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Effect of a Simulated Kilning Regime on the Profile and Antioxidant Activity of the Free Phenolic Acids Extracted from Green Malt

MBAA TQ vol. 42, no. 3, 2005, pp. 204-208  |  VIEW ARTICLE

Elizabeth L. Inns (1), Lesley A. Buggey (2), Harry E. Nursten (1), and Jennifer M. Ames (1). 1. School of Food Biosciences, The University of Reading, Whiteknights, Reading, RG6 6AP, U.K. 2. Brewing Research International, Lyttel Hall, Nutfield, Surrey, RH1 4HY, U.K.

Abstract
Free phenolic acids were extracted from a laboratory-produced sample of green malt. Aliquots of the phenolic acid extract were heated from 25 to 110°C over 27 h, representative of a commercial kilning regime. Samples were taken at regular intervals throughout heating and were assessed for changes in antioxidant activity by both the 2,2(prime)-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical-cation scavenging (ABTS(^•+)) and the ferric-reducing antioxidant potential (FRAP) assays. Changes in the profile of the phenolic acids of the extracts were determined by HPLC. Overall, there was a decrease in both antioxidant activity level and the level of phenolic acids, but as the temperature increased from 80 to 100°C, there was an increase in both the antioxidant activity level and the level of detected phenolic acids.
Keywords: antioxidant activity, kilning, malt, phenolic acids

 

Síntesis
Se extrajeron ácidos fenólicos libres de una muestra de malta verde producida en el laboratorio. Alícuotas del extracto fueron calentadas de 25°C a 110°C en 27 horas, semejante al calentamiento en un horno de malteado. Se tomaron muestras a intervalos regulares durante el calentamiento y se le midió el cambio en la actividad antioxidante, tanto mediante el ensayo del contenido de reductores (“scavengers”) de radicales de cationes (ABTS(^•+)) 2,2´-azino-bis (ácido 3-etilbenzotiazolina-6-sulfonico) como por el ensayo de la potencial antioxidante reductor del ion férrico (FRAP, por sus siglas en inglés). Cambios en el perfil de loa ácidos fenólicos de los extractos fueron determinados por HPLC. Al final del calentamiento hubo una reducción total tanto en la actividad antioxidante como en el nivel de los ácidos fenólicos, pero en la etapa de 80°C a 100°C aumentó tanto la actividad antioxidante como el nivel de los ácido fenólicos detectados.
Palabras claves: actividad antioxidante, horneado, malta, ácidos fenólicos

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