factor affecting the properties of water-in-oil-in-water...

Review Article

Factor affecting the properties of water-in-oil-in-water emulsions forencapsulation of minerals and vitamins

Nattapong Prichapan and Utai Klinkesorn*

Department of Food Science and Technology, Faculty of Agro-Industry,Kasetsart University, Chatuchak, Bangkok, 10900 Thailand.

Received: 15 November 2013; Accepted: 20 October 2014

Abstract

The direct fortification of minerals and vitamins into food may induce chemical degradation, change the level ofbioavailability or decrease the sensory quality of food products. The strategy to solve these problems is encapsulationtechnology. Numerous investigations described the use of water-in-oil-in-water (W/O/W) emulsions as encapsulation system.The properties and encapsulation efficiency of W/O/W emulsions are influenced by emulsion components, the emulsifica-tion processes, and environmental conditions. The recently published results of research done on the factors affecting theproperties of W/O/W emulsions for encapsulation of minerals and vitamins including form and concentration of corematerials, concentration of inner water phase and lipophilic emulsifier, type and concentration of oil phase, type and concen-tration of hydrophilic emulsifier and stabilizer and the pH of the outer water phase have been reviewed in this article.

Keywords: water-in-oil-in-water emulsions, encapsulation, minerals, vitamins

Songklanakarin J. Sci. Technol.36 (6), 651-661, Nov. - Dec. 2014

1. Introduction

Minerals and vitamins are very important to sustainbody functions and are essential for all parts of the body.Although minerals and vitamins are present in various foodsfrom both animal and plant sources, many people still havemineral and vitamin deficiencies. This does not only occurwith poor people in developing countries who do not haveenough food to eat, but also with other people around theworld. These mineral and vitamin deficiencies may appear insome groups of people such as the elderly, pregnant andlactating women, some people with limited consumptionchoices, such as vegetarians or vegans and may also comefrom changing food consumption behaviors to eating highprocessed food more than fresh whole foods (Bonnet et al.,2009; Guzun-Cojocaru et al., 2010; Kroner, 2011).

The direct fortification of minerals and vitamins intofood is not straightforward. Some micronutrients may causeadverse effects to the sensory quality of the food such ascolor changes, undesirable flavor, and a sandy texture, whilesome micronutrients may accelerate chemical reactionsleading to decreased nutritional quality of the food and mayalso lead to toxicants. Furthermore, some micronutrients arevery sensitive to high temperatures, exposure to light, changesin pH, high levels of oxygen, and moisture content, whichcan lead to degradation during preparation, processing, andstorage (Ball, 2006; Mehansho et al., 2006; Jimenez-Alvaradoet al., 2009; Liu, 2009; Lutz et al., 2009; Stevanovic andUskokovic, 2009; Guzun-Cojocaru et al., 2010; Lakkis et al.,2011; Giroux et al., 2013).

The strategy to solve these problems is encapsulationtechnology, a technique that entraps sensitive material, e.g.minerals and vitamins, in the carrier or coating material beforebeing added to food. Emulsion technology is one promisingtechnology for the encapsulation of such materials. Theadvantage of an emulsion system is it allows nutrients to bequite stable and easily dispersed in the medium.

* Corresponding author.Email address: [email protected]

http://www.sjst.psu.ac.th

N. Prichapan & U. Klinkesorn / Songklanakarin J. Sci. Technol. 36 (6), 651-661, 2014652

Usually, emulsion systems consist of two or moreimmiscible liquids, such as oil and water, where one of liquidsis dispersed as small spherical droplets in the other. Emulsionsystems are conventionally classified into two main groups;simple or single emulsions and multiple or double emulsions.Oil-in-water (O/W) emulsions consist of oil droplets dispersedin a continuous aqueous phase (Figure 1A), and water-in-oil(W/O) emulsions that consists of water droplets dispersed ina continuous oil phase (Figure 1B) are examples of a singleemulsion. Whereas, water-in-oil-in-water (W/O/W) emulsionscontaining W/O droplets dispersed in a continuous aqueousphase (Figure 1C), and oil-in-water-in-oil (O/W/O) emulsionswhere O/W droplets are dispersed in a continuous oil phase(Figure 1D) are classified as multiple emulsions.

W/O emulsions and W/O/W emulsions are normallyused to encapsulate water-soluble substances. The W/Oemulsions are suitable used for nutrient fortification inoil-based foods, while W/O/W emulsions are properly usedin water-based food products. O/W emulsions and O/W/Oemulsions are mostly used for encapsulation of oil-solublesubstances. The O/W emulsions encapsulate nutrients forfortification in water-based foods products, while O/W/Oemulsions are used for fortification in oil-based foods.Furthermore, W/O/W emulsions and O/W/O emulsions canbe used as a co-encapsulation system which is encapsula-tion together of both water-soluble and oil-solublesubstances. For example, W/O/W can entrap water-solublenutrients in the inner water phase and also entrap oil-solublesubstances in the oil phase of the same system (Benichouet al., 2002; Benichou et al., 2007; Bonnet et al., 2009; Lutzet al., 2009; Bonnet et al., 2010a; Bonnet et al., 2010b;O’Regan et al., 2010; Li et al., 2012; Giroux et al., 2013).

