Glycosides: The Hidden Flavors

One of the aspects of beer flavor that has interested me the most are what are called “glycosides”. The reason they are so interesting to me is because it seems they add a whole new level of complexity to hop flavors beyond the traditionally accepted sources such as hydrocarbons, oxygenated compounds, and sulfur-containing compounds. Glycosides are compounds which contain two parts: a sugar component which is in its cyclic (ring) form, and another component attached to the sugar at the number 1 (or “glycosidic” carbon). Some of these companion molecules can also be sugars, so sucrose, being a 2-sugar molecule (disaccharide) made of one glucose unit and one fructose unit attached through the appropriate carbon, is an example of one of these types of glycosides. The glycosides which appear to influence beer flavor are found in hops and have aromatic compounds bonded to the carbohydrates. In their combined state, the glycosides have no flavor; no sweetness and no aroma. However, once this glycosidic bond is broken the aromatic compound is free to volatilize into the headspace of the beer and ultimately into your nose.