CC BY-NC-ND
0«h«* Noo p,^_ARTICLE IN PRESS
HOSTED BY
ELSEVIER
Available online atwww.sciencedirect.com
ScienceDirect
Food Science and Human Wellness xxx (2014) xxx.e1-xxx.e8
Micro-encapsulation of Pacific white shrimp oil as affected by emulsification
condition
Sirima Takeungwongtrakula, Soottawat Benjakula'*, Aran H-kittikunb
a Department of Food Technology, Faculty of Agro-Industry, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand b Department of Industrial Biotechnology, Faculty of Agro-Industry, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand
Received 29 August 2014; received in revised form 28 October 2014; accepted 11 December 2014
Abstract
Micro-encapsulation of shrimp oil using the mixture of whey protein concentrate (WPC) and sodium caseinate (SC) (1:1, w/w) as a wall material was carried out. The impact of core/wall material ratios (1:2 and 1:4, w/w) and homogenizing pressures (13.79 and 27.58 MPa) on characteristics and stability of emulsion was investigated. The size of emulsion oil droplets decreased with increasing homogenizing pressure (P <0.05) but was not influenced by core/wall material ratio (P >0.05). During the extended storage, particle size, flocculation factor (Ff) and coalescence index (Ci) of all emulsions sharply increased, especially in emulsions prepared at 13.79 MPa with a core/wall material ratio of 1:2 (P<0.05). After spray drying, micro-encapsulated shrimp oil (MSO) prepared at 13.79 MPa with a core/wall material ratio of 1:2 had the larger size than others (P < 0.05). MSO prepared using a core/wall material ratio of 1:4 with homogenizing pressure of 27.58 MPa exhibited higher encapsulation efficiency (EE) (51.3%-52.8%) than others. Thus, both core/wall material ratio and homogenizing pressure directly affected micro-encapsulation of shrimp oil. © 2014 Beijing Academy of Food Sciences. Production and hosting by Elsevier B.V. All rights reserved.
Keywords: Shrimp oil; Emulsion; Pressure; Encapsulation; Spray drying
1. Introduction
Hepatopancreas, a byproduct generated from the manufacturing of hepatopancreas-free whole shrimp, has been reported to contain high content of n-3 PUFA and astaxanthin [1]. However, n-3 PUFA are easily oxidized due to their high degree of unsaturation. As a consequence, off-flavour compounds [2] as well as toxic products [3] are formed. To lower such a deterioration, encapsulation can be as a key technology in delaying or inhibiting oxidation and masking undesirable odours and flavours in the final product [4]. Furthermore, the process converts the oil into a free flowing powder, which can be easily handled and used for nutraceuticals and/or food fortification. Micro-encapsulation can be defined as a process, in which tiny droplets, namely core, are surrounded by a coating of micro-encapsulating agent. This
* Corresponding author at: Department of Food Technology, Faculty of Agro-Industry, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. Tel.: +66 74 286334; fax: +66 74 558866.
E-mail address: soottawat.b@psu.ac.th (S. Benjakul).
Peer review under responsibility of Beijing Academy of Food Sciences.
coating wall can be made of a variety of food grade materials and can protect the entrapped core by providing a physical barrier against environmental conditions [5]. Protein is widely used in the preparation of emulsion and serves as coating wall material during micro-encapsulation process. In recent years, the interest in milk proteins as encapsulating agents has increased and the concept of using milk products as wall materials has been established [6]. The wall material must have emulsifying properties and be capable of dehydration. The milk protein products including sodium caseinate and whey protein concentrate have excellent emulsifying and dehydration properties [7]. Whey protein and sodium caseinate act as the emulsifier, which can stabilize the emulsion before drying [8].
Additionally, emulsification is one of the critical steps in micro-encapsulation of oils by spray-drying, as the emulsion stability and droplet size play a key role in the encapsulation efficiency during and after the process [9]. To ensure the uniform distribution of oil droplet, homogenization with sufficient pressure for emulsification has been widely used in emulsion preparation and encapsulation in the food industry [10,11]. The advantage of high pressure homogenization over other technologies is that strong shear and cavitation forces
http://dx.doi.org/10.1016/j.fshw.2014.12.001
2213-4530/© 2014 Beijing Academy of Food Sciences. Production and hosting by Elsevier B.V. All rights reserved.
ARTICLE IN PRESS
xxx.e2
S. Takeungwongtrakul et al. / Food Science and Human Wellness xxx (2014) xxx.e1-xxx.e8
efficiently decrease the diameter of the original droplets [12]. High pressure homogenization induces significant changes in the interfacial protein layer because of the considerable increase in interaction between adsorbed proteins at the interface of the emulsion [13]. Several factors such as process conditions, protein concentration and oil volume fraction have been reported to affect the properties of emulsion [14]. Spray-drying is the most common micro-encapsulation technology used in food industry due to its low cost and available equipment [15]. The process involves the atomization of emulsions into a drying medium at a high temperature, resulting in very fast water evaporation. The micro-encapsulated oil was reported to have higher oxidation stability during the extended storage [16]. Although the micro-encapsulation of several oils or lipids has been reported, no information regarding the micro-encapsulation of shrimp oil has been reported. Due to the differences in composition of oils from different sources, emulsification conditions prior to spray drying can be varied and determine the characteristics of the obtained powder. Thus, this study aimed to investigate the impact of homogenization at varying pressure levels and the ratio of core/wall material on characteristics of encapsulated shrimp oil.
