Influence of elasticity on the syneresisproperties of κ-carrageenan gels

Komla AKO1,2

1Univ. Grenoble Alpes, LRP, F-38000 Grenoble, France2CNRS, LRP, F-38000 Grenoble, France

1

Laboratoire Rhéologieet Procédés

AMC2-2014

Outline

Contex:influence of sol-gel transition on the dried materials

Kappa-carrageenan (κ-car):Polyelectrolyte biopolymer gives aqueous solution and hydrogel

Results and discussion:Result on conditions affecting syneresis of k-car are discussed

Conclusion and outlook:Some key points from results and discussion will be presented in perspective

Syneresis:contraction of a gel resulting in the expulsion of a liquidRelation between structure, rheology and syneresis

2

3

Contex: influence of sol-gel transition on the dried materials

Collo

idal

solu

tion

~ nm to µmobjects Macroscopic

material

dry

dry

osm

otic

pres

sure

4

Contex: influence of sol-gel transition on the dried materials

Contex: influence of sol-gel transition on the dried materials

Solid stateTransient state

glass

film

cristal

0.740.494 0.545

Homogeneous gel

Heterogeneous gel

Aggregats

Fluid + solid

Key words: colloids, drying, evaporation, dehydration, stress, osmotic stress

Region Of Interest

5

Contex: influence of sol-gel transition on the dried materials

Liquid statePolymers solution

Key words: colloids, drying, evaporation, dehydration, stress, osmotic stress

Liquid stateColloids

6

Kappa-carrageenan (κ-car):Polyelectrolyte biopolymer gives aqueous solution and hydrogel

CH2OH

n

o

oOH

OSO3-

oo o

OH

T°C

10 20 30 40 50

G'(P

a)

0.1

1

10

100 Td Tm

200 mM NaCl

edible filmscoil helix Cold gel

Region Of Interest

Na+, K+, Ca2+ and Cl-, I-

Na+

K+

Ca2+

Cl-I-

Tgel

Tm

T↓

T↑

Tgel

G’↑

G’↓

T↓

T↑

κ-car powderdissolved in hotdemineralised water

κ-car powderin pure K+ form

7

Kappa-carrageenan (κ-car):Polyelectrolyte biopolymer gives aqueous solution and hydrogel

T (°C)20 25 30 35 40 45

G' (

Pa)

10-1

100

101

102

103

8g/L with 0.04M KCl

Hermansson et al., 1989

weak gel

20°C

15°C

10°C5°C

Chen et al., 2002Syneresis is not presentin the purified samples

Syneresis liquid

gel

Richardson et al., 1994

pure K+ form

pure K+ form

pure K+ form

pure K+ form

8

10 g/L

10 g/L

Kappa-carrageenan (κ-car):Polyelectrolyte biopolymer gives aqueous solution and hydrogel

20°C

10°C5°C

Chen et al., 2002Syneresis is not presentin the purified samples

Syneresis liquid

gel

pure K+ form

9

10 g/L

1g/L with 0.01M KCl

15°C

15°C

Meunier et al., 1999

weak gel

weak gel

2g/L with 0.01M KCl

Na+ 5°C

B.T. Nguyen et al., 2014

05101520253035404550

Citation on syneresis from 2000 - 2014

A multidisciplinary study on syneresis

0

50

100

150

200

250 ALL

FST

POLS

MMS

MSB

%

Syneresis:contraction of a gel resulting in the expulsion of a liquid

Food science, biomacromolecules, colloidsMilk gel by enzyme and/or acidificationPolysaccharides (alginate, starches etc.)Exopolysaccharides (to limite syneresis)

Polymer science, macromolecule, biomaterials, colloidsBloc or star copolymers of (PEG, PLGA, PLLA, PNIPAAm)Bloc copolymers (PCL-PEG-PCL > 15 wt%)PVA gel → spinodal decomposition/syneresis

Materials science multidisciplinary, geology, colloidsColloidal particle gels (clay, silica) → sedimentation/syneresisBarium titanate (BaTiO3) ceramics → crystallisation/syneresis

10

b ca

Desiccation cracks: subaerial shrinkage cracking

Syneresis cracks: subaqueous shrinkage cracking

Syneresis induces cracking in clay gel structureis confused with desiccation phenomena

