1. Filtration Difficulties
Molly Kelly
Virginia Tech Enology Extension
Wineries and Breweries Unlimited
March 13,2014

2. Overview Factors Types Deformable vs Non-deformable particles
Integrity testing
Filter?
Other

3. Why Filter? Remove particulates Remove fining agents Remove colloids
Remove yeast and bacteria
All of these particles are easily deformed so excess pressure can cause coating that retards filtration

4. Factors impacting filterability
Variety
Rot
Fruit type
Season
Processing
Enzymes
Fining/residual fining agents
Yeasts/bacteria

5. Types of filtration Depth filtration Wine moves through tortuous path
Filtration occurs on surface AND interior matrix
Rated with nominal or normal porosity
Some % (70-98%) of particles of that size will be retained
Use specified flow rates
Ex: DE, plate and frame filters, disc filters
Gusmer Inc.

6. Disadvantages of Depth filtration
Media migration
Increases with surge vs uniform flow
Microbial growth within filter matrix
Contamination of filtrate
Some product can remain in filter matrix
“Sterile” pads?; cannot validate porosity

7. Types of filtration Absolute filtration Membrane filtration
Filtration occurs at the surface
Standard sized pores;99%+ reliability
Trap all particles larger than pore size
Clog easily
0.45 micron, “sterile”; sequential depth plus absolute filtration
Gusmer Inc.

8. Disadvantages of Absolute filtration
Low “dirt handling”capacity
Use only with “clean”wines to remove microorganisms
Not all particles with diameters less than pore size flow through
May be retained in pore passage, blocking flow
Do not wait >48 hours after prefilter

9. Deformable vs. Non-deformable particles
Non-deformable: retain shape
Diatoms or diatomaceous earth: various grades
Rigid nature: act as filtration medium
Tartrate crystals
Shape will not change with applied pressure
Deformable-majority of wine/juice particles
Yeast, bacteria, colloids (including fining agents ex: gelatin), protein/phenol/polysaccharide complexes
Elastic nature-spread over surface area; block filtrations
Proactive: rack, fine, enzymes

10. Deformable vs Non-deformable
Gusmer Enterprises, Inc.
<0.2 microns-1000 microns

11. Colloids Protein fractions: mw 20-40 Kda
Polysaccharide fractions: mw Kda
Grapes
Yeast
Botrytis cinerea
Marginally soluble fractions
Form fine dispersed aggregates in solution
Deposits on surfaces
Membrane filter fouling

12. Botrytis Beta-glucan insoluble in 30% ethanol (v/v)
Filament like precipitate
Specific detection for this polysaccharide
Prevents natural sedimentation of particles (like pectin)
Alcohol acts as aggregation factor; polymerization
Most severe at end of fermentation
Beta-glucanase
Stemstore.tumblr.com

13. Beta-glucan
Villettaz et al. 1984

14. Agglomeration
Image  by Kathryn Erbe
Many suspended particles will adhere to similar particles
Result in single larger particle
Larger particles may precipitate naturally or by fining
Easier to remove by filtration

15. Polysaccharides Includes pectins and glucans Deformable particles
May be colloidal in juice and wine
Impede filtration
In alcoholic solution, both are unstable
Form gelatinous aggregates

16. Polysaccharides
Polysaccharides may derive from the plant or from microbial activity

17. Pectins Structural component of plant cell walls
Can impede clarification
Test : add pectolytic enzyme and perform precipitation test
Proactive enzymatic treatment of must/juice recommended
Pectins and glucans high in concentrates

18. Glucans Result of Botrytis growth on grapes Result of spoilage LAB
Gel formation with acidified ethanol
(Zoecklein et al., 2005)
Laffort.com

19. Starch Can cause haze in apple juice and cider
Affects clarity and filtration
Test for starch haze (Zoecklein et al. 2005)

20. Sterile filtration Integrity Testing
Membrane filters must be preceded by 99.9% filtration
Must be bubble tested before, during, and after run
If fails, product between that time is suspect

21. Bubble point
Gas pressure where surface tension of water in filter pores is overcome
Gas passes through pores
Dependent on pore size
Are leaks present anywhere?
Means of checking integrity
of system

22. Bubble point
Millipore inc.

23. Pressure Hold Integrity Test
Monitor upstream pressure decay as gas diffuses through wetted membrane
Pressurize housing to 80% bubble point
Turn off gas
Monitor how quickly upstream pressure drops (<2 psig in 5 min)
Precise pressure gauges

24. Filter sheets Ruptured sheets: major source back-pressure shock
Rapid valve closing, shutting off/pulsation of pump
Winesand vines.com

25. Does filtration change sensory character?
Soluble flavor and aroma compounds are well below 0.45 microns
Sensory impact hard to quantify
subjective nature of sensory analysis
Soluble species are probably not removed by macro and micropore filtration
Maybe colloidal macromolecules that impact mouthfeel

26. Colloidal macromolecules
May be present as large aggregates of polysaccharides, mannoprotein or protein-phenolic complexes (500+kd)
May play role in wine’s texture/structure
Interaction between macromolecules and and low mw volatile compounds may account for aromatic changes after sterile filtration

27. Mouthfeel Colloids-viscosity
May have tannins and anthocyanins attached
Does filtration (0.45 micron) remove significant amount of colloids?
No conclusive evidence
Possible?

28. Aging Phenols bind together and polymerize
Molecular weight and size increases
Filtration can remove these
Older red wines have more polymerized phenols
Greater negative effect from filtration
Color reduction
Ezramagazine.com

29. Sorbate? Can replace with filtration to 1 micron
Removing yeast, not bacteria
Sensory changes due to ethyl sorbate
Sorbate and ethanol
Candied fruit, Juicy fruit
Geranium taint
microbial

30. Conclusions No filtration?-can lead to instabilities Sanitation
Follow manufacturers operating directions
Flow rate, pressure differential
Test wines for filterability
Wines with similar turbidity can have different filterability indices (Cattaruzza et al. 1987)
Keep good records

31. References
Zoecklein, B. Filtration. Wine/Enology and grape Chemistry Group, Virginia Tech
Mansfield, A.K. Cellar Dweller. Cornell Extension Enology Lab, February Accessed Feb 29.
Bisson, L. Post Fermentation Processing. Accessed Feb
Butzke, C. Winemkaing Problems Solved. Woodhead Publishing, Oxford
Reynolds, A. Managing Wine Quality. Woodhead Publishing, Oxford
Alarcon-Mendez and R. Boulton Automated measurement and interpretation of wine filterability. Am. J. Enol. Vitic. 52:3.
Villettaz, J.C. et al The use of a beta glucanase as an enzyme in wine clarification and filtration. Am. J. Enol. Vitic. 35:4.
Patterson, T. If filtration strips wine, what’s getting stripped?. Wines and Vines. Oct 2008.

32. Questions? mkkelly@vt.edu