It’s another guest post from Andy Kirk, a MSc (Horticulture) candidate at Lincoln University in New Zealand and alumnus of The Ohio State University! Having grown up in Akron and Canton, he worked under the employ of Arnie Esterer at Markko Vineyard in Conneaut for much of 2011 and 2012. He enjoys New Zealand, but often finds himself relating his viticulture and enology learnings back to the shores of Lake Erie. Many thanks to Andy, and for you, dear readers, enjoy!
The facts are in front of us. As long as the Lake Erie Viticulture Area remains a continental climate with no mountain range to the north and a lake that freezes over, there will always be the risk of unmitigated polar air descending in the winter months. That said, the wine glass is half full, in this humble author’s opinion. While the rest of the world is stuck in the Middle Ages, arguing over whose varietiy is the most “noble”, open-minded regional wine industries like ours could be transforming the world of wine as we know it. The human race has come a long way since the 1300s, when Pinot Noir arrived on the scene. Maybe it’s time for our list of culturally acceptable wine grapes to catch up.
It seems that often the same people who call for the elimination of agricultural chemicals will turn their nose up at the very mention of a hybrid grape? This might actually be an attainable goal with newly emerging varieties! Furthermore, if wine is to express a sense of place, why should developing regions be shackled by a list of ten or so grape varieties, most of whom share a parent? Observationally, the wine market in Northeast Ohio has proven very receptive over the years to unorthodox varieties and blends. Perhaps we can utilize this lack of pretentiousness to build a hybrid wine industry that is unique and sustainable. To do that, it is important to address, head on, some of the challenges that are unique to hybrid winemaking. This article will attempt to discuss some of these issues, through the lens of an emerging variety from the University of Minnesota.
Introduction to Marquette
With some highly necessary reflection out of the way, it is time to acquaint ourselves with a potential new best friend of the Ohio wine industry, Marquette. Every revolution needs a hero and, in our case, that distinction may belong to Elmer Swenson, a Wisconsin dairy farmer who, every spring in his “free time”, developed genetic crosses of local grapevines. To skip ahead a few chapters, his work was eventually noticed and continued by researchers at the University of Minnesota, where it importantly received both publicity and resources. (Marshall 2013) One of their first commercially successful crosses, Frontenac, happened in 1978 and has since become one of the most widely planted wine grapes in the Upper Midwest, Northeast, and Quebec. Several decades after that cross, the research center struck gold again in 1994 with Marquette, which is effectively a grandchild of Pinot Noir with additional Vitis Riparia genetic influence. Marquette became commercially available in 2006, and by many accounts, now represents the gold standard in cold-hardy red wine grapes. Marquette is known to withstand winter lows of -20 degrees farehnheit (-29 celsius) or lower, and has a relatively low level of susceptibility to powdery mildew, downy mildew, bunch rot, and black rot. (Smiley 2008)
Principle Winemaking Challenges & Solutions
If you happen to be new to the world of hybrid red wines, you might as well dust off your puckering face. While there are certainly exceptions, the trend towards high acidity seen in many hybrids is probably the primary obstacle in the way of widespread acceptance. The crux of the issue is that the grapes accumulate sugar faster than they lose said acidity. According to the “Marquette Enology” information provided by the University of Minnesota, Marquette was harvested in their vineyard at average Brix,TA, and pH levels of 25.7°, 12.3 g/l, and 2.9 pH respectively, over three years. These numbers should illustrate the problem pretty clearly. There is an ongoing risk of an end product that is extremely high in alcohol, yet unpleasantly tart. As a reference point here, it is generally accepted that red winegrape TA and pH should fall in the ranges of 6-8 g/l and 3.4.-3.5 pH. (Amerine 1980)
However, not all acids are created equal. For our purposes, Tartaric Acid and Malic Acid are the two primary grape acids of interest. Unlike their pure-bred Vitis Vinifera cousins, Vitis Riparia-based hybrids like Marquette often have more Malic Acid than Tartaric Acid. That said, these inter-specific hybrids have a lot of tartaric acid, too. They just have a lot of acid, really. A recent trial with Marquette in Iowa reported Malic and Tartaric acid levels of between 5-6 g/L and 4-5 g/L, respectively, with Brix levels between 23-24°. (Vos 2014) If those seem more reasonable than the numbers reported from the University of Minnesota research station, it would still be a stretch to call them ideal for winemaking. With that in mind, what are some of the ways in which Ohio growers might try to solve this problem?
