The complex array of flavors and aromas present in different varieties of wine come from the many chemicals that are produced within grapes as they ripen or during the subsequent fermentation and aging processes. Many of these molecules create desirable, fruity, smoky, or spicy notes; yet some are simply off-putting.
One of the worst offenders is a compound called 3-Isobutyl-2-methoxypyrazine (IBMP), which introduces a potent green bell pepper odor that can be detected by the human nose at very low concentrations. A longstanding thorn in the side of winemakers, IBMP can occur in all wine types but is present at particularly high levels in those made from Cabernet Sauvignon grapes, especially harvests picked too early or grown in cooler climates.
Currently, the options for removing IBMP’s unpleasant “vegetal” characteristic are quite limited: they either just mask the flavor or suck out good compounds at the same time.
But now, thanks to the wine scientists at the University of Adelaide, Australia, vintners may soon have an effective and delightfully high-tech new method.
As described in the Journal of Agricultural and Food Chemistry, the team led by professor David Jeffrey have developed tiny iron oxide and plastic polymer beads that can absorb the IBMP from a batch of wine, then be easily removed themselves using magnets.
When tested in fermented Cabernet Sauvignon wines with deliberately high levels of IBMP, the novel particles reduced the chemical’s concentration by up to 74 percent, seriously beating the 18 percent reduction observed for the leading commercially available removal material, a polylactic acid (PLA) film.
A group of official sniffers then confirmed that the bead-filtered wine had a lovely aroma, noting that “except for PLA treatments, all the other polymer treated wines were perceived to be much lower in 'green' characters ('capsicum', 'fresh green', and 'herbaceous') compared to the [untreated] control wines and were generally perceived to be fruity.”
According to Jeffrey, the crucial step in creating the composite material, dubbed putative imprinted magnetic polymer, or PIMP (an unfortunate acronym), was engineering a polymer that binds only to IBMP. Once that substance’s formula was perfected, it was transformed into magnetic beads by fusing it, in liquid form, with iron nanoparticles and grinding down the solid block that forms after it cools.
Jeffrey’s team modified the production process and were the first to test it in wine. Based on the success demonstrated here, they suspect PIMPs will soon pave the way toward even more tasty wines in years to come.
"In the making of this polymer you could tune it for other taint compounds or off-aromas," Jeffery said in a statement.
"The idea would be to be very selective for the compounds you're wanting to use and that's been the problem with other treatments, they're quite non-selective."
Before the flavor-absorbing beads can be used commercially, however, it must be proven that their temporary presence in wine does not render it unsafe to drink.