Molecularly imprinted polymers help eliminate smoke-tainted wine odor

Wildfires can damage crops even if the flames don’t get close to the plants. One result can be an unpleasant taste and odor in wine made from grapes exposed to smoke. But researchers report in the Journal of agricultural and food chemistry that they developed a way to reduce this smoky odor to improve the palatability of the wine.

Volatile compounds are responsible for many of the aromas and flavors of foods and beverages, including wine. These compounds come from the grapes themselves, as well as from the fermentation and aging processes. But not all volatile compounds in wine are desirable: Some, produced by bacteria or yeast, smell like nail polish remover, rotten eggs, burnt rubber, or onions. If grapes absorb volatile compounds from wildfires, the resulting wine can take on an unpleasant smoky, ash-like, or medicinal character that compromises quality and reduces value.

Producers use a variety of adsorbents to remove these unpleasant compounds from wine. However, these techniques can also remove desirable constituents that contribute to the color, bouquet, and flavor of the beverage. So Kerry Wilkinson and his colleagues decided to determine whether the volatile compounds responsible for smoke taint could be selectively removed using molecularly imprinted polymers (MIPs).

MIPs are synthetic materials that can bind to one or more target compounds. The researchers hoped to use these polymers to extract the smoky substances from wine, while retaining the flavorful and visually appealing components.

The team added MIPS beads, either contained in muslin or mesh bags or floating freely in the liquid, and then used chemical analysis, as well as taste panels of experts, members of the public, students and staff, to evaluate the results. In some cases, the MIPS were regenerated by rinsing them after extraction to remove smoke compounds, allowing them to be reused.

In terms of improving the sensory characteristics of wines and removing unpleasant volatile phenols, the researchers found that adding MIPs to wine after fermentation was more effective than adding MIPs during fermentation. Additionally, regenerating MIPs generally improved the removal of volatile smoke compounds. While MIPs also adsorbed some desirable compounds associated with the aroma, flavor, and color of red wine, the researchers say the project showed that the method can be used successfully to reduce the perception of smoke flavor.