VEN124 Section V Post-Fermentation Processing

Lecture 14: Clarification and Filtration and the Compositional Adjustment of Wine

Reading Assignment: Text, Chapter 7 pages

The 5 Goals of Post-Fermentation Operations: 1.Clarity 2.Compositional adjustment 3.Stability 4.Style 5.Packaging

The 5 Goals of Post-Fermentation Operations: 1. CLARITY

Clarification GOAL: to eliminate existing cloudiness

Clarification Options Natural settling/racking Centrifugation Filtration

Natural Settling/Racking Decanting wine off of solids May add a settling aid to “tighten” lees Volume loss high Gentle process

Settling and Racking Settled Lees Racking Valve

Centrifugation: Types Desludging Decanting

Centrifugation: Function Removal of particles using centrifugal force Can be adjusted to remove larger or smaller particles

Centrifugation: Problems Aeration Cost –Modified atmosphere –Low temperature

Filtration Types of filtration processes Kinds of filter units

Filtration Processes Sieve Adsorption

Sieve Particles larger than pore size are retained by filter

Adsorption Particles adhere to matrix

Adsorption and Sieving

Kinds of Filter Units Depth-bed

Depth-Bed Filtration Filter matrix mixed with wine Filter matrix builds as wine is filtered through coated screen Constantly laying down new matrix with wine

Depth-Bed Filtration Screen Wine Wine + Matrix Pre-coat

Depth-Bed Filtration Diatomaceous earth; cellulose; perlite Cost effective Minimal clogging “Rough” filtration: sieving action is minimal Principle of “torturous path” for particles to travel

The “Torturous Path”

Kinds of Filter Units Depth-bed Pad

Pad Filtration Filter matrix is a preformed sheet or pad Sieving as well as adsorption Pads come in a variety of porosities, but pore size is heterogeneous Flow of wine perpendicular to pad “Dead end” filtration

Pad Filtration Wine Filtered wine

Kinds of Filter Units Depth-bed Pad Membrane

Membrane Filtration Like pad filtration, but uses a membrane Fixed pore size Sieving as well as adsorption Clog easily “Finishing” filtration

Membrane Filtration WineMembrane Filtered Wine XX XX XX XX XX

Kinds of Filter Units Depth-bed Pad Membrane Cross-flow

Cross-Flow Filtration Same porosities as membrane filtration Wine flows across matrix, not through it Wine retentate can be re-circulated Back flux can be used to clear membrane Does not clog that easily

Cross-Flow Filtration Wine Retentate Filtered Wine

Order of Filtration: Rough Before Finishing XXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

The Question: Does filtration impact wine flavor and aroma?

The Belief: Filtration removes flavor and aroma compounds and is therefore undesirable. “Unfiltered” wines are more complex than filtered.

The Facts: Several studies have shown that expert tasters are not able to recognize filtered versus unfiltered control wine. Unfiltered wine allows continued microbial activity, which may explain differences perceived in unfiltered wines in general.

The 5 Goals of Post-Fermentation Operations: 2. COMPOSITIONAL ADJUSTMENT

Compositional Adjustment Acidity

To increase acid add: –Malate –Tartrate –Citrate To decrease acid add: –Calcium carbonate To remove volatile acidity: –Reverse osmosis

Compositional Adjustment Acidity Sugar level

Sugar Level Add juice concentrate Arrest fermentation –Addition of ethanol Fortified wine Fortified juice –Temperature shock

Compositional Adjustment Acidity Sugar level Ethanol level

Evaporative removal with return/replacement of co-stripped volatiles Reverse osmosis followed by adjustment of flavors/aromas

Compositional Adjustment Acidity Sugar level Ethanol level Tannin removal

Tannin Removal Time of aging: to allow polymerization to occur Ultrafiltration: mw cut-off

Compositional Adjustment Acidity Sugar level Ethanol level Tannin removal Sulfide/mercaptan removal

Sulfide/Mercaptan Removal Copper sulfate (formation of CuS  ) –H 2 S –Some thiols Copper sulfate + SO 2 + ascorbate –Disulfide removal –VERY SLOW