Influence of elasticity on the syneresis properties of κ-carrageenan gels

Transcription

1 Laboratoire Rhéologie et Procédés Influence of elasticity on the syneresis properties of κ-carrageenan gels Komla AKO 1,2 1 Univ. Grenoble Alpes, LRP, F Grenoble, France 2 CNRS, LRP, F Grenoble, France AMC

2 Outline Contex: influence of sol-gel transition on the dried materials Kappa-carrageenan (κ-car): Polyelectrolyte biopolymer gives aqueous solution and hydrogel Syneresis: contraction of a gel resulting in the expulsion of a liquid Relation between structure, rheology and syneresis 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 2

3 Contex: influence of sol-gel transition on the dried materials Colloidal solution osmotic pressure ~ nm to µm objects dry Macroscopic material dry 3

4 Contex: influence of sol-gel transition on the dried materials 4

5 Contex: influence of sol-gel transition on the dried materials Region Of Interest Transient state Solid state 0.74 Homogeneous gel Heterogeneous gel Aggregats Fluid + solid glass film cristal Key words: colloids, drying, evaporation, dehydration, stress, osmotic stress 5

6 Contex: influence of sol-gel transition on the dried materials Liquid state Colloids Liquid state Polymers solution Key words: colloids, drying, evaporation, dehydration, stress, osmotic stress 6

7 Kappa-carrageenan (κ-car): Polyelectrolyte biopolymer gives aqueous solution and hydrogel OSO 3 - CH 2 OH OH κ-car powder dissolved in hot demineralised water Na +, K +, Ca 2+ and Cl -, I - o o T o o OH o κ-car powder in pure K + form n T m G'(Pa) 100 Td Tm Region Of Interest G T 200 mm NaCl T gel T C G T T T gel coil helix Cold gel Na + K + Ca 2+ Cl - I - edible films 7

8 Kappa-carrageenan (κ-car): Polyelectrolyte biopolymer gives aqueous solution and hydrogel g/l 10 2 G' (Pa) g/L with 0.04M KCl pure K + form T ( C) pure K + form pure K + form 10 g/l 10 C 5 C Hermansson et al., 1989 Richardson et al., C 20 C gel weak gel pure K + form Chen et al., 2002 Syneresis is not present in the purified samples Syneresis liquid 8

9 Kappa-carrageenan (κ-car): Polyelectrolyte biopolymer gives aqueous solution and hydrogel Na + 5 C 15 C 2g/L with 0.01M KCl weak gel 1g/L with 0.01M KCl Meunier et al., 1999 B.T. Nguyen et al., g/l 10 C 15 C 5 C 20 C gel weak gel pure K + form Chen et al., 2002 Syneresis is not present in the purified samples Syneresis liquid 9

10 Syneresis: contraction of a gel resulting in the expulsion of a liquid A multidisciplinary study on syneresis Citation on syneresis from % ALL Food science, biomacromolecules, colloids Milk gel by enzyme and/or acidification Polysaccharides (alginate, starches etc.) Exopolysaccharides (to limite syneresis) FST POLS MMS MSB Polymer science, macromolecule, biomaterials, colloids Bloc or star copolymers of (PEG, PLGA, PLLA, PNIPAAm) Bloc copolymers (PCL-PEG-PCL > 15 wt%) PVA gel spinodal decomposition/syneresis Materials science multidisciplinary, geology, colloids Colloidal particle gels (clay, silica) sedimentation/syneresis Barium titanate (BaTiO3) ceramics crystallisation/syneresis 10

11 Syneresis: contraction of a gel resulting in the expulsion of a liquid a b Syneresis cracks: subaqueous shrinkage cracking Pratt Brian R., 1998, Sedimentary Geology Syneresis induces cracking in clay gel structure is confused with desiccation phenomena c gel F F Consolidation behavior of a gel under external forces t gel s Spontaneous consolidation behavior of a gel: endogeneous syneresis gel t gel s Desiccation cracks: subaerial shrinkage cracking 11

12 Syneresis: Relation between structure, rheology and syneresis Contraction behavior of a gel : Endogeneous syneresis Fluid Gel Gel + solvent Gelation Syneresis Dispersed Compressible fluid Continuous network Particules in «touching» form Compressible gel Curds and whey Continuous network Particules in «fusion» form uncompressible gel Internal forces Depletion forces Electrostatic attraction forces hydrogen bonds (~0.8nm, ~2kT to ~5kT) hydrophobic interactions van der Waals interactions Steric interactions Understand the syneresis mechanism through the relation between the syneresis and the rheological properties of gel 12