The first solution is sort of a “freebee”. The growing conditions at the University of Minnesota, which reported the troublingly imbalanced numbers seen in the first paragraph of this section, are reasonably different to those conditions in Northeast Ohio. We know that the degradation of malic acid through respiration in grapes is largely a function of temperature, although it is a somewhat complex function. (Coombe 1992) From May to September, the average highs and average lows in Cleveland are consistently higher than in Chaska, Minnesota, the nearest town to the university of Minnesota Horticulture Research Center. The difference is particularly noticeable in September, where the average low in Chaska is a whole seven degrees Fahrenheit lower than in Cleveland. The point is that over the crucial ripening months, temperatures in the Lake Erie growing region will generally encourage lower levels of malic acid in the grapes. Perhaps someone has some more direct insight here?
In cool and cold climate viticulture, canopy management is one of the tools available to address the challenges presented by less than ideal conditions. While canopy management is an incredibly broad topic, here we are particularly interested in the practice of pulling leaves and lateral shoots in the fruiting zone, in order to increase sun exposure and raise the temperature of the berries. According to Smart and Robinson, the rate of respiration in the berries doubles for every 10 degrees Celsius increase in temperature. (Smart and Robinson 1991) As noted before, an increased rate of respiration corresponds to more degradation of malic acid. This relationship has been widely observed with Vitis Vinifera (Jackson and Lombard 1993, Kliewer et al. 1967, Reynolds et al. 1986), but the jury is still out with regards to its effectiveness on Marquette malic acid levels. A recent study from Iowa State University has found shoot thinning to be an effective means of reducing malic acid in Marquette, albeit at the cost of some amount of yield. (Rolfes 2014) As it stands now though, there does not appear to be any information available regarding the effectiveness of leaf pulling, by itself, in reducing malic acid in Marquette. That said, the principle behind the practice is sound and well-proven in other varieties.
With the weather being the weather, we must look at other ways to address the problem of acidity in Marquette. Again, here, the relatively high concentration of malic acid is critically important. If you are reading this you probably do not need to be told that Malolactic fermentation is the conversion of malic acid to the weaker lactic acid, by malolactic bacteria. (Davis et al. 1985) The fact that we are working with high malic acid and not tartaric acid means that there is some potential to alleviate our acid problem with malolactic fermentation. Anecdotally, some producers are having to use reasonably high-performance bacteria strains to start things off, given the sometimes low pH and high alcohol. While this seems to be a great option to reduce malic acid, it’s worth considering the unintended consequences. Potential bi-products of malolactic fermentation include acetaldehyde, acetic acid, ethanol, diacetyl, and acetoin. Particularly concerning here is Diacetyl, which can lead to a buttered popcorn smell at concentrations between 5-7 mg/L. (Davis et al. 1985) Still, I think I would prefer buttered popcorn to eating an extremely under-ripe apple.
(Note: Chemical deacidification is highly relevant here, but definitely a topic for a different week. For more information, here is a link to a pdf from Domenic Carisetti, via Iowa State University.)
