Brewing with pea sugars: Norwegian researchers speed up sour beer fermentation

Scientists in Norway have harnessed field pea sugars to accelerate sour beer production. The fermentation-based method develops fruity, complex drinks without “beany” flavors, similar to the tart and intricate flavors of commercial Belgian-style sour, with “shorter, simpler brewing steps.”

Lactic acid-producing bacteria (LAB) and Brettanomyces yeast produce acids that give sour beer its characteristic “mouth-puckering taste.” Brewers either add these during production or introduce them naturally from the environment. However, they often take months or years to ferment the original sugary, steeped-grain liquid (wort) into beer.

To overcome this delay, the scientists utilized sugars in peas called “raffinose-family oligosaccharides” (RFOs) to feed the LAB for faster sour beer brewing.

Food Ingredients First catches up with the study’s authors, Catrin Tyl, Phillipp Garbers, and Bjørge Westereng from the Norwegian University of Life Science, to understand the method’s implications for sour beer manufacturers and overcoming the flavor challenges associated with plant proteins.

“Even though pulses have received a lot of press over the last few years, challenges remain when it comes to increasing their use and cultivation. Field peas have the advantage that they can be cultivated in Norway, but the current cultivation areas are relatively small,” Tyl tells us.

Catrin Tyl, Phillipp Garbers and Bjørge Westereng, who conducted the study (Image credit: Tommy Normann).“Moreover, the consumption of pulses is low, and although the product palette has increased in recent years, an even wider range of products could lead to a market pull in the sense that if more consumers buy products with pulses, more will be grown.”

Additionally, peas and pulses generally consist of a considerable amount of RFOs (2-6%) that are easily extracted, and the study demonstrates their potential to be used in “unconventional ways that can lead to appealing products,” says Westereng.

Targeting favorable flavor profiles

The team brewed four experimental sour beers using three different LABs— two with the field pea RFOs and two without — and then compared the final product to a commercial Belgian sour.

They fermented all the samples for 19 days with Brettanomyces clausennii yeast together with combinations of LAB. 

Results revealed that beers brewed using the RFO extract had more lactic acid, ethanol and fruity flavor-imparting compounds than the beers brewed without RFOs.

They also had “fruitier flavors, more acidic tastes and higher total taste intensity.” Still, the total taste intensity was comparable to the commercial beer.

Tyl says the team has hypothesized that its study design could lead to “a more well-rounded flavor profile” and views “controlled fermentation” as a tool that can impart flavor benefits to sour beer.

“We performed a screening of various lactic acid bacteria and chose those that gave the best flavor profile.” 

The researchers investigated RFOs derived from pulses as selective carbon sources for sour beer production (Image credit: Journal of Agricultural and Food Chemistry).

Overcoming consumer skepticism

Consumers are often concerned about the beany off-flavors associated with pulse-derived ingredients. These compounds did not increase when RFOs were added to the sour beers, notes the study, published in Journal of Agricultural and Food Chemistry.

Additionally, the LAB consumed all the RFOs despite the short fermentation time, and left no detectable traces in any of the experimental beers. This is important, since RFOs might cause gastrointestinal discomfort in some consumers, explains Tyl.

“We targeted the beer production to reduce these compounds, which could expand the consumption of such a beverage.”

The researchers also found that a range of food-borne and food-grade bacteria can use RFO extracts, which can be obtained from other pulses for various fermented foods and beverages. 

“This could lead to a shift in how RFOs are viewed, i.e., mitigate dietary concerns and instead regard them as valuable raw material,” underscores the study.

Sensory analysis by the scientists revealed that adding a pea-derived ingredient did not impair the sour beer’s aroma profile (Image credit: Tommy Normann).

Slashing production times

Garbers says the team conducted microbial studies using a dry powder containing the RFOs. The “easy to handle” ingredient was used as a starting material for beer brewing.

“Some of the bacterial strains are suppressed by the conditions in beer, so their ability to withstand this ‘stress’ was part of our selection criteria.”

Meanwhile, the researchers claim their fermentation process could cut sour beer production times considerably.

This includes the time during both fermentation and the work in the brewhouse “as the addition of RFOs could replace some constituents that are otherwise introduced through a long and technically complex mashing process,” explains Garbers.

Westereng adds that the RFOs also give manufacturers some control over the process since they are “not fermented by the yeast.”

Scalability potential

The extraction process of the RFOs is easily scalable, utilizing “relatively cheap processes already used in the food industry,” continues Westereng.

The researchers highlight only two limitations — the availability of RFOs on the market or the scale at which a brewery could produce RFOs itself if this is technically feasible and desirable.

The team has not conducted cost calculations for the process, with the price being dependent on “when and how RFOs become available as a side-stream from plant-protein productions,” Garbers tells us.

“Currently, only pure and expensive preparations are available for laboratory and research use. In addition, the current applications of RFOs are limited. Therefore, they are currently not considered a valuable side-stream, which in turn motivated us to make a case for their use.”

“However, we would like to point out that the majority of the ingredients still consisted of grains (50% barley & wheat),” he concludes.

The researchers presently have no explicit expansion plans but are open to discussions on potential contributions and collaborations if industrial players are interested.