July 2017 Issue of Wines & Vines
 
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A Conversation with Scott McLeod

On tannin analysis and maceration management

 
by Laurie Daniel
 
 

 

Winemaker Scott McLeod, a native of Marin County, Calif., got interested in fermentation when he tried his hand at making beer while he was in high school. That interest took him to the University of California, Davis, where he graduated in 1985 with a degree in fermentation science.

While he was studying at Davis, McLeod spent a year at Isole e Olena in Chianti Classico, and he returned to the Italian wine region after graduation to work for another year at Badia a Passignano. When he returned to California, he bounced around the Napa Valley, working for several wineries, until winemaker Tony Soter introduced him to Francis Ford Coppola. Coppola hired McLeod in 1991 to make the wines at his Napa Valley estate, then known as Niebaum-Coppola. As director of winemaking, McLeod made the estate wines, including the flagship Rubicon Estate red, and oversaw wines such as the Diamond Series bottlings.

After 18 years working for Coppola, McLeod struck out on his own in May 2010. He’s a partner in WineXRay and Safe Harbor Wine Storage, both in Napa. He’s also the winemaker for George Lucas’ Skywalker Vineyard in Marin County as well as consulting winemaker for Daou Vineyards and Parrish Family in Paso Robles and Monte Xanic in Mexico’s Guadalupe Valley. McLeod also consults for several other winery and vineyard projects and is a partner in 180 acres of vineyards in El Dorado and Monterey counties.

QOne of your ventures is an analytical service in Napa called WineXRay. Please explain what sort of analysis you provide.
Scott McLeod: Our platform is based on the Adams-Harbertson Assay from the University of California, Davis. The assay is intended for measuring concentration of families of phenolic compounds found in grape skins and seeds as they migrate into wine during fermentation. Our system allows for near real-time evaluation of this process, provided a client has the necessary equipment at their facility, as this eliminates the physical transfer of the sample. This is hugely valuable for wineries in need of turning tanks or for blending early for space consolidation. Luxury-tier producers have other concerns such as reproducibility, maximizing very expensive grape supplies, new barrel allocations to their various lots, and experimental validation of new equipment and grape handling. Phenolics play an important role in all of these pursuits.

The hardware required in a client’s lab is about $11,000, but many labs already have pieces of the necessary equipment, like a scanning UV-visible spectrophotometer, a micro-centrifuge, flow-through cell and sipper and a laptop for connection to the cloud. Basically, the cellar gathers samples in the morning after the pumpover and takes the samples to the lab, where the client spins the sample in the centrifuge and then runs the sample, via the sipper, into the flow cell of the spectrophotometer. A file is created to land the raw spec data, then the client accesses our web portal and uploads the file. Seconds later, their phenolic scan is returned to their desktop, laptop or handheld.

The first time a client experiences the speed and accuracy of the information is transformational in how a cellar executes a maceration protocol. Otherwise, a client packs up samples and sends them to the lab, and we return the results in two or three days, depending on when the samples arrive. But in the heat of battle, three days may as well be three weeks, as the information is forensic at that point.

The co-founder of WineXRay is Dr. Gianni Colantuoni, and he has worked extensively in the chemical engineering and process-control industries. Gianni is the creator of the models that allow for the interpretation of raw spec files into tangible, meaningful and rapid results for WineXRay. Our industry is lucky to have him.

The power of the analysis is virtually limitless and is not dependent on the scale of a winery. As a tool in support of sensory evaluation, the information allows for the more rapid determination of lot allocation and confidence in the blending process. From the perspective of a CEO or CFO, the highest cost of goods in a bottle of wine is the grape cost, so having a tool that allows for a non-sensory assessment is extremely important. For the vineyard manager or director of grower relations, they can have a tool to compare appellations and growers inside the same appellation, vintage effects on phenolic intensity, data to illustrate the real effects of virus, and an evaluation tool to compare clones and rootstock, even yield effects on phenolic intensity. Finally, for the production winemaker, we have the ability to monitor macerations by the day or by the hour, ensure that maceration protocols are being followed by the cellar, and adjust to yearly variations of the grape supply. Perhaps the two most important points to remember are that phenolic concentrations vary yearly and so do their extractabilities.

We have approximately 70 clients in the United States and Italy, with most of them in California.

QOnce you and the client have the data, how much advice do you provide on how to proceed?
McLeod:
It’s very client-specific. Some clients have worked with phenolic results but never had a way of having the data quickly enough for actionable implementation. So they have a strong baseline but just need to see the results. Other clients are not very aware of the use or understanding of phenolic results, so we spend more time in the initial phase, and then they are off and running. But every client we have has really embraced the technology and improved their winemaking and/or the understanding of their winemaking, cellar, vineyards, growers, processing equipment and the differences in the vintages.

QCan you give us some specific examples of how clients use your services?
McLeod:
One area that we focus on is maceration management, as the process is a partial extraction of a partial extraction. When you think about it, we start with a ton of grapes (2,000 pounds), and 30 days later we only have 1,300 pounds of wine. Over a third of the mass is lost. But what is really the concern is that we are only able to remove perhaps 50% to 75% or less of the available color in grape skins and (thankfully) about 5% to 15% of the available skin and seed tannin. So a tremendous amount of money is at risk each year, and we have found that some wineries are better at maceration management than others. In some cases, a grower might be penalized, or even dropped, based on a finished wine assessment, even though their grapes may have been poorly managed in the fermentor.

