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Often tannin is linked to wines, and actually there is a link between this product and the substance we want to talk about, but there is much more to say about tannin, to know and to deepen. Moreover, we do not find it only in red wines but also in the fruits of persimmon, in the rowan, in the medlar and in the dogwood, quince. If you want to get tannin in nature, you will find it in abundance in the bark of plants such as oak, chestnut, fir, acacia but not only. This substance is not only at the table or in the woods, we also find it in the workshop of many painters who, at the time, feared it because, emanating from already seasoned supports, could darken some parts of the painting and ruin it in one stroke, definitely.
The term is used to define a chemical substance used for the first time in 1796 and present in plant extracts. It has the ability to combine with the proteins of animal skin to form insoluble complexes and, in this form, it comes to prevent the putrefaction that enzymes can induce, and transform it into leather.
They have therefore been known for some time the tanning properties of tannin for animal skins: it reacts with collagen and other proteins and the product thus treated is no longer putrescible. For similar mechanisms we find it also used, and for centuries, in the treatment of fabrics, in the dyeing and printing phase, or when preparing lacquers and inks. In the kitchen it is not only feared or avoided, on the contrary, it reveals itself very useful for procedures such as clarification of wine and beer, but for those who are teetotal, it also applies to fruit juices.
If tannin is synthesized, a group of products is obtained that show characteristics similar to those just described and to those shown by the natural tannins of vegetable origin. There is no chemical analogy between natural tannins and tannins obtained by chemical synthesis, yet this is what happens. A pack of this can also be purchased online substance, of tannic acid soluble in alcohol and water: 10 grams on Amazon cost 5 euros, it is brownish powder (min. Tannic acid title: 98.4%).
Tannin: what it is
We often speak of tannins in the plural because it is a class of compounds that we can find in nature in a series of plants that are apparently very different from each other but which have tannic acid in common. It appears soluble in water, ha an astringent flavor and is capable of precipitating the salts of heavy metals, alkaloids and proteins.
Tannin in the wood
Tannin is in the wood, in the bark, of some plants, as we will see, but it is also used to improve its conservation, especially when we are in a humid environment such as when wood is used in the naval sector. There presence of tannins prevents or slows down the degeneration of this material.
We find tannins in woods, barks, fruits and rhizomes, roots, a bit everywhere, in short. It can be extracted from gallnuts, for example, with various procedures based on the use of water, alcohol or ether.
These polyphenolic compounds are present in large quantities in European chestnut and in many other vascular plants. The chestnut, however, is definitely the one that contains the most, as a plant: about 7-9% of the total of its tissues are tannins. The chestnut is a majestic tree, it can even reach 30 meters in height and live for centuries and centuries, it shows a silvery-gray and smooth stem that fills with cracks with age, its leaves are large, lanceolate and serrated, the flowers are yellowish and pendulous, its chestnuts are notoriously protected by a hedgehog.
Angiosperm plants contain tannins, and also herbaceous like many Rosaceae. One of all, to be mentioned, is the eupatoria Agrimonia. This plant grows in shady and cool areas and produces yellow flowers collected in spikes, it is known for its high tannin content.
Let's go back to wine. This is perhaps the context in which most of us have heard of tannins. Present in reds, they have the ability to precipitate some saliva proteins and this is what then gives the typical feeling of astringency.
Their effect is not finished: when combined with food proteins, the compounds form complexes resistant to gastrointestinal proteases and inhibit digestive processes. Here's whyafter drinking red wine, it may happen that you no longer have an appetite. Another "symptom" of tannins is the alteration of the perception of taste, often in a negative way; food takes on an unpleasant taste. Internally, tannic acid can inhibit the absorption of iron and zinc and also of some vitamins. While sipping wine, the term Polyphenols will also come to mind, find out more in the dedicated article: Polyphenols: what they are and where they are found
Whether administered topically or orally, i tannins have an antibacterial and antifungal effect, orally also antidiarrheal, purely topically also vasoconstrictor. We find these substances, therefore, applied on small wounds and burns, or used in the treatment of dermatitis. In creams and products for the skin, they are used to limit sebaceous hypersecretion and against acne as well as against dandruff.
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