The aim of this work is to offer an overview of thehealth effects of some minerals and vitamins including iron,calcium, magnesium, vitamin C (ascorbic acid), vitamin B1(thiamine), vitamin B2 (riboflavin), and vitamin B12 (cobalamin).In addition, the use of W/O/W emulsions for encapsulationand the factors affecting the properties of W/O/W emulsionsincluding form and concentration of core material, concen-tration of inner water phase and lipophilic emulsifier, typeand concentration of oil phase, type and concentration ofhydrophilic emulsifier and stabilizer, and pH of outer waterphase are also highlighted.

2. Health Benefits, Deficiency and Fortification of Mineralsand Vitamins

Minerals and vitamins have different health benefitsand they are important for normal functions. Minerals andvitamins are essential for all parts of the body. Deficiency ofminerals and vitamins may cause dysfunction and lead toill-health. Thus, we gathered the health benefit, deficiencyproblem, and food source of some minerals and vitamins thathave the important health effect on our body including iron,calcium, magnesium, ascorbic acid, thiamine, riboflavin, andcobalami as shown in Table 1.

Fortification of minerals and vitamins in foods maysolve the problem of mineral and vitamin deficiency. However,direct fortification of some minerals and vitamins into foodsis not straightforward because it may not be stable or maycause adverse effects on the food products (Table 2). Inaddition, bioavailability of the nutrients is also an importantpoint and should be considered. Bioavailability is the amountof nutrients that can be absorbed and utilized by our body.There are three main factors that affect bioavailability,including personal factors, nutrient stability, and dissolutionor release of nutrients. The personal factors include age, sexand physiologic state (e.g. pregnancy) which affect thegastric residence time and permeability through the gastro-intestinal tract. Formulation (form of nutrients, pH andpresence of other nutrients), food processing, and storageconditions (temperature, light and oxygen) are factors thataffect nutrient stability.

The factors that influence dissolution or release ofnutrients are the encapsulation process and formulation suchas coatings or fillers excipient and surfactants. Thus, thedesign and utilizing the proper encapsulation technique maybe a promising way to enhance the fortification and bioavail-ability of nutrients in food products by protecting them untilthe time of consumption and delivery them to the target sitewithin the human body (Yetley, 2007; Fang and Bhandari,2010).

3. Encapsulation Technology

Generally, encapsulation technology is a techniquethat entraps sensitive materials, solid, liquid, or gas state, inwall material in small sealed capsules to protect them fromadverse environmental conditions such as high temperatures,high or low pH, exposure to UV light, and high levels ofdissolved oxygen. Moreover, the freeing of this substancefrom the encapsulated capsule can be controlled to releaseat certain rates and specific conditions. The size of theencapsulated particle may cover a range from sub-micron tomillimeters. Encapsulation technology can be also used toreduce the evaporation of aromatic compounds, mask un-desirable flavors and tastes of some substances or improvethe dispersion ability of some substances by making themdisperse more uniformly throughout the medium (Fang andBhandari, 2010; Abbas et al., 2012).

Figure 1. Schematic diagram of oil-in-water (O/W) emulsions (A),water-in-oil (W/O) emulsions (B), water-in-oil-in-water(W/O/W) emulsions (C), and oil-in-water-in-oil (O/W/O)emulsions (D) (not to scale).

653N. Prichapan & U. Klinkesorn / Songklanakarin J. Sci. Technol. 36 (6), 651-661, 2014

Tabl

e 1.

Sum

mar

y of f

ood

sour

ces,

heal

th b

enef

it, an

d de

ficie

ncy p

robl

em o

f som

e min

eral

s and

vita

min

s.

Nut

rient

sFo

od s

ourc

esH

ealth

bene

fitD

efic

ienc

y pro

blem

Refe

renc

es

Iron

Mea

ts, p

oultr

y, fis

h, sh

ellfi

sh,

Esse

ntia

l for

blo

od ci

rcul

ator

yA

nem

ia, h

igh

risk

of h

eart

atta

ck, s

low

Kro

ner,

2011

and

som

e pl

ants

syst

em, t

rans

ports

oxy

gen

deve

lopm

ent

in ch

ildre

n, an

d co

mpl

icat

ions

thro

ugho

ut t

he b

ody

of p

regn

ancy

Calci

umM

ilk, c

erea

ls, a

nd th

eir p

rodu

cts.

Esse

ntia

l for

bon

e an

d te

eth,

Cal

cium

rele

ase f

rom

bone

s, hi

gh ri

sk of

Theo

bald

et a

l., 2

005;

