 Lignin, a highly complex arrangement of interlocked phenolic molecules, also produces a number of distinctive aromatic elements when burnt, including smoky, spicy, and pungent compounds such as guaiacol, phenol, and syringol, and sweeter scents such as the vanilla-scented vanillin and clove-like isoeugenol.Guaiacol is the phenolic compound most responsible for the "smoky" taste, while syringol is the primary contributor to smoky aroma.Wood also contains small quantities of proteins, which contribute roasted flavors.