Winemaking in the Classroom 2Alcoholic FermentationAlcoholic Fermentation

Sirromet Wines Pty Ltd850-938 Mount Cotton Rd

Mount Cotton Queensland, Australia 4165www.sirromet.com

Courtesy of Jessica Ferguson

Assistant Winemaker & Site ChemistDownloaded from seniorchem.com/eei.html

What is the primary objective?

Making clean wine with an aim to bottling Making clean wine with an aim to bottling (giving to parents etc)?(giving to parents etc)?

No plan to bottle wine for drinking, making No plan to bottle wine for drinking, making wine to test or investigate parameters?wine to test or investigate parameters?

Study of fermentation process only?Study of fermentation process only? In all cases, aim for clean, complete In all cases, aim for clean, complete

fermentation to dryness fermentation to dryness

Preparation of Fruit/Juice: If preparing from fresh fruit, crush or press fruit If preparing from fresh fruit, crush or press fruit

to separate gross solids/skins (do not puree!)to separate gross solids/skins (do not puree!) Some fruit should be peeled prior to pressing Some fruit should be peeled prior to pressing

(citrus, apples, pears etc)(citrus, apples, pears etc) If making red wine from grapes – ferment on If making red wine from grapes – ferment on

solids (crush only, don’t remove skins)solids (crush only, don’t remove skins) Can add 20-30mg/L SOCan add 20-30mg/L SO22 to prevent browning to prevent browning

(optional) during settling(optional) during settling Suggest cold settling (<10Suggest cold settling (<10˚ C)˚ C) 24-48hrs to 24-48hrs to

remove solids (protect from light and air)remove solids (protect from light and air) Cold settling may be assisted by adding enzyme Cold settling may be assisted by adding enzyme

which will break down the pectinswhich will break down the pectins

Preparation of Fruit/Juice (cont) If cold settled, rack off cold juice and discard heavy solids If cold settled, rack off cold juice and discard heavy solids Allow juice/must to warm back up to at least 15Allow juice/must to warm back up to at least 15˚C˚C If SOIf SO22 has been used (to prevent browning or clean up has been used (to prevent browning or clean up

juice), check that FSO2 is <20mg/Ljuice), check that FSO2 is <20mg/L Consider adjusting sugar to 17-22Consider adjusting sugar to 17-22˚̊ Brix (9-12 Brix (9-12˚ Baume) by ˚ Baume) by

adding table sugar (or diluting juice with water) as adding table sugar (or diluting juice with water) as necessarynecessary

Adjust acidity to taste, ideally pH between 3.2 – 3.6 (some Adjust acidity to taste, ideally pH between 3.2 – 3.6 (some fruits may be higher, pH>4.0 to be avoided)fruits may be higher, pH>4.0 to be avoided)

Treatment of Yeast The viability of the yeast is the single The viability of the yeast is the single

most important factor to a successful most important factor to a successful fermentationfermentation

Critical parameters are :Critical parameters are : correct culture preparation correct culture preparation avoid temperature and/or mechanical avoid temperature and/or mechanical

shock (no vigorous mixing)shock (no vigorous mixing) ensuring that nutrient levels are ensuring that nutrient levels are

adequateadequate Always prepare a yeast culture (starter) Always prepare a yeast culture (starter)

– never add dry yeast to must/juice– never add dry yeast to must/juice

Starting Fermentation - Culture Prepare culture: hydrate yeast at 35Prepare culture: hydrate yeast at 35ooC in 10x vol water C in 10x vol water Stir very gently to wet yeast grains and leave to sitStir very gently to wet yeast grains and leave to sit Add a little juice or sugar solution within 10-15 minutes (juice must Add a little juice or sugar solution within 10-15 minutes (juice must

be within 5be within 5˚C of culture temp)˚C of culture temp) Continue to add juice at regular intervals once yeast is active (note: Continue to add juice at regular intervals once yeast is active (note:

fermentation will generate heat)fermentation will generate heat) Build culture up to 5% of final ferment volumeBuild culture up to 5% of final ferment volume Temperature difference between culture and juice <5Temperature difference between culture and juice <5 °°C before C before

adding culture to bulk of juice/mustadding culture to bulk of juice/must Pour culture gently into top of must/juice in one motionPour culture gently into top of must/juice in one motion Don’t mix or stir the culture into the must, Don’t mix or stir the culture into the must, it will gradually it will gradually

expand and mix into the must as yeast growth occursexpand and mix into the must as yeast growth occurs