2. Materials and methods
2.1. Chemicals
Sodium azide (NaN3) was purchased from Fluka Chemical (Buchs, Switzerland). Sodium dodecyl sulphate (SDS) and sodium caseinate were procured from Sigma Chemical Co. (St. Louis, MO, USA). Whey protein concentrate was obtained from I.P.S. International Co., Ltd. (Bangkok, Thailand).
2.2. Collection of hepatopancreas from Pacific white shrimp
Hepatopancreas of Pacific white shrimp (Litopenaeus van-namei) with the size of 50-60 shrimps/kg was obtained from the Sea wealth frozen food Co., Ltd., Songkhla province, Thailand during July and August 2013. Pooled hepatopancreas (3-5 kg) was placed in a polyethylene bag. The bag was imbedded in a polystyrene box containing ice with a sample/ice ratio of 1:2 (w/w) and transported to the Department of Food Technology, Prince of Songkla University, Hat Yai, Songkhla within approximately 2 h. The sample was stored at -18 °C until use, but the storage time was not longer than 1 month. Prior to oil extraction, hepatopancreas was thawed using running water (25 °C) and ground in the presence of liquid nitrogen using a blender (Phillips, Guangzhou, China) for 30 s.
2.3. Extraction of oils from hepatopancreas
Oil was extracted from hepatopancreas following the method of Sachindra et al. [17] with some modifications. The prepared hepatopancreas (20 g) was homogenized with 90 mL of cold solvent mixtures (isopropanal:hexane, 50:50, v/v (4 °C)) at the speed of 9500 rpm using an IKA Labortechnik homogenizer (Model T25 basic, Selangor, Malaysia) for 2 min at 4 °C. The
extract was filtered using a Whatman filter paper No. 4 (Whatman International Ltd., Maidstone, England). The residue was extracted with cold solvent mixtures for another two times. The hexane fractions were pooled and repeatedly washed with an equal quantity of 1% NaCl in order to separate the phases and remove traces of polar solvents. Hexane fraction was then added with 2-5 g of anhydrous sodium sulphate, shaken very well, and decanted into a round-bottom flask through a Whatman No. 4 filter paper. The solvent was evaporated at 40 °C using an EYELA rotary evaporator N-1000 (Tokyo Rikakikai, Co. Ltd, Tokyo, Japan) and the residual solvent was removed by nitrogen flushing. The obtained oil was used for micro-encapsulation.
2.4. Characteristics of shrimp oil-in-water emulsion as affected by core/wall material ratio and homogenizing pressure
2.4.1. Preparation of shrimp oil-in-water emulsion
Aqueous stock solution (20%, w/w) of whey protein concentrate and sodium caseinate (1:1, w/w) in deionized water containing 0.03% (w/w) sodium azide was prepared, and stirred overnight using a magnetic stirrer at room temperature (28-30 °C). The solution obtained was used as 'wall material'. Shrimp oil was added into the solution at different ratios (1:2 and 1:4, core/wall material). The mixtures were homogenized at a speed of 10,000 rpm for 3 min using a homogenizer (Model T25 basic, IKA Labortechnik, Selangor, Malaysia). The coarse emulsions were then passed through a Microfluidics homoge-nizer (Model HC-5000, Microfluidizer, Newton, MA, USA) at different pressure levels (13.79 and 27.58 MPa) for four passes. The emulsions were stored at room temperature and taken for analyses at day 0, 1, 7 and 14 as follows:
2.4.1.1. Droplet size. Droplet size distribution of emulsions was determined using a ZetaPlus zeta potential analyzer (Brookhaven Instruments Corporation, Holtsville, NY, USA). Prior to analysis, emulsion was diluted with 1% (w/v) sodium dodecyl sulphate (SDS) solution in order to dissociate flocculated droplets. The surface-weighted mean (d32) and the volume-weighted mean particle diameter (d43) of the emulsion droplets were measured as described by Palazolo et al. [18].
2.4.1.2. Flocculation and coalescence. To determine floccula-tion factor (Ff) and coalescence index (Ci), the emulsions were diluted with distilled water in the presence and absence of 1% (w/v) SDS. Ff and Ci were calculated using the following equations:
^43-SDS
^43+SDS
^43+SDS,i - ^43+SDS,in X 100
^43+SDS,in
where d43+SDS and d43-SDS are the volume weight distribution of the emulsion droplets in the presence and absence of 1% SDS, respectively. d43+SDS,in is initial volume weight distribution of the emulsion droplets in the presence of 1% SDS; d43+SDS,t is
I+H1 'IWW^M I IIILE IN PRESS
S. Takeungwongtrakul et al. / Food Science and Human Wellness xxx (2014) xxx.e1-xxx.e8
the volume weight distribution of the emulsion droplets in the presence of 1% SDS at the designated storage time.
2.4.1.3. f-Potential. The electrical charge (f-potential) of oil droplets in the emulsions was determined using a ZetaPlus zeta potential analyzer (Model ZetaPALS, Brookhaven Instruments, Co., Holtsville, NY, USA) at room temperature. The shrimp oil-in-water emulsions were diluted 250-fold prior to measurements. The diluted emulsions were mixed thoroughly and then injected into the measurement chamber of the instrument. The f-potential of each individual sample was calculated from the average of five measurements on the diluted emulsion.
