Wine / Enology Grape Chemistry Group

Enology Service Lab

The Enology Service Laboratory, part of the Wine/Enology Grape Chemistry Group at Virginia Tech, was established to fulfill the analysis requirements of the regional wine industry. The goal of this analysis program is to provide very rapid turn-around, with optimum precision and accuracy.

Designed as a fee-based, full-service enology laboratory, we will provide chemical, physical, microbiological and sensory analyses, including standardized reagents. The services are available to wineries in any state, including importers and wholesalers.

We will provide analytic procedures to the individual wineries as requested. These procedures are equipment-relevant, and do not necessarily reflect the types of analyses performed at the Enology Service Lab.

For data reporting a secure website has been established. Results of analyses are only avaliable to the individual winemaker and to select staff members of the Enology Service Lab. The data is posted as results are obtained. Results of previous analysis are continuously maintained, allowing winemakers to see trends in their juice, must, or wine samples. The website is continuously monitored for security and system back-ups are performed daily to provide the utmost in stability, security, and availability.

Analysis Information and Forms

The following forms are available for download:

Analysis Request Form (Updated 03/01/2006)
Analysis Price Form (Updated 01/26/2009)

The analyses performed by the Service Lab are listed below along with the range of typical values. This list was last updated 3/01/06.

 
Analysis Result
Range / Scale / Definition
General Wine Chemistry
 
Alcohol (Ethanol)
% (v/v)
~0% in Juice up to 18% in finished wine; in dessert wines it may be as high as 24%
pH
pH Units
The pH scale ranges from 0 - 14. Neutral pH is 7. Wine pH is in the range of 2.9 to 4.2
Total Acidity
g/L
The range of TA in wine is 5 - 8 g/L (calculated as tartaric acid equivalents)
Volatile Acidity
g/L

The legal limits for VA (as acetic acid equivalents) are:
Red Wine - 1.4 g/L (1.2 g/L in CA)
White Wine - 1.2 g/L (1.1 g/L in CA)
Dessert Wine - 1.2 g/L (1.1 g/L in CA)
Wines for export - 0.9 g/L

Tartaric Acid
g/L
Approximately 0.5 - 4 g/L
Malic Acid
g/L
<35 mg/L following MLF
Lactic Acid
g/L
Approximatley 2 g/L following MLF, depending on initial malic acid concentration
Glucose + Fructose (Reducing Sugars)
g/L
A dry wine may have no detectable reducing sugars. Sweet wines may be in excess of 30 g/L
Free SO2
mg/L
The total sulfites in wine cannot exceed 350 mg/L. TTB requires that the wine label must say "Containing Sulfites" when the level is greater 10 mg/L (ppm)
Total SO2
mg/L
 
 
Microbiological Profiles
 
Yeast Viability and Percent Budding, Microscopic
Viabile / Not-Viable
A statement of Viable means that living yeast were seen under a microscope
MLF Viability    
 
 
Phenols
 
Anthocyanins - Total
mg / L
Typical values for Vitis vinifera red wine is 150 mg/L
Copigmented Anthocyanins
mg / L
Average values may be in the range of 0-10% of the total anthocyanins
Hue (420 nm / 520 nm)
#
A higher number indicates that a wine has a brownish tint that may or may not be visually perceptible. A higher number indicates oxidation / aging of phenolics
Intensity (420 nm + 520 nm)
AU
Higher values indicate a darker wine, but does not distinguish which color
Phenols - Total
mg/L
Typical values range from 150 - 450 mg/L in aged white wines to 2,500 mg/L or more in red wines
 
 
Sensory Evaluations
 
Oxidative/Degradative
Detected / Not-Detected
Indicates which, if any, defects are detectable in the wine sample
Palate - Structural Defects
Volatile sulfur compounds
 
