Enology Notes

Enology Notes #83, November 19, 2003

To: Regional Wine Producers

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

Subject: Chile; Grape, Wine and the Environment Symposium.

1. Chile. I recently participated in a VinoTech Chile-sponsored symposium titled: Fermentation Problems: Causes, Prevention, Detection and Solutions. After the symposium, speakers were taken on a tour of several of the important wine-producing regions of the country.

The Chilean wine landscape has changed considerably since my last visit in 1996. The country is not the land of sleepy bodegas, but a vibrant, international wine community with an annual production of 900 million hL/year. Investments from Mondavi, Chateau Mouton-Rothschild, Miguel Torres, and Antinori, among others, have set a tone of technical advancement.

Climate. Chile, a country squeezed between two barriers, the Andes and the Pacific Ocean, is roughly 2700 miles long, but only 96 miles wide at its narrowest point. The northern hemisphere's latitude counterparts to Chiles wine-growing regions are Northern Africa/southern Spain. Thanks to the moderating effect of the ocean and mountains, the temperature rarely exceeds 90°F in most of the valleys. Chilean wine producers describe their climate as somewhere between Napa and Bordeaux.

The country's wine-producing regions are composed of numerous valleys, some of which are reaching relative fame. The most important of these are the Aconcagua and Casablanca, north of the capital, and the Maipe, Rapel, Curico and Maule valleys in the center of the country. These central valleys, collectively know as the Valle Central, are separated by rivers from the Andes, which provide ample irrigation water.

In most of these valleys, the summers are dry and generally mildew-free. In the Casablanca region, which is near the coast, vineyards are cooled by morning fog, which slows ripening. Almost all of the vineyards in this region have wind machines to help reduce the potential from late spring frost.

More than twenty varieties of wine grapes are grown in Chile. The largest planting is Pais (Mission), but that is rapidly changing. I tasted Sauvignon blancs produced in the Casablanca, which had varietal intensity and integration reminiscent of New Zealand wines. Edward Flaherty, the winemaker for Robert Mondavi's Errazuriz winery, suggested that their varietal intensity was a result of fewer daytime temperature spikes, compared with many other wine regions.

This may be a very important issue. What are the effects of short-term temperature spikes on grape aroma/flavor? It may not be realistic to rely too heavily upon the maximum and minimum temperatures to describe the thermal characteristics of a region or site. As suggest by Happ (1999), if the movement of temperature between the daily max. and min. exhibited the properties of a straight line, the mean would provide the average temperature experience. However, the true average lies away from the mean.

The rise in a temperature curve is asymmetrical, and changes with cloud cover, wind, etc. The optimum temperature for enzymatic reactions which govern aroma/flavor development and retention is about 22°C. Therefore, it has been suggested that the periodic difference between the temperature experienced throughout the day (for example, every twenty minutes) and 22°C, is the true measure of site climate. An issue may be the consistency of temperature during the entire day, for the final 28 days before harvest.

Happ (1999) has calculated a heat load index, which takes into account that a temperature rise does not necessarily have a linear effect on aroma/flavor. For example, a temperature increase to 25°C does not have the same impact on aroma/flavor as a rise to 35°C.

The subject of indices to help define sites for maximum aroma/flavor will be discussed and explored during our Grapes, Wines and the Environment Symposium (see below for details).

Cost of Production. Chiles standard of unmatched quality for the money has been somewhat eroded. There are a lot of players in the $5-9 per bottle market. Most industry members we visited expressed the importance of maintaining a low production cost. This philosophy limits the widespread use of enzymes, membrane filtration, etc.

Yield and Vigor. The average Chilean vineyard yield is well over 70 hL/ha (4 tons per acre), but that is rapidly changing. Like most premium wine producers around the world, they are concerned about yield, as it may relate directly to quality, and/or as a function of delaying maturity. The question of how yield impacts quality is complex, due to the interactions of growing season, vineyard site, vine density, clone, variety, pruning, crop thinning and timing, fruit weight/exposed leaf area, solar exposure, etc.

We have been examining the impact of crop vs. quality. We have seen a correlation between time from set to fruit maturation, and fruit and wine quality. The longer this period, such as can orrur with excess crop, the lower the quality. This concept is discussed in Effects of Crop Load on Aroma/Flavor (from the Enology-Grape Chemistry Group web page, click extension, then on-line publications).

Traditionally, many vineyards in Chile were planted on a Tendone system in a high, arbor-like trellis which provides shade, similar to the Parral used extensively in Argentina.

Almost all of the new plantings are on VSP. There were a few vineyards planted on various divided canopy systems, however these are not common due to establishment costs.

