## 3 Results and Discussion
### p-Couramic Acid Kinetic in Fermented Wort and Beer  
The \(p\)-couramic acid in each composite wort prior to fermentation was 2.26 mg/L, 2.65 mg/L, 3.18 mg/L, 3.72 mg/L, and 4.20 mg/L in B100, R40B60, R60B40, R80B20, and R100, respectively (Figure 3). The difference in malt composition influenced \(p\)-couramic acid in words significantly (\(p<0.05\)). The concentration of \(p\)-counamic acid was dependent on the malted rice fraction. [PERSON] et al. [13] reported that malted paddy rice contained high \(p\)-counaric acid because of the rice husk containing more \(p\)-counaric acid [1]. The \(p\)-counaric acid varied significantly (\(p<0.05\)) with fermentation period and among the yeast strains. In POF\({}^{+}\) fermented wort, \(p\)-counaric acid declined with fermentation period (Figure 3A) because of the decarboxylation of \(p\)-counaric acid to 4-vinylphenol by POF\({}^{+}\) metabolism [5]. This resulted in a reduction in \(p\)-couramic acid by 1.9%, 19.2%, 9.9%, 13.4%, and 8.7% in B100, R40B60, R60B40, R80B20, and R100, respectively, after 72 h of fermentation. The \(p\)-couramic acid content was stable in POF\({}^{-}\) fermented wort (Figure 3A). For the bottled maturation of beer produced with POF\({}^{+}\), \(p\)-couramic acid declined after a week of maturation, and it maintained a relatively stable concentration into week 4 of beer maturation (Figure 3A). POF\({}^{+}\) beer recorded a final \(p\)-couramic acid concentration of 2.10 mg/L in B100, R40B60 (1.98 mg/L), R60B40 (2.74 mg/L), R80B20 (3.07 mg/L), and R100 (3.66 mg/L). The beers produced with POF\({}^{-}\) had \(p\)-couramic acid of 2.08 mg/L in B100, R40B60 (2.42 mg/L), R60B40 (2.96 mg/L), R80B20 (3.50 mg/L), and R100 (3.96 mg/L). The observed effect of brewing with R100 on the hydroxycinnamic acid profile contradicts with that of \(p\)-counaric acid reported by [PERSON] et al. [12] in rice beer, which was below the ferulic acid concentration. The variation in results reported can be associated with the mashing schedule, boiling period, the type of rice cultivar, and the phenolic acid extraction process. In this study, prior to phenolic extraction, the acidification was carried out, which was absent in the work by [PERSON] et al. [12]. Nevertheless, worts produced with 50% of rice and 50% barley malt contained higher \(p\)-couramic acid than ferulic acid [2], which corroborates with this study. However, inadequate data exist on rice malt as an adjunct on hydroxycinnamic acid in beer. This study suggests that paddy rice malt additions changed the dynamics of hydroxycinnamic acid and the potential of more decarboxylated \(p\)-couramic acid during boiling and fermentation with POF\({}^{+}\), unlike conventional beer brewed with barley malt [2] or wheat malt [3], which have higher concentrations of ferulic acid and 4-vinylguaiacol. vanillic acid from words to beer, there was a similar pattern observed in all black rice malt beer (a decline from 3.37 mg/L in word to 3.06 mg/L in beer), but in white kernel rice malt beer, vanillic acid increased from 0.29 mg/L to 0.52 mg/L despite using the same yeast strain Nottingham ale dried yeast [12]. These comparisons suggest that vanillic acid can be metabolised by the brewing yeasts or reduce via precipitation in the pigmented fermented word, as observed in this study. Vanillic acid concentrations after 4 weeks in beer were 3.43 mg/L, 4.05 mg/L, 4.15 mg/L, 5.94 mg/L, and 6.37 mg/L in B100, R40B60, R60B40, R80B20, and R100, respectively, with \(\mathrm{POF}^{-}\). In addition, in \(\mathrm{POF}^{+}\) matured beer, vanillic acid content was 2.76 mg/L, 3.47 mg/L, 3.56 mg/L, 4.89 mg/L, and 5.06 mg/L in B100, R40B60, R60B40, R80B20, and R100, respectively, which were above the vanillic acid concentrations reported by [PERSON] et al. [12] in rice beer produced from pigmented rice (3.06 mg/L) and non-pigmented (0.52 mg/L) rice. However, vanillic acid concentrations in this study and those reported by [PERSON] et al.