The Implications of Composite Dark Purple Rice Malt on Phenolic Acid Profiles, 4-Vinyl Guaiacol Reduction and Enhancing the Antioxidation of Beer

Abstract

This study highlights the dynamics of phenolic acids, antioxidation, and 4-vinylguaiacol in beer produced with dark purple rice malt, also known as Riceberry rice malt, as an adjunct and base malt. Riceberry rice malt substituted barley malt at 40% (w/w), 60% (w/w), 80% (w/w), and 100% (w/w) with 100% (w/w) barley malt as the control. Two types of ale beer were produced with two yeasts, designated as POF− and POF+. The wort produced with the Riceberry rice malt had higher anthocyanin and vanillic acids relative to all barley malt wort. Fermentation and beer maturation reduced phenolic acids and antioxidant activity in all treatment. Nevertheless, beer produced from 40% (w/w)–80% (w/w) Riceberry rice malt maintained higher p-coumaric acid, vanillic acid, anthocyanin, and antioxidant activity in beers with lower 4-vinylguaiacol relative to all barley malt beer, which also had higher ferulic acid and sinapic acid contents. The beers made from POF+ yeast contained more 4-vinylguaiacol contents than those found in beers made from POF− yeasts. This study suggests that Riceberry rice malt or POF− yeast are suitable raw materials for phenolic acid off-flavour reduction and the stabilisation of antioxidant activity in beer.