Chemical Characterization of Diketopiperazines in Beer

• Published in: Journal of agricultural and food chemistry Vol. 45; no. 8; pp. 3183 - 3189
• Main Authors: Gautschi, Markus, Schmid, Joachim P, Peppard, Terry L, Ryan, Thomas P, Tuorto, Raymond M, Yang, Xiaogen
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 18.08.1997
• Subjects: Beers; Biological and medical sciences; Fermented food industries; Food industries; Fundamental and applied biological sciences. Psychology; Volatile compound; Alcoholic beverage; Angular nitrogen heterocycle; Organoleptic properties; Lactam; Bicyclic compound; Sensory analysis; Flavor; Beer
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf9700992

Diketopiperazines (DKPs) corresponding to cyclic dipeptides have been detected in a variety of natural products as well as in processed foods, beverages, and food and beverage ingredients. A series of seven proline-based diketopiperazines, namely, cyclo(Ala-Pro), cyclo(Val-Pro), cyclo(Ile-Pro), cyclo(Leu-Pro), cyclo(Met-Pro), cyclo(Phe-Pro), and cyclo(Pro-Pro), has now been identified in beer. A marketplace cross-section of five commercial beers was studied, involving products manufactured in different countries using distinctly different raw materials and brewing styles; maximum concentrations of individual diketopiperazines in various beers ranged from below detection limit to approximately 24 ppm. The flavor characteristics of these compounds were described variously as bitter, mouth coating, drying, astringent, salty, metallic, and grainy when evaluated in water at concentrations ranging from 10 to 50 ppm. However, it is questionable whether or not the diketopiperazines reported here make a significant contribution to either the aroma or taste of most beers. Keywords: Amino acid; beer; diketopiperazine; gas chromatography−mass spectrometry; flavor; proline; volatile component