The focus of the presentation was a comparison of "native" or "natural" yeasts against "commercial" or "industrially-prepared" yeasts for primary fermentation of wine. Many of the conclusions were drawn from years of practical experimentation by Californian wineries, and in particular through Mr. Ramey's own experiences at Chalk Hill Winery.
The Chalk Hill Winery is established in the Sonoma Valley in California. Its vineyard area is 1100 acres, and produces 75,000 cases of wine annually, 45,000 of which is chardonnay. Mr. Ramey, who has a Master of Science degree from Davis University, was taught to use commercial yeasts through his University training, and it was not until he completed his qualifications and worked at various wineries did he run experiments on a regular basis dealing with native fermentation.
The experimentation focussed on the "French varieties" of chardonnay, cabernet sauvignon, and sauvignon blanc. An outcome of comparative studies lead the winemakers involved to conclude that the "French approach" to winemaking often produced "tastier" wines than those produced under the "New World" framework - the winemaking practices used to establish the comparisons involved extensive lees contact, full barrel fermentations, full malolactic fermentation, and the absence of skin contact.
Mr. Ramey indicated that his French winemaking experience in 1979 in Pomerol, where he returned in 1989, had encouraged him to reconsider the opportunities to harness native fermentation in California. Simultaneously, other experimentation occurred in California during the 1989 vintage on the same subject by other wineries. Results indicated that wines fermented with natural yeasts produced notable differences in the texture or mouth-feel of the wines, being; richer, rounder, "fatter" yet also possessing more delicate characteristics as well - a phenomenon difficult to explain given that "delicacy" and "fatness" are usually paradoxical terms. Subsequent comparative experiences in the next vintages confirmed the initial impressions.
Chalk Hill Wines pursued the "Burgundian Model";
Presentation of comparative data of "natural" versus "industrial" yeast fermented wines, stemming from five years' of Chardonnay data and four years' Sauvignon Blanc data, indicated that wines fermented with natural yeasts;
- No Skin Contact
- Cluster Pressed
- Full Barrel Ferment in French Oak
- Full Malolactic Fermentation
- Full Natural Yeast Fermentation
- Fined with Whole Milk and Isinglass
- Bottled with Minimal Filtration.
Demonstrated better oak integration, in that the oak influence tended to be less obvious.
Reduced "butter" character as a result of lower concentrations of diacetyl. All yeasts (which are still active towards the conclusion of fermentation) contain an enzyme which reduced the prevalence of diacetyl (which lends to the "buttery character"). Since natural yeast ferments last longer, the yeast stay in suspention longer, putting them in contact with the diacetyl as it is produced by bacteria. It was suggested that this presented a more integrated overall style.
Bisulfite compounds, which are created microbiologically, occurred to a greater extent in (some) commercial-yeast fermentations than in natural-yeast fermentations.
Residual sugar levels tended to be higher in naturally fermented wines (1.5 grams per litre, compared to 0.9 grams per litre in wines fermented from commercial yeasts). It was suggested that the variation was minimal - both levels characterising dry and microbiologically stable wines. It was also suggested that the differences in residual sugar could explain the textural differences in the wines.
Volatile acidity was marginally higher in naturally fermented wines, but the variation being at a statistically insignificant level (this indeed can lead to greater complexity at low levels).