Journal of Microencapsulation, 2009; 26(3): 263–271

Alginate/starch composites as wall material to achievemicroencapsulation with high oil loading

Lay Hui Tan, Lai Wah Chan and Paul Wan Sia Heng*

Department of Pharmacy, National University of Singapore, Singapore

AbstractAlginate/starch blends were used as wall material to encapsulate fish oil by spray-drying. The effects ofalginate type and content on microsphere morphology, yield and microencapsulation efficiency wereinvestigated. The ability of microspheres to confer protection to the microencapsulated fish oil on storageunder stress was also determined. The results showed that the addition of alginate to the wall componentresulted in rounder microspheres with higher oil encapsulation efficiencies. Microencapsulated oil wasfound to be more stable to degradation compared to unencapsulated oil.

Key words: Alginate; fish oil; spray-drying

Introduction

Microencapsulation has been carried out on oils for

reasons including protection, controlled release and/or

taste masking1–2. Fish oils, in particular, have received

much attention in recent years. Studies have shown that

the !-3 polyunsaturated acids, mainly eicosapentaenoic

acid (EPA) and docosahexaenoic acid (DHA), in fish oils

have beneficial effects on human physiology and health3–6.

However, due to their high degrees of unsaturation, fish

oils are prone to oxidative degradation and rancidity.

Commercially available fish oil products are predomi-

nantly in the emulsion or oil-containing gelatin capsule

forms. The former dosage form is multi-dose, bulky and

requires careful administration to avoid spillage, while the

latter is associated with issues concerning production cost

and efficiency, as well as patient acceptability due to diet-

ary and religious reasons. As such, it is advantageous to

develop a microencapsulated, powder form of fish oil for

increased ease of processing, storage, delivery and admin-

istration. Such a product can also be used in combination

with other dry bioactive ingredients.

Different methods and polymers have been used

for fish oil microencapsulation with the primary objective

of achieving oxidative protection of the core compo-

nents7–11. Spray-drying is a one-step, continuous drying

process which involves the transformation of a fluid feed

into a dried particulate form by spraying the feed into a hot

drying medium12. Although the initial capital outlays for

commercial microsphere production using spray-drying

may be high due to equipment costs, this is mitigated by

the relative ease of scale-up compared to other encapsula-

tion methods like freeze-drying or emulsification. This

method also does not require the use of organic solvents

and is relatively simple. The potential to operate continu-

ously also offers commercial advantage in terms of

reduction in time and product losses during process

start-up and shut-down. In addition, the integrity of the

ingredient to be encapsulated is preserved as product

exposure to heat is limited due to rapid drying. Polymers

used as wall materials include carbohydrates, milk

proteins and starches, alone or in blends. These studies

were able to demonstrate the reduction in oxidation of fish

oil by microencapsulation. The oil-to-wall weight ratios

usually ranged from 0.4 : 1–1 : 1. However, it was difficult

to compare and quantify the merits of the different wall

systems used due to variations in compositions of the

microspheres studied.

Address for correspondence: Lay Hui Tan, Department of Pharmacy, National University of Singapore, 18 Science Drive 4, Singapore 117543.Tel: 65-65162930. Fax: 65-67752265. E-mail: phapaulh@nus.edu.sg

(Received 14 Feb 2008; accepted 26 Jun 2008)

ISSN 0265-2048 print/ISSN 1464-5246 online � 2009 Informa UK LtdDOI: 10.1080/02652040802305519 http://www.informapharmascience.com/mnc

(Received 14 Feb 2008; accepted 26 Jun 2008)

ISSN 0265-2048 print/ISSN 1464-5246 online � 2009 Informa UK LtdDOI: 10.1080/02652040802305519 http://www.informapharmascience.com/mnc

