This past summer, SWLF students Alexander Ka'eokulani and Jaycee Kalama embedded with professional journalists visiting OSU as part of the Food and Agriculture Media Fellowship program. They toured labs where OSU researchers are developing new plant-based technologies to replace plastic packaging, and turning whey into vodka. They watched demos of apple picking robots, and sampled student-made ice cream from our very own food truck. Best of all, our students got to interact with professional journalists, making connections that will enrich their budding writing careers. Below, you’ll find a story from Alexander inspired by his experience that day.
Left: Alexander Ka'eokulani; Right: Jaycee Kalama
Chasing Smoke
by Alexander Ka'eokulani
Deep within the Dundee Hills of Northern Oregon, rolling acres of fresh grapes bask in the graceful warmth of the summer sun. Within the next few months these rich fruits will be processed into delicious wine that will be shipped and sold all over the country. From the top of the hill one can usually spot the impressive visage of Mt. Hood towering in the distance, but today it is shrouded in a smoky haze. For those of us that experienced the wildfires during the fall of 2020, the ominous haze brings memories of smoke and ash in our lungs and a blood red filter choking the sun during our commute to work in late August. As climate change becomes a more pressing issue in the PNW, we can only expect these “once in a generation” events to become a seasonal regularity.
Since as early as last year, Oregon’s new fire season has been found to negatively affect the flavor of various wines produced from local grapes that were exposed to heavy amounts of wildfire smoke. While the phenomenon was originally observed in Australia, wildfire smoke has also affected vineyards in Northern California and local winegrowers in Oregon. Simply titled “Smoke taint,” the resulting harsh taste differs depending on the variety of wine. A breezy Chardonnay may only have a subtle masking flavor that annoyingly prevents a full taste of the vintage, but a Pinot noir will taste like someone had dumped an ashtray into your glass.
In Oregon, wine production and tourism is a booming industry which generates up to an estimated 7.19 billion dollars in economic activity according to WineAmerica. Across the multitude of wineries in our great state, over 23,000 acres are solely devoted to growing Pinot noir. Grapes are especially vulnerable because typically they are only harvested once a year. Which means that if the year’s harvest is found to be tainted, it can be a huge hit to local farms. That’s why wineries are pushing Oregon State researchers to find at least a partial solution to this problem, and we might be closer than we think.
For the last few years, Professor Elizabeth Tomasino, Dr. Cerrato, and PhD Student Jenna Fryer have been trying to identify the exact cause of smoke taint. If we can identify the culprit behind the ashy taste, we can then begin to find specific preventative measures that will benefit the entire industry. Cole Cerrato, an Assistant Professor at Oregon State University, hopes to clear the haze around this insidious issue, and spoke with me personally about his research. Cerrato says that “What is special about [our team here at OSU] is that we do both the wine chemistry, and the wine sensory.” Wine sensory in this context means using a series of double-blind experiments that rely on surveys performed by a human subject’s olfactory senses to gather data. In this case, the experiment entailed a tasting session where the participants in the study were not aware of what wine they were tasting.
But why rely on our merely human senses of taste and smell? As a matter of fact the human olfactory system is extraordinarily sensitive to stimuli and is capable of detecting traces of chemical compounds in the trillionths of a percentage (or ppm). That’s the reason why wine connoisseurs can detect hints of oak or leather and chocolate in certain vintages. They are trained to interpret and recognize the various chemical elements that make up a particular brand of wine. The tricky part is putting a name to the face of the culprit behind the taste. Which comes with its own set of challenges.
Initially, Tomasino and her team only set out to create a scientific standard of an “ashy” taste and potentially find an effective palate cleanser solution that could reduce the amount of time winemakers take between barrels to test their wines for smoke taint. Except that one chance discovery along the way seemingly changed everything.
Like all experiments, the first step is to recreate the circumstances of the phenomena you want to experiment with, which in this case means creating our own smoked wine. To recreate the smoke one would find naturally Cerrato spent most of his pandemic in a greenhouse growing barley which is a significant source of lignin. When burned, this chemical compound forms most of what we perceive as smoke. Lignin is present in tree bark and other similar plant matter. After growing the plants the team then began to smoke some grapes over the course of several days, one group of white grapes and one of red grapes, and then fermented them to create a simple wine. The resulting drinks were then tested among anonymous volunteers who recorded what tastes they perceived from a designated list as well as commenting on how long the flavor lasted in their mouths after the tasting.
Unsurprisingly, smokey and ashy were the top descriptors. In fact across the board all of the wine tasted like a campfire of burned rubber, which meant that the experiment was a smashing success! The standard was now set, and the team could promptly use these wines as a potential future case study to find the culprit. Yet, there was still more to be discovered.
There were already several suspects in the case. A class of compounds known as volatile phenols, which were mostly derived from decomposed lignin, have been used as a chemical marker by industry professionals to test for tainted batches over the last few years. However, due to the differing chemistry between varieties of wine, testing for these compounds was never completely accurate as the chemical makeup of chardonnay is slightly different than that of a Bordeaux. To further complicate the matter, simply adding these volatile phenols into the wine did not produce the smoky flavor that was noted by the test subjects. Which meant there had to be another aspect that wasn’t being considered.
As the quest for the standard continued, Jenna Fryer was conducting independent research and found several studies that used common leeks for their unrelated experiments with ash. Pursuing this avenue of thought, she then promptly spent the weekend burning leeks in her Corvallis apartment, coming back to her superiors with substantial results that suggested that leeks worked even better as an ash standard. Tom Collins, a Professor at Washington State University who was working in collaboration with the OSU team, raised his eyebrow and immediately got to work analyzing the plant. Collins knew from experience that leeks have a ton of sulfur, chemically present as thiols, and wondered if those compounds were present in the smoked wine. He then went back and tested the smoked wine again and found that there was a significant amount of thiols. Further confirmed by Cerrato, This meant that the volatile phenols truly weren’t the sole culprit, they had help. In fact, thiophenols (the resulting compound) were found in every smoked wine the team had created. Turning the investigation on its head.
Upon further testing, the skins of smoked grapes were found to have significant presence of thiophenols, indicating them as the most likely chemical source of smoke-taint. Skins of grapes are extremely porous and may absorb chemical elements from wildfire smoke. This discovery also may help confirm why it affects individual classes of wines differently. Although both varieties are essentially fermented grapes, the process into distilling them into alcohol is subtly different.
In order to make white wine, white grapes are pressed and then immediately dumped into a steel fermentation vat. In order to fully capture the flavor and color of a rich dark vintage however, red grape skins are more heavily involved in the process. First the grapes are crushed and fermented with the skins in the proto-wine, then pressed before finally separating them to prepare for aging. Since there is less contact with the skin of the grape in the stages for creating white wine, it may be the reason that Chardonnay and Pinot Gris are less affected by smoke taint.
These findings are a revolutionary first step into solving smoke-tainted wines. Tomasino and her team are now looking into thiophenols in earnest and all the evidence seems to support it as the leading cause of smoke taint. At this time of writing, the study is currently under review at Proceedings of the National Academy of Science Journal (PNAS). Now that we know the exact compounds most likely responsible, these findings will allow future mitigation strategies to be tailored specifically to offending compounds instead of broad strokes tactics that may end up destroying salvageable vintages, potentially saving millions of dollars worth of tainted wine.
Even though we might still see smoke on the horizon, there is renewed hope for the wine industry to circumvent the difficult challenges brought on by a changing climate. Thanks to the incredible work done by the team here in OSU, the Dundee hills of northern Oregon will continue to produce delicious wine for generations to come.
Elizabeth Tomasino
Photo from OSU Extension Service