Researchers at Penn State University in the US have developed a method to accurately identify and analyze procyanidins, which are plant-based compounds found in foods and drinks such as red wine, cider, and dark chocolate. 

Procyanidins contribute to taste and mouthfeel, including properties like perceived astringency and bitterness. Food scientists have been able to assess the total number of procyanidins in F&B but have not yet identified which specific procyanidins are present and correlate to specific perceptions.

The study, published in the Journal of Agricultural and Food Chemistry, describes an advanced analytical chemistry method the researchers have named Condensed Tannin Fragmentation Fingerprinting.

It is a technique based on in-source fragmentation. First, compounds are separated in the sample. Then, different voltages are applied to crack the procyanidins into fragments that the researchers can match to known standards, enabling them to identify and value each type of procyanidin.

“Drinking red wine, sometimes that tannic element is really harsh, like dragging sandpaper across your tongue, and sometimes it is velvety or smooth — and yet those two wines can have the same absolute amount of procyanidins,” explains Dr. Misha Kwasniewski, senior author and associate research professor of fermented beverage science and technology at the university’s College of Agricultural Sciences.

Kwasniewski notes that current analytical tools only measure the total tannin content of a food or beverage without distinguishing it. This limitation makes it difficult to link procyanidin composition with specific sensory outcomes or health-related benefits.

“We wanted to understand the biological activity of taste and mouthfeel, but this goes beyond taste and mouthfeel because procyanidins also are responsible for antioxidant activity and health-related benefits, and current analytical methods often show a lack of correlation with biological activities and health-related benefits.”

The researchers tested their technique on 19 samples containing known quantities of condensed tannins. The method showed accuracy and precision in characterizing the tannins present. It was then applied to various commercially available ciders.

The results confirmed the technique’s applicability across complex beverage samples.

Improving wine profiles

Kwasniewski’s research group is now collaborating with winemakers in Pennsylvania. Cooler growing conditions can result in wines that do not have the same “big” mouthfeel as those produced in warmer regions.

“We want to learn how winemakers here — whether it be through new breeding programs and new grape varieties, or wine-making techniques or any number of interventions — can make the type of wines that they want to make, and sometimes that will be wines that have greater amounts of astringency,” says Kwasniewski.

“The current methods available for understanding what was going on with the tannin structure don’t work with Pennsylvania wines.”

The study was funded by the US Department of Agriculture’s National Institute of Food and Agriculture, along with support from the Crouch Endowment for Viticulture, Enology, and Pomology Research in the College of Agricultural Sciences.