Methyl Anthranilate Exposes Differences in Expert and Consumer Likeability
A recent study conducted at jointly at Penn State University and the University of California Davis illustrates significant differences in what consumers and self-described wine experts find likeable in wine.
The wines in question were six pairs of unoaked Chardonnay that had been doctored with increasing amounts of the compound – methyl anthranilate (MA) – that gives some native American vitis labruscana grape varieties their “grapey-ness.”
Grapey is the labruscana winegrowers preferred synonym for the more common descriptor “foxy” that is used to characterize the distinct, often pungent aromas associated with certain varieties most notably the Concord grape. In contrast, the descriptor “grapey” is also used when describing the characteristics of vitis vinifera varieties like Riesling and Torrontes and, as such, it isn’t always viewed negatively by experts or consumers.
According to researcher and Ph.D. student Demetra “Demi” Perry, “We didn’t record if the experts could identify MA. The study is meant to address reasons for the [low market value] of labruscana grapes reflected in price per ton.”
It hypothesized that wines with high concentrations of methyl anthranilate would be largely rejected by wine experts in California who view the compound which is inherent to vitis labruscana and found only in those varieties as a fault. Consumers from California and Pennsylvania which has 30,000 acres of Concord under vine and self-described wine experts from California were asked to rate their preferences against a control wine.
As anticipated, the California-based experts were far more likely to reject the MA-spiked wines. Their rejection threshold (130.3 ng/l) was significantly lower than that of non-experts (1704.9 ng/l). But contrary to the belief that experts disdain labruscana characteristics, neither group wholly rejected the samples that had the highest level of methyl anthranilate. The study also tested 2-aminoacetophenone (2AAP) but the compound wasn’t rejected by subjects at any intensity.
When consumer subjects were further divided in to low and high-interest groups, no wine was “too grapey” for the low-interest consumers. Acceptance of grapey aromas in wine by consumers in Pennsylvania where Concord jams, jellies and grape juice are commonplace can be attributed to the propensity to like the familiar, a phenomenon known as mere exposure. The more familiar you are with a pleasant odor, the more likely you will rate it as pleasant.
Interestingly enough, not all wines described as “grapey or foxy” exhibit high levels of this compound. MA may be an important aroma constituent in some native varieties but their characteristic grapey flavor isn’t solely attributed to its presence. As an isolated compound MA which is also found in gardenias and jasmine is described as fruity, grape-like, orange blossom and musty with a floral, powdery nuance.
The perfume industry deconstructs its aroma precisely in percentages of odorants: fruity (37%), citrus (25%), narcotic (22%) which is a heady, intoxicating floral note, linalool (9%), muguet (3%) Lily of the Valley, aliphatic (1%) fatty notes, and vanilla (1%). Highly pungent oxidized aliphatic notes are also found in fox musk but that association has more to do with ripe grapes being an attractive meal for a fox than smelling like one.
Non-vinifera wines also have higher concentrations of compounds with vegetative and earthy aromas: eugenol (clove), cis-3-hexenol (fresh cut grass, leafy), 1,8-cineole (eucalyptus), and the pyrazines 3-isobutyl-2-methoxypyrazine (IBMP), and 3-isopropyl-2-methoxypyrazine (IPMP). Concentrations of IBMP and IPMP in non-vinifera wines have been measured well above concentrations reported in physiologically-ripe vinifera grapes. The result is seemingly an entourage effect that creates labruscana’s distinct aromatic signature.
If, as the Penn State study hypothesizes, MA is universally viewed by experts as an indicator of lower quality wine and a fault, it’s surprising that the experts in this study failed to reach a complete rejection threshold. While that question wasn’t explored, it’s easy to surmise that even at the highest concentrations tested experts are aware MA is an inherent varietal characteristic and, unless it detracts noticeably from wine quality, its presence wouldn’t constitute a fault.
Perry is also working on another study with Dr. Gavin Sacks involving de odorizing Concord grape juice in an effort to make it more commercially viable. Their goal is to remove grape-derived odorants, such as MA, while retaining the important base chemistry (e.g., pH, titratable acidity, soluble solids) of the juice and without sacrificing color. “There are similar processing technologies currently utilized in the wine industry for remediation of wine flaws, but most are targeted at processing wine whereas we have taken a step back and decided to target the juice instead,” she said.