2.4.2. Preparation of micro-encapsulated oil
Emulsions were subjected to drying using a laboratory scale spray-dryer (LabPlant Ltd., LabPlant SD-05, Huddersfield, UK) with a 1.5 mm diameter nozzle. The emulsion was fed into the main chamber through a peristaltic pump. Feed flow rate was 8.08 mL/min; drying air flow rate was 4.3 m/s and compressor air pressure was 0.28 MPa. Air inlet temperature was 180 ± 2 °C. The outlet temperature was controlled at 90 ±2 °C. Moisture contents of all samples were in the range of 2.92%-3.28%. The obtained powder was determined as follows:
2.4.2.1. Encapsulation efficiency (EE). The surface oil was measured by adding 15 mL of hexane to 2 g of powder and shaking with a vortex mixer (G-560E, Vortex-Genie 2, Scientific Industries, Inc., Bohemia, NY) for 2 min at room temperature. The solvent mixture was then filtered through a Whatman No. 1 filter paper and the collected powder on the filter paper was rinsed three times with 20 mL of hexane [19]. The filtrate solution containing the extracted oil was transferred to a clean flask, which was left to evaporate and then was dried at 60 °C until constant weight was obtained. The surface oil (SO) content was calculated based on the extracted oil [20].
The total oil was determined using the method described by Shahidi and Wanasundara [21]. 5 g of powder was dissolved in 25 mL of a 0.88% (w/v) KCl solution. Then 50mL of chloroform and 25 mL of methanol were added. The mixture was then homogenized using a high-speed mixer (Model T25 basic, IKA Labortechnik, Selangor, Malaysia) for 5 min at 9500 rpm. The mixture was transferred to a separation funnel; the chloroform layer was separated and then evaporated using a rotary evaporator at 60 °C to recover the oil. Total oil (TO) content was then calculated.
EE was calculated as follows:
/TO-SO\ EE = - x 100
I TO j
where TO is the total oil content and SO is the surface oil content.
2.4.2.2. Powder size. Powder size distribution was measured using a laser light diffraction instrument (Laser Scattering Spectrometer Mastersizer model MAM 5005, Malvern Instruments Ltd., Worcestershire, United Kingdom). The powder sample was dispersed in 99.5% ethanol and the particle distribution was monitored during five successive readings. The particle size was
xxx.e3
expressed as the volume-weighted mean particle diameter (d43), which is the mean diameter of a sphere with the same volume, and is generally used to characterize a particle [22].
2.4.2.3. Powder morphology. Powder morphology was evaluated by a scanning electron microscopy (SEM). Powder was mounted on a bronze stub and sputter-coated with gold (Sputter coater SPI-Module, West Chester, PA, USA). The specimen was observed using a scanning electron microscope (Quanta 400, FEI, Eindhoven, Netherlands) at an acceleration voltage of 15 kV with magnifications of 3000 x.
2.5. Statistical analysis
All experiments were run in triplicate. All analyses were conducted in five replications. Statistical analysis was performed using one-way analysis of variance (ANOVA). Mean comparison was carried out using Duncan's multiple range test. For pair comparison, r-test was used [23].
3. Results and discussion
3.1. Characteristics of shrimp oil-in-water emulsion
3.1.1. Emulsion droplet size.
Particle size of shrimp oil droplet in emulsions containing whey protein concentrate and sodium caseinate (1:1, w/w) prepared with different ratios of core/wall material (1:2 and 1:4) and homogenizing pressure levels (13.79 and 27.58 MPa) expressed as the surface-weighted mean (d32) and the volume-weighted mean particle diameter (d43) was monitored during 14 days of storage at room temperature (Table 1). The d32 is directly related to specific surface area. The smaller d32 contributes to the higher specific surface area, which offers the increase in protein loads for adsorbing at interface of emulsions [24]. d43 can be used as the index of coalescence and flocculation. The increase in d43 reflects the association of individual droplets into larger flocs [24]. The d32 is more influenced by the small particles, whereas d43 is highly influenced by larger ones [25]. The emulsion made with core/wall material ratio of 1:2 and 1:4 with the same homogenizing pressure had no differences in the d32 and d43 of emulsions at 0 day of storage. During the storage, the increases in d32 and d43 were noticeable in all samples up to day 14 (P <0.05), suggesting the aggregation of droplets. During the storage time, the core/wall material ratio of 1:4 could retard the increase in particle size in emulsion more effectively than that of 1:2, regardless of homogenizing pressure used. The result suggested that the high amount of wall material must be sufficient so that oil droplets are surrounded by thick and strong film during emulsification.
With the same ratio of core/wall material, the decrease in both d32 and d43 of droplets was obtained when homogenizing pressure increased (P < 0.05). This decrease in oil droplet size might be related to the greater turbulence and shear forces associated with increased homogenizing pressure applied [26]. Homog-enization includes two steps: firstly high shear stress leads to droplet deformation which increases their specific surface
ARTICLE IN PRESS
xxx.e4
S. Takeungwongtrakul et al. / Food Science and Human Wellness xxx (2014) xxx.e1-xxx.e8
Table 1
Particle size of droplets in shrimp oil emulsions containing whey protein and sodium caseinate with different core/wall material ratios and homogenizing pressures during the storage.
