pre-fermentation considerations forconsiderations for...
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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?