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Alginates are naturally occurring polymers that are

widely regarded as biocompatible and non-toxic. They

are readily available, relatively inexpensive and commonly

used in food and pharmaceutical preparations. Chen

et al.13 used alginate as wall material for oil encapsulation

by the emulsification method. Although high oil encapsu-

lation was achieved, the method was limited by small

batch size, difficulty in scale-up and involved the use of

organic solvents. Limited studies have been carried out on

the use of alginates for oil encapsulation by other

methods. Hence, this study aimed to investigate the use

of alginate as a wall material for microencapsulation of fish

oil by spray-drying. The capacity of the microspheres to

encapsulate a high oil load was studied. In addition, the

ability of the microspheres to preserve the integrity of

the encapsulated fish oil on storage under stress was

also determined.

Materials and methods

Materials

ROPUFA, a marine oil, was supplied by Roche Vitamins

(Basel, Switzerland). Modified food starch, Capsul, was

obtained from National Starch and Chemical Company

(New Jersey, USA). The alginates used, Manucol LB (low

guluronic acid content) and Manugel LBB (high guluronic

acid content), were supplied by ISP Alginates (UK) Limited

(Surrey, UK). All other chemicals used were of analytical

grade.

NMR of alginates

Acid hydrolysis of the alginates was carried out according

to the procedure described by Hang and Larsen14 and

modified by Schurks et al.15. Briefly, alginate was dissolved

in water to form a 1% solution and the pH adjusted to 3.0.

Hydrolysis was then carried out at 100�C for 1 h, after

which the solution was cooled down and neutralized.

The resulting solution was dialysed against deionized

water for 24 h and dried under reduced pressure. For the

acquisition of the 13C NMR spectra, the samples were first

dissolved in D2O to a concentration of �80–100 mg ml�1.

The solutions were then incubated at 60�C for 5 h to main-

tain their solubility and to de-gas them. The spectra were

recorded using a Bruker DPX-300 NMR spectrometer and

analysed. The internal reference was sodium 3-(trimethyl-

silyl)propionate. Major signals were assigned according to

Grasdalen et al.16.

Preparation of fish oil-containing microspheres

Emulsions were prepared according to the formulae

shown in Table 1. The amount of oil used was 150% of

the dry weight of the total wall material used. Except for

formulation C, the alginate solutions were left to hydrate

overnight before they were subjected to autoclaving at

121�C for 45 min. This was carried out to reduce their

viscosity and facilitate droplet formation during the ato-

mization step of the spray-drying process. The required

amounts of modified starch were subsequently added

and allowed to hydrate. ROPUFA was then homogenized

(L4RT, Silverson Machines, Waterside, UK) with the wall

material solutions. The homogenization conditions used

were 4500 rpm for 3 min, followed by 5000 rpm for 2 min.

The emulsions were then spray-dried using a pilot-scale

spray-dryer (Mobile Minor, Niro A/S, Soeborg, Denmark)

equipped with a rotary atomizer. The operational condi-

tions used were: air inlet temperature 150�C, air outlet

temperature 80�C and atomizer wheel speed 25 000 rpm.

The emulsions were subjected to gentle stirring during the

spraying process to minimize oil droplet coalescence. The

powders collected were sealed in plastic bags and stored

in a freezer while awaiting further tests.

Microsphere characterization

The roundness, size, yield and microencapsulation

efficiency (ME) of the microspheres were determined

according to the methods mentioned in a previous

paper17. Briefly, scanning electron microscopy was used

for morphological characterization. Light microscopy

interfaced with an image analysis system was used for

size and roundness determination. Roundness was

calculated by the following equation:

Roundness ¼P2

4 � � � Að1Þ

Table 1. Composition of different microsphere formulations studied.

Wall material (g)

Formulation Capsul Manucol

LB

Manugel

LBB

Core (g)

ROPUFA

C 225 337.5

LB1 210 15 337.5

LB5 150 75 337.5

LB10 75 150 337.5

LBB1 210 15 337.5

LBB5 150 75 337.5

LBB10 75 150 337.5

264 L. H. Tan et al.

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where P is the perimeter of microsphere and A is the cross-

sectional area of the microsphere.