Core/wall material ratio (w/w)
Pressure used (MPa) Storage time (day) d32 (nm) d43 (nm)
13.79 0 169.12 ± 0.51Ad 188.64 ± 1.02Ad
1 171.64 ± 0.32Ac 192.86 ± 0.22Ac
7 239.02 ± 1.18Ab 269.47 ± 1.37Ab
14 334.00 ± 2.42Aa 377.84 ± 2.12Aa
27.58 0 167.73 ± 0.54Bd 186.00 ± 0.57Bd
1 171.84 ± 0.70Ac 191.76 ± 0.34Bc
7 222.29 ± 0.62Bb 247.81 ± 1.24Bb
14 293.42 ± 2.24Ba 328.26 ± 2.63Ba
13.79 0 168.20 ± 0.57Ac 188.54 ± 1.45Ad
1 170.16 ± 2.55Ac 190.49 ± 0.37Ac
7 198.61 ± 0.56Ab 223.06 ± 0.87Ab
14 262.54 ± 1.43Aa 295.85 ± 1.76Aa
27.58 0 167.09 ± 0.34Bd 185.19 ± 1.34Bd
1 170.73 ± 1.54Ac 189.76 ± 0.25Bc
7 193.48 ± 1.24Bb 216.75 ± 1.11Bb
14 244.35 ± 2.45Ba 273.57 ± 2.68Ba
Data are expressed as mean ± SD (n = 5).
Lowercase letters in the same column within the same pressure and core/wall material ratio indicate significant difference (P < 0.05). Uppercase letters in the same column within the same storage time and core/wall material ratio indicate significant difference (P <0.05).
area up to disruption. Then the new interface is stabilized by emulsifiers [27]. This process causes the modification of protein conformation, particularly globular protein. Those proteins or peptides with more exposed hydrophobic domains likely adsorbs at increasing droplet interface more effectively. Adsorption of sodium caseinate and whey protein concentrate surrounding interfacial oil droplet provided steric hindrance [28]. The reduction of emulsion droplets size, which generally represents an increased stability, results in greater retention of core material [29,30]. Emulsion droplet size has a pronounced effect on the encapsulation efficiency of core materials during spray drying
[31]. The micro-encapsulation of emulsion with small droplet size confers the advantages in terms of emulsion stability, retention of oil in the dried powder and less extractable surface oil
[32]. During the storage, d32 and d43 of emulsion prepared using higher pressure (27.58 MPa) had the slower rate of increase in size, compared with emulsion prepared using the lower pressure (13.79 MPa). The results indicated that emulsion prepared with higher homogenizing pressure was more stable during the extended storage time.
pressure, the emulsion with core/wall material ratio of 1:2 and 1:4 had the similar Ff and Ci at day 0 and 1 of storage (P >0.05). After the first day of storage, Ff and Ci increased (P <0.05), especially for emulsion with the core/wall material ratio of 1:2. The result indicated that the amount of wall material must be enough to stabilize the oil droplets in emulsion.
When comparing Ff and Ci of emulsion with the same core/wall material ratio subjected to different homogenizing pressures, no differences in Ff and Ci were found in emulsion using 13.79 and 27.58 MPa at 0 and 1 day of storage (P >0.05). With the increasing storage time, Ff and Ci increased (P < 0.05). Such changes were more pronounced in emulsion with homogenizing pressure of 13.79 MPa and the core/wall material ratio of 1:2. The result was related well with droplet size of emulsion (Table 1), showing the highest change in d32 and d43 in emulsion with homogenizing pressure of 13.79 MPa with the 1:2 of core/wall material ratio during the storage. Based on Ff and Ci, emulsion with the highest stability could be prepared when homogenizing pressure was 27.58 MPa and the core/wall material ratio was 1:4.
3.1.2. Flocculation and coalescence
Flocculation factor (Ff) and coalescence index (Ci) of shrimp oil-in-water emulsion prepared under different conditions during 14 days of storage at room temperature are shown in Table 2. During storage, all emulsion samples had the increase in Ff, however the rate of change varied. Similar results were found for Ci. Emulsion underwent flocculation when the repulsive forces between the drops were not too strong and if adhesion energies were large enough, the adhesion could be promoted [33]. Coalescence occurs when two or more oil droplets approach together and join together to form a larger one after the interfacial membrane is ruptured. The process is irreversible and results in the instability of emulsion [34]. With the same homogenizing
3.1.3. Z-Potential
Z-Potential of shrimp oil-in-water emulsions as affected by core/wall material ratio and homogenizing pressures is shown in Table 2. Zeta-potential is the potential difference between the dispersion medium and the stationary layer of fluid attached to the dispersed droplet. This value can be related to the stability of emulsion [14]. All emulsion samples had Z-potential values higher than -45 mV at 0 day of storage. Negatively charged residues on oil droplet governed by wall material surrounding the shrimp oil droplets mostly contributed to repulsion between droplets, thereby lowering coalescence. At day 0 and 1, no change in Z-potential was observed (P >0.05). Subsequently, Z-potential of all samples decreased, especially emulsions with the
^ ARTIOLE IN PRESS
S. Takeungwongtrakul et al. / Food Science and Human Wellness xxx (2014) xxx.e1-xxx.e8 xxx.e5
Table 2
Flocculation, coalescence and f-potential of droplets in shrimp oil emulsions containing whey protein and sodium caseinate with different core/wall material ratios and homogenizing pressures during the storage.