Temperature Control Temperature tolerance depends on yeast strain Temperature tolerance depends on yeast strain Too cold will inhibit or kill yeast (<10Too cold will inhibit or kill yeast (<10˚C)˚C) Too hot will ‘cook’ yeast (problems may start once temp >30˚C), plus Too hot will ‘cook’ yeast (problems may start once temp >30˚C), plus

‘burnt’ flavours‘burnt’ flavours Ferment will generate considerable heat of its own, particularly in the Ferment will generate considerable heat of its own, particularly in the

first 3-8 daysfirst 3-8 days Start ferments with cool musts (15˚C)Start ferments with cool musts (15˚C) If ‘cool store’ available (16-18˚C) use it!If ‘cool store’ available (16-18˚C) use it! Otherwise set air-conditioning to low in roomOtherwise set air-conditioning to low in room In general white wines 14-20In general white wines 14-20°°C, red wines 18-27C, red wines 18-27˚C˚C Consider fermenting in winter!Consider fermenting in winter!

Red Wine – Cap Immersion For red (grape) wine, ferment on skinsFor red (grape) wine, ferment on skins Colour and astringency from skinsColour and astringency from skins Skins will rise into a thick ‘cap’ on top of liquidSkins will rise into a thick ‘cap’ on top of liquid Must keep immersing cap into liquid at regular intervals to aid extractionMust keep immersing cap into liquid at regular intervals to aid extraction Don’t let cap dry out – spoilage can occurDon’t let cap dry out – spoilage can occur Leave solids in ferment 5-10 Leave solids in ferment 5-10 daysdays

Red wine - Dejuicing

Around Around ⅔ to ⅔ to ¾ through ferment duration¾ through ferment duration Usually assessed on tasteUsually assessed on taste Solids removed to avoid over-extraction of bitter Solids removed to avoid over-extraction of bitter

compoundscompounds Lift cap off with a sieve or strainerLift cap off with a sieve or strainer Strain and press liquid through coarse stainless Strain and press liquid through coarse stainless

sieve into narrow-necked vessel and fit sieve into narrow-necked vessel and fit fermentation valvefermentation valve

Note: don’t remove yeast solids that may have Note: don’t remove yeast solids that may have sunk to bottom – ensure they stay in fermentsunk to bottom – ensure they stay in ferment

Discard skins and gross solidsDiscard skins and gross solids

Nutrient – What to add DAP – Diammonium Phosphate, inorganic source DAP – Diammonium Phosphate, inorganic source

of nitrogen and phosphorusof nitrogen and phosphorus DAP alone can be ineffective and may exacerbate DAP alone can be ineffective and may exacerbate

VA productionVA production DAP + Vitamin formulations – also supply essential DAP + Vitamin formulations – also supply essential

B Vitamins and trace nutrientsB Vitamins and trace nutrients Fermaid® – includes DAP, MgSOFermaid® – includes DAP, MgSO44, yeast hulls, B , yeast hulls, B

vitamins – more ‘healthy’ supplementvitamins – more ‘healthy’ supplement Other similar ‘organic’ mixed nutrients ok tooOther similar ‘organic’ mixed nutrients ok too

Nutrient – When to add If using highly clarified/filtered juice, add to juice If using highly clarified/filtered juice, add to juice

prior to fermentprior to ferment For ‘cloudy’ white juices, add once specific gravity For ‘cloudy’ white juices, add once specific gravity

has begun to drop (after lag phase)has begun to drop (after lag phase) For red wines on solids, may not need to add nutrientFor red wines on solids, may not need to add nutrient Consider adding to reds if they get a bit smelly Consider adding to reds if they get a bit smelly

(hydrogen sulphide, rotton egg)(hydrogen sulphide, rotton egg) Nutrient added late in ferment is not very effective – Nutrient added late in ferment is not very effective –

add prior to 50% sugar depletionadd prior to 50% sugar depletion

How long does fermentation take?

