Have you ever noticed how your mouth feels dry and puckered after eating an unripe banana, too many walnuts, or sipping on red wine? It’s a bit like your mouth is turning into leather! This sensation is caused by something called tannins, which are chemicals found in certain plants.
Tannins are natural compounds that plants produce to protect themselves from being eaten. They have a special ability to bind with proteins. When you eat or drink something with tannins, they latch onto the proteins in your saliva and on the surfaces inside your mouth. This causes the proteins to stick together, creating that dry and rough feeling.
The process of tanning is similar to how leather is made. When animal skin is turned into leather, it’s soaked in water with plant materials that release tannins. These tannins bind to the collagen in the skin, making it resistant to rotting. In your mouth, tannins bind to proteins, temporarily creating a similar effect.
Even though tannins can make our mouths feel dry, many people enjoy the unique taste they bring to foods and drinks. Tannins are found in things like grapes, pomegranates, pecans, chocolate, coffee, and tea. While a little bit of tannin can add a nice flavor, too much can make your mouth feel uncomfortable.
The good news is that the effect of tannins is temporary. Your mouth will eventually produce enough saliva to wash them away. If you want to speed up the process, try drinking tea or coffee with milk. The tannins will bind to the milk’s proteins instead of yours, leaving your mouth feeling smooth. Eating grapes with cheese can have a similar effect.
Understanding tannins can help you appreciate the complex flavors in your favorite foods and drinks. Next time you experience that dry feeling, you’ll know it’s just the tannins at work, and you can enjoy the unique taste they bring.
Gather a variety of foods and drinks that contain tannins, such as red wine (non-alcoholic for school), unripe bananas, walnuts, and tea. Taste each item and note the sensation in your mouth. Discuss with your classmates how the tannins affect the taste and texture of each item.
Conduct a simple experiment to observe how tannins bind to proteins. Use gelatin as a protein source and mix it with tea or coffee. Observe the changes in texture and discuss how this relates to the dry feeling in your mouth when consuming tannin-rich foods.
Pair tannin-rich foods with other foods that can reduce the dry feeling, such as cheese or milk. Create a tasting menu and explain why each pairing works to minimize the tannin effect. Share your findings with the class.
In groups, create a short skit where plants use tannins as a defense mechanism against predators. Each group should explain how tannins protect plants and how this relates to the sensation in your mouth. Perform your skit for the class.
Create an art project that illustrates the process of how tannins bind to proteins in the mouth. Use materials like clay or paper to represent proteins and tannins. Present your artwork and explain the science behind it to your classmates.
You know that feeling you get when you bite into an unripe pear or banana, munch on too many walnuts, or sip red wine, and your mouth gets dry, rough, and puckery? That feeling is your mouth temporarily turning into leather. We make real leather through a long and complex process, with a central step called “tanning,” in which we soak animal skin in water along with plant material. If we took skin off an animal and didn’t tan it, bacteria would release enzymes that break down the skin’s main protein – collagen – into digestible bits, essentially causing it to rot. But when we tan the skin before it can rot, chemicals called tannins leak from the plants and bond to the collagen, blocking the sites the enzymes could cut, and giving us rot-resistant leather.
Plants don’t make tannins for human benefit; they produce them partly to protect themselves from being eaten. This brings us back to your mouth. When a deer or a human eats a leaf, the protein-bonding tannins in those plant parts latch onto the proteins in our saliva and on our tongues and cheeks, causing them to stick together, resulting in that dry, rough feeling. Some animals learn to avoid plants that are particularly astringent, but we humans, who enjoy a variety of flavors, have come to appreciate this feeling—in moderation—so we seek out foods that contain tannins, like grapes, pomegranates, pecans, chocolate, coffee, and tea. However, if we consume too much, our mouths’ proteins can become overly tangled, leading to discomfort.
Fortunately, the bonds between tannins and proteins are temporary, meaning that a “tanned” tongue can be “un-tanned.” Just wait for your mouth to produce enough new saliva to dilute the tannins and wash them away. Alternatively, you can drink your tea and coffee with milk and eat your grapes with cheese—the tannins will bond to the milk’s proteins instead of yours, leaving your mouth smooth.
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Tannins – Natural compounds found in plants that can bind to proteins and other organic compounds, often giving a bitter taste. – Tannins in oak trees help protect them from being eaten by insects.
Proteins – Large molecules made up of amino acids that are essential for the structure, function, and regulation of the body’s cells, tissues, and organs. – Enzymes, which are proteins, speed up chemical reactions in our bodies.
Saliva – A watery fluid secreted by the salivary glands in the mouth that contains enzymes to help digest food. – Saliva begins the process of breaking down food as soon as you start chewing.
Plants – Living organisms that typically produce their own food through photosynthesis and have cell walls made of cellulose. – Plants release oxygen into the air as a byproduct of photosynthesis.
Compounds – Substances formed when two or more chemical elements are chemically bonded together. – Water is a compound made from hydrogen and oxygen.
Flavor – The distinctive taste of a food or drink as perceived by the sense of taste and smell. – The flavor of chocolate comes from a complex mix of compounds.
Grapes – Small, round fruits that grow in clusters on vines and are often used to make wine. – Grapes contain natural sugars and acids that contribute to their sweet and tart flavor.
Coffee – A beverage made from roasted coffee beans, known for its stimulating effects due to caffeine. – Coffee contains various compounds that contribute to its rich aroma and taste.
Tea – A drink made by infusing dried leaves of the tea plant in boiling water, often containing caffeine and antioxidants. – Green tea is known for its high levels of antioxidants, which can be beneficial to health.
Leather – A durable and flexible material created by tanning animal rawhide and skins, often used for clothing and accessories. – The process of making leather involves treating animal hides with tannins to preserve them.