 
Wine Physical/Chemical Stability, Sediments and Particulates
 
Atypical Aging
Pass / Fail
Indicates whether atypical aging may occur in the wine
Chill Haze
Pass / Fail
Indicates if wine components are prone to precipitation when chilled
Cold Stability
Pass / Fail
Indicates if bitartrate in the wine is stabile or prone to precipitate
Filterability/Glucan/Pectin
Present / Absent, Pectin / Glucan
Indicates the presence of Pectins or Glucans, which may impact the filterability of the wine
Protein Heat Stability
Nephel Transmittance Units (NTU) and Hot Box
Both tests estimate likelihood of protein precipitation
Turbidity
NTU
Used to determine quantity of lees for sur lie storage and bottle clarity

Sample Submission Requirements

Sample Size & Shipping Information

The quality and applicabilty of the results obtained by the Service Lab are direclty affected by the sample submitted. For this reason, all samples must be 375 mL (Split) or 750 mL (Full Bottle).

ANALYSIS WILL NOT BE PERFORMED WITHOUT THE FOLLOWING:

1. A completed Analysis Request Form
2. A completed in PENCIL Sample Label ATTACHED to the sample bottle
3. Included with the Analysis Request Form should be a check to cover the cost of all the requested analyses, made out to:

Treasurer of Virginia Tech

The completed forms, labeled samples, and checks should be packaged together and sent to:

Wine/Enology-Grape Chemistry Group
Enology Service Lab
Attn: Ken Hurley
Rm.113, FST Bldg.
Virginia Tech (0418)
Blacksburg, VA 24061-0418

Samples should be shipped overnight by UPS or FedEx, and each winery is responsible for establishing service with the shipping company. Included with the samples should be a Analysis Request Form. To avoid protracted shipping or storage by the shipping company, samples should not be mailed on Friday or Saturday. The Enology Service Lab will accept personal drop-off of wine samples, but for safety, security, and privacy reasons, only Service Laboratory staff are allowed in the laboratory area.

After analyses, the remainder of the sample will be retained for 1 month if further testing is required. Beyond this period of time, additional requests for analysis will require submission of a new bottle.

Sampling Methods

Tanks

When sampling it is crucial to ensure the sample is representative. Samples collected from the top, bottom, or racking valves may vary and may contain bitartrate crystals, which may resolubilize during transit. It is preferable to minimize this effect, and to obtain a representative sample. This can be accomplished by mixing.
Top sampling - Top sampling involves lowering a bottle with a restricted opening (via an attached nylon cord) down through the wine such that it fills on the way to the bottom. An examination of the wine surface should be conducted to determine the presence of film yeast and acetic acid bacteria. It is important to know how long it takes the bottle takes to fill so that the rate at whichit is lowered can be adjusted to suit the tank size.
Racking Valve - When taking samples from valves it is important to clean the valve effectively by rinsing with water prior to and immediately after sampling. allow approximatley 1 liter of wine to run through the valve before taking the sample. This prevents dilution from the rinsing water and contamination by any bitartrate crystals which have formed on the ferule wall.

Barrels

Barrel sampling procedures include: checking the bung area for signs of growth, looking for stains or spills on the floor, looking for film on the surface of the wine with a flashlight and checking for VA smell. If the barrel was properly sealed a vacuum should have been created. If, when the bung is removed, vacuum pressure was not noticed, check to see if the barrel is leaking or if there is some reason for improper bung closure. A clean and sterile wine thief is best used for removing barrel samples. Wine thieves should be immersed in pH-adjusted sulfur dioxide solution (200 mg/L SO2, pH 3.0 - 3.3) to avoid microbiological contamination barrel to barrel. It should be noted that wines in individual barrels may have significant differences in their chemistry and biological content. An individual barrel therefore may not be representative of the entire wine lot.

Contacts

Ken Hurley
Enology Service Lab Director
Room 113, FST Building
Virginia Tech 0418
Blacksburg, VA 24061
Phone: 540-231-7447

Dr. Bruce Zoecklein
Professor and Enology Specialist
Head, Wine/Enology-Grape Chemistry Group
Department of Food Science and Technology
Virginia Tech 0418
Blacksburg, VA 24061
Phone: 540-231-5325