The Fundamentals of Fining

Linda F. BissonDepartment of Viticulture and

Enology, UCD

Introduction to Fining

DEFINITION: Fining refers to the removal of components from a juice or wine that are currently soluble or in small aggregates that will associate with the insoluble fining agent thereby being pulled out of the wine

Introduction to Fining

• Fining agents may be used alone or in combination with other agents

• Natural settling may be sufficient to remove fining agent and its associated components

• Centrifugation or filtration may be needed to remove fining agent

Types of Fining Agent Interactions

• Charge-based• Disulfide bridging• Hydrophobic interactions• Affinity interactions

Charge-Based Interactions

• Hydrogen bonding• Salt bonding

Hydrogen Bonding

Salt Bonding

Disulfide Bridging

Can Get a Mixture of Types of Bonding

Hydrophobic Interactions

• Takes advantage of regions of molecules that “abhor” water and will associate with other non-polar components

• Many macromolecules have both hydrophobic and hydrophilic regions

• Hydrophobic regions associate with each other in juice but as protein denatures regions may be exposed to water and then will associated with the hydrophobic region of another molecule

Hydrophobic Interactions

Denatured protein Soluble protein

Hydrophobic Complex Formation

Both Hydrophobic and Charge Interactions May Occur

Affinity Interactions• Affinity interactions refer to a more complex

recognition of a component by another component

• These reactions often require a step of recognition

• These reactions are more specific in terms of partners being able to participate than charge or hydrophobic interactions

• Usually multiple points of contact• Generally used to remove specific wine

components like phenolic compounds

Affinity Interactions

Protein

Target Compound

Choice of Fining Strategy

• What are you trying to remove?• Will you remove positive characters along

with the negative character?• Will the fining agent leave and impact (over-

fining)• Nothing replaces fining trials!

Fining Can Be Used For

• Chemical Instability• Macromolecular Instability

Chemical Instabilities

• Metal ions

• Tartrate

• Polymerized phenols

• Oxidation products

Metal Ions

• Fe and Cu can form a precipitate “casse”

• Caused by use of iron or copper containing materials in winery or from pesticides

Tartrate

• At low temperature, tartrate will crystallize• Mistaken for ground glass by consumers• Unstable in presence of Ca++

• Solubility depends upon pH, K+, tartrate concentrations

• Can get co-crystallization with other organic acids

Polymerized Phenols

• Can precipitate during aging

• Maybe undesired in bottle

Oxidation Products

• Off-colors– Brown– Pink– Orange

• Off-characters– S- volatile compounds

• Prevented by using antioxidants

• Prevented by removal of off-color potential

Macromolecular Stability

• Protein

• Polysaccharide

Protein Instability

• Proteins involved are from grape• Denature over time causing visible haze

– Hydrophobic regions interact– Agglutination complexes formed– Complex becomes visible

• Accelerated by treatment of wine at high temperature (HTST)

• Can be prevented by fining to strip protein

HTST

• “High Temperature Short Time”

• Used on juices with high oxidase levels– Polyphenol oxidase from plant– Laccase from Botrytis

• Used on wines– Pasteurization (Kosher wines)– Inactivation of added enzymatic activity

Alternatives to Removing Protein

• Stabilizing protein via protective colloid formation

• Use of yeast polysaccharides to “coat” protein and hold it in soluble conformation

Stabilization of Particles

Protein Particles

Agglutination

StabilizationPolysaccharides

Polysaccharide Instability

• Polysaccharides come from either plant or microbial activity

• Insoluble at high ethanol causing visible haze

• Insoluble at low temperatures

• More difficult to prevent/remove

Mechanism of Fining

• Take advantage of either hydrophobic or hydrophilic interactions to remove offending component

• Wine will initially be cloudy, but particles will eventually become large and sink

• Clarify by racking or filtration

Mechanism of Fining

• Add a charged component that will interact with oppositely charged components followed by precipitation of the neutral complex

• Add a denaturing component that will expose hydrophobic surfaces that will then interact allowing a hydrophobic complex to form

The Fining Agents

• Proteins• Earths• Colloids• Synthetic polymers• Silica suspensions• Activated carbon• Yeast-derived components• Yeast cell walls (ghosts)• Lees fining

The Protein Fining Agents

• Casein

• Gelatin

• Albumin

• Isinglass

• Plant proteins

The Earths: Bentonite

• Silicate (SiO2)

• Large surface area: occurs in sheets

• Net negative charge at wine pH: ideal for interaction with wine proteins that generally have a net positive charge

• Different forms occur differing in salts associated with silicate: Na+, K+, Ca++

Bentonite

• Functions by exchange of associated cation for wine components having a higher affinity

NaNaNaNaNaNaNa NaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNa

Na+

Na+

Na+

Na+

Na+

Na+

Na+Na+

Na+

Bentonite Levels

• Typically 1 – 4 lbs/1000 gal (0.12 –0.48 g/L) is ample to remove wine protein

• If 10 lbs/1000 gal (1.0 g/L) is needed, haze problem might not be due to protein!

Bentonite: The Problems

• Must swell properly in water or water/wine mixture before use

• High lees volume

• Addition of ions that may encourage tartrate instability

Colloidal Fining Agents

• Natural polysaccharides

• Agar

• Gum Arabic

• Sparkolloid: alginate based

• Ferrocyanide colloidal preparations

Colloidal Fining Agents

• Naturally dispersed or “protective” colloids can hold proteins, tartaric acid crystals, other colloidal materials in suspension

• Colloidal fining agents neutralize surface charges on naturally dispersed colloids thereby allowing them to dissolve or coagulate

Synthetic Polymers

• Polyglycine

• Polyamide

• Polyvinylpolypyrrolidine (PVPP)

Have carbonyl oxygen atoms on surface that act as adsorption sites.

Synthetic Polymers

• Absorb monomeric phenolic compounds– Pinking potential– Browning potential– Bitter catechins

• Narrow spectrum

Silica Suspensions

• The “sols”

• Used primarily with gelatin

Activated Carbon

• High and broad affinity

• Removes color, wide range of phenolics

• Strips wine: used only as a last resort to salvage a wine for blending

Today’s Program• Pending potential labeling regulations for fining

agent use: Mari Kirrane, TTB• Supplier Panel: Innovative agents and proper use

of agents• Design and Evaluation of Fining Trials: Anita

Oberholster• Winemaker Panel: Strategies for use of fining

agents• Fining for Defects Removal: A case study: Chik

Brenneman

Importance of Diagnosis of Problem

• To avoid over-fining• To avoid positive character removal• To consider alternatives when appropriate

– Patience– Oxygen treatments– Lees treatments

• To make sure problem is truly addressed