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
Wine Quality Control Basics Sugar as “Brix”
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
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”
Alcoholic Fermentation
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
Alcoholic Fermentation
% 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”)
Alcoholic Fermentation
1 Brix adds 0.62% Alcohol
1 Brix = 41 grams of sugar/gallon
Residual Sugar “R.S.”
What’s dry?
Alcoholic Fermentation
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
SO2 & Sorbate Management
Oxygen Management
Skin Contact Time
Residual Nutrients
Temperature, pH & Browning
Bulk & Bottle Storage
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
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
SO2 & Sorbate Management
Oxygen Management
Skin Contact Time
Residual Nutrients
Temperature, pH & Browning
Bulk & Bottle Storage
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
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
SO2 & Sorbate Management
Oxygen Management
Skin Contact Time
Residual Nutrients
Temperature, pH & Browning
Bulk & Bottle Storage
... 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
SO2 & Sorbate Management
Oxygen Management
Skin Contact Time
Residual Nutrients
Temperature, pH & Browning
Bulk & Bottle Storage
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
SO2 & Sorbate Management
Oxygen Management
Skin Contact Time
Residual Nutrients
Temperature, pH & Browning
Bulk & Bottle Storage
SO2 & Sorbate Management
Oxygen Management
Skin Contact Time
Residual Nutrients
Temperature, pH & Browning
Bulk & Bottle Storage