VIEW ARTICLE DOI: 10.1094/ASBCJ-60-0098
Spectrophotometric Analysis of Isomerized alpha-Acids. John Paul Maye, Susan Mulqueen, Jianping Xu, and Scot Weis, Haas Hop Products, Inc., Washington, DC 20016. (1) Corresponding author. E-mail: <jpmaye@haashopproducts.com> J. Am. Soc. Brew. Chem. 60(3):98-100, 2002. Accepted January 8, 2002.
Most of the isomerized and reduced hop extracts being used to bitter beer today, such as iso-alpha-acids, rho-iso-alpha-acids, tetrahydro-iso-alpha-acids, and hexahydro-iso-alpha-acids, are formulated and sold based on spectrophotometric analysis. Isomerized and reduced alpha-acids absorb ultraviolet and visible light, making quantitative analysis by spectrophotometric analysis a simple and accurate tool. Although these hop products have been in use for over 30 years, there have been no published procedures for measuring their concentration by spectrophotometric analysis. This article presents a simple and convenient spectrophotometric test method to measure the concentrations of isomerized and reduced alpha-acids in alkaline methanol. Keywords: Alkaline methanol, Hexahydro-iso-alpha-acids, Iso-alpha-acids, Rho-iso-alpha-acids, Spectrophotometric analysis, Tetrahydro-iso-alpha-acids
Análisis
Espectrofotometrico
de Ácidos Alfa
Isomerizados
La mayoría de los extractos de lúpulo isomerizados y reducidos que se utilizan para amargar cerveza hoy, tal como iso-alfa-ácidos, rho-iso-alpha-ácidos, tetrahydro-iso-alpha-ácidos, y hexahydro-iso-alpha-ácidos, se formulan y se venden a base de análisis espectrofotometrico. Los alpha-ácidos isomerizados y reducidos absorben luz ultravioleta y visible, haciendo del análisis espectrofotometrico una simple y exacta herramienta de análisis cuantitativo. Aunque estos productos se han utilizado por mas de 30 años, no se ha publicado un procedimiento para medir sus concentraciones a través de análisis espectrofotometrico. Este articulo presenta un método de prueba espectrofotometrica simple y conveniente para medir las concentraciones de alfa-ácidos isomerizados y reducidos en metanol alcalino. Palabras claves: Análisis espectrofotometrico, Hexahydro-iso-alfa-ácidos, Iso-alfa-ácidos, Metanol alcalino, Rho-iso-alfa-ácidos, Tetrahydro-iso-alfa-ácidos