ult ltrafil iltration Floriane Doudis M. Loginov, N. Hengl, F. - PowerPoint PPT Presentation

Structural organization of casein mic icelle les concentrated la layer durin ing cross-flow ult ltrafil iltration Floriane Doudiès M. Loginov, N. Hengl, F. Pignon, N. Leconte, F. Garnier-Lambrouin, J. Pérez, L. Sharpnack, M. Granger-Delacroix, M. Belna, G. Gésan-Guiziou Paris Rennes FRANCE Grenoble UMR 1253 STLO INRA-Agrocampus Ouest Joint Research Unit on Science & Technology of Milk & Egg F-35000 Rennes, France 1 15 to 17 October 2018

Milk ilk filtr filtration Skimmed milk: Soluble proteins (0.7%wt) Casein micelle (3%wt) Water (91%wt) Ions, lactose, minerals … (6%wt) Casein micelles are large globular aggregates of caseins with calcium phosphate, they are porous, deformable, compressible and dynamic particles (50-500nm) Skimmed milk contains 26 g/L of casein micelles or 3%wt Micro- and ultrafiltration of skimmed milk are largely used in the dairy sector ( ≈ 40% of the membrane area installed in food sector) ultrafiltration → proteins concentration (cheese manufacture, standardization) microfiltration → proteins fractionation (high added value ingredients) 2

Membrane fou oulin ing by y cas asein in mic icell lles Bouchoux et al., Biophys. J., 2009 Cross-flow Membrane Permeate Transmembrane pressure ≈ 1 bar Increase of micelles Gel with high concentration concentration of casein micelles with time Formation of fouling gel layer: - limitation of the filtration performance reduces permeate flux, decreases permeate quality (low transmission of soluble proteins) - difficulties of cleaning operation large consumption of water , detergents and energy… 3

Objective & Str trategy Understand the structural organization and behaviour of concentrated casein micelles accumulated at the membrane surface during cross-flow ultrafiltration - Analyse fouling layer development during filtration step and redispersion during pressure relaxation step - Focus on the effect of temperature (12-45°C) Organic spiral membranes Mineral membranes 4 8-12°C 50-53°C

In In-sit itu SAXS cr cross-flow filt filtration Jin et al., J. Memb. Sci. (2014) Typical SAXS «spectra» of casein micelles suspension Calibration curve 1.2 Scattered beam intensity, I (a.u.) 1 0.8 12°C 100 25°C 0.6 I / I max 44°C 1 0.4 0.2 0.01 Concentration 0 0 100 200 0.0001 0.01 0.1 1 10 Casein concentration, C (g/l) 5 Scattering vector, q (nm −1 )

SAXS an anal alysis of of fou oulin ling la layer z , µm CCD detector Collimated Fouling layer X-ray beam 20 µm 250 µm Membrane Scattered intensity I(q) mm -1 0.01 0.1 1 Calibration curve Scattered beam intensity, I (a.u.) 1.E+03 10 3 Casein concentration, C (g/l) 1.E+02 300 Concentration distribution Distance to membrane in fouling layer 10 1 1.E+01 z = 20 µ m 1.E+00 200 1.E-01 10 −1 1.E-02 100 z = 2000 µ m 1.E-03 10 − 3 Initial suspension 1.E-04 0 0 100 200 300 0.1 1 0.05 0.5 0 100 200 300 Scattering vector, q (nm − 1 ) Distance to membrane, z ( µ m) 6

Quantification of of fou ouli ling la layer Predicted concentration of sol-gel Accumulated mass Casein concentration, C (g/L) transition: Casein concentration, C (g/L) of casein micelles 12°C – 150 g/l in fouling layer 25°C – 174 g/l 42°C – 181 g/l C sol-gel (from Nöbel et al., Int. Dairy J.(2016)) Gel thickness Distance to membrane, z ( µ m) Distance to membrane, z ( µ m) Filtration Removed mass, Relaxation mr (g/m²) Mass, m (g/m²) Mass, m (g/m²) Relaxation time, tr (min) Filtration time, tf (min) Relaxation time, tr (min) 7

Filt Filtration protocol Suspension: 50 g/L of casein micelles in milk ultrafiltrate Membrane: Polyethersulfone 100 kDa (Orelis, France) Filtration cycle: 2 steps Temperature: 12, 25 or 42°C Filtration Relaxation 150 min 45 min TMP, crossflow velocity TMP = 1,1 bar Crossflow velocity, v = 3 cm/s TMP = 0,1 bar Time 8

25°C Filtration kin Filt kinetics TMP = 1.1 bar v = 3cm/s 25 350 At 150 min of filtration Casein concentration (g/L) 300 Flux, J (L∙m −2 ∙h −1 ) 20 250 150 min 20 µm 15 200 Time 280 µm 10 150 100 Distance 5 7 min 50 0 Initial suspension 0 0 50 100 150 Filtration time, tf (min) 0 200 400 40 Distance to membrane z (µm) 5.E-07 35 Mass, m (g/m 2 ) 30 4.E-07 14 Flux, J (10 − 7 m ∙ s − 1 ) 25 3.E-07 20 15 12 2.E-07 10 5 1.E-07 0 0.E+00 0 50 100 150 0 10 20 30 40 50 00 Filtration time, tf (min) Mass, m (g/m 2 ) Flux decrease over time linked to casein micelles accumulation 9