13 Syneresis: Relation between structure, rheology and syneresis Polymers Poloxamer Carrageenan Xanthan Agarose Fibrous proteins Gelatin myosin Gel κ-car gel Fluid G max Pa (elasticity of tissus) C (κ-car) 2 g/l 20 g/l C(Gelatin) 20 g/l 150 g/l C(PEO) 200 g/l 650 g/l Gel network by long linear molecules Connection at points Connection at junction zones Globular proteins Serum albumin Egg albumin Insulin Lysozyme Soybean glycin Ribonuclease Pea casein Beta-lactoglobulin Whey protein myosin G max (OVA) Pa C(OVA) 120 g/l 450 g/l G max (βlg) Pa C(βLg) 20 g/l 150 g/l Polymers-polymers / polymers-solvent interactions => gel rheological properties Gel network by aggregation of globular proteins String of beads Fluid Gel Milk gel Random aggregation 13

14 Results and discussion: Kinetic studies of syneresis Gel g/L κ-car with 40mM KCl R s ( W ) w w e g 100 R s 1.2R (W ) = wiping (P) = pipetting ( P) s 5 After 5 days Fluid 4g/L κ-car with 40mM KCl R s (P) (%) car (g/l) time (Days) time (Days) w g at room temperature ( 22 C) and at 9 C 14

15 Results and discussion: Kinetic studies of syneresis Gel g/L κ-car with 40mM KCl R s ( W ) w w e g 100 R s 1.2R (W ) = wiping (P) = pipetting ( P) s 5 After 5 days Fluid 4g/L κ-car with 40mM KCl Statistical analysis w g All determinations were replicated three timesandmeanvaluesandstandard deviations reported. Analyses of variance (ANOVA) were performed and the mean separations were performed by Tukey s HSD test (P<0.05) using SigmaStat1 version 2.0 (Jandel Scientific/SPSS Science, Chicago, IL, USA). R. Hoover, W.S. Ratnayake / Food Chemistry 78 (2002) R s (P) (%) car (g/l) time (Days) time (Days) at room temperature ( 22 C) and at 9 C 15

16 Results and discussion: Kinetic studies of syneresis R S g/l 2 g/l 3 g/l 4 g/l 40mM KCl R S / t mM KCl time (days) car (g/l) at room temperature (T syn 22 C) 16

17 Results and discussion: Effect of κ-car and KCl on the syneresis mM KCl at room temperature (T syn 22 C) 10mM 30mM 40mM 30 G' (Pa) 10 0 R S car (g/l) 10-1 before after T ( C) 25 4 g/l 60 sol R S T gel ( C) T g ( C) gel KCl (mm) KCl (mm) before after 17

18 Results and discussion: Effect of KCl and temperature on the syneresis 25 T syn = 22 C KCl T g T syn T R s R s /(T g -T) 40 mm 39 C 22 C 17 C 24% 1.41%/ C R S g/L 40 mm 39 C 9 C 30 C 24% 0.80%/ C KCl (mm) KCl T g T syn T R s R s /(T g -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 Syneresis (a.u) R s 4g/L 40mM KCl T gel = 39 C 18

19 Results and discussion: (T gel T) C Effect of KCl and temperature on the syneresis 25 T syn = 22 C KCl T g T syn T R s R s /(T g -T) 40 mm 39 C 22 C 17 C 24% 1.41%/ C R S g/L 40 mm 39 C 9 C 30 C 24% 0.80%/ C KCl (mm) KCl T g T syn T R s R s /(T g -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 Syneresis (a.u) R s 4g/L 40mM KCl T gel = 39 C R s app Rs rel T gel T s rel R R T s gel app T 19

20 Results and discussion: Relation between the elasticity and syneresis G'(Pa) G max G max G'(Pa) (Pa) G max G' (Pa) (Pa) R S car (g/l) -car (g/l) R S mM KCl 4 g/l T C KCl (mm) KCl (mm) 20

21 Results and discussion: Relation between the elasticity and syneresis G'(Pa) 10 2 G max T C G max G'(Pa) (Pa) G max G' (Pa) (Pa) car (g/l) KCl (mm) R S / (T g - T) R S / (T g - T) mM KCl car (g/l) 4 g/l KCl (mm) 21

22 Results and discussion: Relation between the elasticity and syneresis RS / (Tg - T) car KCl G' max (Pa) G max G'(Pa) (Pa) G max G' (Pa) (Pa) car (g/l) KCl (mm) R S / (T g - T) R S / (T g - T) mM KCl car (g/l) 4 g/l KCl (mm) K. Ako / Carbohydrate Polymers 115 (2015)

23 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 (R s /(T g -T)) is considered to reflect the gelation temperature variation when salt concentration is changing Drying of syneresis gel to thin film Syneresis induces wrinkling or cracks 45 mm K. Ako/Carbohydrate Polymers 115 (2015)