Pucker Up

Biting into a tart green apple is a different taste and sensory experience than sucking juice from a lemon—and both significantly vary from sipping spoiled milk. Each of these foods contains a different organic acid that gives rise to the flavor commonly referred to as “sour,” even though the taste and related mouthfeel sensations, such as puckering and drying, vary drastically from food to food and person to person.

Penn State researchers have found that while some of that difference comes from individual perceptions, the acids themselves vary in sourness, even at the same concentrations.

Their findings, published in Food Quality and Preference, build on the team’s 2024 study, which found that roughly one in eight adults likes intensely sour sensations and exceptionally sour foods. The more recent study dives deeper into why different acids taste differently sour, why people disagree on how sour things taste, and why some people love sour foods while others do not.

“Beyond just being interesting, these findings might help guide the food industry in making formulations for sour foods because these different acids have subtle taste and mouthfeel nuances to them,” said study senior author Helene Hopfer, associate professor of food science in the college.

 Participants tasted water solutions containing equal amounts of five acids: lactic, found in sauerkraut, pickles, and milk; malic, found in Granny Smith apples; fumaric, found in papayas, pears, and plums; tartaric, found abundantly in grapes; and citric, found in citrus fruits and juice. Participants rated sourness, puckering, drying, and overall liking. 

—Jeff Mulhollem