HEMA Coffee

二酮哌嗪（DKPs）是咖啡烘焙之後所出現的主要苦味物質。 它的形成是一種環化反應，胺基酸的胺基（-NH₂）與同一鏈上的另一個胺基酸之羧基（-COOH）發生反應，從而形成環狀結構。
此反應在咖啡豆烘焙期間尤為顯著，因為熱能提供了反應所需的能量。
此外，烘焙時發生的梅納反應（胺基酸與糖類之間的化學反應）也參與了DKPs的生成。。

DKPs are known to be bitter compounds, and their presence in roasted coffee contributes to the overall bitterness of the brew. 

DKPs are formed through a cyclization reaction where the amino group of one amino acid in a peptide chain reacts with the carboxyl group of another amino acid within the same chain, forming a ring structure. This process is particularly prominent during the roasting of coffee beans, where heat provides the energy for the reaction to occur. The Maillard reaction, a chemical reaction between amino acids and sugars that occurs during roasting, also plays a role in DKP formation. Precursors to DKPs are peptides and amino acids released from proteins during the fermentation and drying of coffee beans, and these are further transformed during roasting.