Roundness values closer to 1 were indicative of

rounder microspheres. ME was calculated by taking the

difference between total oil and surface oil of a known

constant weight of microspheres. Total oil was determined

by taking the difference in microsphere weight before

and after Soxhlet extraction (Buchi Extraction System

B-811, Buchi Labortechnik AG, Flawil, Switzerland)

with n-hexane, while surface oil was the weight loss of

microspheres after quick rinsing with n-hexane and

subsequent drying.

The specific surface area of microspheres was

determined using the Brunauer, Emmett and Teller

(BET) technique (SA 3100TM Surface Area and Pore Size

Analyser, Beckman Coulter, California, USA). Samples

were de-gassed under vacuum for�16 h at room tempera-

ture. Triplicate experiments were performed for each

formulation produced.

Oil content on storage

For each batch of microspheres produced, samples of

30 mg each were weighed into amber-coloured wide

mouthed jars (3 cm i.d. and 4 cm height) with screw cap

closures. The jars were placed in an environment-con-

trolled chamber at 70% relative humidity and 40�C.

At intervals of 0, 3, 7, 14, 28, 42 and 56 days, samples

were removed from the chamber. Four millilitres of

n-hexane was added to each sample, which was then

placed in a shaker bath at room temperature for 24 h to

allow complete extraction of oil to take place. The samples

were then filtered and the residue rinsed with fresh

solvent. The filtrate was collected and made up to 10 ml

for analysis. The EPA and DHA contents were determined

by gas chromatography equipped with a flame ionization

detector (HP 5890 II, Agilent Technologies, California,

USA). The inlet and outlet temperatures were 190 and

240�C respectively, and heating rate was 5�C min�1 to

220�C followed by 3�C min�1 to 240�C. This final tempera-

ture was held for 5 min. One microlitre of each sample was

injected for each analysis. Triplicates were performed.

Statistical analysis

Results were reported as means of triplicate experiments.

Treatments with three or more groups were analysed by

one-way analysis of variance, while those with two groups

were analysed by the Student’s t-test (SPSS 11.5, SPSS Inc.,

Chicago, USA). Tukey’s and LSD tests were applied to

determine significance of differences between means.

Results and discussion

Most studies conducted for oil encapsulation for spray-

drying have used oil loadings of less than 100% of the

weight of the wall component. Therefore, in this study,

higher oil loadings (150%) were used to allow evaluation

of the ability of alginate to achieve superior oil holding

capacities when used as a wall material component for

microsphere production by spray-drying. From prelimin-

ary studies, this was also the threshold value above which

microspheres with excessive amounts of surface oil result-

ing in significant agglomeration with greatly reduced

yields were formed. However, the viscosities of the alginate

solutions were too high to allow effective atomization of

the feed into small droplets during the spray-drying pro-

cess. Instead of obtaining spherical products, filamentous

particles were formed. Alginate solutions were thus auto-

claved to reduce their viscosities, as well as to sterilize the

solutions.

Sterilization treatments of alginate, either in hydrated

or dry powder form, have been conducted for cell immo-

bilization18–19. It was reported that depolymerization with

resultant decrease in solution viscosity occurred when

alginates were subjected to high heat or irradiation. An

NMR study on the alginate solutions before and after auto-

claving was performed to assess the effect of autoclaving

on alginate, especially the possibility of other degradation

processes besides depolymerization. It was found that the

frequency of M and G fragments remained unchanged

with autoclaving for both grades of alginate. Similarly,

the M/G ratio was unaffected by the autoclaving process

(Table 2). This finding was evident that macromolecules of

alginate were broken down by depolymerization into

smaller sub-units and not appreciably affected chemically.

