Polymer strips off-taste from wine

Ahh, the taste of garden-fresh veggies. Perfect for a summertime salad. For wine, not so perfect. That’s the taste sometimes imparted to wine by methoxypyrazines (MPs), a group of compounds typically found in grapes and wine at low nanogram-per-liter levels. Grapes grown in cool climates and those harvested early may contain higher concentrations of these compounds, causing an off-flavor. For example, 3-isobutyl-2-methoxypyrazine (IBMP) adds a green pepper note, and the isopropyl analog (IPMP) smells like asparagus. Wine makers can remove those compounds with heat treatments and activated charcoal. But those methods can also remove flavorful compounds. Some vintners recently began filtering with polylactic acid (PLA) because it scavenges MPs without altering wine’s flavor. Now, there’s a more efficient methoxypyrazine scavenger: magnetic polymers (J. Agric. Food Chem. 2018, DOI: 10.1021/acs.jafc.8b01397). Chen Liang, David W. Jeffery, and coworkers at the University of Adelaide prepared an MP-templated methacrylic acid polymer and treated it with magnetic iron oxide particles. Magnets easily separated the powdered form of the polymer from wine. Chromatography analyses and olfactory tests on cabernet sauvignon samples showed that the magnetic polymer outperformed PLA without altering the aroma. For example, it removed up to 74% of the IBMP compared with 18% for PLA.