Describe the Ehrlich pathway and its importance in the formation of fusel alcohols.

The Ehrlich pathway is a metabolic route used by yeast to produce fusel alcohols from amino acids. Fusel alcohols are higher alcohols (alcohols with more than two carbon atoms) that contribute to the flavor profile of fermented beverages. While small amounts can add complexity, excessive amounts can lead to harsh, solvent-like, or burning flavors, often described as 'hot'. The Ehrlich pathway is activated when yeast catabolizes (breaks down) amino acids present in the wort or must. This catabolism typically occurs when readily available sugars, like glucose, are depleted or limited, forcing the yeast to seek alternative energy sources. The pathway i....