Introduction to Winemaking
Chris Gerling
NYSAES
Source: Chris Owens
Variation in Aroma
Lack of Genetic Diversity in Grapes
V. vinifera
Sauvignon Blanc
Little aroma in ripe grape
Lots of aroma in wine
V. labrusca
Concord
V. vinifera
Zinfandel
Lots of aroma in grape
V. vinifera
Autumn Royal
V. vinifera
Selma Pete
V. labrusca
Concord
(lit
tle
ar
om
a)
PO
G R TE
AP NT
E- LY
Y!
Fermentation
V. vinifera
Zinfandel
W
i
ar ne l
om ike
as
ST
GR ILL
AP
EY
3‐Alkyl‐2‐methoxypyrazines (MP)
N
N
OCH3
Detection threshold for IBMP
2 parts per trillion (water)
5-15 parts per trillion (wine)
R
The measures of acidity
 pH = the molar concentrations of free protons
pH = -log [H+]
R = alkyl group
Predominant
MP in grapes
Predominant
MP in Asian
lady beetle
Name
Abbr.
Aroma
IsobutylIsobutyl-MP
IBMP
Bell pepper, vegetal
secsec-ButylButyl-MP
sBMP
Peas, potatoes, earthy,
nutty
IsopropylIsopropyl-MP
IPMP
Green beans, earth, peas
Wine Flavor: Sources
 Grape metabolism
 “Varietal character”
 Fermentation metabolisms
 Yeast, LAB
 Aging and additional processing
 Esterification, oxidation
1 strong acid
7
strong base 14
*Juice/ Wine is usually between pH 2.93.7, especially in cool climates.
The measures of acidity
 TA (titratable acidity) = total concentration of titratable protons (free and otherwise)
Expressed in grams/ Liter
4 g/ L (California Chard
16 g/L (Cold Climate Hybrid)
Organic Acids of Grapes…
pH vs. TA
pH = “Strength” of acid
TA = Amount of acid
Acid
Concentration
pKa
Tartaric
2‐6 g/L
2.98
Malic
2‐7 g/L
3.40
Lactic
0‐3 g/L
3.86
Citric
0‐1 g/L
3.15
Succinic
1 g/L
4.16
Acetic
0‐1 g/L
4.76
These are all weak acids. The same g/L can result
in different pH values.
Fruit Ripening
 As grapes mature, acid levels decline and sugar levels increase.
 Measuring these parameters (along with tasting) helps inform harvest decisions.
Gavin Sacks
 These are imperfect measures, but they’re still useful.
Processing‐ Solids to Liquid
 De‐stem?
 Crush
 Press
 Remove seeds/ stones?
Crushing/ De-stemming
Crushing/ De-stemming
Must: mixture of juice, skins and seeds
Source: Henderson, 2006
Presses
 Hydraulic/ Ram/ Basket
 Bladder
Basket Press
 Weighted top screwed or ratcheted down onto must
Source: Henderson, 2006
Bladder or Pneumatic
Press
 Air or water bladder
 Thin layer of grapes pressed against slotted walls
Crushing/ De-stemming
Clarification: Racking
 Natural clarification: gravity
Fermentation
 Can occur any time during process
Source: Henderson, 2005
Fermentation
Sugar
Ethanol
Carbon Dioxide
Net: 2 ATP
Yeast
Aerobic vs. Anaerobic
• Single Celled Organisms
• Facultative Anaerobes
• Ubiquitous
 Aerobic respiration is more efficient and allows for more biomass growth.
 Fermentation leaves energy on the table (in the fermenter) in its waste product (alcohol).
 Alcohol is toxic to yeast.
Aerobic Respiration
Net: 36 ATP
Yeast
Lallemandwine.com
Yeast Growth
“Un‐natural?” Fermentations
 Inoculated Fermentation: Select Yeast Strain
 Added Yeast Will Dominate and Overtake Indigenous Strains
 Pros:  Control
 Repeatability
 Performance
 Cons:  Cost
 Following Directions
 Worse Marketing?
“Natural” Fermentations
 Spontaneous Fermentation‐ Yeast is not added
 Indigenous yeast are used
 Pros:  Cheaper
 Lower Carbon Footprint
 Complexity
 Better Story
 Cons:  Mystery Yeast
 Potential Off‐aromas
 Lack of Efficiency
 Repeatability
The Catch…
 Spontaneous seems cheaper & easier but is really harder when done right.
 “Dipback,” other methods of yeast recycling require intensive work to maintain strain integrity.
 Without tools and/or experience, purchased strains can give a much more consistent experience in the beginning.
Thriving in a Hostile Environment
 Like any living organism, microbes need certain conditions to survive.
 They also have dietary needs and restrictions. Dailymail.co.uk
 Yeast & bacteria have temp., pH ranges that affect their growth and survival.
Yeast: Dietary Restrictions
An Environment?
 Yeast can metabolize small, 6‐carbon sugars
 Yes: glucose & fructose
•Alcohol: 8-14%
 No: starches, cellulose
•pH 3.0-4.0
 To access the more complex and/ or structural sugars: enzymes, heat, acids etc.