Core/wall material ratio (w/w) Pressure used (MPa) Storage time (day) Flocculation factor (Ff) Coalescence index (Q) f-Potential (mV)
0 0.98 ± 0.05Ac
1 1.00 ± 0.04Ac
7 1.37 ± 0.02Ab
14 1.93 ± 0.10Aa
0 0.84 ± 0.10Ac
1 0.87 ± 0.09Ac
7 1.07 ± 0.02Bb
14 1.45 ± 0.10Ba
0 0.96 ± 0.05Ac
1 0.97 ± 0.05Ac
7 1.11 ± 0.03Ab
14 1.45 ± 0.03Aa
0 0.92 ± 0.06Ab
1 0.92 ± 0.02Ab
7 0.94 ± 0.04Bb
14 1.15 ± 0.02Ba
2.24 ± 0.31Ac 42.85 ± 2.42Ab 100.30 ± 3.46Aa
2.89 ± 0.31Ac 33.23 ± 2.42Bb 76.49 ± 3.46Ba
2.03 ± 0.71Ac 18.30 ± 2.52Ab 56.90 ± 3.23Aa
2.47 ± 0.64Ac 17.04 ± 1.55Ab 47.72 2.21Ba
46.76 46.71 37.64
31.26 46.84 46.56 37.15 31.01
46.27 44.66 38.15 47.83 46.32 43.41 37.94
± 0.75Ac ± 1.21Ac ± 2.11Ab ± 1.07Aa ± 1.14Ac ± 0.73Ac ± 0.54Ab ± 0.89Aa
± 0.69Ac ± 0.93Ac ± 0.85Ab ± 0.61Aa ± 1.78Ac ± 1.00Ac ± 1.19Ab 1.32Aa
Data are expressed as mean ± SD (n = 5).
Lowercase letters in the same column within the same pressure and core/wall material ratio indicate significant difference (P < 0.05). Uppercase letters in the same column within the same storage time and core/wall material ratio indicate significant difference (P < 0.05).
core/wall material ratio of 1:2. The layers of protein surrounding droplets might undergo aggregation via ionic interaction during the extended storage as indicated by the change in zeta potential. The insufficient electrostatic repulsion might lead to the development of flocculation and coalescence. Emulsions exhibiting absolute f-potential higher than +30 mV or lower than -30 mV tend to be electrostatically stable, whilst emulsions within the range of -30 to 30 mV tend to coagulate or flocculate [35]. Emulsion with core/wall material ratio of 1:2 had low absolute f-potential value, regardless of homogenizing pressure. As a result, there was no enough force to prevent the molecules to align together. During the storage, change in f-potential of emulsion with the core/wall material ratio of 1:2 was higher than that of 1:4 for both homogenizing pressure levels used. The results suggested that the core/wall material ratio of 1:4 yielded the emulsion with higher stability. In general, high value of f-potential means better stability because of the mutual repulsion between the electrical double layers of macromolecules [36]. When comparing f-potential of all samples with both homogenizing pressure levels, no differences in f-potential were observed at both core/wall material ratios (P > 0.05). Particle size of the resulting emulsions and emulsion stability were governed by zeta potential surrounding droplets, which was more likely associated with the charge of protein films at interface.
3.2. Characteristics of micro-encapsulated shrimp oil
Emulsions with different processing conditions were subjected to spray drying. The powder containing oil as the core was characterized.
3.2.1. Encapsulation efficiency (EE)
EE of micro-encapsulated shrimp oil prepared using the different core/wall material ratios and homogenizing pressures is
shown in Table 3. EE reflects the degree of protection afforded by the wall material to oil droplets [26]. EE varied from a minimum value of 14.65% to a maximum value of 52.05%. EE values from 0% to 95% were reported [37-40]. This was dependent on the type and composition of wall material, the ratio of core/wall material, the drying process used, and the stability and physico-chemical properties of the emulsions. The highest EE was found in the sample prepared from emulsion with core/wall material ratio of 1:4 and homogenizing pressure of 27.58 MPa. The surface oil was lower with coincidental increase in EE in sample prepared from emulsion with core/wall material ratio of 1:4 than those of 1:2. This result was in agreement with Rodea-González et al. [9] who reported that EE was increased and surface oil decreased when core/wall material increased from 1:2 to 1:3. The core material is embedded as micro-particles within the wall material. As the ratio of core/wall material is increased, the ability of the wall material to retain and protect the core material is increased [41], resulting in a lower surface oil and higher EE. The surface oil represents non-encapsulated oil and has been used as an important parameter determining the quality of encapsulated products. Non-encapsulated oil is prone to oxidation, thus leading to the development of off-flavour and lower acceptability of the product [42]. Furthermore, the surface oil increases the wettability but lowers dispersibility of the powders [43].
The powder made from the emulsion having a core/wall material 13.79 and 27.58 MPa showed the similar surface oil and EE (P >0.05). For the powder prepared from emulsion with core/wall material ratio of 1:4, the lower surface oil and higher EE was noticeable when homogenizing pressure of 27.58 MPa was implemented, compared with those of 13.79 MPa. This result indicated that the emulsification condition (core/wall material ratio and homogenizing pressure) had the marked influence on encapsulation as well as the characteristic of powder.
BW-aBBPB^^Barticle in press
xxx.e6
S. Takeungwongtrakul et al. / Food Science and Human Wellness xxx (2014) xxx.e1-xxx.e8
Fig. 1. Surface morphology of micro-encapsulated shrimp oil prepared from emulsion containing a mixture of whey protein concentrate and sodium caseinate (1:1, w/w) with different core/wall material ratios and homogenizing pressures (magnification: 3000 x). F = fused together.
