Lecture 3 (10/23/2011)
Nano/Micro Encapsulation Technologies
Qingrong Huang
Department of Food Science
Tel: 732-932-7193
Email: [email protected]
Food Delivery Systems
Motivations:
- Encapsulated materials can be protected from moisture,
heat, oxidation, or other extreme conditions;
- Enhance food stability and maintain viability;
- Some bad odors or tastes can be masked, etc…
Food Ingredients of Interest:
- Food flavors, enzymes, nutraceuticals, and food colors.
others: nutrients, food microbial, etc.
Encapsulation Basics
Encapsulation: a process by which one material or mixture of
materials is coated or entrapped within another material or system.
The material that is coated or entrapped can be a liquid, a solid
particle, or gas, and is referred as core material (or fill, internal
phase).
The material that forms the coating is referred to as wall material
(or carrier, shell, membrane, coating).
Common Encapsulation Methods
1. Spray Drying
• First, the carrier or wall material (such as maltodextrin, modified starch, gum,
etc…) is hydrated. The flavor or ingredient to be encapsulated is added to the
carrier and homogenized or thoroughly mixed into the system using a similar
technique. Typical ratio of carrier:core materials is 4:1.
• The mixture is homogenized to create small droplets of flavor or ingredient
within the carrier solution, and then fed into a spray dryer where it is atomized
through a nozzle or spinning wheel. Hot air contacts the
atomized particles and evaporates the water, producing a
dried particle that is a starch or carrier matrix containing
small droplets of flavor or core. The dried particles fall
to the bottom of the dryer and are collected.
Common Encapsulation Methods
1. Spray Drying
0
50
100
150
200
250
300
350
400
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 2,4
-Decad
ien
al Level (p
pm
)
Days of Shelf Life
Spray Dried 2,4-Decadienal Encapsulated in
Neobee; Shelf Life Study
5 Degrees Celcius 25 Degrees Celcius
40 Degrees Celcius 60 Degrees Celcius
Reference @ 40 Degrees Celcius Reference @ 60 Degrees Celcius
Common Hydrocolloids
Natural Semisynthetic
Sulfated:
Carrageenan, furcellaran, agar,
iridophycan, fucoidan, hypnean
Sulfated starch
Carboxylic
Alginate, pectin, Arabic, tragacanth,
karaya, ghatti, xanthan gum, quince seed,
larch, psyllium seed gum, okra gum, gellan
gum, flax seed gum
Carboxymethylcellulose, low
methoxylpectin, propylene glycol alginate,
triethanolamine alginate, carboxymethyl
locust bean gum, carboxymethyl guar gum
Phosphorylated
Phosphomannans Starch phosphate
Nonionic
Dextran, starch and its fractions, locust
beam gum, guar, tamarind seed gum,
laminaran
Methylcellulose, hydroxypropylcellulose,
hydroxyethylcellulose,
hydroxypropylmethylcellulose,
ethylhydroxyethylcellulose
SEM Images
(a) (b)
Characterization of Capsules
Optical image AFM height image
50 μm
Common Encapsulation Methods
1. Spray Drying
Advantages:
• Most economical and widely used method of encapsulation;
• Equipment is readily available and production cost is low;
• Also a dehydration process and used in the preparation of dried
materials such as powered milk;
Disadvantages:
• Producing very fine powder which needs further processing
such as agglomeration to instantized the dried material;
• Not good for heat sensitive materials.
Common Encapsulation Methods
2. Spray Cooling
• Similar to spray drying in that core material is dispersed in a liquified
coating or wall material and atomized, but unlike spray drying, there is
no water to be evaporated;
• The core and wall mixtures are atomized into cooled air which causes
the wall (typically a vegetable oil, melting point 45-120 °C) to solidify
around the core;
• this method is often used to encapsulate solid materials such as
vitamins or minerals;
• With the ability to select the melting point of the wall, this method of
encapsulation can be used for controlled release.
Common Encapsulation Methods
3. Media Milling (part 1)
• Media milling involves placing solid particles to be mechanically reduced to
nano dimensions in a ball mill or milling unit that contains milling media
beads. Dry and wet media milling procedures can be used.
• In a dry milling process, no solvent or liquid is added to the ball mill. In a
wet milling process a liquid is present. It usually is water, but can be a food
grade vegetable oil.
• In both dry and wet milling procedures, a dispersing agent is present. It may
be a polymer or nonpolymeric surfactant.
