Embed Size (px)
Citation preview
Grape “Quality”Optimizing the Quality of Grape
Cultivars
By: Paul Gospodarczyk
Des Moines Area Community College
What is “Quality?”
• Nobody knows!
• Easy to define what quality is NOT
• Hard to define what it IS
• Grapes are at the highest potential quality—winemakers maintain or detract from that potential
Most important factor:
How does the wine TASTE?
Nothing else matters.
ECON 101
Supply
Demand
Supply vs. Demand
ECON 101
Supply
Demand
Commodity Market
ECON 101
Supply
Demand
Specialty Market
Communication:-It’s up to you!
-Push the winemaker
Goals Today
• Investigate attributes worth talking about
• Understand the importance of these attributes
Some basics…
Grape Ripening
Time
AmountAcid
Sugar
Grape Ripening
Time
AmountAcid
Sugar
1
Grape Ripening
Time
AmountAcid
Sugar
1 2
Ripeness Effects
• Flavor
• Acid– pH– TA
• Color– Hue– Intensity
Ripening and Flavor
Time
AmountAcid
Sugar
1 2
Flavor change!
Acid Expression
• Paradox of acid expression:– Titratable acidity: grams per Liter– pH: inverse logarithmic representation of the
hydrogen proton concentration
TA vs pH
Acid Expression
Ripening and Hue
Low pH, 20-25% High pH, 10%
Flavylium State Quinoidal State
Most Anthocyanins colorless at wine pH
Ripening and Color Intensity
• Rim Variation
• I wanted to see this in a lab…
Wine A: High Color Intensity
Wine B: Low Color Intensity
Ripening and Color Intensity• Wine A; Hue = .6; Intensity = 3
• Wine B; Hue = .9; Intensity = 1.8
White Wine Tasting:Investigating Effect of TA
Don’t finish the samples!
Monitoring Fruit
• It’s a sample!
• Striving for even ripening:– Dormant season pruning– Shoot positioning– Green harvest
Hungry?
Want to use this plate?
Sanitation vs. Sterilization
Sulfur Citric Sanitation
• Requires:– 200 ppm Sulfur; 2-3 tablespoons– < 3.0 pH; couple scoops
• Buying Potassium Metabisulfite
• Efficacy
Hungry?
Sulfur Dioxide Additions
• Inhibits enzymatic oxidation– Polyphenoloxidase– Laccase
Sulfur Dioxide Additions
• Calculating sulfur dioxide– Based on JUICE YIELD– Average 150 gallons juice/ton– Clean Fruit 30 ppm = 30 grams (1.06 oz.)– Rotten Fruit 75 ppm = 74 grams (2.65 oz.)
Hungry?
Lady Bugs
• Green, peas, peanuts, gross mushrooms
• Identification threshold is at PPT– 1 trillion seconds = 31,546 years
Spray Records
Cellar Handling
• Chaptalization– $.75/pound C&H– $9.39/T ($.06/gal.) to raise 1 Brix
• Amelioration
Red Wine Tasting:Investigating Effect of TA
Don’t finish the samples!
Correlation
• Comparison of 2 independent data sets
• R value explains variability– Low ‘r’ = no relationship– High ‘r’ = possible relationship (r > 85%)– R = .65 means 65% of variability is accounted
for
• CAUSATION is not implied
CorrelationShark Attacks
Ice Cream Sales
R = .24R squared = .0576
CorrelationShark Attacks
Ice Cream Sales
R = .89R squared = .79
Not Causal!
Searching for a correlation…
A model to predict ‘quality’ wines
Frontenac Project
• 11 Iowa Frontenac wines
• Chemical analysis performed in triplicate
• Sensory data from 3 panelists– Majority of panelists had completed VIN 150
sensory training– Assigned No medal, Bronze, Silver, and Gold
Frontenac Project
R = 66.5%
R = 60.6%
Perc
enta
ge
Frontenac Project
Frontenac Project
Frontenac Project
r = 68.3%r = 60 %r = 47%r = 63.5%r = 58.5%
Frontenac Project
r = 78.8%
Des
crip
tor F
requ
ency
Intensity Rating
Red Wine Tasting:Investigating Effect of TA on
Tannin Perception
Obviously, quality indicators of wine will be multivariate…
Suppleness Index
• Suppleness aka richness
• Relationship of alcohol, tannin, and acid
• Review:– Alcohol measured in percent– Acid measured in grams/liter
• In France it’s calculated as ‘Sulfuric Acid’ and not ‘Tartaric Acid’
– Tannin measured in g/L
Suppleness Index
Alcohol – (Acid + Tannin) = Suppleness
Suppleness Index
• The equation:
ETOH% - (T.A. + Tannin) = Suppleness
• > 5 = supple wine
Suppleness Index
• Cabernet examples:
Wine 1:
12% Alc - (3.6 TA + 1.8 Tannin) = 6.6
Supple
Wine 2:
10.5% Alc – (4.2 TA + 2.4 Tannin) = 3.9
Not Supple
Suppleness Index
• Frontenac examples:
Sample 743: 12.73%–(7.45 TA + .5 Tannin) = 5.78
Sample 291: 11.5% – (6.6 TA + .5 Tannin) = 4.4
Sample 238: 11.9% – (16.2 TA + .5 Tannin) = -4.8
Correlation: Suppleness and Numeric Award:
r = .52; 52% of variability accounted for
Amelioration?!
Frontenac—Ordered by SupplenessSample Supple (.5 tan.) Award Award Num.
743 5.78 Gold 7.11272 5.67 Silver 5.26291 5.40 Silver 5.18787 5.03 Silver 4.58662 4.97 Silver 5.26588 4.78 Silver 5.38781 4.77 No Medal 1.93374 4.40 Silver 4.93453 4.20 Gold 6.83
61 1.83 Bronze 3.03238 -3.82 No Medal 2.86
1. No2. B-3. B4. B+5. S-6. S7. S+8. G
Suppleness: Key Lessons
• Acid reinforces bitter/astringent flavors
• High acid and high tannin are not good
• High alcohol and low acid required for elevated tannin levels
Suppleness in Perspective:
• Developed by Peynaud and Gayon
• Bordeaux wine production in the 50’s and 60’s
• High suppleness = riper fruit
Who is Hungry?…because lunch is in 15 minutes!
Paul Gospodarczyk
Des Moines Area Community College