To this point, one of the first things we look at is the total phenol (iron-reactive phenolics) of a given sample set. For example, this could be all Cabernet samples from the same AVA or county, from the same year. Since the total phenol value is a record of the total extraction, it is a great way to see the adherence to the winemaker’s maceration protocol as performed by the cellar master and cellar staff. When we see variances of 30% or greater, that means that pumpovers are not being performed on schedule, or that temperatures are not being uniformly maintained across the cellar, or even the simple truth that most wineries have too much to do in a short period of time. But we can shed some light on this process and ensure that the winery is getting the most out of a partial extraction.

Let me give a little more insight into some experiences that we have had—and this is not a specific client’s information, to be clear. But we have seen wineries that significantly under- and over-extract the same grape varieties from the same appellation following the same protocol. A winemaker is expecting the difference in finished wine to be driven by differences in the grape supply, but that is not always the case. In fact, when the grape supply is incorrectly managed, the results are less tons making a given program, loss of grower or block information, and it turns blending into finding strengths to support weaknesses as opposed to blending strengths on strengths to build a stronger and larger blend overall.

One area that is critically important to all red wines is the stabilization of color, as the anthocyanin (color molecule) can bind with a molecule of tannin and form a stabilized form of the anthocyanin that decays very slowly (as compared to the anthocyanin without the tannin attached). There are also textural properties to these compounds that are beneficial to sensory. This polymerization reaction is manageable, and there are ways of increasing the polymerization rate and amount for a given wine.

Also, we measure tannins that are very specific to sensory (astringency). The Harbertson-Adams Assay measures tannins that react with salivary proteins as a link between the sensory lab and the production environment. Tannins come in all shapes and sizes, but the ones that react with your palate are the ones we care about.

QDoes this process have any applicability to white wines?
McLeod:
No, we do not run our models on white wines, as they are very low in skin and seed tannins. We are a red wine assessment assay.

QYou’re also a partner at Safe Harbor Wine Storage in Napa, Calif. What services do you provide there?
McLeod:
Safe Harbor Wine Storage has two facilities in Napa storing approximately 8 million gallons of wine for 60 or so clients. Our client list is private, but we have wines from $100 a bottle to $15 a bottle, with the majority of our clients in the $20-$40 range. We have clients that have large facilities but need more capacity, or Napa wineries that are subject to the 1990 Winery Definition Ordinance that cannot increase production on their bond, so we do it for them.

We have a wonderful staff, led by Joel Green, our general manager and winemaker, cellar master Jose Flores and Leticia Chacon-Rodriguez, our director of operations.

When you think of a storage facility, you tend to think of a static environment. Safe Harbor is anything but static, as we perform all sorts of blending operations, white wine fermentation, finishing and filtrations, even bottling. We also do a lot of work with staves and micro-oxygenation, as two of our partners, Alan and Steve Sullivan, are the founders of Stavin Inc., the commercial wine tank stave company. They established the use of staves as an economical and environmentally positive alternative to either barrel use or no barrels at all. I think it is safe to say that they changed our industry and the flavor profile of commercial winemaking in general. And not just our industry in the U.S., but also in South America, Australia and New Zealand, South Africa and, recently, the European Union. Safe Harbor was designed using 20 years of stave and micro-oxygenation information and experience.

QIn your work as a consulting winemaker, you see a lot of new winery technology. Is there anything you’re particularly excited about?
McLeod
:
I am very impressed with the improvements to the mechanization of the wine industry, most notably some of the optical sorters from Pellenc and Bucher-Vaslin and the mechanical harvesting platforms led by Pellenc Selectiv’ harvesters. I was exposed to them while working in the luxury division at Beringer Vineyards, and the results were impressive, to say the least. We all know that labor is our No. 1 issue, and we need to adapt. But these systems are additional to quality in most cases. When you see an optical sorter or the Pellenc harvester in operation, you have to acknowledge the achievement, as they are that impressive.

Also, packaging continues to change, and agglomerated corks are here to stay. In fact, at the I+Q Conference in St. Helena, Calif., in March, there were advocates of the Diam closure for not just its very low amounts of TCA, but also for the uniformity of oxygen ingress. The oxygen transmission rate has a huge effect on SO2 decline and bottle variation in a finished, packaged wine. So high-end producers who would not have used an agglo closure 10 years ago are now considering them as an option.

For the producers who will always use natural cork, the ability for cork suppliers to test their corks individually for taint is a game changer. We are appreciative and happy to see them invest in the equipment, additional floor space and sophisticated detection equipment to give winemakers the highest level of confidence possible for use in their wines.


A resident of the Santa Cruz Mountains, Laurie Daniel has been a journalist for more than 35 years. She has been writing about wine for publications for more than 21 years and has been a Wines & Vines contributor since 2006.

 
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