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Antioxidant Properties of Free, Soluble Ester and Insoluble‐Bound Phenolic Compounds in Different Barley Varieties and Corresponding Malts
Author(s) -
Dvořáková Markéta,
Guido Luis F.,
Dostálek Pavel,
Skulilová Zuzana,
Moreira Manuela M.,
Barros Aquiles A.
Publication year - 2008
Publication title -
journal of the institute of brewing
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.523
H-Index - 51
eISSN - 2050-0416
pISSN - 0046-9750
DOI - 10.1002/j.2050-0416.2008.tb00302.x
Subject(s) - chemistry , ferulic acid , catechin , gallic acid , dpph , antioxidant , food science , fraction (chemistry) , composition (language) , high performance liquid chromatography , chromatography , polyphenol , organic chemistry , linguistics , philosophy
Ten different barley cultivars and their corresponding malts were used to obtain different fractions. Phenolics extracted belonged to free, soluble esters and insoluble‐bound fractions. Total phenolic content (TPC) of the free fraction, as measured according to the Folin‐Ciocalteu method, ranged from 37.7 to 167.2 mg gallic acid equiv/kg of dried material (GAE/kg dw ) for barley and between 34.1 and 72.3 mg GAE/kg dw for malt. The bound phenolic content ranged from 210.3 to 320.5 and between 81.1 and 234.9 mg GAE/kg dw for barley and malt, respectively. The contribution of bound phenolics to the TPC was significantly higher than that of free and esterified fractions. Catechin and ferulic acid, quantified by high performance liquid chromatography with diode array detector (HPLC‐DAD), were the most abundant phenolics in the free and bound fractions, respectively. The p ‐coumaric acid content was lower in hulless genotypes, as compared to hulled genotypes, showing that it is mainly concentrated in the hull. The antioxidant activities of the phenolic fractions were investigated using the radical scavenging assay (DPPH) and ferricyanide reducing power. The bound phenolics demonstrated a significantly higher antioxidant capacity compared to the free and esterified phenolics. During the malting process, a significant decrease of the bound phenolics was observed with a corresponding increase of the esterified fraction.