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Practical Considerations for

Managing WineAcidity

Ellen ButzDepartment of Food Science

Purdue Universityembutz@purdue.edu

http://www.foodsci.purdue.edu/research/labs/enology

2007 Spring Workshop Purdue Wine Grape Team

March 26, 2007Ertel Cellars, Batesville, IN

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Total Acidity Titration for Wine or Juice

Sample Preparation to remove dissolved CO21. Accruately measure 10 ml of room temperature wine into a 50 ml beaker2. Heat wine sample in microwave for about 15-20 seconds until steaming hot, not boiling, swirl vigorously, cool to

room temp

Titration Procedure1. Fill 25 ml buretwith commercially prepared and standardized 0.1 NaOH (N/10) solution2. Standardize pH electrode with pH 7 & pH 4 buffers. Phenolphthalein indicator may be used with white wines,

but is not accurate for measuring red wine endpoints3. Place beaker under buret tip, and immerse standardized electrode into wine4. Read and record wine pH

5. Add 0.1 N NaOH slowly with stirring while watching pH meter. As pH approaches 7.0, slow addition to drops.Continue adding drop by drop and stirring between additions until pH reaches 8.2. Record volume of 0.1NNaOH used. If using phenolphthalein indicator, look for the drop which causes a pink color that does not fadefor at least 10 seconds of stirring.

6. Calculation of TA:Milliliters of 0.1% NaOH used multiplied by 0.075 = TA as % or gm/100 ml

For example: it it takes 12.6 ml of 0.1% NaOH to complete the titration, then 12.6 X 0.075 = 0.945 % TA

SuggestionsWine must be free of tartrate crystals as they will dissolve during titration procedureJ uice must be free of pulp pass thru tight cheesecloth to clarify

Purchase fresh 0.1 N NaOH at least every year. Keep in tightly sealed bottle at room temperature, always discardunused 0.1N NaOH solution from buretat the end of each day.

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Equipment Needed

Total acidity titration assembly $100

pH meter & standards$250-$375

metric balance accurate to 0.1 gram$195

metric graduate cylinders, 100 ml & 1 liter$35

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Definitions

Acids: Substances which produce H+ ions Ions: Charged particles, either - or +

Tartness or Sourness: Sensory perception of H+ ions

on taste buds pH: Measure of free H+ ions, acid strength,

lower pH number equals higher acid strength

Total Acidity: TA - Measure of potential H+ ions insolution, acid concentration

Fixed Acidity: Acids which cannot be steam distilled -tartaric, malic, citric

Volatile Acidity: VA - Acids which can be steamdistilled - acetic, lactic +

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Organic Acid

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Definitions, cont'd

TOTAL ACIDITY

USA

grams tartaric acid per 100 ml wine/must, also written as %0.9 grams tartaric/100 ml wine, or 0.9% TA

Europe

grams tartaric acid per liter wine or mustsame concentration9 grams tartaric / liter wine or 9.0 TA

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TartaricMalic

Citric

AscorbicLactic

Acetic

Propionic

Pyruvic

Gluconic

Formic

Butyric

Wine Acids

Grape Origin

Acetic

Succinic

Carbonic

Sulfurous

Yeast OriginAlcoholic fermentation

Bacterial &

Fungal OriginSpoilage

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Contributionof Wine Acids

Establish pH by providing H+ ionsat pH of 3.0 - 3.5

optimum color hue in red winesreduced rate of oxidationreduced microbial spoilage

rapid precipitation of unstable proteinsincreased efficiency of SO2optimum overall palatability

(aroma and taste)

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Sensory Effect of Acids

Taste - tartness, sourness one of basic tastes - in wine 1 part acid addition will balance 10 parts or more

of sugarTotal Acidity is the major factor in TASTE of tartness,

pH is a minor concern

Bouquet volatile acids -very distinctive character - complex in smallamounts, spoilage in larger amounts

acids combine with alcohols making esters, very aromatic

compounds

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Optimum Wine Acidity

pH range from 2.75 - 3.6 below 2.75, yeast are inhibited below 3.0 malolactic bacteria are inhibited

Total Acidity: Must Wine

Dry 4% RS 1.0-1.3% 1.0-1.1%

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Vineyard Effect onWine Acidity

Hi Acid Conditions

Grape Variety, i.e.. Vignoles

Cool Climate regionOvercast weather conditionsLate spring/early fall

Overgrowth of canopy, shadingOvercropping of fruitEarly harvest date

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Ripeness vs Acidity

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From Concepts in Wine Chemistry, Y. Margalit