Anything from 7 days to 4 weeksAnything from 7 days to 4 weeks Monitor sugar content daily using hydrometer Monitor sugar content daily using hydrometer

(S.G. preferred)(S.G. preferred) when S.G. reaches 1.030, raise temperature by up when S.G. reaches 1.030, raise temperature by up

to 5to 5ooC (to a max of 25 deg)C (to a max of 25 deg) Once S.G. near or under 1.000, test for residual Once S.G. near or under 1.000, test for residual

sugar using Clinitestsugar using Clinitest®® tablets, ( tablets, (notnot Clinistix Clinistix ® ® ), ), Sugar must be under 20gm/lt to use Clinitest Sugar must be under 20gm/lt to use Clinitest

(otherwise dilute into range)(otherwise dilute into range) Benedict’s Test can also be used (same principle)Benedict’s Test can also be used (same principle)

Observe your ferment regularly

Smell, taste, think, check, style, structure, Smell, taste, think, check, style, structure, primary indicatorsprimary indicators

Bad smells can be a warning sign of Bad smells can be a warning sign of undesirable side reactionsundesirable side reactions

Consider addition of Diammonium Phosphate Consider addition of Diammonium Phosphate or other Nor other N supplement or B vitamin or B vitamin supplement to the ferment supplement to the ferment

Add nutrients pre 1.040 SG to be effectiveAdd nutrients pre 1.040 SG to be effective Don’t leave it indefinitely if nothing seems to Don’t leave it indefinitely if nothing seems to

be happening!be happening!

‘Stuck’ fermentations Indicators are: Indicators are: SG flat-line – no change for 3+ daysSG flat-line – no change for 3+ days smell of bruised apples/sherry notes (indicates smell of bruised apples/sherry notes (indicates

presence of excess acetaldehyde)presence of excess acetaldehyde) Other smells that are unpleasant (HOther smells that are unpleasant (H22S, ‘vegetable’ or S, ‘vegetable’ or

‘rubber’ smells, acetic smell)‘rubber’ smells, acetic smell) Most common causes are: Most common causes are: Poor yeast culture preparationPoor yeast culture preparation Initial S.G.>1.100 – very high sugar must can cause Initial S.G.>1.100 – very high sugar must can cause

alcohol stress in yeastalcohol stress in yeast Nutrient deficienciesNutrient deficiencies

How to fix stuck ferments If temperature is <16If temperature is <16ooC and SG<1.020 – raise C and SG<1.020 – raise

temperaturetemperature Add nutrients (‘Go-FermAdd nutrients (‘Go-Ferm®’ or ‘Fermaid’®) (less ®’ or ‘Fermaid’®) (less

effective late in ferment)effective late in ferment) Extreme solution: Rescue ferment – labour intensiveExtreme solution: Rescue ferment – labour intensive Involves growing a fresh yeast culture up Involves growing a fresh yeast culture up acclimatising it gradually to high alcohol environment by acclimatising it gradually to high alcohol environment by

additions of wine from stuck fermentadditions of wine from stuck ferment Increase addition volumes to fresh culture each dayIncrease addition volumes to fresh culture each day Combine with stuck ferment when new culture is 10% of Combine with stuck ferment when new culture is 10% of

ferment volumeferment volume Pray…Pray…

When to call it quits….

even when sugar remains….?even when sugar remains….? depends on desired style to be depends on desired style to be

achievedachieved Keep in mind that an untrained Keep in mind that an untrained

palate probably won’t detect up to palate probably won’t detect up to 10gm/L residual sugar10gm/L residual sugar

At 1-1.5g/L reducing sugars, At 1-1.5g/L reducing sugars, generally no fermentable sugar generally no fermentable sugar remainsremains

Safer to wait until sugar <2g/L Safer to wait until sugar <2g/L (Clinitest dark green/blue)(Clinitest dark green/blue)

What next?

