The Department of Food Physics and Meat Sciences (FPMS)

Jochen Weiss

Dept. of Food Physics and Meat Sciences (150g)Institute of Food Science and BiotechnologyUniversität HohenheimGarbenstrasse 21/25, 70599 Stuttgart

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Overview

Ongoing Projects in FPMS

• Food Physics:– Emulsion, Microemulsions, Liposomes, Solid Lipid

Nanoparticles• Fat crystallization in confined spaces• Polymer-micelle complexes• Block copolymers and protein mixed micelles

– Colloidal and Molecular Interactions / Hierarchical Assembly

• Coacervates (Growth Phenomena, Use as stabilizers)• Phase separated dispersions• Oppositely charged colloids• Multilayering• Enzymatic Crosslinking & Mineralization (New)

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Ongoing Projects in FPMS - Continued -

• Food Antimicrobials:– New Antimicrobials: Phenolipids, Peptidolipids, Naturl

Occurring Antimicrobials– Mechanism of Action– Improving Functionalities in Complex Matrices

• Meat Science:– New Ingredient Systems (Fibers, Bioactives)– New Processing Techniques: Continuous

emulsification, Co-extrusion– Role of Physical Processes (e.g. Blooming, Texture

Developments)

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FPMS Facilities• Wet Chemistry Lab:

– Elemental and Macromolecular Analysis

• Analytical Chemistry Lab – 4 HPLCs, 2 GCs, 1 FTIR, 1 Preparatory HPLC (?)

• Biophysical Analysis Lab – Surface Tension, Optical Rheometry, Zetasizing, SLS,

DLS, Thermal Analysis, QCM, Confocal Microscope, Isothermal Titration Calorimetry, Electronic Nose, UV-NIR

• Micro- and Nanofabrication Lab– Microfluidizier, HPH, Ultrasound, Coaxial

Electrospinning, NEW RESEARCH SPRAY DRYER

• Microbiology Lab (S1)– Microplate Reader, Sterile Hood, Spiral Plater, etc.

• Pilot Plant – Meat Products Focused – European Food Hygiene

Law Approved (Smokehouses, Bowl Choppers, High Speed Grinders, Stuffers, etc.

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One of Our Focus AreasHierarchically Organized Food Structures

Solid LipidNanoparticles

SimpleDroplets

LaminatedEmulsions Covered

Emulsions

MultipleEmulsions

The Lipid Family The Biopolymer Family

The Surfactant Family

Fundamental principles in food structure design on nano, micro, macrolevels have led to an explosion of new dispersed structures Many

More….

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“Solid Lipid Nanoparticles” (SLN) and SLN Colloidosomes

• Liquid lipid in emulsion is replaced by high melting point lipid

• Glycerides or waxes suitable

• Typical medium size ranges from 50 - 500 nm

• At small sizes, crystal structures become dependent on surfactant and size

• Polymorphism

Emulsion

Solid LipidNanoparticle

SurfactantLayer

liquidlipid (oil)

solidlipid

lipophiliccompound

exchangedegradation

No exchangeLess degradation

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Why Solid Lipid Nanoparticles?• Better control over release kinetics of encapsulated

compound– Engineering via size and lipid composition– Melting can serve as trigger

• Enhanced bioavailability of entrapped bioactives• Chemical protection of labile incorporated compounds• Much easier to manufacture than biopolymeric

nanoparticles– No special solvents required– Wider range of base materials (lipids)– Conventional emulsion manufacturing methods

applicable• Raw materials essential the same as in emulsions• Very high long-term stability• Application versatility:

– Can be subjected to commercial sterilization procedures

– Can be freeze-dried to produce powdered formulation

Conventional Carrier

Microcarrier

Nanocarrier

20-50 mm

2-5 mm

200 nm

dc/dt

dc/dt

dc/dt

cs

cs

csDissolution velocitySaturation solubility

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Storage Time at 20oC (Days)

0 5 10 15 20 25

Re

l. -

Ca

rote

ne

Co

nte

nt

(%)

0

20

40

60

80

100

120

HLPPPULPPPTw80PPPTw60PPP

A Success: β-Carotene Stability in SLN

Managed to stabilize omega-3s now as well!

Figure 5. β-carotene breakdown over time at 20°C, using tripalmitin as an lipid matrix

Measured as relative decrease in concentration

Dramatic improvement in stability of β-carotene in HLPPP systems

Surface-initiated crystallization

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From SLN to Colloidosomes

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• Based on an old idea: About a century ago, Pickering discovered that fine solid particles can be used as stabilizers in emulsion.

• These “Pickering” emulsions provide excellent protection against coalescence due to the presence of densely packed solid particles at the o/w interface

• If suitable particles and oil are dispersed in water the particles adsorb to the oil due to free energy reductions in the system

• The key factor for the use of particles as a stabilizing agent is therefore their wetting behavior by the two phases, the oil and the aqueous phase wetting angle a key factor, must be just right, otherwise particle remains in the aqueous phase or disperses in the oil droplet

• NOTE: Wetting angle is not suitable in the case of solid lipid and liquid lipid particles!!!

