Stopping Bell Pepper Flavors Through Viticulture

In the past, the wet, cold, growing season of 2008 would have worried Larry Perrine, CEO of Channing Daughters winery. Northern Long Island is already a difficult place to grow wine grapes, and the cool, moist weather of that year seemed to assure that herbaceous, green bell pepper flavors would appear in (and for some, ruin) his red wines. Vintners can leave the grapes on the vine longer to develop more ripe fruit flavors, but they can end up with reduced crop size and weight (and reduced profit), plus they risk losing crop to rains, early frost and other factors.

But with his 2008 wines about to hit the shelves, Perrine isn’t worried at all. Armed with new research from Cornell University’s Gavin Sacks, Perrine didn’t need to put his crop at greater risk to get the flavors he wanted in his wines. Over the last three years, Sacks and his colleagues at Cornell’s enology and viticulture program conducted the most exhaustive study to date of methoxypyrazine (MP), the chemical that causes green bell pepper flavors. They discovered that performing leaf removal as early as possible allows vineyard owners like Perrine to control MP more precisely than ever before, saving both the profit and the taste of the wine.

"Everybody that grows red wine grapes in marginal climates is concerned with MPs,” said Perrine. “We learned from this work that the timing of the leaf removal is everything. We just didn't realize how much impact being really early had."

For grapegrowers and winemakers, especially those in colder, wetter climates, MP poses a significant economic problem. MP costs growers through expensive countermeasures such as increased hang time or complex irrigation schemes, and it costs wine producers when vintages with green bell pepper flavors receive a poor reaction from critics and lower sales. In fact, many Cabernet Sauvignon vintages from Central California were so heavy with MP that wine industry professionals derisively nicknamed them the “Monterey veggies.”

Sacks hoped to help wine producers reduce the levels of MP exclusively through viticulture, as previously developed methods removed both good and bad wine flavors.

“The chemical methods for removing methoxypyrazine strip out everything, and you're basically left with dilute vodka," said Sacks.

To begin with, Sacks tested the MP levels of grapes from fruit set to harvest. He found that MP begins to appear at fruit set, peaks right before the fruit changes color, and then decreases as the grape matures. He also found that hang time doesn’t actually reduce the level of MP, but instead allows the grape to develop flavors that mask the green bell pepper taste.

Intrigued by the fact that hang time doesn’t actually reduce MP levels, the Cornell researchers began a botanic epidemiological study of red wine grapes in upstate New York to discover what variables actually did cut MP concentration. Using similar techniques as the previous study, Sacks and his team surveyed MP levels across grapes in a wide variety of light, temperature and moisture conditions. The study showed that exposure to light and vine growth correlated more closely with green bell pepper flavor than any other variables.

Thus, by removing leaves from around the grapes as soon after fruit set as possible, growers can both expose the fruit to light and limit the growth of the plant before MP begins to accumulate in the grape. Like many other growers and wine producers, Larry Perrine changed his leaf removal schedule as soon as he heard about the outcome of Sacks’ work.

As far as Perrine is concerned, the taste of the wines is enough data to prove Sacks’ conclusions correct. Said Perrine, "I just tasted some of the ’08s, and despite ’08 being a challenging year, those wines are right."