mus

cle c

ontra

ctio

n, d

iges

tion,

oste

opor

osis

, and

frac

ture

of b

ones

Saei

dy et

al.,

201

3an

d ne

urot

rans

mitt

er se

cret

ion

Mag

nesiu

mVe

geta

bles

, fru

its, a

nd p

ulse

sEs

sent

ial f

or p

rote

in sy

nthe

sis,

Car

diov

ascu

lar d

isea

ses,

hype

rtens

ion,

Bonn

et et

al.,

200

9; K

rone

r, 20

11en

zym

atic

reac

tions

, and

mus

cula

rm

uscu

lar w

eakn

ess,

and

diar

rhea

cont

ract

ion

Asc

orbi

c ac

idFr

uits

and

veg

etab

les

such

as

Deg

ener

ativ

e ch

roni

c di

seas

es,

Dry

and

split

ting

hair,

roug

h, d

ry an

dLi

u, 20

09; L

utz e

t al.,

200

9;(v

itam

in C

)ci

trus f

ruits

, gua

va, p

otat

oes,

invo

lved

in s

ynth

esis

of c

olla

gen

hem

orrh

age s

kin,

dec

reas

ed w

ound

Stev

anov

ic an

d U

skok

ovic

, 200

9;an

d to

mat

oes

and

epin

ephr

ine,

amin

o ac

id an

dhe

alin

g ra

te, w

eake

ned

toot

h en

amel

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rone

r, 20

11ch

oles

tero

l met

abol

ism, a

gain

stsc

urvy

, gin

givi

tis, a

nem

ia, a

nd h

igh

risk

ofox

idat

ive d

amag

e and

canc

ers

infe

ctio

nsTh

iam

ine

Mea

t, w

hole

gra

in ce

real

s, nu

ts,

Role

in ce

llula

r ene

rgy p

rodu

ctio

n,Sy

mpt

om to

two

syst

ems i

nclu

ding

Bate

s, 20

07; O

sieza

gha e

t al.,

2013

(vita

min

B1)

and

bean

san

d he

lps n

euro

n to

be n

orm

alca

rdio

vasc

ular

sys

tem

and

ner

vous

sys

tem

activ

esRi

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vin

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ry p

rodu

cts,

cere

als,

offa

l,Pr

otec

ting

agai

nst c

ance

rs,

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ht b

lindn

ess,

high

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of ca

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wer

s, 20

03(v

itam

in B

2)fis

h, a

nd d

ark-

gree

n ve

geta

bles

card

iova

scul

ar d

isea

ses,

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play

sca

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ular

dise

ase,

per

iphe

ral

a rol

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thyr

oxin

e met

abol

ismne

urop

athy

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rode

gene

ratio

n, a

ndm

enta

l illn

ess

Coba

lam

inFo

und

in a

nim

al ti

ssue

sEs

sent

ial f

or p

rodu

ctio

n of

blo

odA

nem

ia, i

rrita

bilit

y, m

emor

y los

s, w

eakn

ess,

Kro

ner,

2011

(vita

min

B12

)ce

lls a

nd D

NA

, and

nec

essa

ry fo

rtre

mbl

ing

and

unst

able

mov

emen

ts, a

ndno

rmal

neu

rolo

gic f

unct

ion

psyc

hosi

s

N. Prichapan & U. Klinkesorn / Songklanakarin J. Sci. Technol. 36 (6), 651-661, 2014654Ta

ble 2

.Su

mm

ary o

f for

tific

atio

n fo

rm, r

ecom

men

ded

daily

dos

ages

and

dire

ct fo

rtific

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n pr

oble

m of

som

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eral

s and

vita

min

s.

Nut

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F

orm

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ortif

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ende

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D

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prob

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luco

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ric1-

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mg,

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year

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Sens

itive

to re

actio

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lor c

hang

e, li

pid

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oniu

m ci

trate

, sod

ium

iron

ED

TA,

girls

14-

18 ye

ars 1

5 m

g, bo

ys 1

4-18

year

s 11

mg,

oxid

atio

n, p

reci

pita

tion

(Guz

un-C

ojoc

aru

ferr

ous b

isgl

ycin

ate,

ferr

ous f

umar

ate,

wom

en 1

9-50

year

s 18 m

g. P

regn

ancy

27

mg,

et a

l., 20

10; Z

imm

erm

ann

and W

indh

ab,

ferr

ic sa

ccha

rate

, fer

rous

citra

te, f

erric

lact

atio

n 9

mg,

afte

r 51

year

s 8 m

g 20

10)

citra

te, c

arbo

nyl i

ron,

and

ferr

icpy

roph

osph

ate (

Lync

h, 2

005;

Kro

ner,

2011

)Ca

lcium

Cal

cium

carb

onat

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lciu

m tr

ipho

spha

te,

0-6 m

onth

s 210

mg,

6-1

2 m

onth

s 270

mg,

1-3

year

sFl

occu

latio

n, sa

ndy

text

ure,

pre

cipi

tatio

nan

d ca

lciu

m m

alat

e (Th

eoba

ld, 2

005;

500

mg,

4-8

year

s 800

mg,

9-18

year

s 1,3

00 m

g,(L

akki

s et a

l., 2

011)

Kre

ssel

et a

l., 2

010;

Kro

ner,

2011

)19

-50

year

s 1,0

00 m

g, 50

year

s and

old

er 1,

200 m

g,pr

egna

ncy

and

lact

atio

n: 1

8 ye

ars o

r you

nger

1,30

0 mg,

19-5

0 yea

rs 1,

000 m

gM

agne

sium

Mag

nesi

um p

hosp

hate

, mag

nesi

um0-

6 m

onth

s 30

mg,

7-1

2 m

onth

s 75

mg,

1-3

year

sPr

otei

n ag

greg

atio

n, n

utrie

nts d

egra

da-

pyro

phos

phat

e, a

nd m

agne

sium

pot

assi

um80

mg,

4-8

year

s 130

mg,

9-1

3 ye

ars 2

40 m

g, m

en:

tion,

unf

avor

able

tast

e (B

onne

t et a

l.,ph

osph

ate (

Skel

cey e

t al.,

197

4)14

-18

year

s 410

mg,

19-

30 ye

ars 4

00 m

g, m

ore t

han

2009

)30

year

s 420

mg,

wom

en: 1

4-18

year

s 360

mg,

19-3

0 ye

ars 3

10 m

g, ov

er 3

0 ye

ars 3

20 m

g,pr

egna

ncy:

