Often shortened to 4VG, 4-vinyl-guaiacol is one of the most important flavor and aroma chemicals in the alcoholic-beverage world.
This compound belongs to a large class of chemicals known as phenols, which are defined by having one or more hydroxyl groups attached to an aromatic ring. While many kinds of phenols occur in beverages, only a relative few are sensory-active. Besides 4VG, other flavor-active phenols include guaiacol, phenol, vanillin, acetovanillone, eugenol, 4-vinyl-syringol, and 4-vinyl-phenol (4VP).
The presence of 4VG is common in many foods as well as perfumes. Many describe it as having a strong clove or spicy smell, while others describe it as smelling of carnations or apples. Part of what makes 4VG important is its extremely low flavor threshold—in the parts per billion (ppb) range, with some picking it up at concentrations as low as 4 ppb.
That low threshold makes controlling the level of 4VG in a finished product extremely important.