9/6/19: Characterization of craft beers and their bioactive compounds

For our inaugural Journal Club, we chose to review a 2017 study conducted by Marques et al. from State University of Maringa, Brazil, as an introduction to various physicochemical and phenolic aspects to consider in brewing. Our key objectives were to gain a solid understanding of which properties can be measured, how they are analyzed, and why they are important for the sensory aspects of the finished beer. How do properties such as pH, color, foam stability, and levels of phenolic compounds affect the quality of beer, and how do differences in these factors set apart a particular beer style from another? Based on what we learn, how should we adjust target parameters for our brews?

To begin, we reviewed the list of properties that are important to beer characterization in the first column of Table 2, which reports the physicochemical analyses of the authors’ chosen beer styles. While many of them are straightforward measurements based on analytical methods adapted from general chemistry, reviewing this table provided a chance to delve into beer-specific units, such as IBU (International Bitterness Units, with one IBU equaling one parts per million of iso-alpha acids from hops to serve as a measure of beer’s bitterness) or EBC (European Brewery Convention unit of beer color and haze classification). Reviewing which physicochemical aspects are analyzed to describe a beer style helped us think through the qualities we sought to achieve in our first set of brews: a porter and a cream ale.

​​However, the authors failed to provide a context for the sample beers brewed for the study, making it difficult to understand why these physicochemical properties were being compared among the four beer styles; we could only assume that they were chosen for having notably different flavor profiles. In addition, we found the scope of the study to be too narrow for our purposes of understanding how these values translate into sensory characteristics of the finished beer. The omission of explaining sensory significance extended to the phenolics analysis. Based on data presented in Table 3, the authors highlight high levels of caffeic acid in all sample beers, adding that high caffeic acid levels have previously been correlated to high radical scavenging activity and thus lipid oxidation prevention (Zhao et al., 2010). While they touch on potential benefits of beer’s bioactive compounds on cardiovascular health, a discussion on the sensory effects of lipid oxidation on beer, such as flavor stability, would have been more informative for our needs. 

​While we acknowledged that it was outside the scope of the study, incorporating a sensory standpoint would have helped us better understand the significance of the study’s findings. After all, we are targeting specific ranges of physicochemical properties for a given beer style in hopes of brewing a delicious beer! However, this study served as a reminder that beer is a complex matrix, in which numerous variables are at play. As we set out to brew our first batch of beers, we will establish a protocol for taking necessary measurements for possible analyses in the future and continue reading up on factors that could unexpectedly shift these properties.


References

Marques D.R., Cassis M.A., Quelhas J.O.F., Bertozzi J., Visentainer J.V., Oliveira C.C., Monteiro A.R.G., 2017, Characterization of craft beers and their bioactive compounds, Chemical Engineering Transactions, 57, 1747-1752. DOI: 10.3303/CET1757292
 
Zhao H., Chena W., Lub J., Zhao M., 2010, Phenolic profiles and antioxidant activities of commercial beers, Food Chemistry, 119, 1150-1158. DOI: 10.1016/j.foodchem.2009.08.028