Pre-fermentation Considerations forConsiderations for...

Pre-fermentation Considerations forConsiderations for Aromatic Varieties

Winemaking style for aromaticsWinemaking style for aromatics

– Removing phenolics via oxidation Hyper-oxidative

– Delayed use of SO2 Oxidative

– Some use of SO2; no fining Traditional

– SO2/ascorbic acid; juice fining Reductive

– Use of inert gases Hyper-reductive

AromaAroma

What are the main compounds contributingWhat are the main compounds contributingto varietal aroma?

– Terpenes: Riesling, Gewurztraminer, MuscatN i id Ri li S ill– Norisoprenoids: Riesling, Semillon

– Thiols: Sauvignon Blanc (mainly)

TerpenesTerpenes

– Free and bound forms found in grapesFree and bound forms found in grapes– Monoterpene alcohols most odoriferous– High proportion found in skinsHigh proportion found in skins– Bound forms more soluble in juice

• Citronellol – citronella aromas• Linalol rose ‘turkish delight’ lychee• Linalol – rose, turkish delight , lychee• Geraniol – rose, blossom, orange

C13-norisoprenoidsC13 norisoprenoids

– These are 40-carbon terpenesThese are 40 carbon terpenes– Formed by oxidative degradation of

carotenoids (not well understood)( )– 13-carbon derivatives have interesting

aromas

• β-damascenone – flowers, tropical fruitβ da asce o e o e s, t op ca u t• TDN –bees wax, kerosene/petrol, hay

Ratio of free to bound volatile terpenesp

Variety FVT (µg/L) BVT (µg/L) C13-norisoprenoidsGewurz. 282 4325 NDRiesling 73 262 182S. Blanc 5 107 104Semillon 17 91 26517 91 265Chardonnay 41 12 140

Ad t d f Rib G H db k f O l V l 2 2006 T bl 7 2Adapted from: Ribereau-Gayon Handbook of Oenology Volume 2 2006 Table 7.2 pg 209

ThiolsThiols

– Sulphur containing compounds (mercaptans)Sulphur containing compounds (mercaptans)– Very important contributor to S. Blanc aroma– Found in skin and pulpFound in skin and pulp– Exist in fruit/must as S-cysteine conjugates

Amplified by fermentation with S cerevisiae– Amplified by fermentation with S. cerevisiae

• 3MH grapefruit zest passion fruit• 3MH – grapefruit zest, passion fruit, • 4MMP – boxwood, broom, gooseberry

Example of thiol formationExample of thiol formation

Note: yeast have similar enzymes that cleave the sulphur bond during fermentation

Influence of must oxidation on 4MMP concentrations

2000

2500

ak

1500

2000

f odo

r pea

500

1000

Surfa

ce o

f

0Control (50ppm) No sulphite Hyperoxygenation

S

Adapted from: Ribereau-Gayon Handbook of Oenology Volume 1 2006 Table Fig. 13-7 pg 418

Juice oxidationJuice oxidationWhat happens when juice is exposed to

?oxygen?

P t ti l l f /fl– Potential loss of aroma/flavour– Juice becomes brown

Off flavours/aromas may develop– Off flavours/aromas may develop– Microbes thrive

Finished wines can be heavy/dull– Finished wines can be heavy/dull– TSO2 can climb due to aldehydes

Substrates of concern: phenols/polyphenolsSubstrates of concern: phenols/polyphenols

– These are the compounds that brown in juice– Red wines: color, structure, flavour– White wines: bitterness, astringency

M i fl id fl id– Main groups: flavonoids, non-flavonoids

Examples:Examples:

Fl id Non-flavonoids:Flavonoids:– flavan-3-ols

Catechin

Non flavonoids:– Hydroxycinnamates– Caffeic/caftaric acid– Catechin

– Trace amountsCaffeic/caftaric acid

– Main group

Responsible for:– Bitterness

Responsible for:Browning– Bitterness

– Astringency– Browning

– Browning

Browning

Three types of oxidation:Three types of oxidation:

(1) Chemical – metals acting as catalysts(1) Chemical metals acting as catalysts(2) Enzymatic – Polyphenol oxidase; Laccase(3) Microbial – Kloeckera; Candida; Pichia(3) Microbial Kloeckera; Candida; Pichia