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Tartaric

Malic

Citric

Lost 25-50%

Lost 10-50%

MAY BE

Lost 100%

MAY BE

Lost 100%

Destination of Grape AcidsDuring Vinification

Precipitates as K & Ca Salts

Berry enzymes to CO2& ETOH

Yeast enzymes to CO2

Malolactic fermentation toLactic acid & CO2

Malolactic fermentation toAcetic acid

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Increasing Wine Acidity

BATF Regulations may add fruit and berry acids (specific for each fruit) tomust or wine to correct natural deficiencies, IF juice or

wine has not had water added

fixed acid level of adjusted wine must not exceed 9.0grams/liter (0.9%TA) unless Residual Sugar exceeds

7.99%, then may adjust to 11 grams/liter (1.1% TA)

ANY juice or wine may be "stabilized" ( to prevent iron

haze) with up to 5.8 lbs/1000 gal (2.6 grams/gal) (TAincrease of 0.07%)of CITRIC ACID

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Acid Additions Allowed

Grape Wines Before Fermentation: Tartaric and/or Malic

After Fermentation: Tartaric, Malic, Citric,Fumaric or Lactic

Fruit Wines Citrus fruits - Citric only Apples - Malic only All other fruits, berries, etc - Malic or Citric

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Acid Additions to Must

Suggested when pH exceeds 3.7 todiscourage microbial spoilage duringfermentation

use Tartaric for grape mustless likely to be metabolizedstronger acid, more pH effect per gramaddedmust do lab trial to determine addition sincepH effect cannot be predicted

use specific acids for specific fruits

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Acid Additions to Wine

Grape wineBefore cold stabilizing

Tartaric, Malic, Citric, Lactic or FumaricAfter cold stabilizing

all except Tartaric

Wine from other fruitSpecific acids for specific fruits, i.e.. applewine / malic acid

and citric for "stabilizing"

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Alternative Methods

Increases sugars, acids and phenolicsadd to must if higher alcohol needed

add to wine if higher sugar neededcheck for cold stability after addition to wine

Juice Concentrate:

Wine Blending:

Check for cold stability after blending

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DecisionsWine StyleTiming of addition, pre/post cold stabilization

don't use Tartaric acid after cold stabilizationlegal requirements

Sensory Trials100 ml volumes in small containers, sweetened

add 0.1 gm, 0.2 gm, etc., acid to wine samplesafter several hours, taste at proper temperatureif tartaric is added, cold stabilize by freezing &thawing before tasting

calculate addition to bulk volume

Acidifying WinesPage16

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Decreasing Wine Acidity

Options

do nothing, sweeten until balanced

blend with low acid winesreduce acidity of must or wine byprecipitation (cold stabilization)

amelioration (water addition)carbonic macerationmalolactic fermentation

chemical neutralization

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Precipitation

Potassium (K) and Tartaric Acid (H2T) arealways in equilibrium

Potassium bi tartrate (KHT) is a crystalline

precipitatePrecipitation occurs when:

alcohol increasestemperature decreasespH approaches 3.7

wine ages, phenolic content reduced

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Precipitation, cont'd

-+ +-H T H HT H T

2

+ +

pH of greatestconcentration: pH 2.5 pH 3.7 pH 4.5

+K KHT

Crystals

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Tartaric Acid

Bitartrate Ion

Tartrate Ion

Potassium Bitartrate

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Precipitation, cont'd

Evaluation of cold stabilityFreeze or slush test

48 hours frozen, 12 hours room temp, evaluatesediment:

many crystals = UNSTABLEfew crystals = probably OKsediment that re-dissolves = OKno sediment = OK

Conductivity testingRequires conductivity (mV) electrode & pH meter with mVSeed a chilled wine with KHT crystals, observe change inconductivity: if difference in values is less than 5% wine is

considered stable.