Microspheres produced generally had a spherical

shape with no obvious surface cracks. They had the typical

appearance of spray-dried products. However, different

degrees of surface indentations were observed for micro-

spheres made from the different formulations. This was

more apparent for microspheres produced with a high

proportion of alginate. It appeared that microspheres

Table 2. Compositional data of the alginates before and after

autoclaving.

Alginate aFMbFG

cFMMdFGG M/G ratio

Manucol LB 0.69 0.31 0.49 0.17 2.22

Manucol LB (autoclaved) 0.69 0.31 0.45 0.20 2.20

Manugel LBB 0.40 0.60 0.22 0.54 0.67

Manugel LBB (autoclaved) 0.39 0.61 0.21 0.55 0.65

aMannuronic acid fraction; bGuluronic acid fraction; cMM doublet

fraction; dGG doublet fraction.

Alginate/starch composites as wall material to achieve microencapsulation with high oil loading 265

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produced using a greater proportion of alginate had a

lower degree of surface indentations. The type of alginate

used also affected the microsphere appearance. At the

same amount of alginate added, microspheres produced

using Manugel LBB (Figure 1b) appeared to have a greater

degree of surface indentation than those made using

Manucol LB (Figure 1c). Microspheres produced using

purely starch as wall material (Formulation C) had the

highest degree of surface indentations (Figure 1a).

Morphological studies by other workers have identified

three distinct forms of spray-dried product: crystalline,

agglomerate and skin-forming20. It was reported that inor-

ganic materials formed spray-dried products that

are mainly composed of crystalline structures, whereas

agglomerates were formed from insoluble or partially solu-

ble materials. Polymeric materials like the starch and algi-

nates used in this study produced skin-forming particles

with a continuous non-liquid phase. Single droplet drying

experiments demonstrated characteristic drying beha-

viours for each of the morphological types. For polymeric

materials, it was observed that at 200�C, a skin was formed

on the droplet surface almost immediately, followed

by several cycles of internal bubble nucleation, particle

collapse and re-inflation. The skin finally dried up and

hardened, forming inflated hollow particles with smooth

surfaces or collapsed particles with surface indentations as

seen in this study. The ability of the particles to inflate,

collapse and re-inflate to eventually form a continuous

skin was due to the flexible nature of the polymeric mem-

brane. Other researchers postulated that the formation of

indentations was due to uneven particle shrinkage caused

by rapid droplet drying during the spray-drying process21.

Indentations could also have been formed from inter-par-

ticle collisions or particle impact with the walls of the spray

dryer. From the appearance of the microspheres produced

using the different wall materials employed in this study, it

could be deduced that those containing alginate, espe-

cially Manucol LB, were less prone to irregular shrinkage

or collapse during drying.

Particle morphology is also affected by spray-drying

process variables including atomization conditions,

drying temperatures, feed properties and the chemical

and physical nature of the material being dried.

Since spray-drying conditions were kept constant for the

different microspheres produced in this study, the likely

cause for the differences in microsphere morphology was

the nature of the material being spray-dried. Although

they were all polymeric materials, they differed in chemi-

cal composition. Wandrey et al.22 have studied the effect of

alginate composition on the mechanical properties of algi-

nate microbeads and microcapsules made by gelation

with calcium chloride. It was observed that less shrinkage

was observed with the high G alginates, which was

the reverse of what was observed in this study.

High G alginates, due to the stronger affinity of G residues

for calcium ions, formed stronger beads and gels than high

M alginates. However, in this case, no ionic cross-linking

was involved. Manucol LB could have formed a less flex-

ible microsphere wall resulting in fewer surface indenta-

tions or it could be inferred that the addition of Manucol

LB resulted in the formation of a stronger microsphere

matrix that was more resistant to collapse.

Figure 1. SEM of spray-dried microspheres using formulation (a) C, (b)

LBB10 and (c) LB10.

