2018 PWGT Fall Workshop - Purdue Agriculture...Re-fermentation Rules Microbial Stability !Sensory perception of dryness is different from microbial stability !Wine is dry when its

Christian ButzkeProfessor of Enology

Purdue Wine Grape Team

2018 PWGT Fall Workshop

Purdue Wine Grape Team

FS 470 Wine Appreciation

Indy InternationalWine Competition

New/Ancient Techniques/Winemakers

Wine Quality Control Basics Sugar as “Brix”

Why?

How?

• Indicates fruit ripeness• Determines alcohol in wine• Indicates state/end of fermentation

• In grapes, fresh juice: Refractometer• In fermenting juice/wine: Hydrometer


How? • In grapes, fresh juice: Refractometer

Based upon sugars’ ability to refract light

Sugar as “Brix”

• Introduced in 1870 by Adi Brix.

• A concentration calibrated at a specified temperature (68°Fin the US).

• Equals the weight percentage of sugar in juice/wine.

• Expressed in grams of sugar in 100 grams of juice/wine.

Wine Quality Control Basics

Sugar as “Brix”

Brix Comparison:

Grape juice: 18 to 26

Apple juice: 14

Cola: 11

Ginger ale: 9.5

Wine Quality Control Basics

Sugar as “Brix”

Sugar as “Brix”

Brix20.0 - 21.121.1 - 22.122.1 - 23.023.0 - 24.9

Range: 20.0 - 24.9Mean: 22.1 +/- 0.9

Sugar as “Brix”


How? In fermenting juice/wine: Hydrometer

Start Finish

Alcoholic Fermentation

SUGAR

ALCOHOL

CO2

WINE YEAST (Saccharomyces cerevisiae)

+

human

hair


87.0

89.0

91.0

93.0

95.0

97.0

99.0

101.0

0 5 15 20Time (days)

Juice Weight (%)

“dry”

Sugar as “Brix”

Conversion of sugar to alcohol


% Alcohol = (Brix - 3) * (0.58 to 0.66)

Example: 22 Brix => 11.0 – 12.5Average: 11.8 ± 0.8

Alcohol Labeling

27 CFR §4.36 - Alcoholic content.“Alcohol __ % by volume”

A tolerance of 1%, in the case of wines containing more than 14% of alc by vol, and of 1.5%, in the case of wines ("table wines") containing 14% or less of alc by vol, will be permitted either above or below the stated percentage.

Sugar as “Brix”

Addition of sugar (“Chaptalization”)


1 Brix adds 0.62% Alcohol

1 Brix = 41 grams of sugar/gallon

Residual Sugar “R.S.”

What’s dry?


Recognition threshold sweetness > 5 g/L (0.5%) To smoothen a wine 1 to 4 g/L Very acidic wine styles (incl. sparkling) 15 g/L R.S.Microbial stability (no growth/carbonation) < 1 g/L (0.1%)If measuring all reducing sugars < 2 g/L (0.2%)Brettanomyces yeast or ML bacteria < 2 g/L Visible Brettanomyces haze 0.1 g/L (pentoses)

500 mg/L CO2 1 g/L Spritz at 800 mg/L CO2 > 1.6 g/L R.S.Pushing of corks at 1,400 mg/L (68˚F) > 2.8 g/L R.S.


SO2 & Sorbate Management

Oxygen Management

Skin Contact Time

Residual Nutrients

Temperature, pH & Browning

Bulk & Bottle Storage


Oxygen Management

Skin Contact Time

Residual Nutrients



SO2 DeficienciesExample: 26 Traminettes

Deficient!

Fine!

Free SO

2.9 3.2 3.5 3.8 4.12.9 3.2 3.5 3.8 4.1

- 150- 150

SO 2molecular

pHpH

Free SO2required

- 75- 75

- 0- 0

(mg/L)

SO2 Management

pH and Required SO2

Free SO2 = 0.85 • (1 + 10pH - 1.83)required

)

Or see chart @www.foodsci.purdue.edu/research/labs/enology/FreeSO2(pH)Pro.pdf

pH and Required SO2

Free SO2 =required

(pH -3) *100

Example: pH =3.55

Free SO2= 55

Free SO2 Decline

Percentage of decline in SO2 for 3 different temperatures

Sorbic Acid

Yeast growth inhibitor: 200 mg/L

Legal limit: 300 mg/L

Sensory threshold: 135 mg/L

Some yeasts are resistant!

NO effect against bacteria

Likely effective against Brett

Added as potassium salt (Sorbate @ 268 mg/L)) => Watch cold stability!

Basics

Sorbic acid + Malolactic bacteria

Cause

PreventionAvoid sorbate as preservativeUse sorbate only with proper SO2

Add no earlier than day before bottlingAlways bubble test/sterile filterNO removal option from wine

Geranium Off-Odor

Sorbate sensitivity:

Malolactic bacteria? NO!

Saccharomyces? YES!

Brettanomyces? MAYBE?

Sorbate Management

Sorbate

I mixed up potassium sorbate and citric acid together to make a sorbate addition and an acid adjustment prior to bottling.

An amorphous white precipitate has formed and is floating on top of the mixture.

What is it and what should I do about it?

