September 16, 2016

Fermentation institute research provides new tools to brewers

by Tim Crosby

CARBONDALE, Ill. -- Making beer is and always has been a fairly straight-forward process. Create a solution of sugars from grain, add yeast and hops, maybe other flavorings, and let it do its thing. 

But the proliferation of American craft brewers in recent decades is also leading to more experimentation, creativity and variations on this theme. Researchers at Southern Illinois University Carbondale, in cooperation with several craft brewers, recently looked at a brewing trend to help understand the science behind the process, and ultimately the all-important flavor. 

Matt McCarroll, professor of chemistry and biochemistry and director of the Fermentation Science Institute at SIU, said researchers examined whether the relative bitterness of hops in beer can be used to fine-tune flavor in certain types of beers that use wild yeast and bacteria for fermentation. The experiments they ran with the help of three commercial breweries, including one in Southern Illinois, found that higher bitterness affects flavor by inhibiting such strains of bacteria. 

The study’s findings, presented in August at the World Brewing Congress in Denver, are the first major research from the FSI, which officially came online earlier this year. SIU researchers collaborated with Scratch Brewing Co. of Ava; Fonta Flora Brewery of Morganton, N.C., and Jester King Brewery of Austin, Texas.  

The trend that researchers from the institute looked into involves using “mixed cultures” of bacteria and yeast that occur in the wild. Many breweries have begun using such mixed cultures in the fermentation of beers they are producing, McCarroll said, collecting them from their own, unique geographic area and bringing a sense of place to such brews. 

“This generally implies fermenting with a culture that is a mixture of yeast, wild yeast and/or bacteria that produce beers with complex and often sour flavors,” he said. “In many cases, both the yeast and the bacteria are wild, meaning they were recently collected from the environment.  The basic idea of the research project was to gain additional information about how brewing conditions can affect the fermentation behavior and beer flavor in mixed fermentations.” 

Hops are technically flowers, and when added to the sugary brews they act as a counterpoint, bringing a bite and bitter flavor. There is a wide variety of hops for brewers to choose from, and the amount of bitterness they bring to a brew is measured in International Bittering Units, or IBUs. Brewers have used them for 400 to 500 years because of their ability to prevent spoilage of beer, as well. 

Bacteria, such as lactobacillus, are known to produce sour beers through the production of lactic and other organic acids, but they are inhibited during fermentation by the bittering compounds in hops.  Yeast is more resistant to the presence of hops during fermentation. 

The researchers specifically tried to determine the effect that the amount of bittering hops had on the fermentation. McCarroll said collaborator and co-author of the study, Marika Josephson, of Scratch Brewing Co. in Ava, had noted this behavior in brewing beer.  

Working with mixed cultures from the three breweries, researchers collected genetic material for each culture, using it to identify the various yeast and bacteria in the culture before and after fermentation. They then fermented the beer at three different IBU levels. 

The researchers found the IBU level can effectively “tune” the evolution of the bacteria and yeast, and thereby the flavor of the finished beer.  

The study provided a controlled look at the effect, including collection of the genetic data and sensory evaluation of the finished beers, McCarroll said. Although it confirmed why brewers have used hops in the production of beer, it also will help take the guess work out just how much of an impact IBUs have on the finished taste of sour and Belgian-type beers, which are growing in popularity. 

“While many brewers are finding great success, they have largely relied on anecdotal and empirical experience to guide their process,” McCarroll said. “We believe our research has the potential to provide brewers and barrelhouse managers with new tools to better understand how to control production quality and flavor profile in beers produced with mixed cultures.” 

McCarroll said the results of the study and the collaboration with commercial brewers is an important milepost for the newly created FSI, which uses an interdisciplinary approach on campus, as well. Other SIU research collaborators on the project include: Kelly Bender, associate professor of microbiology; Katie Strain, laboratory operations coordinator at the FSI; and Lucas Rose, a senior in fermentation science and one of the first majors in the new program. 

“The project is an exciting representation of the FSI’s mission of fostering fermentation research on campus and supporting the fermentation industry at regional and national levels,” McCarroll said. “The research represents something of a maiden voyage for the FSI facilities in the McLafferty Annex.  It would have been difficult to carry out the project without our pilot brewery, which required the production of 12 controlled batches of beer that differed only in the IBU level and fermentation culture.”