Most of the Chilean vineyards are planted on the very fertile alluvial soils of the valley floors. This has resulted in excess vine vigor, which many growers suggested was their primary viticultural concern. They are attempting to control the vigor by the use of irrigation. Most were well aware of the research conducted on the use of deficit irrigation, both to help control vigor and improve quality.

Organic Farming. The interest in organic farming is universal. As I reported in Enology Notes #75, many of the Loire Valley producers believe that organic farming increases wine quality. The Chileans perhaps agree, but also see a rapidly-increasing market for such products. Their generally dry climate will allow them to take advantage of this trend.

Maturity Gauges. For the reds, mainly from the Maipo Valley, winemakers place a primary importance on phenol maturity. As such, virtually all the red wines evaluated were supple, with "new world" round, soft palate profiles. The concern with phenol maturity has resulted in wines with high alcohol levels (14 - 15+). This universal problem of high alcohol stems from the asynchrony among sugar development, aroma/flavor, and phenol maturity, as discussed in several past Enology Notes.

Elevated pH values reduce longevity, a feature that most Chilean winemakers seemed to be willing to live with. This problem is somewhat offset by the alcohol concentrations.

Some producers appear to ameliorate with water, to help assure that fermentation goes to completion. The amelioration volume is calculated from the loss of berry weight due to dehydration.

Protracted Cold Soak. Uninoculated fermentations are very common. These are not without risks, particularly when used in conjunction with protracted prefermentation cold maceration. Many Chilean producers use multiple days of prefermentation maceration, sometimes up to 20. This was somewhat surprising, given the cost of keeping a tank below 10°C for that long a period. Temperatures warmer than 10°C run the risk of growth of Kloeckera spp., a cold-tolerant yeast.

In a study conducted by our group (The effects of prefermentation maceration temperature and percent alcohol (v/v) at press on the concentration of Cabernet Sauvignon grape glycosides and glycoside fractions, McMahon et al., 1999), prefermentation maceration at 10°C increased the glycosides extracted into the juice by 103% vs. control non-cold-soaked wines. Cold soaking increases long-term color stability and may increase aroma intensity.

It is likely that prolonged cold soaking would have an influence on red wine color, among other things. Color is a function of three components, anthocyanins, color cofactors, and the degree of polymerization. This season, we are evaluating the impact of prolonged cold soaking, which would likely be dependant upon the cultivar, maturity, and degree of berry breakage (see Enology Notes # 61, 62).

Fermentation. Many ferment their red must uninoculated, relying on the native flora of the winery. In a study from our group (Quantification of glycosidase activities in selected yeasts and lactic acid bacteria, McMahon et al., 1999), we evaluated the hydrolytic activity of 32 strains of yeasts isolated from wineries and vineyards. Several of these had a significant ability to hydrolyze glycosides, that is, convert grape-derived aroma/flavor precursors to their odor-active forms. This work, and that of others, suggests the possible benefits of uninoculated fermentations. There are, however, some substantial risks of microbial and oxidative degradation.

Carmenere. One advantage that Chile has is that it is the leading producer of the variety Carmenere. After the phylloxera crisis, the production of Carmenere in Bordeaux declined, as a result of its late ripening and frequent degradation due to late season rains.

It has found a home in Chile, producing well-structured red wines. Most suggested that the variety has some significant potential, but that a lot of work remains. Where it should be planted seems still an open question. It is the last to ripen, frequently has uneven development, and is a rather reductive grape. The interest in this seems to be overshadowed by those who are focusing on the so-called international varieties.

The question for many is, to what extent should this variety be developed? In the world of international marketing, how important is it to have a single identity? New Zealand is know for Sauvignon blanc, Oregon for Pinot Noir, Uruguay for Tannat, etc. Regional distinction is an important marketing consideration, one that we in Virginia have been considering as well.

Finally, there was one very interesting point stressed several times: that the industry would only reach its full potential with greater unity among producers. In order to help reach that goal, the Chilean Winemakers Society, as a group, visits wine regions around the world. They have been to California, Europe, and other South American countries.

2. Symposium. American Society for Enology and Viticulture annual meeting. The meeting of the American Society for Enology and Viticulture, eastern section, will be held at the Hotel Roanoke, Roanoke, Virginia, July 14-16, 2004.

In addition to the technical meeting associated with this event, we will be holding a symposium titled Grapes, Wine and the Environment. The goal of this symposium is to present, in practical terms, the best and current thoughts on soils, mesoclimates, and practices that promote high fruit and wine quality in a warm climate. Mark your calendars! More to follow.

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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: http://www.vtwines.info/
Phone: (540) 231-5325
Fax: (540) 231-9293