3.2.2. Powder particle size
Powder particle size of the encapsulated shrimp oil produced with the different core/wall material ratios and homogenizing pressures is shown in Table 3. Powders had the average diameter ranging from 9.14 to 10.18 ^m, except the powder prepared from emulsion having core/wall material ratio of 1:2 and homogenizing pressure of 13.79 MPa, which had the diameter of 13.05 ^m. Homogenizing pressure had no effect on size of powder when core/wall material ratio of 1:4 was used. The result indicated that core/wall material ratio of 1:4 was sufficient to align themselves surrounding shrimp oil droplets prior to spray drying. However, there was difference in EE between both homogenizing pressures. Thus, higher pressure more likely dissociated the oil droplets, in which wall material could occupy rapidly and acted as wall of droplets. This was evidenced by high EE when high
homogenizing pressure (27.58 MPa) was used. Finney et al. [44] and Jafari et al. [29] reported that particle size had no impact on retention of some volatile and oil, as solid in emulsion, was sufficiently high. When comparing the size of shrimp oil emulsions and powder, an increase in powder particle size was observed after spray drying process. The increased powder size partly arose from coalescence of oil droplet in emulsion during the spray drying process [45]. Additionally, the wall generated also contributed to the increased diameter. The diameter of microcapsules depends on homogenization parameters, the materials used and conditions of the spray drying process [46].
3.2.3. Powder morphology
SEM microphotographs of the powders produced from emulsion with the different core/wall material ratios and
Table 3
Powder size, surface oil, total oil and encapsulation efficiency of different encapsulated shrimp oil powders prepared from emulsions containing whey protein and sodium caseinate with different core/wall material ratios and homogenizing pressures.
Core/wall material ratio (w/w) Pressure used (MPa) Powder size, d4,3 (^m) Surface oil (w/w%) Encapsulation efficiency (%)
1:2 13.79 13.05 ± 1.12aA 23.86 ± 0.47aA 14.65 ± 1.38aB
27.58 9.74 ± 0.32bA 23.51 ± 1.53aA 14.96 ± 0.39aB
1:4 13.79 9.55 ± 0.27aB 12.42 ± 0.28aB 31.50 ± 1.81bA
27.58 9.66 ± 0.52aA 9.01 ± 1.23bB 52.05 ± 0.71aA
Data are expressed as mean ± SD (n = 3).
Lowercase letters in the same column within the same core/wall material ratio indicate significant difference (P <0.05). Uppercase letters in the same column within the same pressure indicate significant difference (P < 0.05).
ШНЯЯ^М ARTICLE IN PRESS
S. Takeungwongtrakul et al. / Food Science and Human Wellness xxx (2014) xxx.e1-xxx.e8 xxx.e7
homogenizing pressures are shown in Fig. 1. All powders exhibited similar surface morphologies. Powders prepared from emulsions with core/wall material ratio of 1:2 using both homogenizing pressure levels appeared to be agglomerated. Clumps of particles were observed (Fig. 1A and B). This was plausibly due to high surface oil levels (Table 3), which made the particles stick together. For powders prepared from emulsion with core/wall material ratio of 1:4 with both homogenizing pressure levels (Fig. 1C and D), a higher level of surface indentation was obtained, compared with those prepared from emulsion with a core/wall material ratio of 1:2. The different morphologies and surface irregularities were governed by composition of the emulsion, droplet size, and temperature during the drying process [47]. Wrinkles or dimples on the surface were observed in all powders. These results are consistent with Klinkesorn et al. [40] and Ahn et al. [48], who detected wrinkles on the surface of the particles in spray-dried powder. Wrinkles were attributed to the results of mechanical stresses induced by uneven drying at different parts of the droplets during the early stages of drying [49], to the movement of the moisture during the surface drying period [50], and to the effect of a surface tension-driven viscous flow [49]. Wrinkles of the particle followed by an incipient expansion may induce changes in the size of particles and causes the broken wall material [51].
4. Conclusion
Shrimp oil was encapsulated from emulsion stabilized by whey protein concentrate and sodium caseinate (1:1, w/w). Core/wall material ratio and homogenizing pressure directly had the impact on emulsion and resulting encapsulated powder. Higher homogenizing pressure reduced droplet size of emulsion. Emulsification at 27.58 MPa with a core/wall material ratio of 1:4 yielded the emulsion with the highest stability during 14 days of storage. After spray drying, emulsion with high core/wall material ratio and homogenizing pressure rendered the micro-encapsulated shrimp oil powder with higher EE. Thus, shrimp oil could be encapsulated using a mixture of whey protein concentrate and sodium caseinate (1:1, w/w) as encapsulating agents with core/wall material ratio of 1:4 and homogenizing pressure level of 27.58 MPa, followed by spray-drying. However, the conditions used in the present study still showed the low encapsulation efficiency, the improvement of encapsulation process for shrimp oil is still required.
Acknowledgements
This work was supported by the Higher Education Research Promotion and National Research University Project of Thailand, Office of the Higher Education Commission. The TRF Senior Research scholar program and Prince of Songkla University were also acknowledged.
References
[1] S. Takeungwongtrakul, S. Benjakul, A. H-Kittikun, Lipids from cephalothorax and hepatopancreas of Pacific white shrimp (Litopenaeus
vannamei): compositions and deterioration as affected by iced storage, Food Chem. 134 (2012) 2066-2074.
