# Acid and Volatiles of Commercially-Available Lambic Beers
## Results and Discussion
### Organic Acids  
The organic acids present in beer play important roles in aroma and taste. First, organic acids are one of the primary groups of compounds that contribute to the sourness. All organic acids have their own characteristic flavor, aroma, and taste [35; 36; 37]. Citric acid possesses a fresh acid flavor, which is very different from that of malic acid, while succinic has both a salty and bitter flavor in addition to its sourness. Second, acids can help protect beer from harmful microorganisms by decreasing the pH [36]. Third, the organic acids present in beer can aid in prolonging the shelf life by providing the beer with a strong buffering capability [36; 38]. Acetic acid has a flavor threshold of 200 ppm, while lactic acid has a flavor threshold of 400 ppm [26; 39].  
Acetic and L-lactic acid were found in varying concentrations within different styles of lambic beer [39]. It has been reported that the concentration of lactic can be as high as 10,000 mg/L for lactic in ropy lambics and 1200 mg/L for acetic lambics [12].The comparison of acetic and lactic acid found in commercial lambic beer can be found in Table 6. In comparison to gueuzes, ales and lagers have a much lower concentration of acetic and lactic acid. Ales and lagers normally contain anywhere from 60 to 140 ppm acetic acid. The concentration of acetic acid in gueuze beer can range between 500 and 1500 mg/L. The concentration of acetic acid in the commercial samples ranged from 723 mg/L for Oude Boon to 1642 mg/L for Hanssens Artisans. There was no difference in acetic acid concentration between the different brands (\(p>0.05\)).  
The concentration of lactic acid in gueuze beer can range between 1500 and 3500 mg/L, while typical American lagers tend to have much lower concentrations, around 40-150 ppm [1]. Table 6 shows a comparison of means for lactic acid. The concentration of lactic acid ranged from 1098 to 2979 mg/L. Cantillon Bio had the highest level of lactic acid at 2979 mg/L followed by Cuveee Renee at 2563 mg/L. Oude Gueuze Villie had the lowest concentration of lactic acid at 1098 mg/L. Based upon the comparison of means, Cantillon Bio is significantly different from Girardin, Cantillon, Hanssens Artisans, 3-Fonteinen, Boon, Oude Boon, and Oude Gueuze Viellie. Cuveee Renee was found not to be significantly different from any of the other brands.  
The origins of the volatiles in gueuze lambic include raw materials, and chemical/microbial changes occurring during fermentation and aging. [PERSON] et al. [40; 41] reported a consistent core microbial population including _Pediococcus damosus_, _Dekkera anomala_, _Dekkera bruvellensis_, _Saccharomyces cerevisiae_, and _S. pastorianus_ during production to just _D. bruvellensis_ after production. _Brettanomyces_ and _Dekkera_ are used interchangeably with _Dekkera_ most often used to describe the spore form of the yeast. Extended aging was associated with higher levels of ethyl lactate and lower levels of isoamyl acetate and ethyl decanoate with aging. Thus, the differences in some of the volatiles that we have observed in our samples could represent production or age differences.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Brand** & **Acetic Acid (mg/L) \({}^{*}\)** & **Lactic Acid (mg/L)** \\ \hline Cuveee Renee & 916 \(\pm\) 12.02 & 2557 \(\pm\) 8.26 \\ Oude Gueuze Villie & 1019 \(\pm\) 211.43 & 1094 \(\pm\) 13.54 \\ Cantillion & 1224 \(\pm\) 1.41 & 1417 \(\pm\) 184.25 \\ Hanssens Artisan & 1642 \(\pm\) 847.82 & 1389 \(\pm\) 55.64 \\ Cantillion Bio & 1473 \(\pm\) 79.21 & 1658 \(\pm\) 890.05 \\
3 Fonteinen & 1204 \(\pm\) 129.78 & 1294 \(\pm\) 61.2 \\ Girardin & 1499 \(\pm\) 109.53 & 1403 \(\pm\) 96.95 \\ Oude Boon & 723 \(\pm\) 8.48 & 1228 \(\pm\) 14.12 \\ Boon & 1137 \(\pm\) 13.44 & 995 \(\pm\) 18.55 \\ \hline \hline \end{tabular} \({}^{*}\) No difference was found between the brands.  
\end{table}
Table 6: Comparison of Acids within Commercial Brands of Lambic Beer.