14-

18 ye

ars 4

00 m

g, 1

9 to

30

year

s35

0 m

g, ov

er 3

1 ye

ars 3

60 m

g, la

ctat

ion:

14-1

8 ye

ars

360

mg,

19

to 3

0 ye

ars 3

10 m

g, ov

er 3

1 ye

ars 3

20 m

gA

scor

bic a

cid

(vita

min

C)

Asc

orbi

c ac

id, a

scor

bate

salt,

and

Men

90

mg

and

wom

en 7

5 m

gVe

ry u

nsta

ble t

o hi

gh p

H, h

igh

tem

pera

-es

terif

ied

asco

rbat

etu

res,

UV

ligh

t, di

ssol

ved

oxyg

en (B

all,

(Liu

, 200

9; K

rone

r, 20

11)

2006

)Th

iam

ine (

vita

min

B1)

Thia

min

e hyd

roch

lorid

e9-

13 ye

ars 0

.9 m

g, bo

ys 1

4-18

year

s 1.2

mg,

girl

sU

nsta

ble t

o hi

gh p

H, h

igh

tem

pera

ture

s,(B

enic

hou

et a

l., 2

002)

14-1

8 ye

ars 1

.0 m

g, m

en 1.

2 mg,

wom

en 1.

1 mg,

high

moi

sture

cont

ent (

Ball

et a

l., 2

006)

preg

nanc

y & la

ctat

ion

1.4

mg

Ribo

flavi

n (v

itam

in B

2)Ri

bofla

vin,

and

ribof

lavi

ne-

1-3

year

s 0.5

mg,

4-8

year

s 0.6

mg,

9-1

3 ye

ars 0

.9U

nsta

ble t

o lig

ht an

d hi

gh p

H (B

all e

t al.,

5'-m

onop

hosp

hate

(Ow

usu

et a

l., 1

992)

mg,

boys

14-

18 ye

ars 1

.3 m

g, g

irls 1

4-18

year

s 1.0

2006

)m

g, m

en 1.

3 m

g, w

omen

1.1

mg,

pre

gnan

cy 1

.4 m

gCo

bala

min

(vita

min

B12

)C

obal

amin

and

aden

osyl

coba

lam

in1-

3 ye

ars 0

.9 µ

g, 4

-8 ye

ars 1

.2 µ

g, 9

-13

year

s 1.8

µg,

Uns

tabl

e to

Hig

h pH

(Bal

l et a

l., 2

006)

(Col

lins,

2003

)14

-18

year

s 2.4

µg,

men

& w

omen

2.4

µg,

pre

gnan

cy2.

6 µg

, lac

tatio

n 2.

8 µg

*(St

andi

ng C

omm

ittee

on

the

Scie

ntifi

c Ev

alua

tion

of D

ieta

ry R

efer

ence

Inta

kes

and

its P

anel

on

Fola

te, O

ther

B V

itam

ins,

and

Cho

line

and

Subc

omm

ittee

on

Upp

erRe

fere

nce L

evel

s of N

utrie

nts F

ood

and

Nut

ritio

n Bo

ard

Insti

tute

of M

edic

ine,

199

8; K

rone

r, 20

11; O

sieza

gha

et al

., 20

13)


Many methods and techniques can be applied forencapsulation of nutrients including spray drying, fluid bedcoating, spray chilling or cooling, melt extrusion, coacerva-tion, liposome, inclusion encapsulation, cocrystallization,nanoencapsulation, freeze drying, yeast encapsulation andemulsions (Stevanovic and Uskokovic, 2009; Fang andBhandari, 2010; Zuidam and Shimoni, 2010; Abbas et al.,2012).

An emulsion encapsulation technique can be used toencapsulate both water-soluble and oil-soluble liquidsubstances. The size of the liquid droplets in emulsion isusually in the range from 0.1-5,000 µm. Preparation of multi-layer around the droplets in emulsions may obtain a morestable and effective encapsulated core. The liquid dropletsin emulsion, especially oil-soluble substances, can beproduced in a dry powder form by spraying or freeze dryingtheir emulsion. The advantage of this technique is that it isflexible because it can be used to encapsulate both hydro-philic and lipophilic substances (Fang and Bhandari, 2010;Zuidam and Shimoni, 2010; Abbas et al., 2012).

Abbas et al. (2012) mentioned that there are manymethods that can be applied for encapsulation, but there areno techniques that are effective for all food systems. Eachtechnique has different advantages and limitations. However,W/O/W emulsions are the one encapsulation technique thatis suitable to fortify nutrients in beverages and water-basedfoods because this technique can keep the nutrients to bequite stable and easily dispersed in an aqueous phase.Moreover, it is easily to be scaled up to industrial size(Krasaekoopt et al., 2003).