Chemical oxidationChemical oxidation

– Catalysts: Iron, copperCatalysts: Iron, copper– In presence of O2 forms quinones/peroxide– Iron promotes radical formationIron promotes radical formation– Hydroxyl radical converts ethanol to aldehyde

Potential for other oxidation reactions– Potential for other oxidation reactions– Occurs more in finished wine than in juice

May increase if juice has high metal content– May increase if juice has high metal content

Polyphenol Oxidase = BROWNPolyphenol Oxidase BROWN

– O2 consumption speed increasesO2 consumption speed increases– Oxidization of polyphenols to quinones – Extremely quick reactionExtremely quick reaction– Polymerization of quinones may occur

Temperature/pH/concentration dependent– Temperature/pH/concentration dependent– Reduced by HSO3

- (also binds quinones)

LaccaseLaccase

– Found in fruit infected with botrytisFound in fruit infected with botrytis– Sulphur tolerant/resistant?– Activity can continue in alcoholic solutionsActivity can continue in alcoholic solutions– Wider spectrum of oxidative substrates

Can react with GRP– Can react with GRP– Lower population via bentonite fining

Microbial Oxidation = OFF AROMASMicrobial Oxidation OFF AROMAS

– Wild yeasts: Candida (flor); Kloeckera; PichiaWild yeasts: Candida (flor); Kloeckera; Pichia– Lactic and acetic bacteria– Can come in on fruit or be present onCan come in on fruit or be present on

equipment– Produce off aromas: aldehydes ethyl acetateProduce off aromas: aldehydes, ethyl acetate,

acetic acid– Can be controlled by SO2 and finingCa be co t o ed by SO2 a d g

Sulphur and ascorbic acidSulphur and ascorbic acid

Things to consider:Things to consider:

1. Climate and it’s effect on phenolic ripeness

2. Health of fruit at harvest3. Machine vs. hand

harvesting4 Temperature of fruit4. Temperature of fruit

when picking5. Proximity to the winery

Why should we consider adding SO2 in theWhy should we consider adding SO2 in the vineyard?

– Acts as an antioxidant

– Acts as antioxidasic

– Acts as a antimicrobialActs as a antimicrobial

Why should we consider using ascorbic y gacid?

– Trialing its use on Sauvignon Blanc– Used in winemaking as a reducing agentg g g– It’s use is very controversial – Binds O2 directly; fast reactionBinds O2 directly; fast reaction– Becomes oxidized in the process– Formation of hydrogen peroxideFormation of hydrogen peroxide

– H2O2 can dramatically reduce juice quality– requires the presence of sulphur in order to q p p

be beneficial– SO2 binds hydrogen peroxide

How much SO2 should be added?How much SO2 should be added?

Depends on:Depends on:

– Variety – pH of fruit– Health of fruit– Temperature of fruit– Distance of travel– Harvest type– Ascorbic acid

50 /L (50 ) i d t i hibit id ti– 50mg/L (50ppm) required to inhibit oxidative enzyme activity (healthy)

– More than 50ppm can cause reduction aromas

– 25 and 75mg/L = 75 and 97% inhibition

80 100 /L f tt f it (bi d i kl )– 80-100mg/L for rotten fruit (binds quickly)

– We add 50ppm SO2 and 40ppm ascorbic acid pp 2 ppwith S. Blanc

Processing TreatmentsProcessing Treatments

How should we handle these varieties at the winery?

– Cold soaking for aroma/flavour extraction– Use of pectolytic enzymes – Sulphur additions to juice tray– Temperature control– Fining/clarification

Cold soaking for aroma extractionCold soaking for aroma extraction

– High concentration of terpenes/thiols in skinsHigh concentration of terpenes/thiols in skins– Potassium extraction alters pH/TA– Must should be chilled prior to soak (≤40°F)Must should be chilled prior to soak (≤40 F)– Duration depends on style

May need to fine out tannins– May need to fine out tannins– Works well on GT, SB, WR (not PG?)

