Changes in polyphenol compounds and barley laccase expression during the malting process.

BACKGROUNDPolyphenols and phenolic acid are able to slow down or prevent oxidation processes and are therefore thought to have important effects in malting and brewing. Laccase catalyses the oxidation of a wide variety of substrates, including polyphenols. The aim of this paper was to determine the changes in polyphenol compounds and the relative expression of the HvLac1 gene during malting. RESULTSThe dominant phenolic acid was ferulic acid. The amount of ferulic acid increased, whereas the amount of vanillic acid decreased during malting. The highest levels of expression of the HvLac1 gene were observed during the third air rest period in varieties with the Haruna Nijo' (HN) allele, as recommended for the production of beer with the protected geographical indication (PGI) eske pivo' (Czech beer), whereas the highest expression was observed in the first day of germination in varieties with the Morex' (M) allele. However, the profiles of HvLac1 gene expression in varieties with alternative alleles during malting were similar, and the level of polyphenol compounds throughout malting was different. CONCLUSIONThe polyphenol contents in barley increased several-fold during malting, and the degree of increase differed with variety. The expression of HvLac1 transcript was similar in every barley variety. (c) 2015 Society of Chemical Industry