266 L. H. Tan et al.

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Table 3 gives the results of microsphere size, round-

ness, BET surface area, spray-drying yield and ME for

the different microspheres produced. Microsphere size

was the least affected by the composition of wall materials

used in this study (p4 0.05). As the proportion of alginate

increased, the differences in the other parameters became

more apparent. For both types of alginate used, micro-

spheres became rounder with increasing amounts of

alginate (p5 0.05). The BET surface areas were also

lower when more Manucol LB was used. This suggested

less porous particles or integrally better fused micro-

spheres. Yield and microencapsulation efficiencies, on

the other hand, were significantly higher. The differences

in these properties were more marked when Manucol LB

was used.

The effect of alginate incorporation on microsphere

roundness was most likely due to the phenomenon of

the formation of a more resistant microsphere wall

matrix as mentioned in the earlier section. This also had

an effect on yield, which was the total amount of powder

collected at the end of the process stream. Rounder parti-

cles would tend to flow better and would be less likely to

stick on the internal surfaces of the spray-dryer, allowing

more product to be collected. This could be one of the

factors contributing to the higher yields obtained with for-

mulations LB5, LB10, LBB5 and LBB10. However, the yield

was also affected by the degree of stickiness of the micro-

spheres, which was in turn dependent on the amount of

surface oil present. ME values were higher for the formu-

lations with higher yields, implying that the lower amount

of surface oil reduced microsphere tackiness which facili-

tated their collection. The ME results were also related to

microsphere shrinkage, as oil could have been squeezed

out of the microspheres during the drying process. In

short, substitution of Capsul with the alginates used in

this study allowed the formation of rounder microspheres

and higher microencapsulation efficiencies, giving rise to

greater yields. Manucol LB appeared to be superior to

Manugel LBB in these aspects.

The specific surface area of particles can be affected

by factors such as shape, size and surface roughness.

The microspheres produced from formulations LB5 and

LB10 had significantly lower specific surface areas than

microspheres formed from the other formulations. This

corresponded to the SEM observations, as these were the

batches with lower degrees of surface indentations and

thus smoother surfaces. It could also be related to micro-

sphere roundness, as these particular batches were found

to have roundness values closest to 1. However, the effect

of Manucol LBB addition on microsphere specific surface

area was less apparent, although SEM studies showed that

this batch has a lower degree of surface indentations than

the control. This implied that microspheres formed from

this particular formulation, although having smoother

surfaces, could have more porous walls compared to the

control, thereby balancing out the effects on specific

surface area.

After the microspheres were successfully produced,

it became pertinent to determine the ability of the micro-

sphere wall to preserve the integrity of the encapsulated

components of interest. As EPA and DHA are widely con-

sidered to be the main active components in fish oil, their

levels were monitored. Since polyunsaturated fatty acids

are sensitive to the effects of heat and humidity, the micro-

spheres were stored at 40�C and 70% RH to determine if

they could protect the microencapsulated components.

As a control, bulk unencapsulated oil was also subjected

to the same storage conditions and analysed at the

appropriate intervals. Most studies have focused on ana-

lysing the oxidative products formed9–10 but did not quan-

tify the residual amount of polyunsaturated fatty acids,

which was also an important indicator of microsphere

functionality.

Figures 2a and 2b show the change in EPA and DHA

amounts over time respectively for the different formula-

tions studied. For all the microspheres produced, the

greatest decrease in EPA and DHA content occurred

over the first 3 days of storage. This was likely due to the

Table 3. Mean particle size, roundness, BET surface area, yield and ME of microspheres prepared using the

different formulations.

Formulation Diameter (mm) aRoundness BET surface area (m2 g�1) Yield (%) ME (%)

C 18.9� 0.4 1.13 0.66� 0.04 47.8� 7.5 57.4� 2.9

LB1 18.6� 0.3 1.12 0.64� 0.02 51.3� 5.8 59.4� 2.0

LB5 19.1� 0.2 1.10 0.54� 0.05 65.5� 4.3 67.3� 2.7

LB10 19.8� 0.3 1.08 0.51� 0.05 72.6� 4.5 76.6� 2.1

LBB1 18.8� 0.3 1.12 0.66� 0.03 49.2� 5.2 60.8� 3.4

LBB5 19.0� 0.4 1.12 0.65� 0.00 58.7� 4.9 66.2� 2.8

LBB10 19.2� 0.3 1.10 0.63� 0.02 68.6� 4.7 72.2� 1.1

aStandard deviation 50.001.