•Temperature 50-70 F
•Titratable Acidity 4-15 g/L
•Residual Sugar 0-10%
techliberation.com
Yeast: Inhibitory Factors
 High or low pH
MLF: Inhibitory Factors
•
•
•
•
 Lack of nutrients
 High or low temperature
 High alcohol
pH below 3.20
Free SO2 above 20 ppm
Temperature below 18 ºC (64 ºF)
Lack of nutrients (no contact with lees)
– Stir well
 Rapid temperature changes (temperature shock)
• Competitive yeast
• Ethanol above 13%
Inhibition increases in a
geometric, not additive,
manner.
Malolactic Fermentation (MLF)
 Occurs when Lactic Acid Bacteria (LAB) convert malic acid to lactic acid
Boulton et al., 1998
Malic conversion (direct decarboxylation)
 Pigeage or punchdown: the use of paddles or other implements to reintegrate the cap into the wine
Fermentation: Red Wine
 Cap: the layer of grape skins that form on top of fermenting reds.
 Cap management:
any program designed to keep the skins submerged in the fermenting juice.
Oak
 Allows “appropriate” rate of O2 transfer.
 Good looking in winery.
 Hard to clean/ impossible to sterilize.
 Expensive.
Filtration: General Principles
Plate & Frame/ Pad
 Younger wines require more filtration
 Filtration usually does not remove volatile compounds
 May remove phenolic compounds
 Filtration is not essential for all wines
 Clarification techniques should be kept to a minimum
•NY winery workhorse
•Used for most wine
“intermediate filtrations.”
Cartridge/ Membrane Filter
Fining
 Addition of reactive or adsorptive substances (fining agents) to remove or reduce the concentration of undesired compounds
•Absolute filter
•Lower throughput
•Good starter
Crossflow Filter
Fining
 Goals:
•Fluid runs
perpendicular to
filter medium
•Can take
unfiltered product
to 0.2 micron in
one run
•Expensive
 Enhanced clarity, color
 Increased stability
 Removes:
 Phenolic compounds, inc. browning agents
 Proteins
 Perform prior to cold stabilization
Fining: Principles
Cold (Tartaric) Stabilization
 Removal: form larger particles capable of being removed by settling or filtration.  Precipitation of salts of tartaric acid
 Potassium bitartrate
 Supersaturated solution
 Calcium tartrate
 Small amounts natural; most added
Source: Bird, 2002
 Soluble in water; less soluble in alcohol
 Solubility decreases in cool temperatures
Fining Agents
AGENT
SOURCE
WINE
REMOVES
EGG
WHITES,
ALBUMIN
EGGS
RED
TANNIN
GELATIN
BONES, HIDES
RED,
WHITE
TANNIN,
COLOR
ISINGLASS
FISH
WHITE
TANNIN
CASEIN
MILK
WHITE
PVPP
MANUFACTURED
WHITE
TANNIN,
COLOR
COLOR,
SMALL
TANNINS
How does SO2 get into wine?
 SO2 is added in various forms: powder (esp. potassium metabisulfite), tablets (esp. Campden), gas (requires special equipment), etc.
 Powders, tablets, and anything but gas are not 100% SO2.
 Yeast will also produce varying levels of SO2 , making the labeling requirement tricky (even without additions.)
 These substances are distinct from elemental Sulfur that is sprayed on vineyards to prevent powdery mildew and other fungal problems.
What are “sulfites?”
 Technically, any compound containing the sulfite ion (SO32‐) is a sulfite.
 Sulfites are used to preserve foods and beverages (think dried apricots).
 We are primarily interested in sulfur dioxide (SO2)
 Any wine containing at least 10 ppm of SO2 must carry the designation “Contains Sulfites.”
Functions of Sulfur Dioxide
 Antimicrobial – Inhibits growth of bacteria and some yeasts
 Antioxidasic – Inactivates oxidation enzymes (i.e. polyphenol oxidases)
 Antioxidant – Scavenges H2O2 formed during oxygen reactions
 Binder – Binds undesirable, oxidized compounds in wine (i.e. alcetaldehyde) Forms of Sulfur Dioxide in Wine
 Free SO2 – active as antimicrobial, antioxidant, etc.
 Bound SO2 – no significant activity
 Equilibrium exists between free and bound forms
 Upon oxidation, free SO2 is consumed Headaches
 The “red wine headache” phenomenon is linked to sulfites, but white wines generally have more SO2 than reds.
 Biogenic amines have been more recently linked with headaches, but this link is also mostly speculative.
 Neither sulfites nor amines are unique to wine, but the combination with ethanol may lead to different effects.
 *Insert appropriate joke about not drinking the whole bottle yourself here.*
Health Risks
 A small percentage of the population has an allergy to sulfites. This condition is extremely serious.
 Sulfites are also associated with increased asthma symptoms.
 Always use care when working with the powder or gas.
Packaging
Sanitation
 Because of the alcohol and acid present in wine, we are not worried about pathogenic organisms.
 Bad winery sanitation leads to bad wine quality, however.
Entry Route of Microorganisms
Animals
Rodents &
Pests
WINE
Humans
Environmental
Inanimate
Objects
(bottles, paddles,
wine thief)
Domaine De La
Romanée-Conti,
Romanée-Conti 1964
$8542 per bottle