Impact of Genotype, Environment, and Malting Conditions on the Antioxidant Activity and Phenolic Content in US Malting Barley

Abstract

The phenolic content and antioxidant potential of malting barley are important in brewing. The objective of our study was to investigate the effects of barley genotype, growing environment, and malting conditions on the total phenolic content and antioxidant activities of malting barley grown in North America. Eight barley cultivars grown at three locations over three years were used. For the malting study, a single barley cultivar, separated into different kernel size fractions, was germinated for various periods of time and then processed by kilning or freeze-drying. Total phenolic content (TPC) and some of the antioxidant activities, including DPPH, ABTS, and superoxide anion radical scavenging activities, reducing power, and iron (II) chelating activity, were significantly impacted by the barley genotype, growth environment, and their interactions. The TPC and most antioxidant activities were also influenced by malting conditions and were generally higher in the malted barleys of the thin kernel size fraction, four-day germination, and in samples processed by kilning, when compared to the plumper kernel size fractions, one and two days of germination, and freeze-dried samples, respectively. There were interactions between malting parameters, and stepwise regression analysis was used to suggest the contribution of each parameter to the TPC and antioxidant activities.

Effect of grinding and extraction conditions on the determination of antioxidant activity and phenolic acids in barley

“…Kernel size was also found to have a significant impact on all antioxidant activities and TPC when averaged over cultivars and the other parameters. As we had previously demonstrated [17], the thinnest kernels (2.0 mm) generally had higher levels of antioxidant activities and TPC. Exceptions were SARSA and ICA.…”

“…Many of the results are confirmatory of previous studies. This is especially the case in terms of cultivar effects, where our previous study [17], as well as those of other researchers [18][19][20][21] have demonstrated the genotype of malting barley to have significant effects on the TPC and antioxidant activities (including DPPH, ABTS + , RP, and ICA). Kernel size was also found to have a significant impact on all antioxidant activities and TPC when averaged over cultivars and the other parameters.…”

“…All methodology was detailed in our previous publication [17]. Total phenolic content (TPC) was determined according to the method described by Xu [33].…”

“…Several factors are known to impact the level of antioxidant activity and phenolics in barley. Zhou et al [17] recently reported total phenolic content (TPC) and some of the antioxidant activities were significantly impacted by genotype and growing environment. However, in some cases, there were interactions between genotype and environment.…”

“…The source of phenolics in beer is either from malted barley or hops, with about 3/4 of total polyphenols coming from barley [19]. Phenolic compounds exhibiting antioxidant and antiradical activities include phenolic acids, flavonoids, proanthocyanidins, tannins and amino phenolic compounds [17,23,24]. Phenolic acids can be divided into two groups: hydroxybenzoic acid derivatives (including vanillic, syringic, gallic acids, etc.)…”