Alginate/starch composites as wall material to achieve microencapsulation with high oil loading 267

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degradation of oil present on the surface of the micro-

spheres. Due to their high degrees of unsaturation, degra-

dation of polyunsaturated fatty acids usually occurred via

oxidation7 which was affected by light, temperature and

humidity. Since physical contact between the oil and

oxygen had to take place before degradation could

occur, the surface area of oil exposed to oxygen would

thus affect the rate and degree of degradation, especially

in the initial stages. The film of oil present on the micro-

sphere surface was subject to a high rate of oxidation due

to its large effective surface area for interaction with the

external environment. The unencapsulated oil (control)

was presented in the bulk form and effectively presented

a much lower surface area than the oil on the microsphere

surface. This resulted in the lower initial reduction in EPA

and DHA amounts for the control.

The decrease in EPA and DHA contents became more

gradual after 4 weeks to almost levelling around 6 weeks.

The subsequent gradual decline could be due to the slow

diffusion of oxygen into the encapsulated oil situated

nearer to the microsphere surface, while levelling

indicated the inaccessibility of oxygen to the interior oil

reservoir of the microspheres. Microspheres stored at

elevated temperature and humidity showed susceptibility

to caking and similar findings were also reported by other

workers23–24. This could have also contributed to the

decreased degradation of the encapsulated oil as exposure

became increasingly restricted. As for the unencapsulated

oil, without the protective or insulating barrier present,

almost complete degradation of EPA and DHA took

place at the end of the storage duration and less than

10% each of EPA and DHA remained.

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60

Time (days)

EP

A (

%)

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60

Time (days)

DH

A (

%)

Figure 2. EPA and DHA content on storage for ^ unencapsulated oil, ^ C, * LB1, œ LB5, 4 LB10, f LBB1, g LBB5, m LBB10.

268 L. H. Tan et al.

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Microspheres prepared using Formulations C, LB1 and

LBB1 had generally lower levels of EPA and DHA on

storage compared to microspheres made using higher

proportions of alginate in the wall material composition.

This could be a consequence of the differences in the

morphology of microspheres made using the different

formulations. These microspheres were less round as

a result of a higher degree of surface indentations,

which translated to increased effective surface area (also

shown by BET studies) for oxygen exposure and diffusion.

This resulted in a greater extent of deterioration of

EPA and DHA. As the proportion of alginate increased,

the extent of indentations observed on microspheres was

lower and the more spherical microspheres ensured

that the encapsulated oil was better protected by the

presence of lower diffusion areas. The differences could

also be related to the porosity of the wall material,

although further studies are needed to confirm these.

Nevertheless, effective protection of microencapsulated

oil was achieved for all formulations studied, as �50%

of EPA and DHA were preserved under the harsh

storage conditions compared to the unencapsulated

bulk oil (10%).

It is known that the deterioration of!-3 polyunsaturated

acids occurs mainly via an autocatalytic process which

involves the formation of free radicals25–26. However, for

microencapsulated oil, the process is complicated by

other factors including the presence of the protective

microsphere matrix shielding the encapsulated oil

from the external environment. The Weibull model

(Equation 2) was found to adequately describe shelf-life

failures27–28 and had been used to express the

oxidation kinetics of microencapsulated polyunsaturated

fatty acids29,

C ¼ exp �ðktÞn� �

ð2Þ

EPA

–2.25

–1.75

–1.25

–0.75

–0.25

1 1.5 2 2.5 3 3.5 4

ln (t)

ln [

-ln

(C/C

0)]

DHA

–1.8

–1.6

–1.4

–1.2

–1

–0.8

–0.6

–0.4

–0.2

0

1 1.5 2 2.5 3.5 4

ln (t)

ln [

-ln

(C/C

0)]

3

Figure 3. Application of the Weibull model to DHA and EPA content on storage for ^ C, * LB1, œ LB5, 4 LB10, f LBB1, g LBB5, m LBB10.

