Impact of Esterase Activity in Aseptically Packaged, Unpasteurized Beer
MBAA TQ vol. 41, no. 3, 2004, pp. 293-297 |
VIEW ARTICLE
Petr Vesely (1,2), Antonia Volgyi (1), Lance T. Lusk (1), Gabriela Basarova (2), Alfonso Navarro (1), John Seabrooks (1), and David Ryder (1). 1. Miller Brewing Company, 3939 W. Highland Boulevard, Milwaukee, Wisconsin, 53208, U.S.A. 2. Institute of Chemical Technology, Technicka 5, Prague 6, 166 28, Czech Republic.
Abstract
Yeast extracellular esterase is mostly destroyed during pasteurization. Aseptically packaged, unpasteurized beer, which has become an effective alternative for providing microbiologically stable, packaged beer, does not inactivate esterase activity. The effect of esterase activity on the volatile compound composition and flavor stability of aseptically packaged, unpasteurized beer during storage was studied. Analysis of beer volatile compounds using an SPME/GC/MSD method (solid-phase microextraction, separated by gas chromatography, and detected by a mass selective detector) showed that octyl acetate, its level significantly decreased in beer during storage at 30�C, was a good substrate for yeast esterase. Esterase also acted on ethyl hexanoate, which resulted in slightly increased levels of hexanoic acid. However, since the flavor changes resulting from oxidative and other degradation reactions that occur in beer during aging have a more profound impact than those brought about by yeast esterases, a sensory panel was not able to detect a flavor difference between this unpasteurized beer and pasteurized beer stored at 30�C for up to 12 weeks.
Keywords: esterase, flavor stability, SPME/GC/MSD
S�ntesis
La esterasa extracelular de la levadura es destrozada casi completamente durante la pasteurizaci�n. La cerveza sin pasteurizar, envasada as�pticamente (una alternativa efectiva para mercadear cerveza envasada microbiol�gicamente estable), mantiene su actividad de esterasa completa. Se estudi� el efecto de la actividad de la esterasa sobre los compuestos vol�tiles y la estabilidad sensorial de cerveza durante el almacenamiento de cerveza no pasteurizada envasada as�pticamente. El an�lisis de compuestos vol�tiles de cerveza mediante SPME/GC/MSD (microextracci�n de fase s�lida separado por cromatograf�a de gases y detectado mediante un detector selectivo de masa) mostr� que el acetatato oct�lico (con su nivel reducido en cerveza almacenada a 30�C), era un buen sustrato para esterasa proveniente de la levadura. La esterasa tambi�n act�a sobre hexanoato de etilo, dando niveles levemente aumentados de �cido hexan�ico. Sin embargo, un panel sensorial no pudo distinguir una diferencia entre cerveza pasteurizada y no pasteurizada almacenadas a 30�C por hasta 12 semanas, debido a que los cambios sensoriales ocasionados por reacciones oxidativas y degradativas durante el almacenaje tienen un mayor impacto sensorial que aquellos causados por la esterasa proveniente de la levadura.
Palabras claves: esterasa, estabilidad sensorial, SPME/GC/MSD
