## 1 Introduction  
Phenolic acids are often referred to as aromatic compounds with carboxylic functional groups, which form an integral part of cereal chemical structure and play an important role in antioxidant activity. Phenolic acids consist of two groups: hydroxycinnamic acids and hydroxybenzoic acids. The hydroxycinnamic acids comprise ferulic acids, \(p\)-coumaric acids, and sinapic acids [1], which are the precursors for volatile phenolic compounds in non-alcoholic beverages (fruit juices and coffee) and alcoholic beverages (wine and beer) [2]. In beer, the most profound volatile phenolic compound is 4-vinylguaiacol (4-VG), which is derived from the decarboxylation of ferulic acids [3]. In the beer brewing process, hydroxycinnamic acids solubilise in wort during mashing and are decarboxylated during the boiling of wort. High amounts of decarboxylated hydroxycinnamic acids occur during wort fermentation by yeast activity [2, 3]. Yeast capable of decarboxylating phenolic acid is designated as a phenolic off-flavour producer (\(\mathrm{POF}^{+}\)). This yeast possesses the phenylacrylic acid decarboxylase (PAD1) and ferulic acid decarboxylase (\(\mathrm{FDC1}\)) gene [4]. In addition, the non-decarboxylolating phenolic acid yeast is classified as a non-phenolic off-flavour producer (\(\mathrm{POF}^{-}\)) [5]. Recently, the PAD1 has been renamed as flavin preynly-esterase, which produces a modified flavin cofactor prenylated FMNH2 for the ferulic acids decarboxylase (\(\mathrm{FDC1}\)) enzyme activity [6]. [PERSON] et al. [7] suggested that the mutation of PAD1 and/or FDC1 caused _Saccharomyces cerevisiae_ to lack the ability to produce 4-vinylguaiacol from ferulic acid, which is preferred by German and English beer styles, whereas in wheat beer and Saison beer, 4-vinylguaiacol is a key aroma for its organoleptic character. However, the amount of hydroxcinnamic acid in beer is dependent on the type of raw material, brewing process, and the amount of hydroxcinnamic acid decarboxylated by yeast. Therefore, the phenolic acid profile in the composite wort and their transformation by brewing yeast and the brewing process were investigated in this study. The current surge of craft brewing has had a significant influence on the choice of raw material to obtain diverse organoleptic properties of beer. Moreover, the use of other malted cereals such as rye, oat, rice, sorghum, and buckwheat in substituting barley malt affects phenolic acid profiles, the amount of volatile phenolic aroma compounds produced, and antioxidant [2]. Among these cereals, rice is used globally as an adjunct for beer brewing except in countries such as Germany, which restricts the use of other cereals apart from barley. In Asia, rice is an integral part of many beers produced. The prospects of rice as an adjunct in beer brewing and as a base malt for the production of gluten-free beer have been researched exhaustively with reports on malt attributes, organoleptic properties [8; 9] coupled with the study of specialty rice malt, and functional properties such as antioxidants and total phenolic acid in pigmented and non-pigmented rice cultivars [10; 11]. [PERSON] et al. [12] reported higher oxidation stability in black rice malt beer than in barley malt beer. In addition, the supplementation of barley malt with pigmented rice influenced the colour and antioxidant activity of the wort via anthocyanin [10; 11]. Pigmented rice such as the Riceberry rice (_Oryza sativa_) is a dark purple rice variety that is widely cultivated in Thailand. This rice cultivar is produced via cross-breeding between the Khao Hom Nin rice variety, which contains high antioxidants, and Khao Hom Mali 105, a fragrant rice cultivar. It is cultivated for its nutritional value as a rich source of anthocyanin and antioxidant activity [13]. The attributes associated with rice malt as an adjunct or base material on phenolic acid dynamics, antioxidation, and volatile phenolic aromatic compounds in beer brewing have not been investigated.