The other major stumbling block on the road to hybrid wine acceptance is the unusual phenolic profile. In laymen’s terms, this phenolic profile is responsible for both the unusual color and the relative lack of astringency, bitterness, and palate weight in hybrid wines. A recent study from Cornell University confirmed that vinifera based wines have on average at least 4 times more tannin than hybrid-based wines. (Springer and Sacks 2014) With regards to the unusual color, many hybrid varieties are capable of producing high anthocyanin concentrations, perhaps as a result of their “wild” pedigree. (Liang et al. 2008, Thimothe et al. 2007) Furthermore, hybrid varieties are noted for high concentrations, as well as unusual configurations, of anthocyanin types not typically seen in vinifera varieties. (Burns et al. 2002, Manns et al. 2013) The end result of this complex equation is a tendency towards blue and purple hues, rather than the brick red that is typical of many vinifera wines. (Manns et al. 2013) In the interest of sanity, we will leave color alone, and focus on the extraction of tannin and other phenolic compounds responsible for mouthfeel.
This brings us to a fascinating winemaking conundrum. Although hybrid wines have been generally proven to have less tannin than vinifera counterparts, similar concentrations have been reported in the skins and seeds of the various species. (Harbertson et al. 2008, Sun et al. 2011a, Sun et al. 2011b) New research suggests that this is due to binding reactions between hybrid tannin and cell wall proteins, which could potentially limit the amount of extractible tannin in the grapes. To split these bonds and combat this phenomenon, the authors suggest the addition of proteases and pectinases during maceration. It is worth stressing that this is a very new research area that has not fully been explored. (Springer and Sacks 2014)
That said, there is some information about which winemaking techniques result in more extraction of tannin in Marquette and other hybrids. Interestingly, in a Cornell University trial, Pectinase addition did not have a significant impact on tannin extraction in the must. Nor did cold soak. In fact, “Hot Press” (at 65 degrees Celsius) was the treatment that had the greatest effect on tannin extraction in musts. Even these gains were short lived though, as the tannin level in the finished wines showed little improvement over the control. This suggests that the retention of tannins is more a product of fermentation conditions, rather than the initial level of tannin extraction in the must. (Manns et al. 2013)
On that note, one thing we know for sure is that the degree of polymerization in wine phenols has a huge impact on the sensory characteristics of a wine, as well as the potential for color stability. (Kennedy et al. 2006) Across the board, in the above referenced Cornell study, the hybrid varieties demonstrated a relatively low propensity to polymerize. (Manns et al. 2013) Those authors reported a mean degree of polymerization (mDP) of 3.22 for Marquette, which would stack up similarly to reported values for (surprise) Pinot Noir (del Rio and Kennedy 2006), but would be roughly a fourth of those reported for a tannic wine like Tempranillo (Monagas et al. 2003). As a quick reminder, a low degree of polymerization would suggest less astringent, but potentially bitter tannin. (Peleg et al. 1998)
To sum it all up, we need to pull out all the winemaking tricks in order to make a Marquette wine with adequate tannin levels and composition. Conceptually, it might pay to break this down into three steps that would require our undivided attention:
- Maximize the level of tannin extraction in the must (enzymes, thermovinification, saignée, must freezing)
- Create fermentation conditions that favor the retention of phenols (temperature, extended skin contact, pump-overs, punch downs)
- Encourage the formation of tannin polymers (tannin additions, barrel aging, oak additions, micro-oxygenation, adequate initial levels of monomeric flavonoids and anthocyanin)
(Without a doubt, each one of these steps deserves an article in its own right. Check out “A Review of the Effect of Winemaking Techniques on Phenolic Extraction in Red Wines” by Sacchi et Al. (2006) for a good place to start)
A Few Parting Words
As you can see, the challenges in red hybrid winemaking are very real. Somehow, though, it feels like the good fight. While Marquette is just one of many varieties available, it shows a lot of promise. After many hours of research, there seems to be a general sense among Marquette winemakers that, at the very least, it gives you something manageable and rewarding to work with in the winery. Will it ever receive a 96 from Wine Spectator like its hybrid cousin (fascinating….they appear to have removed the rating!), Landot Noir? Maybe not. However, from a viticulture standpoint, it is a rock star, showing outstanding cold tolerance and disease resistance. If perhaps Marquette is not the “chosen one” to lead hybrid winemaking to the Promised Land, it is certainly a step in the right direction.