Im Impact of of temperature on on filt filtration kin kinetics TMP = 1.1 bar v = 3cm/s 25 16 TMP = 1.1 bar 6.E-07 12°C 12°C v = 3cm/s 25°C 25°C Flux, J (L ∙ m − 2 ∙ h − 1 ) 20 5.E-07 Flux, J (10 −7 m∙s −1 ) 42°C 42°C 14 4.E-07 15 3.E-07 10 2.E-07 12 5 1.E-07 0 00 0.E+00 0 50 100 150 Time, t (min) 0 10 20 30 40 50 Mass, m (g/m 2 ) Flux. filtrate viscosity, J.µ (10 −10 Pa∙m ) 12°C 14 Darcy’s law: 25°C 𝑈𝑁𝑄 42°C 𝐾 × 𝜈 = 13 𝑆 𝑛 +𝑆 𝑔 12 11 Flux is higher under higher temperature due to a lower filtrate viscosity 00 0 10 20 30 40 50 Mass, m (g/m 2 ) 10

Im Impact of of temperature on on cas asein in mic icell lles TMP = 1.1 bar ac accumulation v = 3cm/s At 150 min of filtration 60 500 Casein concentration (g/L) 450 25°C 50 400 42°C 350 Mass (g/m 2 ) 40 12°C 300 30 250 200 12°C 20 150 25°C 100 10 42°C 50 Initial suspension 0 0 0 50 100 150 0 200 400 Distance to membrane z (µm) Time (min) 200 Gel thickness (µm) 150 At 42°C, accumulation is faster and more 100 pronounced: gel is more concentrated and thicker than at 12 or 25°C 12°C 50 25°C 42°C 0 0 50 100 150 11 Time (min)

Im Impact of of temperature on on cas asein in mic icell lles acc accumulation Temperature impacts filtration performances: At 42°C: - Flux is high - Because of a lower filtrate viscosity - And a high accumulation of casein micelles - Concentration of casein micelles at membrane surface is high - Gel thickness is high 12

25°C Pressure rela laxation TMP = 0.1 bar v = 3cm/s 40 35 30 20 Removed mass, mr (g/m 2 ) 18 Mass, m (g/m 2 ) 25 16 14 20 12 10 15 8 6 10 4 2 5 0 Filtration Relaxation 0 10 20 30 40 50 0 Relaxation time, tr (min) 0 100 200 Time (min) Relaxation step allows to remove a part of accumulated casein micelles without using chemical products But, relaxation time is same order of magnitude with accumulation time 13

Im Impact of of temperature on on pressure rela laxation TMP = 0.1 bar v = 3cm/s 60 12°C 25°C 42°C 50 25 Removed mass, mr (g/m 2 ) 40 Mass, m (g/m 2 ) 20 30 15 10 20 5 10 0 Filtration Relaxation 0 10 20 30 40 50 0 Relaxation time, tr (min) 0 100 200 Time (min) Removed mass rises with temperature: likely due to the lower viscosity of accumulated casein micelles layers at high temperature 14

Impact of Im of temperature on on gel l rela laxation TMP = 0.1 bar v = 3cm/s 1 12°C 25°C Relative gel thickness 42°C 0.8 At 12 °C, gel removal seems limited even if the concentration is not the higher Gel is more cohesive at 12°C 0.6 0.4 0 20 40 60 Relaxation time, tr (min) Concentration profiles during relaxation at different temperatures Casein concentration, C (g/L) Casein concentration, C (g/L) Casein concentration, C (g/L) 500 500 500 400 400 400 25°C 300 12°C 300 300 42°C 200 200 200 100 100 100 0 0 0 0 100 200 300 0 100 200 300 0 100 200 300 Distance, z (µm) Distance, z (µm) Distance, z (µm) 15

25°C Pressure rela laxation: gel l swelli lling TMP = 0.1 bar v = 3cm/s Osmotic Strong pressure 14.00 pressure gradient 1 min Casein concentration, C (g/L) 12.00 300 Time 10.00 Filtration Cross-flow 8.00 200 C sol-gel 41 min 6.00 TMP 4.00 100 2.00 0.00 000 Relaxation 0 100 200 300 Cross-flow Distance to membrane, z (µm) TMP Accumulation of casein micelles is removed via gel swelling and re-dispersion of swelled part Gel swelling 16

Pressure rela laxation: im impact of of temperature + Water − Calcium phosphate β -Casein migration 1 12°C from core to surface 25°C Relative gel thickness 42°C 0.8 Low temperature 0.6 0.4 0 20 40 60 Relaxation time, tr (min) High temperature Cohesion of gel (repulsive gel or attractive gel) depends on temperature Gaucheron (2005); Wastra (1990); Creamer et al.(1977) 17

Con onclusions - In-situ SAXS cross-flow filtration allowed analysis of casein micelles fouling layer with an unique resolution of 20µm during filtration step and relaxation step - During filtration of casein micelles, temperature has a significative effect on filtration performances: - Increasing temperature implies: - flux decrease because filtrate viscosity decrease - casein micelles accumulation at membrane surface - But during pressure relaxation, an easily removal of casein micelles and a gel that is less cohesive Future work: 1) rheological characterization of gels at different temperatures 2) local strength force of fouling layer at different temperatures 18

Thank you for your attention! Mohamed KARROUCH Michael Sztucki