gallic acid is a type of phenol and antioxidant created when water-soluble ellagic tannins break down into glucose and either gallic acid or ellagic acid. Both gallic and ellagic acids give woody aromas and flavors to barrel-aged spirits, though gallic acid is more abundant in uncharred woods. Its presence in a spirit is in fact one of the prime guarantors that that spirit has been aged the traditional way, by leaving it in an oak barrel for a number of years.
Gallic acid’s name reflects the traditional use of oak “galls”—abnormal, tumor-like growths on oak trees caused by the larvae of parasitic wasps—for the easy collection of tannic acid.
See also ellagic acid; ellagic tannins; and phenols.
“Gallic Acid.” American Chemical Society. https://www.acs.org/content/acs/en/molecule-of-the-week/archive/g/gallic-acid.html (accessed April 21, 2021).
Lee, K. Y. Monica, Alistair Paterson, John R. Piggott, and Graeme D. Richardson. “Origins of Flavour in Whiskies and a Revised Flavour Wheel: A Review.” Journal of The Institute of Brewing 107, no. 5 (2001): 287–313.
By: Doug Frost