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Amelioration

Ameliorate must, not wineStrict BATF Regulations

cannot go below .5gm/100 ml TA

cannot add more than 35% of total wine volume(Sugar addition counts as part of amelioration allowance)not allowed in California (state regs)

Good News

increased volumeminimum pH shift

Bad Newsdilution effects, reduced body & varietal character

Less effective in reducing acidity than chemical method

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Carbonic Maceration

Fresh Grapes CO2 atmosphere, warm temperature, natural grape enzymes

Sugar ETOH; Malic acid ETOH & CO2

2% ETOH kills cells, stops process

Good NewsGreatly reduced TA

Enhanced flavors & color, reduced astringency

Bad NewsSEVERE risk of spoilage

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Malolactic Fermentation

"natural process", no chemicals, no dilutionadds complexity

adds microbial stabilityBad News:

increased chance of spoilage

takes a long timemay be difficult to initiate and controleffect depends on malic concentration

reduces fruit flavors

Good News:

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Chemical Deacidification

Good News:can be precisely controlledrapid processsulfur dioxide levels can be maintained

Bad News:

must consider calcium or potassium stabilizationlarge pH increase

chalky taste at higher levels

Approved Compounds:

potassium carbonate, potassium bicarbonate,

calcium carbonate

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Carbonates

Potassium carbonate K2CO3

Potassium bicarbonate KHCO3

Calcium Carbonate CaCO3

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Chemical Deacidificationcont'd

CO3 HCO3 H2CO3 H2O + CO2-= H

+H

+

Two step process in GRAPE juice or wine:a) REMOVAL OF HYDROGEN IONS

b) PRECIPITATION OF TARTRATE SALTS

K2CO3 2H2T 2KHT H2O + CO2+ +

CaCO3 H2T CaT H2O + CO2+ +

KHCO3 H2T KHT H2O + CO2+ +

Tartaric Acid Potassium bitartrate

Calcium tartrate

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Chemical DeacidificationConsiderations

REDUCTION OF >0.2 TA TREAT MUST BEFORE FERMENT9 Do lab test on small volume to see pH change9 When using Potassium compounds, must or wine

should be chilled, and then allowed to cold stabilize

9 When using Calcium compounds, wine must be aged4-8 months before bottling

CaCO3 and KHCO3:

3.4 grams/gallon = 0.1 Total Acidity reduction

K2CO3:

2.3 grams/gallon = 0.1 Total Acidity reduction

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Double Salt Deacidification

Patented process using CaCO3 (Acidex)for high acid mustless pH shift, removes both malic and

tartaric acidsComplicated addition process

Requires tank with rapid stirring systemProtect must with CO2 during processEffective tool for cool climate, high acid

wines

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Guidelines forChemical Acid Reduction

Evaluate wine acidity, pH

Determine wine style & change needed

If MLF planned, delay deacidification until coldstabilization

If large reduction needed,>0.3 TA, use combination

of water & carbonate to must or double saltdeacidification

If small reduction ,

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Acid Reduction Experiment:60% Cayuga/40% Vidal, 2006

Sample #

20.1%0.13.540.623

Acid Adjustment:

To reduce acid 0.15%

Added KHCO3,5.1gm/gallon

0%0.053.240.795MLF & Sur Lees

(MLF did not work)

10.5%0.13.20.698Water Addition:

15%

0%1.03.140.780Sugar Addition:+1%

0%0.13.140.780Control:

Actual

changeRSpHTATreatment

Acid Reduction Experiment

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Acid Reduction Experiment60% Cayuga/40% Vidal, 2006

Smell and taste each sample, observe differences in color, aroma,and taste; indicate why you like or dislike it (too sweet, too tart, etc)and rank them in order of preference, (1st choice, 2nd choice, etc.)

#4

#5

#3

#2

#1

RankComments: Differences in color, aroma,

tasteSample

Acid Reduction Experiment:

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Acid Reduction Experiment:60% Cayuga/40% Vidal, 2006

1

3

4

2

5

Sample #

20.1%0.13.540.623

Acid Adjustment:

To reduce acid 0.15%

Added KHCO3,5.1gm/gallon

0%0.053.240.795MLF & Sur Lees

(MLF did not work)

10.5%0.13.20.698Water Addition:

15%

0%1.03.140.780Sugar Addition:+1%

0%0.13.140.780Control:

Actual

changeRSpHTATreatment

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Calendar Items

ASEV - Eastern SectionLehigh Valley, Pennsylvania

J uly 15-17, 2007

Lehigh Valley Winery & Vineyard Tour

Impact of Water Stress on Vine Vigor

http://www.nysaes.cornell.edu/fst/asev/

INDY International Wine Competition

J uly 26-28

Entries due J uly 15http://www.in.gov/iwc/

ASEV EASTERN SECTION2007 cONFERENCE