4. Encapsulation of Minerals and Vitamins in Water-in-oil-In-water Emulsions

The water-in-oil-in-water or W/O/W emulsion system(Figure 1C) consists of small internal water dropletsembedded in larger oil droplets that are also dispersed inanother outer water continuous phase. This can be referredto as emulsions of emulsions that is to say water-in-oil-in-water emulsions consisting of water-in-oil emulsions (Figure1B) dispersed in a continuous water phase. The W/O/Wemulsions have two types of interfaces; these are innerwater-oil interface and oil-outer water interface, so it has touse oil-soluble emulsifiers to stabilize the inner water-oilinterface and water-soluble emulsifiers to stabilize the oil-outer water interface (Benichou et al., 2002; Dickinson, 2011;McClements, 2012).

For fortification of minerals and vitamins into foodproducts that have water as a continuous phase, W/O/Wemulsions are mostly used with different components assummarized in Table 3. Moreover, W/O/W emulsions mayalso be used for co-encapsulation, which is encapsulationfor both water-soluble substances and oil-soluble substancestogether by an encapsulating water-soluble substance in theinner water phase and encapsulating an oil-soluble substancein the oil phase of the same W/O/W emulsion system. For

example, Li et al. (2012) produced W/O/W emulsions for useas an encapsulation system consisting of riboflavin in theinner water phase and -tocopherol in the oil phase.

4.1 Preparation of W/O/W emulsions

W/O/W emulsions are usually produced using a two-step emulsification method (Figure 2). The first step is theproduction of W/O emulsions by homogenizing an oil phaseand the inner water phase together in the presence of a water-soluble core material at high pressure or high shear rate. Inthis step, a lipophilic emulsifier or oil-soluble emulsifier wasused to stabilize the water-oil interface. The second step isthe production of W/O/W emulsions by homogenizing theformer W/O emulsion and an outer water phase at a pressureor shear rate lower than that used in the first stage to avoidrupture or expulsion of inner droplets. To stabilize the oil-water interface, a hydrophilic emulsifier or water-solubleemulsifier was used in this step (Van der Graaf et al. 2005;McClements, 2012).

4.2 Factors affecting the properties of W/O/W emulsionsfor encapsulation

There are many factors that can affect the propertiesof W/O/W emulsions. In this review, we categorize them intofive groups: form and concentration of core material, con-centration of inner water phase and lipophilic emulsifier, typeand concentration of oil phase, type and concentration ofhydrophilic emulsifier and stabilizer and pH of outer waterphase.

4.2.1 Form and concentration of core material

The form and concentration of the core material affectsthe properties of W/O/W emulsions. For the form of the corematerial, different forms of core material lead to differencesin properties such as size, binding capacity, and hydrophilicproperty that all affect W/O/W emulsions characteristics.If the core material has the form of a bigger molecule, the

Figure 2. Schematic diagram of two-step procedure for preparationof water-in-oil-in-water (W/O/W) emulsions (not toscale).


Tabl

e 3.

Exam

ples

of m

iner

als a

nd vi

tam

ins e

ncap

sula

ted

in w

ater

-in-o

il-in

-wat

er em

ulsio

ns.

Nut

rient

sH

ydro

phili

c em

ulsif

ier

and

stabi

lizer

Oil

phas

e;lip

ophi

lic em

ulsif

ier

Hyd

roph

ilic e

mul

sifie

r and

Refe

renc

esin

inne

r wat

er p

hase

stab

ilize

r in

oute

r wat

er p

hase

Iron

-W

hey

prot

ein

isol

ate (

WPI

)-

Cor

n oi

l; po

lygl

ycer

ol p

olyr

icin

olea

te-

Poly

oxye

thyl

ene

Sorb

itan

Choi

et a

l., 20

09-

Pano

dan

SDK

(est

ers o

fes

ter (

PGPR

)m

onol

aura

te (T

wee

n20)

mon

ogly

cerid

es a

nd d

igly

cerid

es-

Min

eral

oil;

PGPR

-W

hey

prot

ein

conc

entra

teof

dia

cety

l tar

taric

acid

)(W

PC) a

nd g

um ar

abic

orm

esqu

ite g

um or

low

met

hoxy

lpe

ctin

(LM

P)Jim

enez

-Alv

arad

o et a

l., 20

09Ca

lcium

--

Sunf

low

er oi

l; PG

PR-

Xan

than

gum

Mar

quez

and

Wag

ner,

2010

--

Can

ola o

il; g

lyce

rol m

onos

tear

ate

-G

elat

in an

d ag

arSa

eidy

et a

l., 2

013

(GM

S)M

agne

sium

--

Ole

in, m

igly

ol, o

live o

il or

rape

seed

oil;

-So

dium

case

inat

eBo

nnet

et a

l., 2

009

PGPR

--

Oliv

e oil;

PG

PR-

Sodi

um ca

sein

ate

Bonn

et et

al.,

201

0aA

scor

bic

acid

--

Med

ium

chai

n tri

glyc

erid

e or l

imon

ene;

-W

PI an

d m

odifi

ed p

ectin

Lutz

et a

l., 2

009

(vita

min

C)

-Pa

noda

n SD

K an

dgel

lan

gum

PGPR

-M

esqu

ite g

um, m

alto

dext

rinCa

rrill

o-N

avas

et a

l., 2

012

-Ch

ia es

sent

ial o

il; P

GPR

and

WPC

Thia

min

e-

-M

ediu

m ch

ain

trigl

ycer

ide;

PG

PR an

d-

WPI

and

xant

han

gum

Beni

chou

et a

l., 2

002

(vita

min

B1)

mon

ogly

cerid

e ole

ate

Ribo

flavi

n-

-So

y oil;