Syneresis:contraction of a gel resulting in the expulsion of a liquid

Pratt Brian R., 1998, Sedimentary Geology

gelgel

∆s∆t

Spontaneous consolidation behaviorof a gel: endogeneous syneresis

F

gelgel

∆s∆t

F

Consolidation behavior ofa gel under external forces

11

Fluid Gel Gel + solvent

Continuous networkParticules in « fusion » form

uncompressible gel

DispersedCompressible fluid

Continuous networkParticules in « touching » form

Compressible gel

Syneresis:Relation between structure, rheology and syneresis

SyneresisGelation

Internal forcesDepletion forcesElectrostatic attraction forceshydrogen bonds (~0.8nm, ~2kT to ~5kT)hydrophobic interactionsvan der Waals interactionsSteric interactions

Understand the syneresis mechanism through the relation betweenthe syneresis and the rheological properties of gel

Curds and whey

Contraction behavior of a gel : Endogeneous syneresis

12

Gel network by aggregationof globular proteins

Gel network by longlinear molecules

Randomaggregation

String of beads

Connectionat points

Connectionat junctionzones

PolymersPoloxamerCarrageenanXanthanAgarose

Fibrous proteinsGelatinmyosin

Globular proteinsSerum albuminEgg albuminInsulinLysozymeSoybean glycinRibonucleasePea

caseinBeta-lactoglobulinWhey proteinmyosin

Gel

Fluid

Fluid

Gel

Milk gel

κ-car gel

Polymers-polymers / polymers-solvent interactions => gel rheological properties

G’ max (OVA) ≈ 106 - 108 PaC(OVA) ≈ 120 g/l – 450 g/l

G’ max (βLg) ≈ 104 - 106 Pa C(βLg) ≈ 20 g/l – 150 g/lG’ max ≈ 103 - 104 Pa

(elasticity of tissus)C (κ-car) ≈ 2 g/l – 20 g/lC(Gelatin) ≈ 20 g/l – 150 g/lC(PEO) ≈ 200 g/l – 650 g/l

Syneresis:Relation between structure, rheology and syneresis

13

Results and discussion:

After 5 days

Gel

Fluid

100g

es w

wR

52.1 )()( Ps

Ws RR

(W ) = wiping(P) = pipetting

time (Days)0 2 4 6 8 10 12 14 16 18 20

8

10

12

14

16

18

20

22

24

26

time (Days)0 4 8 12 16 20

-ca

r (g/

l)

4.44.64.85.05.25.45.6

Rs(P

)(%

)

4g/L κ-car with 40mM KCl

4g/L κ-car with 40mM KCl

wg

Kinetic studies of syneresis

at room temperature (≈ 22°C) and at ≈ 9°C

14

Results and discussion:

After 5 days

Gel

Fluid

100g

es w

wR

52.1 )()( Ps

Ws RR

(W ) = wiping(P) = pipetting

time (Days)0 2 4 6 8 10 12 14 16 18 20

8

10

12

14

16

18

20

22

24

26

time (Days)0 4 8 12 16 20

-ca

r (g/

l)

4.44.64.85.05.25.45.6

Rs(P

)(%

)

4g/L κ-car with 40mM KCl

4g/L κ-car with 40mM KCl

wg

Kinetic studies of syneresis

at room temperature (≈ 22°C) and at ≈ 9°C

15

Statistical analysisAll determinations were replicated three times and mean values and standarddeviations reported. Analyses of variance (ANOVA) were performed and themean separations were performed by Tukey’s HSD test (P<0.05) usingSigmaStat1 version 2.0 (Jandel Scientific/SPSS Science, Chicago, IL, USA).R. Hoover, W.S. Ratnayake / Food Chemistry 78 (2002) 489–498

Results and discussion:

time (days)1 2 3 4

RS

15

20

25

30

35

401 g/l 2 g/l 3 g/l 4 g/l

-car (g/l)1 2 3 4

RS

/ t

1

2

3

4

5

6

7

8

Kinetic studies of syneresis

at room temperature (Tsyn ≈ 22°C)

16

40mM KCl40mM KCl

Results and discussion:

Effect of κ-car and KCl on the syneresis

-car (g/l)1 2 3 4 5 6 7 8

RS

10

15

20

25

30

35

40

17KCl (mM)

0 50 100 150 200

RS

5

10

15

20

25

T (°C)

20 25 30 35 40 45

G' (

Pa)

10-1

100

101

beforeafter

40mM10mM 30mM

KCl (mM)

0 50 100 150 200

T g (°

C)

