The Analytical 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 provide chemical, physical, microbiological and sensory analyses, including standardized reagents. The services are available to wineries in any state, including importers and wholesalers.
We 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.
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. Use Volume Calculator form to determine tests to be requested and volume to submit
2. Complete the Sample Label in PENCIL and attach it to the sample bottle
3. Included should be a check to cover the cost of all the requested analyses, made out to: Treasurer, Virginia Tech along with the Deposit Approval Form
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)
360 Duck Pond Drive
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 2 weeks if further testing is required. Beyond this period of time, additional requests for analysis will require submission of a new bottle.
The lab must be notified if sucrose has been added to the sample. RS tests for reducing sugars (Glucose and Fructose). If sucrose has been added to the sample, a different test must be performed.
Please note: The ACE test only measures acetic acid. For finished wines the VA is generally a better choice to monitor spoilage. The ACE test does not meet the legal definition of volatile acidity.
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.
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.
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.
|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
|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)|
|Yeast Viability and Percent Budding, Microscopic||Viabile / Not-Viable||A statement of Viable means that living yeast were seen under a microscope|
|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|
|Oxidative/Degradative||Detected / Not-Detected||A statement of Viable means that living yeast were seen under a microscope|
|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|