Enology Notes

Enology Notes #51, July 2, 2002

To: Regional Wine Producers

From: Bruce Zoecklein

Subject: Norton Roundtable, Laboratory Service Reminder, New Analytical Technologies, Pre-Harvest Workshop

Norton Roundtable. We will conduct a Norton Roundtable meeting on July 29, 2002, at Chrysalis Vineyards at 1:30 PM. If you are interested in attending, please RSVP via an email note to me.

The meeting is designed as a forum for discussion of the viticultural, enological and marketing issues related to the production and sale of Norton. It will include sensory evaluations. Topics will include:

Please bring Norton wines to share and discuss, if you can, and don't forget to RSVP to me at bzoeckle@vt.edu.

Laboratory Service Reminder. The Enology-Grape Chemistry Laboratory conducts supplemental, quality control analyses for the Virginia wine industry. This service is designed to support, not replace, in-house analyses.

We provide protein, bitartrate and microbial stability analysis and trouble-shooting. HPLC analysis for organic acids (used mainly for monitoring MLF status) is conducted by the Enology-Grape Chemistry Lab on the first and third Wednesday of each month.

New Analytical Technologies. Two technologies which will find increased application in the wine industry are remission photometry and infrared spectrophotometry.

I. Remission Photometry. As discussed at the recent Winemakers Roundtable meeting, remission photometry can be used to measure the light emitted from a test strip. The intensity of that light is then converted into the concentration of an analyte.

Portable, hand-held remission photometry meters are available along with test strips which can measure a variety of analytes including: alcohol, ammonium ion, ascorbate, tartaric, malic and citric acids, and a variety of cations including calcium and potassium.

Remission photometry will be demonstrated and discussed at the Pre-harvest Workshop, August 5, 2002 at White Hall Vineyards. Pre-registration is required. See either issue(s) of Enology Notes, or the web at www.vt.wines.info.

II. Fourier Transform Infrared (FTIR) Spectrophotometry. British scientist Peter Fellgate recognized that all infrared wavelengths travel at the same velocity. This results in the simultaneous adsorption of radiation by different components in a sample. Changes in the chemical composition of the sample will result in a change in the adsorption characteristics. The French mathematician Joseph Fourier developed the mathematical procedure to calculate these differences.

Thus, the analysis of ethanol, TA, pH, reducing sugars, etc. can now be measured in approximately 30 seconds, with precision and accuracy as good as conventional methods.

FTIR systems are commercially available, although expensive. This technology may someday be affordable, even by small wineries. It is hoped that in addition to wine chemistry, non-invasive analysis of fruit could be conducted, such as color and skin-tannin maturity.

Pre-harvest Workshop. A pre-harvest workshop is scheduled for Monday August 5, White Hall Vineyards, 10:00 am-4:30 pm. This program will be conducted by myself and a colleague, Lisa Van de Water, Director, The Wine Lab, Napa, CA and Pacific Rim Enology Services, Blenheim, New Zealand and Richard Cary, President of Vitis Research.

There will be a fee for the Workshop, which includes lunch, payable at the door. More information will be made available in an up-coming issue of Enology Notes.

Subscription to Enology Notes. All past Enology Notes and Vintner's Corner newsjournals are posted on the Enology-Grape Chemistry Group's web site at: http://www.fst.vt.edu/zoecklein/index.html or http://www.vtwines.info/. Enology Notes are slightly different in content from the subscription based Vintner's Corner newsjournal.

To be added to the Enology Notes list serve send an email message to bzoeckle@vt.edu with the word "ADD" or "REMOVE" in the subject line.

Dr. Bruce Zoecklein
Associate Professor and Enology Specialist
Head Enology-Grape Chemistry Group
Department of Food Science and Technology
Virginia Tech
Blacksburg VA 24061
Enology-Grape Chemistry Group Web address: www.vtwines.info or www.fst.vt.edu/zoecklein/index.html
Phone: (540) 231-5325
Fax: (540) 231-9293
Email: bzoeckle@vt.edu