Rhus coriaria in the context of Za'atar

Tannic acid is a specific form of tannin, a type of polyphenol. Its weak acidity (pK_a around 6) is due to the numerous phenol groups in the structure. The chemical formula for commercial tannic acid is often given as C₇₆H₅₂O₄₆, which corresponds with decagalloyl glucose, but in fact it is a mixture of polygalloyl glucoses or polygalloyl quinic acid esters with the number of galloyl moieties per molecule ranging from 2 up to 12 depending on the plant source used to extract the tannic acid. Commercial tannic acid is usually extracted from any of the following plant parts: Tara pods (Caesalpinia spinosa), gallnuts from Rhus semialata or Quercus infectoria or Sicilian sumac leaves (Rhus coriaria).

According to the definitions provided in external references such as international pharmacopoeia, Food Chemicals Codex and FAO-WHO tannic acid monograph only tannins obtained from the above-mentioned plants can be considered as tannic acid. Sometimes extracts from chestnut or oak wood are also described as tannic acid but this is an incorrect use of the term. It is a yellow to light brown amorphous powder.

Sumac or sumach (/ˈsuːmæk, ˈʃuː-/ S(H)OO-mak, UK also /ˈsjuː-/)—not to be confused with poison sumac—is any of the roughly 35 species of flowering plants in the genus Rhus (and related genera) of the cashew and mango tree family, Anacardiaceae. However, it is Rhus coriaria that is most commonly used for culinary purposes. Sumac is prized as a spice—especially in Iranian cuisine, and other Eastern cuisines—and used as a dye and holistic remedy. The plants grow in subtropical and temperate regions, on nearly every continent except Antarctica and South America.Native to Persia, it holds cultural significance as a symbolic item on the Haft-sin table during Nowruz, the Persian New Year.