Enology Notes

Enology Notes #75, May 30, 2003

To: Regional Wine Producers

From: Bruce Zoecklein, Head, Enology-Grape Chemistry Group, Virginia Tech

Subject: Tour of Loire River Valley and Up-Coming Meetings

Tour of Loire River Valley

I recently completed a tour of the Loire River Valley with a few colleagues. The purpose of the trip was to review viticultural and enological practices and philosophies, in preparation for a Virginia grape/wine industry study tour in March 2004.

This will be similar to the study tour we conducted in Southeastern France and the Rhône Valley in December 2003 (full details of this trip, including notes from each vineyard and winery visit, are posted on-line at www.vtwines.info).

For 8 days, we toured along the Loire River. The wine region covers 125,000 acres, half the size of that of Bordeaux, and equivalent to the Rhône’s.

A top variety is the versatile Chenin, also called Pineau of Loire, with wines ranging from light dry to dessert wines, and even fortified products. Two main regions for Chenin include Montlouis and Vouvray in Touraine, and along the river Layon in Anjou.

Sauvignon Blanc is also extensively planted and occupies a special position in Northern Loire, where soil and climate allow for the production of very flavorful wines. We visited the main regions, Pouilly Fumé and Sancerre.

The Cabernet Franc (or Beton as it is called locally) regions of Touraine, Chinon, Bourgueil, St. Nicholas-de-Bourgueil, and Saumur-Champigny were of particular interest, due to our regional success with this variety.

Of the Loire Valley’s various soils, the most significant is the chalky limestone. In the central Loire the soils are rich in limestone and tuffeau (a calcareous rock, like soft limestone).

The climate of the Loire is fairly mild year round. Relatively high temperatures from mid-June to mid-August coincide with low rain fall. For the central part of the Loire (Tours) the average daily mean temperature for September and October is 16.4 and 11.9 degrees Celsius, respectively. The average monthly highest maximum temperature for the two months is 29.2 and 23.1 degrees C, respectively.

Vines are frequently moisture-stressed in the last stage of ripening. Surprisingly, the average total sunshine hours are about 1900 hours/year, about the same as Champagne.

The importance of organic farming with regard to wine quality was an important and frequent topic of discussion. Almost all of the producers stated that they practiced organic farming (no herbicides, only copper sulfate and sulfur spraying).

Claude Papin, of Ch. Pierre Bise at Beaulieu sur Layon, stated that with herbicides, the soil becomes “death to the world.” Some stated that they farmed organically, when they can.

Alfonse Mellot, of Domaine de la Moussiere, Sancerre, said that organic farming allowed for approximately 1.0 g/L increase in TA, mainly as a result of an increase in the tartaric acid concentration.

The increase in TA is associated with a reduction in pH, and an increase in wine longevity, an important quality component for most French vignerons. He also sprays his vines with tartaric acid, which he believes is taken up by the leaves, and results in an increase in fruit acidity.

Most clean cultivate, and all expressed the relationships between soil aeration, root penetration, and organic farming. There was a strong consensus that the avoidance of herbicides, along with soil aeration, allows roots to penetrate deeply into the soil, rather than laterally. This was reported to slow vine growth, that is, had a devigorating impact.

Alfonse Mellot stated that organically-grown Cabernet Franc is more concentrated. Organic wines, although more difficult to produce, were reported to command as much as 30% more in the marketplace, according to Michel Delanoue of Domaine de la Nouraraie-Bourgueil.

The rate of fruit maturation was an important topic of discussion. Some of the research we have conducted in Virginia suggests that this may be an important quality feature. Specifically, we have found an inverse correlation between the length of the growing season and wine quality. (See www.vtwine.info, click extension, then on line publications, Review of Crop Load on Grape Aroma/Flavor).

It appears that the longer the growing season, the lower is the grape glycoside concentration. Grape glycosides are colored anthocyanins and, in part, aroma/flavor precursors. One important reason for the strict AOC yields in France is to make sure that crop loads are not so high as to delay the rate of fruit maturity.

This was particularly evident at Domaine des Rogelins-Varrains Chace. Cabernet Franc parcels of less than a 2-3 acres were surrounded by 7- to 9-foot-high rock walls, not for their fine aesthetic value, but because the increased heat retained advanced the season by an average of 10 days.

The precocity of the phenological stages of plant growth appears to be an important factor in grape and ultimate wine quality.