PG

PR-

WPI

and

LMP

or ê-

carr

agee

nan

Li et

al.,

2012

(vita

min

B2)

Coba

lam

in-

Gela

tin-

Med

ium

chai

n tri

glyc

erid

e; P

GPR

-So

dium

case

inat

e or s

odiu

mO

’Reg

an an

d M

ulvi

hill,

201

0(v

itam

in B

12)

case

inat

e-m

alto

dext

rin co

njug

ate

--

Butte

r oil;

PG

PR-

Skim

milk

or so

dium

case

inat

eG

iroux

et al

., 201

3


encapsulation efficiency will be higher than for smaller forms.If the core material attaches to the molecule that has a higherbinding capacity, the encapsulation efficiency will be higher,because it will occur with a lower free form of the corematerial, so it is harder to release. Moreover, the higher hydro-philic property of the core material also leads to lower release,because higher hydrophilicity molecules are harder to diffusethrough the oil phase.

Marquez and Wagner (2010) encapsulated differentcalcium salts in the inner water phase of W/O/W emulsionsusing sunflower oil as the oil phase, PGPR as a lipophilicemulsifier, soybean milk as the outer water phase, andxanthan gum as the stabilizer. They found that emulsionsthat used calcium lactate as the core material had lower Gand G and higher tan than emulsions that used calciumchloride as the core material. The lower G and G and thehigher tan values mean that the W/O/W emulsions have aweaker structure. This may due to the calcium lactate, whichis a bigger molecule, and has a lower release value thancalcium chloride, which occurs with a lower crosslink to thesoybean proteins and therefore has a weaker structure.

In the same way, Bonnet et al. (2010b) encapsulateddifferent magnesium salts in the inner aqueous phase ofW/O/W emulsions using olive oil as the oil phase, PGPR aslipophilic emulsifier, and sodium caseinate as the hydrophilicemulsifier. They found that the encapsulated MgCl2 had thehighest release rate and completed release in a 15 day-storage, since small molecules of magnesium can easilytransfer through the oil phase. The encapsulated gluconicacid hemimagnesium salt was found to have a lower releasevalue than MgCl2, but a higher release value than phosvitinwith MgCl2. This may due to the fact that gluconic acid has alower binding capacity than phosvitin and is quite a smallmolecule, so it can easily pass through the oil phase. Whereas,encapsulated phosvitin with MgCl2 was found to have thelowest release value because the hydrophilicity and highmolecular weight of phosvitin cause it to be unable to passthough the oil phase.

For the effect of concentration of core material onencapsulation efficiency of W/O/W emulsions, there wasreport that higher concentrations of the core material can leadto higher encapsulation efficiency. For example, Benichouet al. (2002) entrapped thiamine hydrochloride in the W/O/Wemulsions that used medium chain fatty acid triglycerides asthe oil phase, PGPR as the surfactant, monoglyceride oleatefor droplet size reduction and better stability, and wheyprotein isolate and xanthan gum as hydrophilic emulsifiers.They found that increasing vitamin B1 concentrations causeda decrease in vitamin B1 release. This may due to the fact thatthiamine hydrochloride has an amphiphilic structure, so ithas surface properties to reduce interfacial tension.

In a similar way, Lutz et al. (2009) encapsulatedsodium ascorbate in the W/O/W emulsions using PGPR asemulsifier, and WPI and modified pectin as a hydrophilicemulsifier. They found that fresh emulsions had a reducedrelease rate with increasing sodium ascorbate concentration,

but after 28 days there was no significant difference. Thedifference in release rate of fresh emulsions containing differ-ent core concentrations was not discussed by the authors.However, in our opinion, this may due to the effect of theosmotic gradient. The higher core material concentration ledto the higher osmotic gradient, resulting in emulsion dropletswelling. This occurs from diffusion of the water phase fromthe outer water phase to the inner water phase to balance theosmotic gradient (Dickinson, 2011). The intensity of waterdiffused from the outer phase to the inner phase was higherthan the diffusion of water from the inner phase to the outerphase resulting in a low release of sodium ascorbate in freshemulsions. However, for a longer time storage, the diffusion ofwater from the outer phase to the inner phase may cause somedroplets broken and release core material resulting in a highrelease of sodium ascorbate from emulsion droplets after 28days.

4.2.2 Concentration of inner water phase and lipophilicemulsifier

The concentration of the inner water phase and lipo-philic emulsifier affects the properties of W/O/W emulsions.Higher concentrations of the inner water phase lead to lowerrelease rates of the core material. In the same way, higherconcentrations of lipophilic emulsifier lead to lower releaserates of the core material. An example for the effect ofdispersed aqueous phase content was shown by Marquezand Wagner (2010). They found that higher dispersedaqueous phase content led to the formation of lower G andG and higher tan value emulsions. The lower G and Gand the higher tan meant that the W/O/W emulsions werethinner. This can explain why higher dispersed aqueousphase content reduced the calcium concentration leading toreduced osmotic gradient and calcium release, so there wasless crosslink with soybean proteins producing thinneremulsions. For the effect of lipophilic emulsifier concentra-tion, Marquez and Wagner (2010) found that higher PGPRconcentrations produced lower G and G and higher tan value emulsions. This may be due to increases in the PGPRconcentration which reduced the water droplet size of theW/O droplets, so reduced calcium release led to lesscrosslink and less elastic behavior of the emulsion.