Alginate/starch composites as wall material to achieve microencapsulation with high oil loading 269

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where C is the fraction of unoxidized EPA or DHA at time t,

k is the rate constant and n is the shape constant. The

shape constant describes an increasing or decreasing

degradation rate, depending on its magnitude. A shape

constant of greater than 1 indicates that the degradation

rate increases with time while n5 1 indicates the oppo-

site27. Equation (2) can be rearranged into a linear model

as follows:

ln � lnC

C0

� �� �¼ nðln t þ ln kÞ ð3Þ

Figures 3a and 3b show the plot of ln [�ln(C/C0)] against

ln t for EPA and DHA respectively in the microspheres

produced. Table 4 shows the values of k, n and correlation

coefficients derived from the plots. The r2 values showed

linear correlations for the formulations produced, indicat-

ing that the Weibull model was suitable for describing the

degradation of EPA and DHA in the microspheres pro-

duced. From the rate constants, it was evident that as

the alginate content within the microspheres increased,

the rate of degradation of EPA and DHA decreased

(p5 0.05). This was seen for both Manucol LB and

Manugel LBB and corresponded with the discussions

stated earlier. The shape constants were less than 1, indi-

cating that the degradation rates of EPA and DHA

decreased over time. This could be attributed to the

increasing impedence to oxygen penetration into the

microsphere matrix or exhaustion of the surface oil com-

ponent as discussed in the earlier section.

Conclusions

Alginate-composite microspheres were successfully pro-

duced by spray-drying, with high oil loadings achieved.

The use of alginate as a wall material component enabled

the production of rounder microspheres with higher

oil holding capacities. Microspheres prepared using

Manucol LB performed relatively better than those made

using Manugel LBB in terms of yield and ME. Micro-

encapsulation of fish oil brought about increased protec-

tion with lower loss of unsaturated components on storage

compared to unencapsulated oil. The degree of protection

of encapsulated oil increased as the alginate content

within the microsphere matrix increased. The spray-

dried, microencapsulated form of fish oil using alginate

blend as wall material can potentially have widespread

commercial and industrial applications due to the ease

of production and relatively high ME and oxidative protec-

tion achieved.

Acknowledgements

This study was made possible with the research scholar-

ship from the National University of Singapore. The

authors would like to thank Dr Anton Dolzhenko for

performing the NMR studies. The authors would also

like to thank Roche Vitamins, UK, National Starch &

Chemical, USA and ISP Alginates Inc., USA for samples

used during the study.

Declaration of interest: The authors report no conflicts of

interest. The authors alone are responsible for the content

and writing of the paper.

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Table 4. Parameters derived from the Weibull model for EPA

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Formulation Parameters

n k r2

EPA DHA EPA DHA EPA DHA

C 0.422 0.435 19.7� 10�3 18.0� 10�3 0.969 0.969

LB1 0.459 0.430 14.3� 10�3 14.1� 10�3 0.982 0.986

LB5 0.505 0.433 10.2� 10�3 8.73� 10�3 0.976 0.985

LB10 0.524 0.432 7.59� 10�3 6.93� 10�3 0.975 0.980

LBB1 0.422 0.434 10.9� 10�3 15.2� 10�3 0.961 0.969

LBB5 0.429 0.440 8.65� 10�3 10.2� 10�3 0.961 0.972

LBB10 0.485 0.406 8.63� 10�3 7.19� 10�3 0.967 0.970

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