/WPC matrix, single layer W/O/W emulsion stabilized by WPC alone and, double-layer W/O/W emulsion prepared with WPC/pectin (simultaneous and sequential adsorption) (Fig. 4). The FTIR spectra of saffron extract loaded-WPC powders from maltodextrin/WPC matrix and, W/O/W multiple emulsions stabilized by WPC revealed the presence of characteristic functional groups at 1645, 1535, 1456, and 1043 cm1 corresponding to the stretching of C@O, and the bending of NAH, CAH, CAN bonds, respectively (Kacurakova et al., 1999). The spectrum of saffron extract loaded-WPC/pectin encapsulated powders from W/O/W multiple emulsions exhibits a sharp band at 1140 cm1 which is related to the C@O stretching and indicates the formation of WPC/pectin complex. In addition, all the charged complex showed a peak at1553 cm1 which could be the amide bond that formed between the amino groups of WPC and carboxyl groups of pectin. The cross-linking of nanoparticle-loaded WPC/pectin powders from W/O/W emulsions led to the formation of a double-layer structure via establishment of net charge of biopolymers between

A

B

C

D

Fig. 3. SEM micrographs of saffron extract encapsulated powders produced by maltodextrin/WPC matrix (A); single layer W/O/W multiple emulsion (B); double layer W/O/W multiple emulsions; simultaneous adsorption (C), and sequential adsorption (D).

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Trancmittance (%)

154

4000 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800

600

400

Wavenumber (cm-1) Fig. 4. FTIR spectra of maltodextrin/WPC matrix powders (green line), single layer powders (red line), double-layer powders; simultaneous adsorption (blue line), and sequential adsorption (violet line). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

the carboxylate ions of pectin on the amide groups of WPC (Lutz et al., 2009). This most probably accounts for the decreased transmittance of the peaks related to the asymmetrical vibrations (at 1553 cm1) in the spectrum of cross-linked encapsulated powders. In agreement, Chen et al. (2012) reported the bio fabrication of stable WPC/pectin complex coacervations with new characteristics with an identical band at 1108 cm1 and 1557 cm1. 4. Conclusion Our results revealed that the properties of infeed model food system (droplet size and wall material matrix) have a significant influence on the characteristics of encapsulated powders. We introduced the W/O/W multiple emulsions stabilized by WPC/pectin as a good candidate for nano-encapsulation of saffron compounds (crocin, picrocrocin, and saffranal) with minimum amounts of un-encapsulated ingredients at the surface of powders and maximum encapsulation efficiency. Indeed, a spray dried powder containing saffron extract with highest encapsulation efficiency and lowest surface content and, smooth surface and free of pores and cracks can be prepared by double-layer W/O/W multiple emulsions. Acknowledgment It is necessary to appreciate Iran Nanotechnology Initiative Council (INIC) for their financial support. References Adachi, S., Imaoka, H., Ashida, H., Maeda, H., Matsuno, R., 2004. Preparation of microcapsules of W/O/W emulsions containing a polysaccharide in the outer aqueous phase by spray-drying. Eur. J. Lipid Sci. Technol. 106 (4), 225–231. Ahn, J.-H., Kim, Y.-P., Lee, Y.-M., Seo, E.-M., Lee, K.-W., Kim, H.-S., 2008. Optimization of microencapsulation of seed oil by response surface methodology. Food Chem. 107 (1), 98–105. Bagheri, L., Madadlou, A., Yarmand, M., Mousavi, M.E., 2014. Spray-dried alginate microparticles carrying caffeine-loaded and potentially bioactive nanoparticles. Food Res. Int. 62 (2014), 1113–1119. Basker, D., Negbi, M., 1983. Uses of saffron. Econ. Bot. 37 (2), 228–236. Bhandari, B.R., 2004. Spray drying: an encapsulation technique for food flavors. In: Mujumdar, A.S. (Ed.), Dehydration of Products of Biological Origin first ed., pp. 513–533.

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