Antioxidant Properties of Free, Soluble Ester and Insoluble-Bound Phenolic Compounds in Different Barley Varieties and Corresponding Malts

Abstract

S 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/kgdw) for barley and between 34.1 and 72.3 mg GAE/kgdw for malt. The bound phenolic content ranged from 210.3 to 320.5 and between 81.1 and 234.9 mg GAE/kgdw 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.

Comparison of Antioxidant Activity of Barley (Hordeum vulgare L.) and Malt Extracts with the Content of Free Phenolic Compounds Measured by High Performance Liquid Chromatography Coupled with CoulArray Detector

“…The values of TPC depended on variety, growing area and least use of fertilizers. TPC was in accordance with data already published 6 .…”

“…Several types of polyphenol extraction have been described 6,7,11,19,22,23,26,29 . The mixture of water with organic solvent is one of the most used.…”

“…Various techniques have been used for the determination of polyphenolic compounds, including high performance liquid chromatography (HPLC) with electrochemical 8,16 , mass spectrometry detection 4,5,23 , UV spectrophotometric 5,6,7,10 or fluorimetric detection 17 .…”

Brewer's spent grain from different types of malt: Evaluation of the antioxidant activity and identification of the major phenolic compounds

“…In contrast to our results, McCarthy and co-workers (2012) recently reported that black BSG extracts exhibited the highest phenolic content. This difference can partially be explained by the type of malt used in the brewing process which has been shown to interfere with the content of individual phenolic compounds extracted (Dvořáková et al, 2008;Magalhães et al, 2011). In addition, this difference can also be due to the melanoidins generated during kilning by the Maillard reaction, whose content increases with KT.…”

Effect of Maillard reaction on reducing power of malts and beers

“…During malting, a significant decrease of bound phenolics takes place with a corresponding increase of soluble esterified fraction (Dvořáková et al 2008b). This can be explained by the enzymatic release of the bound antioxidants of barley as well as glycosylation reactions during malting and non-enzymatic changes during kilning.…”