In one study done at Montpellier on Shiraz, reducing cluster numbers to one per shoot significantly increased the bound aroma/flavor precursors. This may be the result of increasing the rate of fruit maturity, source-sink relationships or both.

Monitoring the timing of phenological stages of each variety and sub-block should be part of every growers HACCP-like plan (see Enology Notes #8).

Claude Papin, of Ch. Pierre Bise at Beaulieu sur Layon, talked about his perceptions of two distinctively different wine styles produced: varietal wines and terroir wines. Varietal wines are those that possess the expression of the grape variety, but are simple products. These wines are from fruit grown in climates and soils that are not optimal. Terroir wines, on the other hand, are more complex, with the full incorporation of the elements which make up fine wine, the soil, the sun, the wind, etc.

He used this as an example as to why he does not grow Sauvignon Blanc in his region. “It would mature three weeks later than in Sancerre, resulting in increased herbaceousness--a simple varietal wine.” Alfonse Mellot, of Domaine de la Moussiere, had a similar comment in a discussion about ‘wine makeup’--too much winemaker intrusion, which hides the true character of the soil and climate.

Not every producer we met was completely Old World in approach. For example, Domaine Henri Bourgeois-Sancerre is a state of the art, gravity flow facility with conveyer belts, computerized system controls, and an elaborate HACCP plan (see Enology Notes #8, 22, 24, 52, and 59).

Christopher Daviau, of Domaine de Bablut at Brissac, uses post-fermentation, and pre- and post-dejuicing microoxygenation on his Cabernet Franc, for more gentle extraction, color stabilization, and phenolic polymerization (see discussion in Enology Notes #23 and 36).

Domaine Henri Bourgeois uses a procedure that we have reported, thermal vinification, before dejuicing of reds. In our research with Virginia-grown Cabernet Sauvignon, we have heated must to 42 degrees C, post-fermentation, for several hours, cooled down to 15 - 2 degrees C and pressed. The result is the increased extraction of skin-derived aroma/flavor precursors (18%) and anthocyanins (12%).

Additionally, our research demonstrated an increased association of anthocyanins with non-colored phenols. In one study, we reported an increase of 41% and 208% in the formation of small and large polymeric pigments, respectively. This results in increased spectral color, color stability and palate integration. Color and color stability were the primary concerns for the Domaine Henri Bourgeois Pinot noir.

I intend to conduct a Winemaker Roundtable meeting to further discuss Cabenet Franc grape/wine production and to taste wines from the trip.

Up Coming Meetings

Winemaker Technical Roundtable - Mouth feel Management July 15. Location TBA. Dominique Delteil will be our guest. Dominique is the director of research and development for the Interprofessionalle Cooperaty du Vin in Montpelhen, France. Dominique has conducted research on yeast selection, tannin management and mouthfeel. He and I will lead a discussion of phenol management and yeast selection. Details to follow.

Wine Microbiology Workshop July 21, 2003. Location TBA. This day-long program will feature my colleague, Lisa Van de Water, The Wine Lab and Pacific Rim Oenology Service, and will cover practical issues with regard to wine microbiology. I will also cover the subject, Managing Sulfur-Containing Compounds. This will include factors influencing organic and inorganic sulfur compound production, and steps to lower the impact on wine quality. More information to follow. Mark your calendars!

Norton Roundtable. The third annual Norton Roundtable meeting will be conducted at Chrysalis Vineyards, beginning at 1:00 p.m. on July 28, 2003. This meeting is for current Norton grape growers and winemakers. RSVP required. If you are interested in attending, send me an e-mail message at bzoeckle@vt.edu.

Wine Closure Symposium and annual meeting of the American Society for Enology and Viticulture, Eastern Section July 8-11, 2003, Corning, New York. The Closure Symposium (July 9-10) will feature a number of international speakers on practical and relevant subjects including: progress toward elimination of TCA, an overview of cork alternatives, cork QC, screw caps and other wine bottle closures, etc., including sensory analysis. Additional information is available through my office, posted on my website, and posted on the website of the ASEV-ES at www.nysaes.cornell.edu/fst/asev.

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Dr. Bruce Zoecklein
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 http://www.fst.vt.edu/extension/enology/index.html
Phone: (540) 231-5325
Fax: (540) 231-9293
Email: bzoeckle@vt.edu