• Once loaded, the milling unit is rotated or agitated in some manner. Impact
and shearing forces between moving milling media beads reduce the
suspended solid particles to nanoparticles. Stress intensity coupled with
number of contact points with milling beads are primary factors that define
final milled particle size
Common Encapsulation Methods
3. Media Milling (part 2)
• Stress intensity is influenced by kinetic energy transmitted to the grinding
media through the agitator shaft within the machine’s stator housing. The
smaller the beads are, the smaller the nanoparticle produced, because the
number of contacts increases as bead size decreases. The rule of thumb is that
nanoparticle size equals 1/1000 the size of the grinding media;
• Milling media beads of 50-200 µm yield a fine particle size distribution.
Before wet-milled After wet-milled
Wet Milling System
Common Encapsulation Methods: 4.
Emulsion encapsulation/entrapment
• Key step: Formation of a oil-in-water (o/w) emulsion: The active
material to be encapsulated or entrapped is added to a hydrocolloid
solution. A small volume of this aqueous phase is then added to a large
volume of oil and the mixture is homogenized to form the emulsion.
Once the O/W emulsion is formed, the water-soluble polymer must be
insolubilized (cross-linked) to form tiny gels within the oil phase.
• The smaller the internal phase particle size of the emulsion, the
smaller the final microparticles will be. Cross-linking method: e.g.
alginate/Ca++.
2011-10-18 15
b-carotene:
Encapsulation of β-carotene using Polymer Micelles
antioxidant character, anticancer activity, enhancement of the
immune response, inhibition of mutagenesis, and blocking of free
radical-mediated reactions
The demand for b-carotene has increased.
2011-10-18 16
Background b-carotene:
lipophilic unsaturated
susceptible during storage
In order to insert the lipophilic b-carotene into aqueous
food systems and enhance its stability, different
technologies are investigated.
2011-10-18 17
Background Nanotechnology
serve as carriers for nutriceutical, effective vehicles for
drug delivery and controlled release, and gene therapy.
Encapsulation of b-carotene by nanotechnology
• Nanodispersion: protein, polymeric matrices
- B. S. Chu et al. J. Sci Food Agric 2008 88,1764-1769.
- S. C. Sutter et al. Interna. J. Pharmaceutics 2007 332, 45-54.
- C. P. Tan et al. J. Sci Food Agric 2005 85,121-126. (0.024%)
• Nanoparticle: emulsion, amphiphilic polymer
- M. Murakami et al. J. Chem Engin Japan 2008 41, 485-491.
- A. Hentschel et al. J. Food Sci 2008 73, N1-N6.
- X. Y. Pan et al. J. Colloid Interface Sci 2007 315, 456-463.
- J. P. Jee et al. Europ J Pharmac Biopharmac 2006 63 134-139
- S. A. Desobry et al. J. Food Sci 1997 62, 1158-1162.
2011-10-18 18
Background
Chitosan:
is a cationic polysaccharide
is a fully or partially N-
deacetylated product of naturally
abundant chitin
biocompatible, biodegradable, low-toxic, bioadhesive
attract increasing attention in the fields of food,
textile, cosmetics, biomedical, pharmaceutical,
and other industries.
2011-10-18 19
Background
poor solubility in
either water or
organic solvents
limited applications
Modified
Chitosan
hydrophilic
hydrophobic
A number of publications show the suitability of self-
assembled nanoparticles from modified chitosan for
encapsulation of sensitive ingredients.
Simultaneous Modification scarce
2011-10-18 20
Hypothesis and Objective
• Chitosan can be modified using acyl chloride as hydrophobic
group and MPEG* as hydrophilic group, which could exhibit
amphiphilic properties.
A hypothetical scheme of micellization of modified chitosan
• Because b-carotene is very lipophilic, the modified chitosan
nanoparticles can be used to encapsulate it, and to enhance its
solubility and stability.
* polyethylene glycol monomethyl ether
2011-10-18 21
Synthetic scheme of modified chitosan amphiphile:
The Structure
Nuclear Magnetic Resonance Fourier Transform Infrared
acylChitosan
acylChitoMPEG
2011-10-18 22
Sample
DS (Degree of Substitution)
NH2 NHAc NHR OR
chitosan 0.74 0.26 0 0
acylChitosan 0.69 0.23 0.08 0.92
Sample DSR=DS(NHR+OR) DSR/DSM DSM
acylChitoMPEG 1.0 2.18 0.46
Characterization:
Molecular formula of acylChitoMPEG C6H7O2(OH)1.08(OR)0.92(NH2)0.23(NHCOCH3)0.23(NHR)0.08(NHCOCH2CH2COMPEG)0.46
2011-10-18 23
Sample Milli-Q water Ethanol Acetone CH2Cl2 CHCl3 THF Dioxane
Chitosan - - - - - -
acylchitosan -
acylchitoMPEG
Solubility Test:
The improved solubility will make acylChitoMPEG be
easily fabricated into various micro- and/or nanoparticles,
which will extend the use of chitosan derivatives in
biomedical applications.