© Winemaking Problems Solved

Mixing

Sorbate Mixing


Oxygen Management

Skin Contact Time

Residual Nutrients



Presumed White Wine Aging

© Joanna Simon: Discovering Wine

Average white wine

© Vernon L. Singleton: Principles and Practices of Winemaking

Oxygen Management

Oxygen Pickup at Bottling

Oxygen Basics

! Air-O2 solubility (68˚F): 8 mg/L! Air-O2 uptake at bottling 0.17 - 8 mg/L! Uptake per topping: 5 mg/L! Uptake per racking: 20 mg/L! Uptake via cork: 0.1 - 100 mg/L

Young white wine:! Total O2 uptake capacity: <100 mg/L! Optimum O2 uptake: 0 mg/L

Young red wine:! Total O2 uptake capacity: 4,000+ mg/L! Optimum O2 uptake: 60 - 130 mg/L

Added Added Addedat the filler via headspace Total O2

Gravity flow filler only 6.60 1.40 8.00

Removed Removed Removedat the filler from headspace Total O2

1. Vacuum pulled at filler 6.00 - 6.00

2. Bottle sparged with N2 0.51 0.02 0.53

3. Vacuum pulled at corker - 0.15 0.15

4. Headspace sparged with N2 - 1.15 1.15

#1- #4 implemented 6.51 1.32 7.83

[mg O2/L]

= 98%

Oxygen Pickup at Bottling

Uptake via cork: 0.1 - 100 mg/L

Oxygen Pickup after Bottling

O2 uptake at bottling: 0.17 - 8 mg/L

SO2 Loss at/after Bottling

! 8 mg O2 + 32 mg SO2 => Sulfate

= Free SO2 Loss

+ additional losses during filtration etc

! Add 10 – 40 mg/L EXTRA SO2before bottling

pH and Required SO2

Free SO2 =required

(pH -3) *100

Example: pH =3.55

Free SO2= 55+


Oxygen Management

Skin Contact Time

Residual Nutrients



Skin Contact Time

TerpeneTerpene Degradation

... our Traminette had ... our Traminette had skin contact for 24 hours ...

When considering skin extraction, the contact time is as important as the temperature of the incoming fruit.

Contact time for t1 = 24 hours at 39°Fis roughly equivalent to t2 = 7 hours at T = 59°F

Assumed terpene/tannin extraction kinetics:t2 = t1*1/(3(T-39)*0.056)

• Esters– Caprate C10– Laurate C12– Pelargonate C9– Caprylate C8– Myristate C14

Fermentation “Aroma”

Expect hydrolysis in 6 weeks to 6 months!

ISSUES

Pre-mature aging?=> No aging potential

Enzyme vs. natural acid hydrolysis?=> Release of non-varietal aromas

Removal of stable anthocyanin-glucoside?

Additional bentonite fining needed!

Treatment

EVC

EVC

EVC

EVC

EVC

EVC

EVCEVC

EVCEVC

EVC

EVC

EVC

EVC

EVC

EVC

EVC

EVCEVC

EVC


Oxygen Management

Skin Contact Time

Residual Nutrients



Wine Nutrient Status

Do you know how much you’ve got?

! Residual sugars! Nitrogen! Phosphate! Potassium! Vitamins ! Sterols! Other growth factors

Hybrid Nutrient Status By Grape Varietal By Grape Varietal

(Primary Amino Nitrogen by NOPA)

250 mgYAN/L

250 mgYAN/L

Re-fermentation Rules

Microbial Stability ! Sensory perception of dryness is different from microbial stability ! Wine is dry when its combined fermentable sugars are below 1 g/L (0.1%).! Considering all reducing sugars, incl.pentoses, 2 g/L (0.2%) is dry. ! Even below 2 g/L, R.S. can serve as a substrate for our spoilage microbes.

Gas Production! 1,000 mg/L R.S. can produce almost 500 mg/L CO2 gas. ! To push corks about 1,400 mg/L at room/bottling temperature are required.! Strongly influenced by headspace volume and closure type. ! A perceivable spritz may be tasted at 800 mg/L CO2 (from 1.6 g/L R.S.).

Haze Formation! S.c. may grow if the recommended doses of sorbate and SO2 are not met.! Or if sterile filtration prior to bottling was compromised (use bubble test!). ! Even 100 mg/L residual pentoses can lead to a visible Brett haze. ! Visible haze due to S.c. must be expected above 1,000 mg/L R.S.

Yeast

Malic Acid ! Grapes at harvest contain between 0.6 and 6 g/L of malic acid! Malolactic bacteria turn malic acid into lactic acid and carbonic acid (CO2) ! Tartaric acid cannot be metabolized by wine bacteria. ! Absence of a malic acid spot on a paper chromatogram indicates > 30 mg/L.! A barely visible spot about 200 mg/L. ! In wine which completed MLF, residual malic acid is less than 300 mg/L (0.3 g/L).

Gas Production! Malic acid is converted into two thirds lactic acid and one third CO2

! 300 mg/L residual acid could produce 100 mg/L gas. ! A perceivable spritz may be tasted at 800 mg/L CO2 (from 2.4 g/L malic).

Haze Formation! Visible haze in a white wine due to the growth of Oe. oeni above 300 mg/L.

Re-fermentation RulesBacteria

SO2, Alcohol & MLF

Oenococcus oeni suppression:

• free SO2 to 0.85 molecular at 12% EtOH

• free SO2 to 0.6molecular at 14% EtOH


Oxygen Management

Skin Contact Time

Residual Nutrients



Browning & Temperature

% of 50°F Cellar Life% of 50

Browning & pH

Dr. Vernon SingletonProfessor of Enology EmeritusUC Davis (1923-2016)


Oxygen Management

Skin Contact Time

Residual Nutrients



Bottle Storage and Aging

Whites better off at 32 to 40°F?

Wine Shipments

Temperature-controlled trucks that maintain a steady55 degrees will be used to ship to FedEx hubs.

Executive Summary

SO2

O2

°F

[email protected]

765.494.6500

Questions?

Documents

2018 PWGT Fall Workshop - Purdue Agriculture...Re-fermentation Rules Microbial Stability !Sensory perception of dryness is different from microbial stability !Wine is dry when its