α-Dicarbonylic Compounds as Indicators and Precursors of Flavor Deterioration During Beer Aging
Peer-Reviewed Paper
MBAA TQ vol. 39, no. 1, 2002, pp. 13-23 |
VIEW ARTICLE
Adriana Bravo (1), Beatriz S�nchez
(1), Erika Scherer (1), Julio Herrera (2), and Rafael Rangel-Aldao (1).
1. Polar Technology Center, Empresas Polar, Caracas, Venezuela. 2. Department of Chemistry, Sim�n Bol�var University, Caracas, Venezuela.
Abstract
We monitored beer deterioration upon storage at 0 or 28�C by chemical indices determined by HPLC. A chromatogram peak named LC18 gradually decreased until it was barely detected after 50 days at 0�C, and it asymptotically approached a stationary level after 10 days at 28�C. Isolation, synthesis, and decomposition of LC18 showed it to be a Maillard reaction intermediate, generated by the decomposition of 3-deoxy-2-hexosulose, and a direct precursor of 5-hydroxymethylfurfural (HMF). This finding led us to uncover the accumulation of up to 10
alpha-dicarbonyls in beers stored at 28�C, and we determined their structures by 1H and 13C NMR spectroscopy. Four of these
alpha-dicarbonyls have never been reported in beer, and two of them are presumed products of the Strecker degradation of 1-deoxyosones. The concentrations of seven
alpha-dicarbonyls increased up to ninefold during storage at 28�C, compared with their levels in control beers kept at 0�C. The addition of
alpha-dicarbonyl trapping reagents to beer before storage blocked the formation of HMF and retarded the deterioration of beer flavor as determined by sensory evaluation by a descriptive panel.
Sintesis
Se le hizo un seguimiento al deterioro de cervezas almacenadas a 0 � 28�C mediante �ndicadores qu�micos detectados por HPLC. Un nuevo indicador, denominado LC18, disminuy� gradualmente hasta que apenas se pudo detectar despu�s de 50 d�as a 0�C, y decreci�de manera asint�tica hasta un nivel constante despu�s de 10 d�as a 28�C. El aislamiento, s�ntesis, y descomposici�n del pico LC18 demostr� que se trataba de un producto intermediario de la reacci�n de Maillard, generado por la descomposici�n de la 3-deoxi-2-hexosulosa y un precursor directo de 5-hidroximetilfurfural (HMF). Este hallazgo nos llev� a detectar la acumulaci�n de hasta 10 intermediarios
alfa-dicarbon�licos en cervezas guardadas a 28�C, cuyas estructuras fueron determinadas por espectroscop�a de RMN 1H y 13C. Cuatro de estos (-dicarbonilos nunca habian sido detectados en la cerveza, y dos de ellos son presumiblemente productos de la degradaci�n de Strecker de l-deoxiosonas. Las concentraciones de siete
alfa-dicarbonilos almacenados a 28�C aumentaron a m�s de nueve veces su valor en cervezas control guardadas a 0�C. La adici�n de un reactivo bloqueador de
alfa-dicarbonilos a la cerveza antes del almacenamiento, inhibi� la formaci�n de HMF y retras� el deterioro del sabor de la cerveza, de acuerdo a la evaluaci�n sensorial realizada por un grupo de degustadores calificados.