2011-10-18 24
Self-assembly Properties:
Critical Aggregation Concentration (CAC): 0.066 mg/mL.
CAC of chitosan: above 1 mg/mL. M. M. Amiji Carbohydr. Polym. 1995 26, 211-213
360 400 440 480 520
0
5
10
15
20
(a)
I3
I1
Inte
nsi
ty (
a.u
.)
Wavelength (nm)1E-3 0.01 0.1 1
0.90
1.05
1.20
1.35
1.50
1.65
1.80
1.95
(b)
acylChitoMPEG
Concentration (mg/mL)
I 1/I
3
2011-10-18 25
Surface morphology images of acylChitoMPEG.
Left is height image and right is phase image
Atomic Force Microscopy(AFM) Images:
2011-10-18 26
Single stretched exponential fit by dynamic light scattering (DLS)
Particle Size:
100 101 102 103 104 105 106
0.9
1.0
1.1
1.2
1.3
1.4
1.5
G (
q,t
)
t (s)
sample Diameter (nm)
by AFM by SEF
acylChitoMPEG 17.6 24.4
2011-10-18 27
Structure by Synchrotron small-angle X-ray scattering (SAXS):
10-4
10-3
10-2
10-1
100
I(Q
) (c
m-1
)
5 6 7 8
10-2
2 3 4 5 6 7 8
10-1
2 3 4 5 6 7 8
100
Q (Å-1
)
2.5x10-4
2.0
1.5
1.0
0.5
0.0
P(r
) (a
.u.)
200150100500
r (Å)
acylChitoMPEG 20 mg/mL
10 mg/mL
5 mg/mL
2.5 mg/mL
1.25 mg/mL
-2
MΔbnc=)=I(Q /0 2
I - scattering intensity
Q -scattering vector
c -sample concentration
n -association number
-scattering length
difference of one molecule
relative to the surrounding
medium
M -the molecular weight
b
The scattering profile
Slope: large scale
agglomeration of
associated particles
2011-10-18 28
0.1 1 10 100 1000
40
60
80
100
120
140
160
Rel
ativ
e C
ell
Via
bil
ity (
%)
Concentration (g/mL)
Cytotoxicity Analysis:
Suggesting that it was well biocompatible and had the potential to be used
in biomedical applications and encapsulation of active food ingredients.
2011-10-18 29
Picture of sample solutions encapsulating b-carotene:
Concentration of sample in water: 10 mg/mL
ε-Poly(lysine)-Based Micelles
ε-Poly(lysine), or EPL, is generated naturally
• EPL is produced by bacterium Streptomyces
albulus.
• 25-30 (35) lysine monomers.
• Mw 3000-4000Da
Food Applications of EPL
• 1. antimicrobial agent • against both Gram(+) and Gram(-) bacteria
• because of its positive charge
• GRAS (2004), in cooked rice or sushi rice
• 2. dietary agent
• inhibit pancreatic lipase
• suppress dietary fat absorption
ε-Poly(lysine)-Based Micelles
• EPL + octenyl succinic anhydride (OSA)
(J. Agr. Food Chem. 2010, 58, 1290-1295)
Physical Properties
Samples Tg (oC)
EPL 133.1
OSA-g-
EPL6.2 126.1
OSA-g-
EPL8.5 94.0
OSA-g-
EPL12.4 78.9
OSA-g-
EPL20.5 60.6
Micelle Structure
Q (A-1)
10-2 10-1
I(Q
) a
.u.
10-5
10-4
10-3
10-2
OSA103
OSA106
OSA110
OSA103 fit
OSA106 fit
OSA110 fit
Pair distribution function Small-angle x-ray scattering profiles
Antimicrobial vs.
Cytotoxicity
Minimum Inhibition Concentration
(MIC)=12.5 (μg/mL)
Cytotoxicity in Hep G2
cells was found for OSA-g-EPL
between 300-600 μg/mL.
Three loading methods to compare the
encapsulation capacity
Encapsulated curcumin showed
increased cellular antioxidant activity
**: P<0.01
Conclusions of micellar encapsulation
experiments
• Curcumin was able to be solubilized in micelle
solution, exampled by micelles formed by
modified starch and newly synthesized modified
epsilon polylysine.
• Upon encapsulation, in vitro bioactivity of
curcumin was increased, suggesting that solubility
limited the cellular absorption of curcumin.