[2] W. Kolanowski, D. Jaworska, J. Weißbrodt, Importance of instrumental and sensory analysis in the assessment of oxidative deterioration of omega-3 long-chain polyunsaturated fatty acid-rich foods, J. Sci. Food Agric. 87 (2007) 181-191.
[3] M.D. Guillén, A. Ruiz, Oxidation process of oils with high content of linoleic acyl groups and formation of toxic hydroperoxy and hydroxyalke-nals. A study by 1H nuclear magnetic resonance, J. Sci. Food Agric. 85 (2005) 2413-2420.
[4] R.V. Tonon, C.R.F. Grosso, M.D. Hubinger, Influence of emulsion composition and inlet air temperature on the microencapsulation of flaxseed oil by spray drying, Food Res. Int. 44 (2011) 282-289.
[5] G. Gallardo, L. Guida, V.Martinez, et al., Microencapsulation of linseed oil by spray drying for functional food application, Food Res. Int. 52 (2013) 473-482.
[6] A. Goula, K. Adamopoulos, A method for pomegranate seed application in food industries: seed oil encapsulation, Food Bioprod. Process. 90 (2012) 639-652.
[7] M.K. Keogh, B.T. O' Kennedy, Milk fat microencapsulation using whey proteins, Int. Dairy J. 9 (1999) 657-663.
[8] H. Singh, X.Q. Zhu, A. Ye, Lipid encapsulation, US Patent Application EP1,876,905 A1 (2008).
[9] D.A. Rodea-González, J. Cruz-Olivares, A. Román-Guerrero, et al., Spray-dried encapsulation of chia essential oil (Salvia hispanica L.) in whey protein concentrate-polysaccharide matrices, J. Food Eng. 111 (2012) 102-109.
[10] S. Schultz, G. Wagner, K. Urban, et al., High-pressure homogenization as a process for emulsion formation, Chem. Eng. Technol. 27 (2004) 361-368.
[11] W. Ding, N.P. Shah, Effect of homogenization techniques on reducing the size of microcapsules and the survival of probiotic bacteria therein, J. Food Sci. 74 (2009) M231-M236.
[12] J. Perrier-Cornet, P. Marie, P. Gervais, Comparison of emulsification efficiency of protein-stabilized oil-in-water emulsions using jet, high pressure and colloid mill homogenization, J. Food Eng. 66 (2005) 211-217.
[13] S.H. Lee, T. Lefevre, M. Subirade, et al., Effects of ultra-high pressure homogenizatio on the properties and structure of interfacial protein layer in whey protein-stabilized emulsion, Food Chem. 113 (2009) 191-195.
[14] B. Wang, D. Li, L.J. Wang, et al., Effect of concentrated flaxseed protein on the stability and rheological properties of soybean oil-in-water emulsions, J. Food Eng. 96 (2010) 555-561.
[15] A. Gharsallaoui, G. Roudaut, O. Chambin, et al., Applications of spray-drying in microencapsulation of food ingredients: an overview, Food Res. Int. 40(2007) 1107-1121.
[16] P. Calvo, Á.L. Castaño, M. Lozano, et al., Influence of the microencap-sulation on the quality parameters and shelf-life of extra-virgin olive oil encapsulated in the presence of BHT and different capsule wall components, Food Res. Int. 45 (2012) 256-261.
[17] N. Sachindra, N. Bhaskar, N. Mahendrakar, Recovery of carotenoids from shrimp waste in organic solvents, Waste Manage. 26 (2006) 1092-1098.
[18] G.G. Palazolo, P.A. Sobral, J.R. Wagner, Freeze-thaw stability of oil-in-water emulsions prepared with native and thermally-denatured soybean isolates, Food Hydrocoll. 25 (2011) 398-409.
[19] E. Bae, S. Lee, Microencapsulation of avocado oil by spray drying using whey protein and maltodextrin, J. Microencapsul. 25 (2008) 549-560.
[20] S.M. Jafari, E. Assadpoor, Y.He, et al., Encapsulation efficiency of food flavours and oils during spray drying, Dry. Technol. 26 (2008) 816-835.
[21] F. Shahidi, U.N. Wanasundara, Oxidative stability of encapsulated seal blubber oil ACS Symposium Series, ACS Publications, 1995, pp. 139-153.
[22] E.C. Frascareli, V.M. Silva, R.V. Tonon, et al., Effect of process conditions on the microencapsulation of coffee oil by spray drying, Food Bioprod. Process. 90 (2012) 413-424.
[23] R.G.D. Steel, J.H. Torrie, Principles and Procedures of Statistics, vol. 8, McGraw-Hill Book Co., Inc., NY, 1960, pp. 6-8.
[24] E. Hebishy, M. Buffa, B. Guamis, et al., Stability of sub-micron oil-in-water emulsions produced by ultra high pressure homogenization and sodium caseinate as emulsifier, Chem. Eng. 32 (2013) 1813-1818.
ШИИН^^И ARTICLE IN PRESS
S. Takeungwongtrakul et al. /Food Science and Human Wellness xxx (2014) xxx.e1-xxx.e8
xxx.e8
[25] H. Bengtsson, E. Tornberg, Physicochemical characterization of fruit and vegetable fiber suspensions. I: Effect of homogenization, J. Texture Stud. 42(2011)268-280.