Machine harvesting can facilitate– Machine harvesting can facilitate

The use of commercial enzymesThe use of commercial enzymes

– Enzymes are naturally present on the fruitEnzymes are naturally present on the fruit– Commercial preparations work best– Pectinase: add as early as possiblePectinase: add as early as possible – Better yields/clarification

Specific preparations for rotten fruit– Specific preparations for rotten fruit– Specific aroma enhancing enzymes

Adding sulphur as pressingAdding sulphur as pressing

– Should be done if it wasn’t added in fieldShould be done if it wasn t added in field– We do this with our Pinot Gris (color)– This should be done after enzyme has beenThis should be done after enzyme has been

added– Important to disperse well (large juice trays)Important to disperse well (large juice trays)– Adjust to 10-15ppm free in tank (rotten fruit)

Temperature controlTemperature control

– One of the most important factorsOne of the most important factors– Must chilling is optimum– Before vs post pressingBefore vs. post pressing– Hand harvest vs. machine

Keep fruit/juice ≤50 degrees– Keep fruit/juice ≤50 degrees– Warm up for fermentation

Juice fining and clarificationJuice fining and clarification

Why should we consider juice fining?Why should we consider juice fining?

– Improve clarity of juiceImprove clarity of juice– Remove unwanted compounds– Promote better flavor and aromao ote bette a o a d a o a– Control fermentation kinetics– Achieve stabilityy

Note: increased solids volume is a drawback

Fining principlesFining principles

– 3 types of mechanisms:3 types of mechanisms:

• Electrical (charge) interactionElectrical (charge) interaction• Bond formation• Absorption/adsorptionAbsorption/adsorption

– Many fining agents utilize more than oneMany fining agents utilize more than one mechanism; i.e. neutralization and adsorption

Eff ti f fi i d d– Effectiveness of fining depends on:

Fi i t d• Fining agent used• Preparation and addition

Q• Quantity used• pH of the juice• Metal content of the juice• Temperature

Common juice fining agents:Common juice fining agents:

– Gelatin (+)Gelatin ( )– Silica gels (-)– Casein (+)Casein (+)– PVPP

Bentonite ( )– Bentonite (-)– Proprietary blends

GelatinGelatin

– Comes from collagen tissue– Works via hydrogen bonding– Reacts with phenolics (CT)– Charge intensity determines target compounds– Responsible for removing bitterness/astringencyp g g y– Aids in lees compaction– Improves clarification of white mustp

Silica gelsSilica gels

– Is a colloidal suspension of silicon dioxideIs a colloidal suspension of silicon dioxide– Works via adsorption– Used in conjunction with gelatinUsed in conjunction with gelatin– Prevents over fining

Also used to compact bentonite lees– Also used to compact bentonite lees

CaseinCasein

– Milk protein; potassium caseinateMilk protein; potassium caseinate– Insoluble in an acidic medium– Works via adsorption removing tanninsWorks via adsorption removing tannins– Removes/prevents oxidative browning and

maderized aromamaderized aroma– Also can remove Copper/Iron (45/60%)

PVPPPVPP

– Synthetic polymerSynthetic polymer– Used to remove bitterness/pinking precursors– Works via adsorptionWorks via adsorption– Specifically binds with low molecular wt.

phenolics (catechin)phenolics (catechin)– Gentle if used early– Can strip complexity in mature wines– Can strip complexity in mature wines

BentoniteBentonite

– Made of fine clayMade of fine clay– Unique swelling properties– Used for removing protein/clarifying mustUsed for removing protein/clarifying must– Can reduce microbe populations (laccase?)

Have found it can reduce rot aromas in juice– Have found it can reduce rot aromas in juice– Works better at lower pH

Juice processing at Willow CrestJuice processing at Willow Crest

Sauvignon Blancg

– Machine harvest during cool nightsSO / bi i i d– SO2/ascorbic in vineyard

– Pectinase in bins/hopperGelatin in juice tray– Gelatin in juice tray

– Bentonite in tank– Cold settle for 48 hours– Rack off solids and warm to 60°F– Adjust juice according to specs/ratios

Pinot GrisPinot Gris

– No SO2 in vineyard (minimize color)No SO2 in vineyard (minimize color)– Important to bring in cold– 50ppm in the juice tray50ppm in the juice tray– Casein/PVPP if significant extraction

Bentonite– Bentonite– 100ppm PVPP at peak fermentation always

RieslingRiesling

– Standard SO2 in vineyard (rot)Standard SO2 in vineyard (rot)– Adopt a low phenolic style– Phenolic fining depends on RS targetsPhenolic fining depends on RS targets– Always bentonite in juice phase

Usually protein stable post fermentation– Usually protein stable post-fermentation

Q ti ?Questions?