Grapes undergo a remarkable transformation as they change from vine to wine, as naturally-occurring substances contribute to the distinctive flavors and aromas. But sometimes the results of this remarkable transformation are somewhat less than remarkable, taste-wise. Never fear, wine lovers: Scientists have just reported a new method for removing off-tasting substances that makes use of tiny magnetic particles. The technique was developed for cabernet sauvignon, but eventually it could help remove unwanted flavors from other wine types, as well.
A team at the University of Adelaide in South Australia considered the problem of alkyl-methoxypyrazines, also known as MPs, naturally-occurring substances that produce vegetable-like aromas in certain varietal wines such as cabernet sauvignon. In excessive amounts, MPs can overwhelm the fruity or floral bouquet that connoisseurs have come to expect; the phenomenon is common among grapes harvested early, or grapes grown in cool climates.
Vintners have tried, unsuccessfully, to remediate this problem through the use of additives such as activated charcoal and deodorized oak chips. Breaking down and heat-treating grapes prior to fermentation has shown promise, but it can also introduce undesirable cooked aromas to the finished wines. Another option is to employ plastic polymers, widely used in food packaging and known for their “scalping” effects on food flavors.
But the most successful strategy so far has come from a more high-tech solution: magnetic nanoparticles attached to polymers isolate and sop up those MPs, making them easy to remove without altering the wine’s desired bouquet.
At least, that was the verdict of a group of taste testers who tried a cabernet sauvignon that had gone through the process. Researchers led by the university’s David Jeffrey first spiked it with a particular type of MP that produces a strong green bell pepper aroma, before using the magnetic nanoparticles to restore its distinct aroma intensity.
The research appears in the American Chemical Society Journal of Agricultural and Food Chemistry.