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Quality Control of Beer Hopped with Reduced Isomerized Products

MBAA TQ vol. 37, Number 2, 2000, Pages 219-224 VIEW ARTICLE

By Katia Jorge and L. C. Trugo Chemist and Operational Manager, BrewTech, Rio de Janeiro, Brazil. This paper was originally presented at the MBAA 112th Anniversary Convention, Keystone, Colorado, 1999.

Abstract
The traditional method for measuring bitterness in beer by UV absorbance (ASBC 8th Edition) remains a routine quality control method for normally hopped beer. However, after reduction of isoal-pha acids, the specific absorptivity of active components change, and this method is not applicable. This work was intended to adapt math-ematically the spectrophotometrical method and to evaluate an HPLC method to control the composition of different commercial reduced isomerized products added to unhopped wort and partially kettle hopped beer. The results obtained show that the HPLC method is reliable for quality control of reduced isomerized products, however it has been demonstrated in this work that by using adequate factors, the spectrophotometrical method is also viable for quality control of beer bitterness.
Keywords: hop analyses, reduced hop extract, HPLC method for hop analyses  

Sintesis
El método tradicional de medir la amargura de la cerveza mediante la absorción de rayos UV (ASBC9.6) se mantiene como un método de control de calidad de rutina para la cerveza elaborada con lúpulo normalmente. Sin embargo, después de la reducción de ácidos isoal-fa, la absorción específica de los componentes activos cambia y este método no se puede emplear. Este trabajo intenta adaptar matemáti-camente el método espectro fotométrico y evaluar un método HPLC para controlar la composición de diferentes productos isomeriza-dos reducidos comerciales que se añaden al mosto sin lúpulo y a la cerveza parcialmente con lúpulo. Los resultados obtenidos demostraron que el método HPLC es confiable para el control de cal-idad de productos reducidos e isomerizados, sin embargo se ha demostrado en este trabajo que, usando factores adecuados, el méto-do espectro fotométrico es también viable para el control de calidad de la amargura de la cerveza.

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