| Abstract
| - Diketopiperazines (DKPs) corresponding to cyclic dipeptides have beendetected in a variety ofnatural products as well as in processed foods, beverages, and food andbeverage ingredients. Aseries of seven proline-based diketopiperazines, namely,cyclo(Ala-Pro), cyclo(Val-Pro), cyclo(Ile-Pro), cyclo(Leu-Pro), cyclo(Met-Pro), cyclo(Phe-Pro), andcyclo(Pro-Pro), has now been identified inbeer. A marketplace cross-section of five commercial beers wasstudied, involving productsmanufactured in different countries using distinctly different rawmaterials and brewing styles;maximum concentrations of individual diketopiperazines in various beersranged from belowdetection limit to approximately 24 ppm. The flavorcharacteristics of these compounds weredescribed variously as bitter, mouth coating, drying, astringent,salty, metallic, and grainy whenevaluated in water at concentrations ranging from 10 to 50 ppm.However, it is questionable whetheror not the diketopiperazines reported here make a significantcontribution to either the aroma ortaste of most beers. Keywords: Amino acid; beer; diketopiperazine; gas chromatography−massspectrometry; flavor;proline; volatile component
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