Stop ferment, add preservative

when sugar is @ dryness, or by desired sweet style when sugar is @ dryness, or by desired sweet style cool vessel down – colder the better, to help stop cool vessel down – colder the better, to help stop

yeast and encourage settling of dead yeastyeast and encourage settling of dead yeast add SOadd SO22 when cool – Camden tablets or Potassium when cool – Camden tablets or Potassium

Metabisulphite (PMS) saltMetabisulphite (PMS) salt aim for >35mg/L Free SOaim for >35mg/L Free SO22

Consider that PMS is only 57% SOConsider that PMS is only 57% SO22

At least 50% of added SOAt least 50% of added SO22 will convert to bound will convert to bound SOSO2 2

Post ferment clarification

Bentonite – clay mineral used for clarificationBentonite – clay mineral used for clarification 0.25gm/L dose in wine 0.25gm/L dose in wine Make up as 5% slurry in waterMake up as 5% slurry in water Make up day before use to allow swelling of Make up day before use to allow swelling of

particlesparticles Add to wine after SO2 additionAdd to wine after SO2 addition Rack clear wine 2 days after SO2/bentonite Rack clear wine 2 days after SO2/bentonite

additionaddition

Racking

Separation of clear wine form settled Separation of clear wine form settled solids (lees)solids (lees)

Best to use a siphon with the end of Best to use a siphon with the end of the hose held above the leesthe hose held above the lees

Rack wine into a smaller container so Rack wine into a smaller container so that vessel is fullthat vessel is full

Always keep wine vessels fullAlways keep wine vessels full unless unless fermentingfermenting

This prevents spoilage due to This prevents spoilage due to oxidation or aerobic microbesoxidation or aerobic microbes

Safe wine storage

Full containersFull containers low dissolved oxygenlow dissolved oxygen Free SO2 >35mg/l @ Free SO2 >35mg/l @

pH 3.20pH 3.20 no fermentable sugars no fermentable sugars

leftleft Keep wine coolKeep wine cool

Clarification and finishing

Consider acid addition trial for flavour and balanceConsider acid addition trial for flavour and balance Fining with bentonite for further clarification and protein Fining with bentonite for further clarification and protein

stabilisationstabilisation Check flavour, colour, bitterness, and structure first Check flavour, colour, bitterness, and structure first Other fining agents: PVPP, powdered milk, gelatine, Other fining agents: PVPP, powdered milk, gelatine,

isinglass - to alter or reduce bitterness/phenolics/tannins/low isinglass - to alter or reduce bitterness/phenolics/tannins/low MW phenols.MW phenols.

Cold stability: cool to -2oC - +2oC, add 3gm/lt KHT, mix 1 Cold stability: cool to -2oC - +2oC, add 3gm/lt KHT, mix 1 hr, hold @ these temps, then earth or pad off lees within hr, hold @ these temps, then earth or pad off lees within 24hrs. Prevents tartrate precipitation in bottle 24hrs. Prevents tartrate precipitation in bottle

Filtration options – depend on sweetness levels, persistant Filtration options – depend on sweetness levels, persistant turbidity or clarity issues turbidity or clarity issues

Earth or pad filter only after wine is protein and cold stableEarth or pad filter only after wine is protein and cold stable

Bottling Logistics

In industry we would check the following pre-bottling:In industry we would check the following pre-bottling:

pH, titratable acidity, free and total SOpH, titratable acidity, free and total SO22, CO, CO22, H, H22S,S,

alcohol content, flavour, colour, dissolved oxygen, alcohol content, flavour, colour, dissolved oxygen, protein (heat) stability, tartrate (cold) stability, protein (heat) stability, tartrate (cold) stability, residual sugar, turbidity/clarity, specific gravityresidual sugar, turbidity/clarity, specific gravity Adjust Free SOAdjust Free SO22 levels to 35-40mg/L levels to 35-40mg/L Use clean, preferably sterilised bottlesUse clean, preferably sterilised bottles Fill bottles carefully with no splashing (avoid increasing Fill bottles carefully with no splashing (avoid increasing

dissolved oxygen)dissolved oxygen) Seal with screwcaps, crown seals or corksSeal with screwcaps, crown seals or corks