4.2.3 Type and concentration of oil phase

The type and concentration of the oil phase affectsthe properties of W/O/W emulsions. Different types of oilphase lead to variations in properties such as viscosity, andsaturated fatty acid content affecting the encapsulationefficiency of W/O/W emulsions. An oil phase with higherviscosity values lead to higher encapsulation efficiencybecause the viscous oil phase retards diffusion and expulsionof the inner water phase with the core material inside. More-over, oil types with higher saturated fatty acid levels yieldhigher hydrophobicity or lower compatibility with water


causing a faster expulsion of the inner water phase that hasthe core material inside.

For example, Bonnet et al. (2009) encapsulated MgCl2in W/O/W emulsions using olein, miglyol, olive oil orrapeseed oil as the oil phase, PGPR as a lipophilic emulsifier,sodium caseinate as a hydrophilic emulsifier, and lactose tomatch the osmotic pressure between the inner and outerwater phase to avoid water transfer. They found that doubleemulsions produced with miglyol had significantly fastermagnesium release than other oils. This can be explainedsince miglyol has the lowest viscosity and the highest satu-rated fatty acid of these four oils, so the lower viscosity leadsto easier material transfer and release, and higher saturatedfatty acid leads to higher hydrophobicity and lower com-patibility with the water causing faster magnesium release.In contrast, double emulsion produced with rapeseed oil,which has a quite high viscosity and the lowest saturatedfatty acid content, had the highest magnesium retention.

In the same way, Lutz et al. (2009) found that doubleemulsions produced from medium chain triglycerides had alower sodium ascorbate release rate than produced from R(+)-limonene. This can be explained since R(+)-limonene has alower viscosity which leads to easier release of the sodiumascorbate from the inner water phase to the outer waterphase.

For the effect of lipid phase content on property ofW/O/W emulsions, there was a report that higher lipid phasecontent lead to get more viscous W/O/W emulsions. Marquezand Wagner (2010) showed that increased lipid phase contentled to the formation of higher G and G and lower tan value emulsions. The higher G and G and the lower tan values mean that the W/O/W emulsions were more viscous.This can be explained in a way that the higher lipid phasecontent produced in the more water-in-oil droplets led totighter packing and a viscous systems.

4.2.4 Type and concentration of hydrophilic emulsifier andstabilizer

The type and concentration of the hydrophilicemulsifiers and stabilizers affect the properties of W/O/Wemulsions. Some hydrophilic emulsifiers and stabilizers havea synergistic effect on the stabilization of emulsion whenused together. Different types of hydrophilic emulsifiers andstabilizers, which have different properties such as molecularweight and charge, result in different effects on the propertiesof the W/O/W emulsions. Using two hydrophilic emulsifierstogether or hydrophilic emulsifiers with stabilizers mayincrease the encapsulation efficiency more than using eitheralone. For example, O’Regan and Mulvihill (2010) encapsu-lated vitamin B12 in W/O/W emulsions with gelatin to solidifythe inner water phase with medium chain triglyceride oil asthe oil phase, PGPR as the lipophilic emulsifier, sodiumcaseinate or sodium caseinate-maltodextrin conjugate as thehydrophilic emulsifier. They found that the encapsulationefficiency of double emulsion stabilized with sodium

caseinate-maltodextrin conjugate was significantly higherthan that of sodium caseinate, especially in the case of malto-dextrin with a dextrose equivalent (DE) of about 10. This wasbecause the protein-polysaccharide conjugate formed a morebulky polymeric layer at the interface and some parts of thepolysaccharide protruding toward the continuous phasecaused better steric stabilization against droplet flocculationand coalescence.

The greater molecular weight of polysaccharides leadto more effective protection of the core material than lowerones, for example, Jimenez-Alvarado et al. (2009) entrappedferrous bisglycinate in the W/O/W emulsions using mineraloil as the oil phase, and protein-polysaccharide complexes(whey protein concentrate (WPC) with gum arabic (GA) ormesquite gum (MG) or low methoxyl pectin (LMP)) as water-soluble surfactants in outer water phase. They found that theencapsulation yield and ferrous ion content of W/O/Wemulsions stabilized with 5 wt% total concentration of WPC:MG and 0.7 wt% total concentration of WPC:LMP weresignificantly highest at the initial time. This may be due toformation of a thick layer at the interface of the droplet, butonly ferrous ion content of water-in-oil-in-water emulsionstabilized with 5 wt% total concentration of WPC:MG weresignificantly higher at the end of storage time which may bedue to the molecular weight of the polysaccharides. Mesquitegum has a greater molecular weight than gum Arabic and lowmethoxyl pectin, respectively. Since mesquite gum has a highmolecular weight and can form a thick layer at the interface,therefore it was the most effective polysaccharide to protectagainst ferrous bisglycinate oxidation in between thesepolysaccharides.

