Investigation of phenolic acids content and antioxidant activity in malt production

Abstract

The aim of this research was to determine, using a GC-MS method, the total phenolic acids content of different extracts during malt production and to assess the potential antioxidant activity of these extracts based on their ability to scavenge the stable 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical and reactive hydroxyl radical (&z.ast;OH) formed by the Fenton reaction (detected using electron spin resonance spectroscopy). A GC-MS method for determination of phenolic acids (p-hydroxybenzoic, vanillic, gen- tistic, protocatechuic, syringic, p-coumaric, gallic, ferulic, caffeic, sinapic, chlorogenic, and ellagic) was developed. The procedure involved the extraction of phenolic acids from hydrolysate of barley, steeped barley, green malt, and malt with ethyl acetate, followed by derivatization of phenolic acids with N,O-bis(trimethylsilyl) trifluoroacetamide plus trimethylchloro- silane reagent. The trimethylsilyl derivatives formed were separated and quantitated using GC-MS. Sample extracts were subjected to acid, a-amy-lase, and cellulase hydrolyses. For all investigated barley varieties, ferulic, p-coumaric, and vanillic acids were dominant in raw barley samples during malting and in the corresponding malts. The investigated extracts were more effective at scavenging 5,5-dimethyl-1-pyrroline-N-oxide-OH (DMPO- OH) than DPPH. In both cases, antioxidant activity increased with increased concentration of the investigated extracts. © 2009 American Society of Brewing Chemists, Inc.