title: Prediction of the ageing of commercial lager beer during storage based on the degradation of iso-α-acids.
abstract: BACKGROUND
  Iso-α-acids and their chemically modified variants are responsible for the bitterness of beer and play a disproportionately large role in the final quality of beer. The current study was undertaken to predict the degradation of commercial lager beers related to changes in the concentration of trans-iso-α-acids during storage by using high-pressure liquid chromatography.
  
  
  RESULTS
  In the analysed beers the concentration of isohumulone (average concentration 28 mg L(-1)) was greater than that of isocohumulone (20 mg L(-1)) and isoadhumulone (10 mg L(-1)). The kinetic parameters, activation energy and rate constant, of the trans-iso-α-acids were calculated. In the case of dark beers, the activation energy for the degradation of trans-isocohumulones was found to be higher than for trans-isohumulones and trans-isoadhumulones, whereas in pale and alcohol-free beers activation energies for the degradation of the three trans isomers were similar.
  
  
  CONCLUSIONS
  The loss of iso-α-acids can be calculated using the activation energy of the degradation of trans-iso-α-acids and the temperature profile of the accelerated ageing. The results obtained in the investigation can be used in the beer industry to predict the alteration of the bitterness of beer during storage.
authors.affiliation: Dpto. Ingeniería Agrícola y Forestal (Tecnología de los Alimentos), E.T.S. Ingenierías Agrarias, 34004, Palencia, Universidad de Valladolid, Spain.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Blanco
authors.forename: Dieudonné
authors.initials: D
authors.lastname: Nimubona
authors.forename: Isabel
authors.initials: I
authors.lastname: Caballero
mesh_terms: D000143:Acids / Q000737:chemistry*; D001515:Beer / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D003517:Cyclopentanes / Q000737:chemistry*; D004224:Diterpenes / Q000737:chemistry*; D061353:Food Storage; D006801:Humans; D027582:Humulus / Q000737:chemistry*; D007536:Isomerism; D013649:Taste
chemical_list: D000143:Acids; D003517:Cyclopentanes; D004224:Diterpenes; C081209:isohumulone; C533891:isocohumulone
keywords: activation energy; iso-α-acids; lager beer; rate constant; trans-iso-α-acids