30

40

50

60

beforeafter

gel

sol

T gel

(°C

)

4 g/L

40mM KClat room temperature (Tsyn ≈ 22°C)

KCl Tg Tsyn ∆T Rs Rs/(Tg-T)

40 mM 39°C 22°C 17°C 24% 1.41%/°C

40 mM 39°C 9°C 30°C 24% 0.80%/°C

Results and discussion:

Effect of KCl and temperature on the syneresis

KCl (mM)0 50 100 150 200

RS

5

10

15

20

25Tsyn = 22°C

18Sy

nere

sis (

a.u)

4g/L40mM KClTgel = 39°C

Rs

KCl Tg Tsyn ∆T Rs Rs/(Tg-T)

40 mM 39°C 22°C 17°C 24% 1.41%/°C

100 mM 52°C 22°C 30°C 7% 0.23%/°C

4g/L

KCl Tg Tsyn ∆T Rs Rs/(Tg-T)

40 mM 39°C 22°C 17°C 24% 1.41%/°C

40 mM 39°C 9°C 30°C 24% 0.80%/°C

Results and discussion:

Effect of KCl and temperature on the syneresis

KCl (mM)0 50 100 150 200

RS

5

10

15

20

25

KCl Tg Tsyn ∆T Rs Rs/(Tg-T)

40 mM 39°C 9°C 30°C 24% 0.80%/°C

100 mM 52°C 22°C 30°C 7% 0.23%/°C

Tsyn = 22°C

19Sy

nere

sis (

a.u)

4g/L40mM KClTgel = 39°C

Rs

4g/L

(Tgel – T) °C

TTRR gelrelsapps

TTR

Rgel

appsrels

Results and discussion:

Relation between the elasticity and syneresis

T°C30 32 34 36 38 40 42

G'(P

a)

100

101

102

G’max

20

-car (g/l)

2 4 6 8

G' (

Pa)

100

200

300

400

500

600

KCl (mM)

50 100 150 200 250

G'(P

a)

0

500

1000

1500

2000

-car (g/l)1 2 3 4 5 6 7 8

RS

10

15

20

25

30

35

40

KCl (mM)0 50 100 150 200

RS

5

10

15

20

25

G’ m

ax(P

a)G

’ max

(Pa)

4 g/L

40mM KCl

Results and discussion:

Relation between the elasticity and syneresis

T°C30 32 34 36 38 40 42

G'(P

a)

100

101

102

G’max

21

-car (g/l)

2 4 6 8

G' (

Pa)

100

200

300

400

500

600

KCl (mM)

50 100 150 200 250

G'(P

a)

0

500

1000

1500

2000

-car (g/l)1 2 3 4 5 6 7 8

RS

/ (T g

- T)

0.4

0.8

1.2

1.6

2.0

KCl (mM)0 50 100 150 200

RS

/ (T g

- T)

0.0

0.5

1.0

1.5

2.0

2.5

G’ m

ax(P

a)G

’ max

(Pa)

4 g/L

40mM KCl

Results and discussion:

Relation between the elasticity and syneresis

G'max (Pa)

1 10 100 1000

RS

/ (T g

- T)

0.0

0.5

1.0

1.5

2.0

2.5

-carKCl

K. Ako / Carbohydrate Polymers 115 (2015) 408–414 22

-car (g/l)

2 4 6 8

G' (

Pa)

100

200

300

400

500

600

KCl (mM)

50 100 150 200 250

G'(P

a)

0

500

1000

1500

2000

-car (g/l)1 2 3 4 5 6 7 8

RS

/ (T g

- T)

0.4

0.8

1.2

1.6

2.0

KCl (mM)0 50 100 150 200

RS

/ (T g

- T)

0.0

0.5

1.0

1.5

2.0

2.5

G’ m

ax(P

a)G

’ max

(Pa)

4 g/L

40mM KCl

Conclusion and outlook:

Syneresis of k-car is controlled by elasticity rather than the gel composition

but elasticity is not the only parameter that arrest the syneresis

A maximum of syneresis was found at intermediate elasticities wich implies

a complex behavior between elasticity forces and others forces in the gel

The thermal retraction coefficient (Rs/(Tg-T)) is considered to reflect the gelation

temperature variation when salt concentration is changing

Drying of syneresis gel to thin film

45 m

mSyneresis induces wrinkling or cracks

K. Ako/Carbohydrate Polymers 115 (2015) 408–414 23