[26] S.A. Hogan, B.F. McNamee, E.D. O'Riordan, et al., Microencapsulating properties of sodium caseinate, J. Agric. Food Chem. 49 (2001) 1934-1938.
[27] J. Floury, A. Desrumaux, J. Lardieres, Effect of high-pressure homog-enization on droplet size distributions and rheological properties of model oil-in-water emulsions, Innov. Food Sci. Emerg. Technol. 1 (2000) 127-134.
[28] C.C. Sánchez, J.M.R Patino, Interfacial, foaming and emulsifying characteristics of sodium caseinate as influenced by protein concentration in solution, Food Hydrocoll. 19 (2005) 407-416.
[29] S.M. Jafari, E. Assadpoor, B. Bhandari, et al., Nano-particle encapsulation of fish oil by spray drying, Food Res. Int. 41 (2008) 172-183.
[30] A. Soottitantawat, H. Yoshii, T. Furuta, et al., Microencapsulation by spray drying: influence of emulsion size on the retention of volatile compounds, J. Food Sci. 68 (2003) 2256-2262.
[31] A. Soottitantawat, F. Bigeard, H. Yoshii, et al., Influence of emulsion and powder size on the stability of encapsulated D-limonene by spray drying, Innov. Food Sci. Emerg. Technol. 6 (2005) 107-114.
[32] S.J. Risch, G.A. Reineccius, Spray-dried orange oil: effect of emulsion size on flavor retention and shelf stability, Flavor Encapsul. 370 (1988) 67-77.
[33] D. Langevin, S. Poteau, I. Hénaut, et al., Crude oil emulsion properties and thei application to heavy oil transportation, Oil Gas Sci. Technol. 59 (2004)511-521.
[34] Z. Long, Q. Zhao, T. Liu, et al., Influence of xanthan gum on physical characteristics of sodium caseinate solutions and emulsions, Food Hydrocoll. 32 (2012) 123-129.
[35] Y.Wang, D. Li, L.J. Wang, et al., Effects of high pressure homogenization on rheological properties of flaxseed gum, Carbohydr. Polym. 83 (2011) 489-494.
[36] J. Acedo-Carrillo, A. Rosas-Durazo, R. Herrera-Urbina, et al., Zeta potential and drop growth of oil in water emulsions stabilized with mesquite gum, Carbohydr. Polym. 65 (2006) 327-336.
[37] M.Y. Baik, E. Suhendro, W. Nawar, et al., Effects of antioxidants and humidity on the oxidative stability of microencapsulated fish oil, J. Am. Oil Chem. Soc. 81 (2004) 355-360.
[38] N. Hardas, S. Danviriyakul, J. Foley, et al., Accelerated stability studies of microencapsulated anhydrous milk fat, LWT - Food Sci. Technol. 33 (2000) 506-513.
[39] T.C. Kha, M.H. Nguyen, P.D. Roach, Effects of spray drying conditions on the physicochemical and antioxidant properties of the Gac (Momordica cochinchinensis) fruit aril powder, J. Food Eng. 98 (2010) 385-392.
[40] U. Klinkesorn, P.Sophanodora, P.Chinachoti, et al., Characterization of spray-dried tuna oil emulsified in two-layered interfacial membranes prepared using electrostatic layer-by-layer deposition, Food Res. Int. 39 (2006) 449-457.
[41] M. Hojjati, S.H. Razavi, K. Rezaei, et al., Spray drying microencapsulation of natural canthaxantin using soluble soybean polysaccharide as a carrier, Food Sci. Biotechnol. 20 (2011) 63-69.
[42] S. Drusch, S. Berg, Extractable oil in microcapsules prepared by spray-drying: localisation, determination and impact on oxidative stability, Food Chem. 109 (2008) 17-24.
[43] C. Vega, E.H.J. Kim, X.D. Chen, et al., Solid-state characterization of spray-dried ice cream mixes, Colloids Surf. B 45 (2005) 66-75.
[44] J. Finney, R. Buffo, G. Reineccius, Effects of type of atomization and processing temperatures on the physical properties and stability of spray-dried flavors, J. Food Sci. 67 (2002) 1108-1114.
[45] S. Drusch, Y.Serfert, M. Scampicchio, et al., Impact of physicochemical characteristics on the oxidative stability of fish oil microencapsulated by spray-drying, J. Agric. Food Chem. 55 (2007) 11044-11051.
[46] W. Kolanowski, M. Ziolkowski, J. Weißbrodt, et al., Microencapsulation of fish oil by spray drying - impact on oxidative stability. Part 1, Eur. Food Res. Technol. 222 (2006) 336-342.
[47] C.S. Handscomb, M. Kraft, Simulating the structural evolution of droplets following shell formation, Chem. Eng. Sci. 65 (2010) 713-725.
[48] J.H. Ahn, Y.P. Kim, E.M. Seo, et al., Antioxidant effect of natural plant extracts on the microencapsulated high oleic sunflower oil, J. Food Eng. 84 (2008) 327-334.
[49] T. Sheu, M. Rosenberg, Microstructure of microcapsules consisting of whey proteins and carbohydrates, J. Food Sci. 63 (1998) 491-494.
[50] D. Walton, The morphology of spray-dried particles a qualitative view, Dry. Technol. 18 (2000) 1943-1986.
[51] L. Alamilla-Beltrán, J. Chanona-Pérez, A. Jiménez-Aparicio, et al., Description of morphological changes of particles along spray drying, J. Food Eng 67 (2005) 179-184.
