New Zealand 2004

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Enology Analytical Services Laboratory Enology/Gra
pe Chemistry Group Virginia Tech
Bruce Zoecklein - Professor and Head,
Enology/Grape Chemistry Group
Ken Hurley Laboratory Manager, Enology
Analytical Services Laboratory
www.vtwines.info
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The Enology Analytical Services Laboratory
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High-Throughput Infrared Spectrometry
30 Samples per hour
Alcohol
pH
Organic Acids
Total Acidity
Wine Additives
Fermentable Sugars
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Segmented Flow Analysis
45 Samples per hour
Free Sulfite
Volatile Acidity
Total Sulfite
Phenols
Residual Sugars
Malic Acid
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VT Enology Analytical Serivces LabJuice / Must
/ Wine Analysis
General Wine Chemistry
Sensory Evaluations
Microbiological Profiles
Analytical Panels
Wine Stability
Custom Analysis
TTB Certified
www.vtwines.info
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VT Enology Analytical Services LabJuice / Must
/ Wine Analysis

• Competitive Cost of Analysis
• 24 Hour turnaround
• Broad Range of Analysis
• Consulting

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Fermentable Nitrogen Sulfur-Like Off Odors
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Sulfur-Like Off Odors - Definition
Finished wine aromas, reminiscent of sulfur
compounds, that negatively impact aroma and
mouthfeel

• Fermentation derived
• Related to nutrient status of juice
• Present as undesirable aromas or mask varietal
  characteristics
• Not to be confused with desirable VSCs

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Sulfur-Like Off Odors - Occurrence

• March 2006 first samples received
• Sensory panel reviews all samples
• March 2007
• 25 of all samples had SLO
• Samples from 2005 2006 Vintage

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Viticulture Factors - N, S Compounds

• Site
• Variety
• Rootstock
• Climate / season
• Soil, soil moisture
• Fertilization
• Cover crops
• Planting density
• Fruit rot
• Maturity / hang time
• Crop load

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Fermentable Nitrogen - Source

• Ammonium salts (NH4)
• Primary or free amino acids (FAN)
• Arginine, serine, threonine, amino butyric,
  aspartic and glutamic acid 35-40 of total
  N
• Assimilable N (NH4 FAN)
• 200 mg/L at 21Brix
• 250 mg/L at 23Brix

(www.vtwines.info, Enology Notes)
http//www.fst.vt.edu/extension/enology/downloads/
SLOFactorsFinal.pdf
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Viticulture Factors - from Véraison onward

• Ammonina decreases
• Amino Acid Fermentable Nitrogen increases, to a
  point, then declines
• High level of fruit maturity ? reduction in
  Nitrogen
• Correlation to SLO
• 70 correlation between Fermentable Nitrogen and
  SLO formation

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Alpha amino nitrogen (mM) of Cabernet Sauvignon
grapes cluster thinned to low (2.6 kg/vine),
medium (4.9 kg/vine) andhigh (5.3 kg/vine) crop
level in 1997
120
100
80
60
40
20
0
9/18/97
9/28/97
10/3/97
10/8/97
10/13/97
9/23/97
low
medium
high
Source de Bordenave, 1999.
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Fermentable Nitrogen - Berry / Juice Testing

• Berry samples
• Representative Samples
• Juice Samples
• Homogenous crush/press fractions
• Sampling information
• http//www.fst.vt.edu/extension/enology/VC/Jan-Feb
  01.html

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Fermentable Nitrogen - Berry / Juice Testing

• Fermentable Nitrogen
• Juice Panel Testing
• Nitrogen, Brix, pH, Malate, TA
• Enology Analytical Services Laboratory
• Sampling Kits
• Results reported the day samples received

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Fermentable Nitrogen - 2007 Sample Locations
Southwest - lt30 Shenandoah - lt30 Eastern - lt30
Central - 95 Northern 87 Other NC, NJ, PA, WA
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Fermentable Nitrogen - Varietals

• White
• Chardonnay
• Viognier
• Sauvignon blanc
• Vidal blanc
• Petit Manseng
• Riesling
• Seyval blanc
• Traminette
• Pinot gris
• Rkatsiteli
• Muscat
• Cayuga
• Chardonnel
• Gewurztraminer
• Malvasia
• Vignoles
• Rousanne

• Red
• Cabernet Franc
• Merlot
• Cabernet Sauvignon
• Petit Verdot
• Syrah
• Chambourcin
• Norton
• Tannat
• Touriga
• Malbec
• Montepulciano
• Sangiovese
• Tinta Cao
• Pinot Noir

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Fermentable Nitrogen - Levels / White
Note This data represents 1 year of information
only
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Fermentable Nitrogen - Components / White
Note This data represents 1 year of information
only
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Juice Chemistries - White
Note This data represents 1 year of information
only
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Fermentable Nitrogen - Levels / Red
Note This data represents 1 year of information
only
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Fermentable Nitrogen - Components / Red
Note This data represents 1 year of information
only
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Juice Chemistries - Red
Note This data represents 1 year of information
only
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Juice Chemistries - Correlation with Nitrogen
There is no simple marker of Fermentable
Nitrogen Testing is Required
Note This data represents 1 year of information
only
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Fermentable Nitrogen - How much do you need?

• Enough to prevent
• Sulfur-Like Off Odors
• Stuck Fermentations
• Typical desired Nitrogen level is
• Yeast strain dependent
• Classified as Low/Medium/High
• Berry chemistry dependent
• Range 140 350 mg N/L

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Fermentable Nitrogen - How much do you need?

• Differences in Varietals
• Differences in Vineyard locations
• Vineyard-to-vineyard
• Intra-vineyard differences
• Seasonal Variations
• Testing!

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Fermentable Nitrogen Sulfur-Like Off Odors
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Sulfur-Like Off Odors - Occurrence

• March 2007
• SLO Occurrence 25
• December 2007
• SLO Occurrence 17
• February 2008
• SLO Occurrence 13

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More Information

• www.vtwines.info
• Enology Notes
• Online Publications
• Enology.Services_at_vt.edu