Assembly of Solid-Liquid Colloidosomes by Electrostatics

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Mixing

Particle with Negatively Charged Emulsifier

Electrostatic Attraction

Oil-in-Water Colloidosomes

Particle with Positively Charged Emulsifier

Absorption by electrostatic Adsorption

Polarized Light and Fluorescence Microscopy of SLN-Colloidosomes

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Crystals atSurface

FluorescenceStained SLN

Multiphase Food Structures

B. Multilayered Liposomes

Hydrophilic Head

Lipophilic Tail

Most common: Phospholipid: Phosphatidylcholin

CholinPhosphate

Liposomes are particulate core-shell structures that are composed of an aqueous inner core and a bilamellar phospholipid membrane.

Glycerolbridge

Fatty Acids

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General Structure of Liposomes

SUV

LUV

GUV

Differentiation based on particle size

Small (d=30-100 nm, SUV)Large (d=100-5000 nm, LUV), Giant with d=5-200 µm (GUV)

Differentiation based on structure

Unilamellar (Single Layer)Multilamellar (more than one) Multivesicular (more han one liposome in another liposome (MVV) MVV

MLV

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New Approach: Encapsulation of polyphenolic plant extracts in multilayered Liposomes

Filtrated extract inacetate buffer

(0,2 M, pH 3,8± 0,2)

Prinary Liposomes

1% Phospholipid Lipoid S75

Microfluidizer(15000-25000 psi, 5 passes)

Pre-emulsionMagnetic stirrer + UltraTurrax

GelfiltrationSephadex-G50

Positively charged biopolymer Chitosan (1%)

Negatively charged Liposome with extract

-

--

-

-

++

+

+ +

+

+

-

Negatively charged biopolymer Pectin (1%)

Secundary Liposomes Teriary Liposome

-

--

-

-

-

-

-

--

--

Positively charged encapsulated Liposome

Negatively charged double liposomes

Polyphenolisc components

Removal of unencapsulated extract and excess chitosan

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C. Enzyme-Stabilized Multilayer Emulsions

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An emulsion consist of two or more partially or completely immisicible liquids (e.g. oil and water), with one liquid being dispersed in the other in the form of small droplets (d = 0.1 - 100 mm). Emulsions are thermodynamically unstable systems.

“Dispersed” Phase

“Continuous” Phase”

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Specifics

Microfluidizer(700 bar, 3 passes)

Pre-EmulsionUltraturrax

(2 min, 24000 rpm)

Positively charged fish

gelatin membrane

Negatively charged fish

gelatine – sugar beet pectin membrane

Secondary O/W-

Emulsion (2)

++

+

-

-

-

Coating(Vortex)

Fish gelatine: Isoelectric point at pH 6, Mw = 60 kDa

Sugar beet pectin: Degree of esterification 55 %

Soy oilCitrate buffer: pH 3.5; 10 mM

CoarseO/W-Emulsion

PrimaryO/W-Emulsion (1)

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Pectin Concentration [%]

0.0 0.1 0.2 0.3 0.4

-P

ote

ntia

l [m

V]

-30

-20

-10

0

10

20

Droplet Charge as a Function of Sugar Beet Pectin Concentration

O/W-Emulsion

Z-Average

(nm)PDI

ζ-Potential

(mV)

Primary (1) 200 ± 20 0.076 ± 0.018 +20 ± 2

Secondary (2) 350 ± 50 0.101 ±

0.024 -21 ± 2

Primary Emulsion: 5.0% Oil, 0.95% Fish gelatineMicrofluidizer

Secondary Emulsion: 0.1 – 1.0% OilSaturation Method

Mean Droplet Diameter and ζ-Potential of primary and secondary emulsions

Fabrication of Double-Layered O/W-Emulsions

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Time t [min]

0 50 100 150 200

Me

an

Dro

ple

t D

iam

ete

r [n

m]

200

250

300

350

400

450

without enzym with enzyme

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Enzymatic Crosslinking of Emulsions

Evidence of crosslinking: increases in mean droplet diameter after addition of enzyme

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Enhanced Freeze-Thaw Cycling

Anzahl Gefrier-Tau-Zyklen

0 1 2

Mitt

lere

r P

art

ike

ldu

rch

mess

er

[nm

]

0

2000

4000

6000

8000

10000(1) (2) (2+)

Improved stability against freeze thaw cycling after laccase-induced crosslinking or pectin-

stabilized O/W-emulsions

(2) (2+)

1. Cycle

2. Cycle

0. Cycle

Mean Droplet Diameter as a Function of Freeze Thaw Cycles

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