The higher charge of polysaccharides has both posi-tive and negative effects on the properties of W/O/W emul-sions. For the positive effect, Lutz et al. (2009) encapsulatedsodium ascorbate in W/O/W emulsions that used differentmodified pectin types U63 and C63, the modified pectin typesU63 and C63 are 63% degree of esterification, but U63 hasa more negative zeta potential and more intermolecularinteractions than C63. They found that double emulsionstabilized with the WPI/U63 complex had lower sodiumascorbate release rates than found in a double emulsion stabi-lized with the WPI/C63 complex. They explained that U63pectin have more charges which leads to more interactionand causes more elastic and a greater stiffness complex withWPI. Thus, the WPI/U63 complex was more effective toprevent the release of sodium ascorbate than the WPI/C63complex.

In contrast, Li et al. (2012) encapsulated riboflavin inthe W/O/W emulsions with hydrophilic emulsifiers and stabi-lizers of whey protein isolate and low methoxyl pectin (LMP)or -carrageenan (KCG), which has a higher minus chargethan low methoxyl pectin. They found that the encapsulationefficiency of the WPI-LMP complex stabilized emulsion washigher than that of the WPI-KCG complex when the WPI: PSratio was 5:0.5. They explained that the low charge poly-saccharide chain has a flexible worm-like form that easily to


curvature and interact with protein molecule, while the highcharge polysaccharide chain has a rigid stick-like form, solow methoxyl pectin, which has lower charge, has a moreflexible chain, and can more easier bind with proteins to createa dense and seal interface leading to more encapsulationefficiency than that of the WPI-KCG complex.

For the effect of hydrophilic emulsifier or stabilizerconcentration, the higher hydrophilic emulsifier or stabilizerconcentration should have higher encapsulation efficiencybecause increased hydrophilic emulsifier levels lead tostronger interfacial films against core material release. Forexample, Li et al. (2012) found that increasing the polysac-charide concentration caused the encapsulation efficiency toincrease. In the same way, Benichou et al. (2002) found thatincreases in the xanthan gum ratio reduced the vitamin B1release, because more xanthan gum content led to the pro-duction of a more synergistic and rigid film around thedroplet.

However, increasing the concentration of some hydro-philic emulsifiers can lead to decreases in encapsulationefficiency. For example, Bonnet et al. (2010a) encapsulatedmagnesium in the W/O/W emulsions by using olive oil as anoil phase, PGPR as a lipophilic emulsifier, and sodiumcaseinate as a hydrophilic emulsifier. Surprisingly, the highersodium caseinate concentrations led to higher magnesiumrelease. This may due to increased levels of sodium caseinatemeaning more sodium ions leading to more osmotic pressurein the external water phase. When the external osmoticpressure is higher than the internal osmotic pressure, thewater may migrate from the internal to the external waterphase.

4.2.5 pH of outer water phase

When two ionic hydrophilic emulsifiers or stabilizersare used together, the pH of outer water phase will affect theencapsulation efficiency of W/O/W emulsions. The pH thatshould be used is one that allows two ionic hydrophilicemulsifiers or stabilizers to have different charges in order tolet them exhibit electrostatic attraction. For example, whenprotein and anionic polysaccharide are used as a hydrophilicemulsifier and stabilizer, respectively, the pH of the systemshould be lower than pI (isoelectric point) of protein in orderto obtain the cationic structure of protein that can exhibitelectrostatic attraction with an anionic polysaccharidestructure (Figure 3A). The larger difference in charge inten-sity between the ionic hydrophilic emulsifiers or stabilizerslead to increased electrostatic attraction and provides athicker and denser interfacial layer.

Benichou et al. (2007) entrapped thiamine hydro-chloride in W/O/W emulsions by using medium chain fattyacid triglyceride as the oil phase, PGPR as the lipophilicemulsifier, monoglyceride oleate and glycerol for droplet sizereduction and better stability. Whey protein isolate andxanthan gum was used as hydrophilic emulsifier and stabili-zer, respectively. They found that lower pH levels led to

lower vitamin B1 release, but at a pH of 3.5 vitamin B1 wasreleased less than at pH 2 because at pH values more thanabout 4.5 (above the isoelectric point of the whey proteinisolate) this caused the whey protein isolate to have a minuszeta potential as xanthan gum, so the whey protein isolateand xanthan gum did not interact (Figure 3B) which led to aless sealed interface and higher vitamin B1 release. On theother hand, at pH 2 xanthan gum had less minus zeta potentialand a reduced different of zeta potential between wheyprotein isolate and xanthan gum, which led to an interactionbetween them being less than at pH 3.5. This had a greaterdifference in zeta potential between the whey protein isolateand xanthan gum, so the complex interface at pH 3.5 wasmore sealed and had lower vitamin B1 release.

5. Conclusions

W/O/W emulsions can be used as an entrapping anddelivering system for minerals and vitamins. However, thereare many factors that affect the stability and efficiency ofthese emulsion systems that have to be considered such asvolume and properties of oil and inner or outer water phase,concentration and form of core material, type and concentra-tion of emulsifiers and stabilizers, and also process condi-tions. For encapsulation of minerals and vitamins, W/O/Wemulsions should have both high encapsulation efficiencyand physicochemical stability, including being stable toenvironmental stress and chemical reactions. Moreover, itshould still be stable when it is applied to food products andshould not decrease the quality of those products.

Acknowledgements

The authors would like to thank the Thailand ResearchFund under The Royal Golden Jubilee Ph.D. Program (PHD/0001/2555: 2.F.KU/55/I.1.R.03) for their financial support.Special thanks to S. Watmough for his assistance in writingthe manuscript.

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