The centerpiece of the event started with a tour of the LEED Platinum Teaching and Research Winery at UC Davis that introduced attendees to the special equipment that made the study possible. Then Fernando Buscema and Boulton gave a presentation of their research on Malbec cultivars and how they used the state-of-the-art UC Davis winery to conduct their experiments.
Buscema’s M.S. thesis at UC Davis is the most in-depth study of Malbec ever published. It is also the largest single comparative cultivar study ever attempted. The project studied Malbec—comparing 26 different blocks in Mendoza with 16 different blocks from six different counties in California. The blocks selected from Argentina were as uniform as possible. The same irrigation methodology was used; and if hail-protection netting was used, all of the vines in the block had to have it.
Buscema harvested between 500 and 1,000 kg of fruit from each block between 24° to 25° Brix. The Argentine wines were fermented in 500 L plastic bins while the California wines were fermented in 250 L stainless steel fermentors. Winemaking was conventional: 150 mg of SO2 was added at crushing, and 24 hours later 200 mg per liter of Lalvin EC-118 yeast was added. A day later 100 mg/liter DAP was added. Fermentation temperatures were kept between 22° and 25° C. After 11 days of fermentation on the skins, the wine was pressed, and the free run juice was inoculated with Lalvin VP41 malolactic bacteria. Once ML was complete, free SO2 was brought to 35 mg per liter. Twelve bottles of each wine were sealed and kept standing at 15° C until analysis. Roger Boulton commented, “Only someone with Fernando’s enthusiasm and dedication could get this 60-year-old professor up at four in the morning to pick grapes from 16 locations all over the state. I have waited 25 years to do this kind of research. It would have been a complete waste of time to attempt before, but now with this new equipment we have here at the research winery, we are able to exactly replicate each fermentation, isolating out the specific vineyard contributions.”
Using HPLC liquid chromatography, Buscema focused on 30 phenolic compounds with a system called chemotronics to develop a fingerprint of the various wines. The research revealed that the Mendoza wines showed similarities but were significantly different from the California counties. All of the California counties separated from each other except for Sonoma and Monterey. All four of the Mendoza locations separated from each other although two were closely associated. Buscema determined that as expected, the phenolic compounds present in Malbec wines are affected by site characteristics.
The study suggested that California and Argentine Malbecs are different compositionally, and that chemotronics could be used to explore new regions.
That research led them to a methodology that allows them to isolate specific factors they wish to study. State-of-the-art equipment allows them to focus on those factors, running their experiments in triplicate. The information gleaned from these experiments is readily adaptable to real winery production.
Since obtaining his degree, Buscema adapted his techniques to look at different sections within Catena Zapata’s legendary Adrianna vineyard located at a 5,000-feet elevation. He discovered overlap in most sections of the vineyard, but four plots stood out as unique. They experimented with individual lots from the four designated sections using the same rigorous technique he developed at UC Davis. Over time their research proved that three of the plots consistently produced wines recognizably different from one another. They are now trying to figure out if it is soil type or possibly different microbes in the soil that contribute to these differences. If they unlock and identify the keys to differences in the vineyard, they might be able to replicate those conditions that improve quality and consistency from one vintage to another.